Eye Contact Modulates Cognitive Processing Differently in Children with Autism

ERIC Educational Resources Information Center

Falck-Ytter, Terje; Carlström, Christoffer; Johansson, Martin

2015-01-01

In humans, effortful cognitive processing frequently takes place during social interaction, with eye contact being an important component. This study shows that the effect of eye contact on memory for nonsocial information is different in children with typical development than in children with autism, a disorder of social communication. Direct…

Swooping in the Suburbs; Parental Defence of an Abundant Aggressive Urban Bird against Humans.

PubMed

Lees, Daniel; Sherman, Craig D H; Maguire, Grainne S; Dann, Peter; Cardilini, Adam P A; Weston, Michael A

2013-08-13

Masked Lapwings, Vanellus miles, often come into 'conflict' with humans, because they often breed in close proximity to humans and actively defend their ground nests through aggressive behaviour, which typically involves swooping. This study examined whether defensive responses differed when nesting birds were confronted with different human stimuli ('pedestrian alone' vs. 'person pushing a lawn mower' approaches to nests) and tested the effectiveness of a commonly used deterrent (mock eyes positioned on the top or back of a person's head) on the defensive response. Masked Lapwings did not swoop closer to a person with a lawn mower compared with a pedestrian, but flushed closer and remained closer to the nest in the presence of a lawn mower. The presence of eye stickers decreased (pedestrians) and increased (lawn mowers) swooping behaviour. Masked Lapwings can discriminate between different human activities and adjust their defensive behaviour accordingly. We also conclude that the use of eye stickers is an effective method to mitigate the human-lapwing 'conflict' in some, but not all, circumstances.

Comparison of different wavefront measurement setups to judge the position tolerance of intraocular lenses in a model eye

NASA Astrophysics Data System (ADS)

Traxler, Lukas; Reutterer, Bernd; Bayer, Natascha; Drauschke, Andreas

2017-04-01

To treat cataract intraocular lenses (IOLs) are used to replace the clouded human eye lens. Due to postoperative healing processes the IOL can displace within the eye, which can lead to deteriorated quality of vision. To test and characterize these effect an IOL can be embedded into a model of the humane eye. One informative measure are wavefront aberrations. In this paper three different setups, the typical double-pass configuration (DP), a single-pass (SP1) where the measured light travels in the same direction as in DP and a single-pass (SP2) with reversed direction, are investigated. All three setups correctly measure the aberrations of the eye, where SP1 is found to be the simplest to set up and align. Because of the lowest complexity it is the proposed method for wavefront measurement in model eyes.

A generalised porous medium approach to study thermo-fluid dynamics in human eyes.

PubMed

Mauro, Alessandro; Massarotti, Nicola; Salahudeen, Mohamed; Romano, Mario R; Romano, Vito; Nithiarasu, Perumal

2018-03-22

The present work describes the application of the generalised porous medium model to study heat and fluid flow in healthy and glaucomatous eyes of different subject specimens, considering the presence of ocular cavities and porous tissues. The 2D computational model, implemented into the open-source software OpenFOAM, has been verified against benchmark data for mixed convection in domains partially filled with a porous medium. The verified model has been employed to simulate the thermo-fluid dynamic phenomena occurring in the anterior section of four patient-specific human eyes, considering the presence of anterior chamber (AC), trabecular meshwork (TM), Schlemm's canal (SC), and collector channels (CC). The computational domains of the eye are extracted from tomographic images. The dependence of TM porosity and permeability on intraocular pressure (IOP) has been analysed in detail, and the differences between healthy and glaucomatous eye conditions have been highlighted, proving that the different physiological conditions of patients have a significant influence on the thermo-fluid dynamic phenomena. The influence of different eye positions (supine and standing) on thermo-fluid dynamic variables has been also investigated: results are presented in terms of velocity, pressure, temperature, friction coefficient and local Nusselt number. The results clearly indicate that porosity and permeability of TM are two important parameters that affect eye pressure distribution. Graphical abstract Velocity contours and vectors for healthy eyes (top) and glaucomatous eyes (bottom) for standing position.

Indentation and needle insertion properties of the human eye

PubMed Central

Matthews, A; Hutnik, C; Hill, K; Newson, T; Chan, T; Campbell, G

2014-01-01

Purpose Characterization of the biomechanical properties of the human eye has a number of potential utilities. One novel purpose is to provide the basis for development of suitable tissue-mimicking material. The purpose of this study was to determine the indentation and needle insertion characteristics on human eye globes and tissue strips. Methods An indenter assessed the elastic response of human eye globes and tissue strips under increasing compressive loads. Needle insertion determined the force (N) needed to penetrate various areas of the eye wall. Results The results demonstrated that globes underwent slightly greater indentation at the midline than at the central cornea, and corneal strips indented twofold more than scleral strips, although neither difference was significant (P=0.400 and P=0.100, respectively). Significant differences were observed among various areas of needle insertion (P<0.001). Needle insertion through the anterior sclera (adjacent to the limbus) and posterior sclera (adjacent to the optic nerve) required the greatest amount of force (0.954 and 1.005 N, respectively). The force required to penetrate the central cornea (0.518 N) was significantly lower than all other areas except the midline sclera (0.700 N) Conclusion These data form the basis for further research into the development of a tissue-mimicking human eye construct with potential utility as a model for use in ophthalmology research and surgical teaching. PMID:24810571

The effects of two different types of bandage contact lenses on the healthy canine eye.

PubMed

Braus, Barbara Katharina; Riedler, Daniela; Tichy, Alexander; Spergser, Joachim; Schwendenwein, Ilse

2018-02-06

To compare two types of bandage contact lenses on the healthy canine eye. Six healthy Beagles. Two different types of bandage contact lenses (single sized human silicone contact lens 'PureVision 2' (Bausch & Lomb Incorporated, Rochester, NY, USA) and specially designed veterinary hydrogel contact lens 'AcriVet Pat D' (Bausch & Lomb Incorporated) were placed in 12 eyes of healthy Beagle dogs. Retention times and the effects of the lenses regarding irritation of the eye, changes in tear production, impact of contact lenses on tonometric readings, and cytologic and microbiological alterations of the canine eye were investigated. Mean retention times for veterinary hydrogel lenses with special dimensions were significantly shorter (2 days) than for one size human silicon lenses (8.8 days). Irritation scores were overall low for both types of lenses apart from one human lens causing severe irritation and keratoconjunctivitis as a sequel to folding and displacement. Tear production remained stable in human contact lenses. Intraocular pressure readings with a contact lens in place were only slightly altered; the most accurate readings were obtained through a human lens with an applanation tonometer. Cytology revealed a slight, nonsignificant increase in neutrophilic granulocytes with both types of lenses; the microflora did not change significantly. Human silicone lenses have significantly longer retention times and are less expensive than veterinary hydrogel lenses. In regard to irritation, bacterial growth and inflammation, both types of lenses can be recommended for use in canine eyes. © 2018 American College of Veterinary Ophthalmologists.

Monocular zones in stereoscopic scenes: A useful source of information for human binocular vision?

NASA Astrophysics Data System (ADS)

Harris, Julie M.

2010-02-01

When an object is closer to an observer than the background, the small differences between right and left eye views are interpreted by the human brain as depth. This basic ability of the human visual system, called stereopsis, lies at the core of all binocular three-dimensional (3-D) perception and related technological display development. To achieve stereopsis, it is traditionally assumed that corresponding locations in the right and left eye's views must first be matched, then the relative differences between right and left eye locations are used to calculate depth. But this is not the whole story. At every object-background boundary, there are regions of the background that only one eye can see because, in the other eye's view, the foreground object occludes that region of background. Such monocular zones do not have a corresponding match in the other eye's view and can thus cause problems for depth extraction algorithms. In this paper I will discuss evidence, from our knowledge of human visual perception, illustrating that monocular zones do not pose problems for our human visual systems, rather, our visual systems can extract depth from such zones. I review the relevant human perception literature in this area, and show some recent data aimed at quantifying the perception of depth from monocular zones. The paper finishes with a discussion of the potential importance of considering monocular zones, for stereo display technology and depth compression algorithms.

Optics of the human cornea influence the accuracy of stereo eye-tracking methods: a simulation study.

PubMed

Barsingerhorn, A D; Boonstra, F N; Goossens, H H L M

2017-02-01

Current stereo eye-tracking methods model the cornea as a sphere with one refractive surface. However, the human cornea is slightly aspheric and has two refractive surfaces. Here we used ray-tracing and the Navarro eye-model to study how these optical properties affect the accuracy of different stereo eye-tracking methods. We found that pupil size, gaze direction and head position all influence the reconstruction of gaze. Resulting errors range between ± 1.0 degrees at best. This shows that stereo eye-tracking may be an option if reliable calibration is not possible, but the applied eye-model should account for the actual optics of the cornea.

Discrimination between smiling faces: Human observers vs. automated face analysis.

PubMed

Del Líbano, Mario; Calvo, Manuel G; Fernández-Martín, Andrés; Recio, Guillermo

2018-05-11

This study investigated (a) how prototypical happy faces (with happy eyes and a smile) can be discriminated from blended expressions with a smile but non-happy eyes, depending on type and intensity of the eye expression; and (b) how smile discrimination differs for human perceivers versus automated face analysis, depending on affective valence and morphological facial features. Human observers categorized faces as happy or non-happy, or rated their valence. Automated analysis (FACET software) computed seven expressions (including joy/happiness) and 20 facial action units (AUs). Physical properties (low-level image statistics and visual saliency) of the face stimuli were controlled. Results revealed, first, that some blended expressions (especially, with angry eyes) had lower discrimination thresholds (i.e., they were identified as "non-happy" at lower non-happy eye intensities) than others (especially, with neutral eyes). Second, discrimination sensitivity was better for human perceivers than for automated FACET analysis. As an additional finding, affective valence predicted human discrimination performance, whereas morphological AUs predicted FACET discrimination. FACET can be a valid tool for categorizing prototypical expressions, but is currently more limited than human observers for discrimination of blended expressions. Configural processing facilitates detection of in/congruence(s) across regions, and thus detection of non-genuine smiling faces (due to non-happy eyes). Copyright © 2018 Elsevier B.V. All rights reserved.

Binocular eye movement control and motion perception: what is being tracked?

PubMed

van der Steen, Johannes; Dits, Joyce

2012-10-19

We investigated under what conditions humans can make independent slow phase eye movements. The ability to make independent movements of the two eyes generally is attributed to few specialized lateral eyed animal species, for example chameleons. In our study, we showed that humans also can move the eyes in different directions. To maintain binocular retinal correspondence independent slow phase movements of each eye are produced. We used the scleral search coil method to measure binocular eye movements in response to dichoptically viewed visual stimuli oscillating in orthogonal direction. Correlated stimuli led to orthogonal slow eye movements, while the binocularly perceived motion was the vector sum of the motion presented to each eye. The importance of binocular fusion on independency of the movements of the two eyes was investigated with anti-correlated stimuli. The perceived global motion pattern of anti-correlated dichoptic stimuli was perceived as an oblique oscillatory motion, as well as resulted in a conjugate oblique motion of the eyes. We propose that the ability to make independent slow phase eye movements in humans is used to maintain binocular retinal correspondence. Eye-of-origin and binocular information are used during the processing of binocular visual information, and it is decided at an early stage whether binocular or monocular motion information and independent slow phase eye movements of each eye are produced during binocular tracking.

Binocular Eye Movement Control and Motion Perception: What Is Being Tracked?

PubMed Central

van der Steen, Johannes; Dits, Joyce

2012-01-01

Purpose. We investigated under what conditions humans can make independent slow phase eye movements. The ability to make independent movements of the two eyes generally is attributed to few specialized lateral eyed animal species, for example chameleons. In our study, we showed that humans also can move the eyes in different directions. To maintain binocular retinal correspondence independent slow phase movements of each eye are produced. Methods. We used the scleral search coil method to measure binocular eye movements in response to dichoptically viewed visual stimuli oscillating in orthogonal direction. Results. Correlated stimuli led to orthogonal slow eye movements, while the binocularly perceived motion was the vector sum of the motion presented to each eye. The importance of binocular fusion on independency of the movements of the two eyes was investigated with anti-correlated stimuli. The perceived global motion pattern of anti-correlated dichoptic stimuli was perceived as an oblique oscillatory motion, as well as resulted in a conjugate oblique motion of the eyes. Conclusions. We propose that the ability to make independent slow phase eye movements in humans is used to maintain binocular retinal correspondence. Eye-of-origin and binocular information are used during the processing of binocular visual information, and it is decided at an early stage whether binocular or monocular motion information and independent slow phase eye movements of each eye are produced during binocular tracking. PMID:22997286

Precision Pulse Capsulotomy: Preclinical Safety and Performance of a New Capsulotomy Technology.

PubMed

Chang, David F; Mamalis, Nick; Werner, Liliana

2016-02-01

To assess the preclinical safety and performance of a new precision pulse capsulotomy (PPC) method. Human cadaver eye studies and surgical, slit-lamp, and histopathologic evaluation in a consecutive series of 20 live rabbits. Human cadaver eyes and New Zealand white rabbits. Precision pulse capsulotomy uses a highly focused, fast, multipulse, low-energy discharge to produce a perfectly round anterior capsulotomy instantaneously and simultaneously along all 360°. Capsulotomies are performed using a disposable handpiece with a soft collapsible tip and circular nitinol cutting element. Miyake-Apple imaging and scanning electron microscopy (SEM) of PPC were conducted in human cadaver eyes. Surgical, postoperative slit-lamp, and histopathologic assessments of PPC were performed in 20 live rabbits and were compared with manual continuous curvilinear capsulorrhexis (CCC) in the fellow eye. Anterior chamber (AC) thermocouple temperature measurements were evaluated in a subset of rabbit eyes. Capsulotomy edge circularity, SEM morphologic features and zonular movement with PPC in human cadaver eyes. Anterior chamber temperature during PPC and grading of ocular inflammation, corneal endothelial damage, anterior capsular opacification (ACO), and posterior capsular opacification (PCO). Miyake-Apple imaging showed minimal zonular stress, and thermocouple measurements demonstrated negligible AC temperature changes during PPC. Precision pulse capsulotomy produced round, complete capsulotomies in all 20 rabbit eyes, leading to successful in-the-bag intraocular lens (IOL) implantation. Slit-lamp examinations at 3 days and 1, 2, and 4 weeks after surgery showed no significant differences between PPC and CCC in corneal edema, AC inflammatory reaction, capsular fibrosis, ACO, and PCO. Postmortem studies showed no difference in the corneal endothelium between PPC and CCC eyes. All IOLs were well centered in PPC eyes, and histopathologic analysis showed no greater inflammatory infiltrates. Precision pulse capsulotomy is a new method to automate consistent creation of a perfectly circular anterior capsulotomy with a disposable handheld instrument that can be used in the normal phacoemulsification surgical sequence. Compared with CCC in fellow rabbit eyes, PPC was equally safe and showed no greater zonular stress compared with CCC in human cadaver eyes. Human cadaver eye SEM showed a much smoother capsulotomy edge compared to those produced by femtosecond laser. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Genotypes of JC virus, DNA of cytomegalovirus, and proviral DNA of human immunodeficiency virus in eyes of acquired immunodeficiency syndrome patients.

PubMed

Eberwein, Philipp; Hansen, Lutz L; Agostini, Hansjürgen T

2005-02-01

JC virus (JCV) is a human polyomavirus that exists in at least eight different genotypes as a result of coevolution with different human populations all over the world. Well adapted to its host, it usually persists in the kidneys and possibly the brain. If the host becomes immunodeficient, JCV can cause the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML). There is increasing evidence that JCV is transactivated by cytomegalovirus (CMV) and the human immunodeficiency virus (HIV). Both CMV and HIV can infect the retina of acquired immunodeficiency syndrome (AIDS) patients, causing severe necrosis in the case of CMV retinitis or a mild HIV-associated vasculopathy, with bleeding and cotton wool spots. The authors therefore investigated by polymerase chain reaction (PCR) whether DNA of these three viruses was detectable in paraffin-embedded eyes of AIDS patients with a clinical history of CMV retinitis. From a total of 65 eyes, JCV was detected in 21 (32%). Thirty-six (55%) were positive for CMV and 6 (9%) for proviral DNA of HIV. JCV and CMV were found in 13 eyes, JCV and HIV in 3 eyes, CMV and HIV in 1 eye, and DNA from all three viruses in 1 eye. The JCV genotypes were types 1A, 2A, 2E, 3, and 4. In 21 eyes of patients without AIDS, only one sample was JCV positive. In conclusion, JCV DNA can be detected in ocular tissue of AIDS patients at a significantly higher level than in eyes of nonimmunosuppressed patients. Further investigations will help to decide if JCV contributes to the retinopathy caused by CMV and HIV.

Swooping in the Suburbs; Parental Defence of an Abundant Aggressive Urban Bird against Humans

PubMed Central

Lees, Daniel; Sherman, Craig D. H.; Maguire, Grainne S.; Dann, Peter; Cardilini, Adam P. A.; Weston, Michael A.

2013-01-01

Simple Summary We studied the defensive behaviour of 94 pairs of nesting Masked Lapwings, Vanellus miles, in response to two types of human stimuli: a pedestrian and a person pushing a lawn mower. We also examined the effectiveness of a commonly promoted deterrent to swooping (the presence of mock eyes placed on the back of a person’s head) for each stimulus type. Masked Lapwings responded more aggressively to a person pushing a lawn mower compared with pedestrians. Birds also remained closer to the nest in the presence of a lawn mower. The presence of eye stickers on the back of a pedestrian’s head decreased swooping behaviour; however, the presence of eye stickers worn by a person pushing a lawn mower increased swooping behaviour. Abstract Masked Lapwings, Vanellus miles, often come into ‘conflict’ with humans, because they often breed in close proximity to humans and actively defend their ground nests through aggressive behaviour, which typically involves swooping. This study examined whether defensive responses differed when nesting birds were confronted with different human stimuli (‘pedestrian alone’ vs. ‘person pushing a lawn mower’ approaches to nests) and tested the effectiveness of a commonly used deterrent (mock eyes positioned on the top or back of a person’s head) on the defensive response. Masked Lapwings did not swoop closer to a person with a lawn mower compared with a pedestrian, but flushed closer and remained closer to the nest in the presence of a lawn mower. The presence of eye stickers decreased (pedestrians) and increased (lawn mowers) swooping behaviour. Masked Lapwings can discriminate between different human activities and adjust their defensive behaviour accordingly. We also conclude that the use of eye stickers is an effective method to mitigate the human-lapwing ‘conflict’ in some, but not all, circumstances. PMID:26479532

Eye movement-invariant representations in the human visual system.

PubMed

Nishimoto, Shinji; Huth, Alexander G; Bilenko, Natalia Y; Gallant, Jack L

2017-01-01

During natural vision, humans make frequent eye movements but perceive a stable visual world. It is therefore likely that the human visual system contains representations of the visual world that are invariant to eye movements. Here we present an experiment designed to identify visual areas that might contain eye-movement-invariant representations. We used functional MRI to record brain activity from four human subjects who watched natural movies. In one condition subjects were required to fixate steadily, and in the other they were allowed to freely make voluntary eye movements. The movies used in each condition were identical. We reasoned that the brain activity recorded in a visual area that is invariant to eye movement should be similar under fixation and free viewing conditions. In contrast, activity in a visual area that is sensitive to eye movement should differ between fixation and free viewing. We therefore measured the similarity of brain activity across repeated presentations of the same movie within the fixation condition, and separately between the fixation and free viewing conditions. The ratio of these measures was used to determine which brain areas are most likely to contain eye movement-invariant representations. We found that voxels located in early visual areas are strongly affected by eye movements, while voxels in ventral temporal areas are only weakly affected by eye movements. These results suggest that the ventral temporal visual areas contain a stable representation of the visual world that is invariant to eye movements made during natural vision.

Numerical study on statistical properties of speckle pattern in laser projection display based on human eye model

NASA Astrophysics Data System (ADS)

Cui, Zhe; Wang, Anting; Ma, Qianli; Ming, Hai

2013-12-01

In this paper, the laser speckle pattern on human retina for a laser projection display is simulated. By introducing a specific eye model `Indiana Eye', the statistical properties of the laser speckle are numerical investigated. The results show that the aberrations of human eye (mostly spherical and chromatic) will decrease the speckle contrast felt by people. When the wavelength of the laser source is 550 nm (green), people will feel the strongest speck pattern and the weakest when the wavelength is 450 nm (blue). Myopia and hyperopia will decrease the speckle contrast by introducing large spherical aberrations. Although aberration is good for speckle reduction, but it will degrade the imaging capability of the eye. The results show that laser source (650 nm) will have the best image quality on the retina. At last, we compare the human eye with an aberration-free imaging system. Both the speckle contrast and the image quality appear different behavior in these two imaging systems. The results are useful when a standardized measurement procedure for speckle contrast needs to be built.

Is orbital volume associated with eyeball and visual cortex volume in humans?

PubMed

Pearce, Eiluned; Bridge, Holly

2013-01-01

In humans orbital volume increases linearly with absolute latitude. Scaling across mammals between visual system components suggests that these larger orbits should translate into larger eyes and visual cortices in high latitude humans. Larger eyes at high latitudes may be required to maintain adequate visual acuity and enhance visual sensitivity under lower light levels. To test the assumption that orbital volume can accurately index eyeball and visual cortex volumes specifically in humans. Structural Magnetic Resonance Imaging (MRI) techniques are employed to measure eye and orbit (n = 88) and brain and visual cortex (n = 99) volumes in living humans. Facial dimensions and foramen magnum area (a proxy for body mass) were also measured. A significant positive linear relationship was found between (i) orbital and eyeball volumes, (ii) eyeball and visual cortex grey matter volumes and (iii) different visual cortical areas, independently of overall brain volume. In humans the components of the visual system scale from orbit to eye to visual cortex volume independently of overall brain size. These findings indicate that orbit volume can index eye and visual cortex volume in humans, suggesting that larger high latitude orbits do translate into larger visual cortices.

Is orbital volume associated with eyeball and visual cortex volume in humans?

PubMed Central

Pearce, Eiluned; Bridge, Holly

2013-01-01

Background In humans orbital volume increases linearly with absolute latitude. Scaling across mammals between visual system components suggests that these larger orbits should translate into larger eyes and visual cortices in high latitude humans. Larger eyes at high latitudes may be required to maintain adequate visual acuity and enhance visual sensitivity under lower light levels. Aim To test the assumption that orbital volume can accurately index eyeball and visual cortex volumes specifically in humans. Subjects & Methods Structural Magnetic Resonance Imaging (MRI) techniques are employed to measure eye and orbit (N=88), and brain and visual cortex (N=99) volumes in living humans. Facial dimensions and foramen magnum area (a proxy for body mass) were also measured. Results A significant positive linear relationship was found between (i) orbital and eyeball volumes, (ii) eyeball and visual cortex grey matter volumes, (iii) different visual cortical areas, independently of overall brain volume. Conclusion In humans the components of the visual system scale from orbit to eye to visual cortex volume independently of overall brain size. These findings indicate that orbit volume can index eye and visual cortex volume in humans, suggesting that larger high latitude orbits do translate into larger visual cortices. PMID:23879766

Can human eyes prevent perceptual narrowing for monkey faces in human infants?

PubMed

Damon, Fabrice; Bayet, Laurie; Quinn, Paul C; Hillairet de Boisferon, Anne; Méary, David; Dupierrix, Eve; Lee, Kang; Pascalis, Olivier

2015-07-01

Perceptual narrowing has been observed in human infants for monkey faces: 6-month-olds can discriminate between them, whereas older infants from 9 months of age display difficulty discriminating between them. The difficulty infants from 9 months have processing monkey faces has not been clearly identified. It could be due to the structural characteristics of monkey faces, particularly the key facial features that differ from human faces. The current study aimed to investigate whether the information conveyed by the eyes is of importance. We examined whether the presence of Caucasian human eyes in monkey faces allows recognition to be maintained in 6-month-olds and facilitates recognition in 9- and 12-month-olds. Our results revealed that the presence of human eyes in monkey faces maintains recognition for those faces at 6 months of age and partially facilitates recognition of those faces at 9 months of age, but not at 12 months of age. The findings are interpreted in the context of perceptual narrowing and suggest that the attenuation of processing of other-species faces is not reversed by the presence of human eyes. © 2015 Wiley Periodicals, Inc.

Abnormal spatial frequency channels in esotropic cats.

PubMed

Holopigian, K; Blake, R

1984-01-01

A noise masking paradigm was used to measure spatial tuning for the deviating and nondeviating eyes of two esotropic cats and for one eye of a control cat. With increasing noise contrast, masking grew more slowly for both the deviating and the nondeviating eyes of the esotropic cats than for the control cat; apparently, contrast coding is impaired for both eyes of the esotropic cats. Masking with band-reject filtered noise indicated that detection channels for either eye of the esotropic cats were twice as broadly tuned as those for the control cat. In a subsequent experiment, the spatial tuning characteristics of two human esotropes were found to be normal, indicating a fundamental difference between human esotropia and esotropia induced in cats by the section of an eye muscle.

Eye Tracking Based Control System for Natural Human-Computer Interaction

PubMed Central

Lin, Shu-Fan

2017-01-01

Eye movement can be regarded as a pivotal real-time input medium for human-computer communication, which is especially important for people with physical disability. In order to improve the reliability, mobility, and usability of eye tracking technique in user-computer dialogue, a novel eye control system with integrating both mouse and keyboard functions is proposed in this paper. The proposed system focuses on providing a simple and convenient interactive mode by only using user's eye. The usage flow of the proposed system is designed to perfectly follow human natural habits. Additionally, a magnifier module is proposed to allow the accurate operation. In the experiment, two interactive tasks with different difficulty (searching article and browsing multimedia web) were done to compare the proposed eye control tool with an existing system. The Technology Acceptance Model (TAM) measures are used to evaluate the perceived effectiveness of our system. It is demonstrated that the proposed system is very effective with regard to usability and interface design. PMID:29403528

Eye Tracking Based Control System for Natural Human-Computer Interaction.

PubMed

Zhang, Xuebai; Liu, Xiaolong; Yuan, Shyan-Ming; Lin, Shu-Fan

2017-01-01

Eye movement can be regarded as a pivotal real-time input medium for human-computer communication, which is especially important for people with physical disability. In order to improve the reliability, mobility, and usability of eye tracking technique in user-computer dialogue, a novel eye control system with integrating both mouse and keyboard functions is proposed in this paper. The proposed system focuses on providing a simple and convenient interactive mode by only using user's eye. The usage flow of the proposed system is designed to perfectly follow human natural habits. Additionally, a magnifier module is proposed to allow the accurate operation. In the experiment, two interactive tasks with different difficulty (searching article and browsing multimedia web) were done to compare the proposed eye control tool with an existing system. The Technology Acceptance Model (TAM) measures are used to evaluate the perceived effectiveness of our system. It is demonstrated that the proposed system is very effective with regard to usability and interface design.

Microgravity

NASA Image and Video Library

2003-01-22

One concern about human adaptation to space is how returning from the microgravity of orbit to Earth can affect an astronaut's ability to fly safely. There are monitors and infrared video cameras to measure eye movements without having to affect the crew member. A computer screen provides moving images which the eye tracks while the brain determines what it is seeing. A video camera records movement of the subject's eyes. Researchers can then correlate perception and response. Test subjects perceive different images when a moving object is covered by a mask that is visible or invisible (above). Early results challenge the accepted theory that smooth pursuit -- the fluid eye movement that humans and primates have -- does not involve the higher brain. NASA results show that: Eye movement can predict human perceptual performance, smooth pursuit and saccadic (quick or ballistic) movement share some signal pathways, and common factors can make both smooth pursuit and visual perception produce errors in motor responses.

Understanding Visible Perception

NASA Technical Reports Server (NTRS)

2003-01-01

One concern about human adaptation to space is how returning from the microgravity of orbit to Earth can affect an astronaut's ability to fly safely. There are monitors and infrared video cameras to measure eye movements without having to affect the crew member. A computer screen provides moving images which the eye tracks while the brain determines what it is seeing. A video camera records movement of the subject's eyes. Researchers can then correlate perception and response. Test subjects perceive different images when a moving object is covered by a mask that is visible or invisible (above). Early results challenge the accepted theory that smooth pursuit -- the fluid eye movement that humans and primates have -- does not involve the higher brain. NASA results show that: Eye movement can predict human perceptual performance, smooth pursuit and saccadic (quick or ballistic) movement share some signal pathways, and common factors can make both smooth pursuit and visual perception produce errors in motor responses.

Measuring center of pressure signals to quantify human balance using multivariate multiscale entropy by designing a force platform.

PubMed

Huang, Cheng-Wei; Sue, Pei-Der; Abbod, Maysam F; Jiang, Bernard C; Shieh, Jiann-Shing

2013-08-08

To assess the improvement of human body balance, a low cost and portable measuring device of center of pressure (COP), known as center of pressure and complexity monitoring system (CPCMS), has been developed for data logging and analysis. In order to prove that the system can estimate the different magnitude of different sways in comparison with the commercial Advanced Mechanical Technology Incorporation (AMTI) system, four sway tests have been developed (i.e., eyes open, eyes closed, eyes open with water pad, and eyes closed with water pad) to produce different sway displacements. Firstly, static and dynamic tests were conducted to investigate the feasibility of the system. Then, correlation tests of the CPCMS and AMTI systems have been compared with four sway tests. The results are within the acceptable range. Furthermore, multivariate empirical mode decomposition (MEMD) and enhanced multivariate multiscale entropy (MMSE) analysis methods have been used to analyze COP data reported by the CPCMS and compare it with the AMTI system. The improvements of the CPCMS are 35% to 70% (open eyes test) and 60% to 70% (eyes closed test) with and without water pad. The AMTI system has shown an improvement of 40% to 80% (open eyes test) and 65% to 75% (closed eyes test). The results indicate that the CPCMS system can achieve similar results to the commercial product so it can determine the balance.

Measuring Center of Pressure Signals to Quantify Human Balance Using Multivariate Multiscale Entropy by Designing a Force Platform

PubMed Central

Huang, Cheng-Wei; Sue, Pei-Der; Abbod, Maysam F.; Jiang, Bernard C.; Shieh, Jiann-Shing

2013-01-01

To assess the improvement of human body balance, a low cost and portable measuring device of center of pressure (COP), known as center of pressure and complexity monitoring system (CPCMS), has been developed for data logging and analysis. In order to prove that the system can estimate the different magnitude of different sways in comparison with the commercial Advanced Mechanical Technology Incorporation (AMTI) system, four sway tests have been developed (i.e., eyes open, eyes closed, eyes open with water pad, and eyes closed with water pad) to produce different sway displacements. Firstly, static and dynamic tests were conducted to investigate the feasibility of the system. Then, correlation tests of the CPCMS and AMTI systems have been compared with four sway tests. The results are within the acceptable range. Furthermore, multivariate empirical mode decomposition (MEMD) and enhanced multivariate multiscale entropy (MMSE) analysis methods have been used to analyze COP data reported by the CPCMS and compare it with the AMTI system. The improvements of the CPCMS are 35% to 70% (open eyes test) and 60% to 70% (eyes closed test) with and without water pad. The AMTI system has shown an improvement of 40% to 80% (open eyes test) and 65% to 75% (closed eyes test). The results indicate that the CPCMS system can achieve similar results to the commercial product so it can determine the balance. PMID:23966184

Motion-adaptive model-assisted compatible coding with spatiotemporal scalability

NASA Astrophysics Data System (ADS)

Lee, JaeBeom; Eleftheriadis, Alexandros

1997-01-01

We introduce the concept of motion adaptive spatio-temporal model-assisted compatible (MA-STMAC) coding, a technique to selectively encode areas of different importance to the human eye in terms of space and time in moving images with the consideration of object motion. PRevious STMAC was proposed base don the fact that human 'eye contact' and 'lip synchronization' are very important in person-to-person communication. Several areas including the eyes and lips need different types of quality, since different areas have different perceptual significance to human observers. The approach provides a better rate-distortion tradeoff than conventional image coding techniques base don MPEG-1, MPEG- 2, H.261, as well as H.263. STMAC coding is applied on top of an encoder, taking full advantage of its core design. Model motion tracking in our previous STMAC approach was not automatic. The proposed MA-STMAC coding considers the motion of the human face within the STMAC concept using automatic area detection. Experimental results are given using ITU-T H.263, addressing very low bit-rate compression.

Model of the Human Eye Based on ABCD Matrix

NASA Astrophysics Data System (ADS)

González, G. Díaz; Castillo, M. David Iturbe

2008-04-01

At the moment several models of the human eye exist, nevertheless the gradient index models of the human lens (crystalline) have received little attention in optometry and vision sciences, although they consider how the refractive index and the refracting power can change with the accommodation. On the other hand, in study fields like ophthalmology and optometry, exist cases where there is a lack of information about the factors that influence the change of refractive power and therefore the focal length of the eye. By such reason, in this paper we present a model of the human eye based on the ABCD matrix in order to describe the propagation of light rays, that can be understood by professional people in optics, ophthalmology and optometry, and the dispersions of the different ocular mediums are taken into account,. The aim of the model is to obtain data about the refractive power of the eye under different considerations, such as: changes in wavelength, radius of curvature and thicknesses of the ocular mediums. We present results of simulations in Matlab of our model, assuming that the object is punctual and is placed to a certain distance of the eye, and considering at the beginning to the crystalline like a medium with fixed refractive index, and after like a gradient lens. By means of graphs, we show the total refractive power of the eye and its form and type of dependence with respect to variations in radius of curvature and thicknesses of the cornea and crystalline, as well as variations in the thickness of the previous and later cameras.

Evaluation of Eye Irritation Potential of Solid Substance with New 3D Reconstructed Human Cornea Model, MCTT HCETM

PubMed Central

Jang, Won-hee; Jung, Kyoung-mi; Yang, Hye-ri; Lee, Miri; Jung, Haeng-Sun; Lee, Su-Hyon; Park, Miyoung; Lim, Kyung-Min

2015-01-01

The eye irritation potential of drug candidates or pharmaceutical ingredients should be evaluated if there is a possibility of ocular exposure. Traditionally, the ocular irritation has been evaluated by the rabbit Draize test. However, rabbit eyes are more sensitive to irritants than human eyes, therefore substantial level of false positives are unavoidable. To resolve this species difference, several three-dimensional human corneal epithelial (HCE) models have been developed as alternative eye irritation test methods. Recently, we introduced a new HCE model, MCTT HCETM which is reconstructed with non-transformed human corneal cells from limbal tissues. Here, we examined if MCTT HCETM can be employed to evaluate eye irritation potential of solid substances. Through optimization of washing method and exposure time, treatment time was established as 10 min and washing procedure was set up as 4 times of washing with 10 mL of PBS and shaking in 30 mL of PBS in a beaker. With the established eye irritation test protocol, 11 solid substances (5 non-irritants, 6 irritants) were evaluated which demonstrated an excellent predictive capacity (100% accuracy, 100% specificity and 100% sensitivity). We also compared the performance of our test method with rabbit Draize test results and in vitro cytotoxicity test with 2D human corneal epithelial cell lines. PMID:26157556

Objective evaluation of the visual acuity in human eyes

NASA Astrophysics Data System (ADS)

Rosales, M. A.; López-Olazagasti, E.; Ramírez-Zavaleta, G.; Varillas, G.; Tepichín, E.

2009-08-01

Traditionally, the quality of the human vision is evaluated by a subjective test in which the examiner asks the patient to read a series of characters of different sizes, located at a certain distance of the patient. Typically, we need to ensure a subtended angle of vision of 5 minutes, which implies an object of 8.8 mm high located at 6 meters (normal or 20/20 visual acuity). These characters constitute what is known as the Snellen chart, universally used to evaluate the spatial resolution of the human eyes. The mentioned process of identification of characters is carried out by means of the eye - brain system, giving an evaluation of the subjective visual performance. In this work we consider the eye as an isolated image-forming system, and show that it is possible to isolate the function of the eye from that of the brain in this process. By knowing the impulse response of the eye´s system we can obtain, in advance, the image of the Snellen chart simultaneously. From this information, we obtain the objective performance of the eye as the optical system under test. This type of results might help to detect anomalous situations of the human vision, like the so called "cerebral myopia".

Sex differences in a virtual water maze: an eye tracking and pupillometry study.

PubMed

Mueller, Sven C; Jackson, Carl P T; Skelton, Ron W

2008-11-21

Sex differences in human spatial navigation are well known. However, the exact strategies that males and females employ in order to navigate successfully around the environment are unclear. While some researchers propose that males prefer environment-centred (allocentric) and females prefer self-centred (egocentric) navigation, these findings have proved difficult to replicate. In the present study we examined eye movements and physiological measures of memory (pupillometry) in order to compare visual scanning of spatial orientation using a human virtual analogue of the Morris Water Maze task. Twelve women and twelve men (average age=24 years) were trained on a visible platform and had to locate an invisible platform over a series of trials. On all but the first trial, participants' eye movements were recorded for 3s and they were asked to orient themselves in the environment. While the behavioural data replicated previous findings of improved spatial performance for males relative to females, distinct sex differences in eye movements were found. Males tended to explore consistently more space early on while females demonstrated initially longer fixation durations and increases in pupil diameter usually associated with memory processing. The eye movement data provides novel insight into differences in navigational strategies between the sexes.

Optimizations and Applications in Head-Mounted Video-Based Eye Tracking

ERIC Educational Resources Information Center

Li, Feng

2011-01-01

Video-based eye tracking techniques have become increasingly attractive in many research fields, such as visual perception and human-computer interface design. The technique primarily relies on the positional difference between the center of the eye's pupil and the first-surface reflection at the cornea, the corneal reflection (CR). This…

Modeling the influence of LASIK surgery on optical properties of the human eye

NASA Astrophysics Data System (ADS)

Szul-Pietrzak, Elżbieta; Hachoł, Andrzej; Cieślak, Krzysztof; Drożdż, Ryszard; Podbielska, Halina

2011-11-01

The aim was to model the influence of LASIK surgery on the optical parameters of the human eye and to ascertain which factors besides the central corneal radius of curvature and central thickness play the major role in postsurgical refractive change. Ten patients were included in the study. Pre- and postsurgical measurements included standard refraction, anterior corneal curvature and pachymetry. The optical model used in the analysis was based on the Le Grand and El Hage schematic eye, modified by the measured individual parameters of corneal geometry. A substantial difference between eye refractive error measured after LASIK and estimated from the eye model was observed. In three patients, full correction of the refractive error was achieved. However, analysis of the visual quality in terms of spot diagrams and optical transfer functions of the eye optical system revealed some differences in these measurements. This suggests that other factors besides corneal geometry may play a major role in postsurgical refraction. In this paper we investigated whether the biomechanical properties of the eyeball and changes in intraocular pressure could account for the observed discrepancies.

Optics of human eye: 400 years of exploration from Galileo's time.

PubMed

Artal, Pablo; Tabernero, Juan

2010-06-01

We present a brief historical background and a description of the main features of the eye's optical properties: the eye is a simple, but rather optimized, optical instrument. It is only since Galileo's time that the importance of the eye as a part of different optical instruments has driven a continuous scientific exploration of ocular optics. In the past decade, the use of wavefront sensing technology allowed us to complete our understating of eye optics as a robust aplanatic system.

The Effect of Altitude on Intraocular Pressure in Vitrectomized Eyes with Sulfur Hexafluoride Tamponade by the Friedenwald Method: Rabbit Animal Model

PubMed Central

Fromow-Guerra, Jans; Solís-Vivanco, Adriana; Perez-Reguera, Adriana; Quiroz-Mercado, Hugo; Meza-de Regil, Armando; Papa-Oliva, Gabriela; Morales-Cantón, Virgilio

2016-01-01

The aim of this study is to assess the change in intraocular pressure after a road trip, in eyes with different levels of filling with gas tamponade. Five rabbit eyes were subject to pars plana vitrectomy and gas tamponade (filling percentage: 25%, 50%, and 100% of nonexpansile SF6, 100% saline solution, and 100% room air). A sixth eye was injected with 0.35 cc of undiluted SF6 without vitrectomy. Guided by global positioning system, they were driven to the highest point of the highway connecting Mexico City with Puebla city and back, stopping every 300 m to assess intraocular pressure. The rabbit's scleral rigidity and estimation for human eyes were done by using the Friedenwald nomogram. Maximum altitude was 3209 m (Δ949 m). There were significant differences in intraocular pressure on the rabbit eyes filled with SF6 at 100%, 50%, 25%, and 100% room air. Per every 100 m of altitude rise, the intraocular pressure increased by 1.53, 1.0046, 0.971, and 0.97 mmHg, respectively. Using the human Friedenwald rigidity coefficient, the human eye estimate for intraocular pressure change was 2.1, 1.8, 1.4, and 1.1 mmHg per every 100 m of attitude rise. Altitude changes have a significant impact on intraocular pressure. The final effect depends on the percentage of vitreous cavity fill and scleral rigidity. PMID:27957500

The Effect of Altitude on Intraocular Pressure in Vitrectomized Eyes with Sulfur Hexafluoride Tamponade by the Friedenwald Method: Rabbit Animal Model.

PubMed

Fromow-Guerra, Jans; Solís-Vivanco, Adriana; Velez-Montoya, Raul; Perez-Reguera, Adriana; Quiroz-Mercado, Hugo; Meza-de Regil, Armando; Papa-Oliva, Gabriela; Morales-Cantón, Virgilio

2016-01-01

The aim of this study is to assess the change in intraocular pressure after a road trip, in eyes with different levels of filling with gas tamponade. Five rabbit eyes were subject to pars plana vitrectomy and gas tamponade (filling percentage: 25%, 50%, and 100% of nonexpansile SF 6 , 100% saline solution, and 100% room air). A sixth eye was injected with 0.35 cc of undiluted SF 6 without vitrectomy. Guided by global positioning system, they were driven to the highest point of the highway connecting Mexico City with Puebla city and back, stopping every 300 m to assess intraocular pressure. The rabbit's scleral rigidity and estimation for human eyes were done by using the Friedenwald nomogram. Maximum altitude was 3209 m (Δ949 m). There were significant differences in intraocular pressure on the rabbit eyes filled with SF 6 at 100%, 50%, 25%, and 100% room air. Per every 100 m of altitude rise, the intraocular pressure increased by 1.53, 1.0046, 0.971, and 0.97 mmHg, respectively. Using the human Friedenwald rigidity coefficient, the human eye estimate for intraocular pressure change was 2.1, 1.8, 1.4, and 1.1 mmHg per every 100 m of attitude rise. Altitude changes have a significant impact on intraocular pressure. The final effect depends on the percentage of vitreous cavity fill and scleral rigidity.

A Simple Model of the Accommodating Lens of the Human Eye

ERIC Educational Resources Information Center

Oommen, Vinay; Kanthakumar, Praghalathan

2014-01-01

The human eye is often discussed as optically equivalent to a photographic camera. The iris is compared with the shutter, the pupil to the aperture, and the retina to the film, and both have lens systems to focus rays of light. Although many similarities exist, a major difference between the two systems is the mechanism involved in focusing an…

OCT angiography by absolute intensity difference applied to normal and diseased human retinas

PubMed Central

Ruminski, Daniel; Sikorski, Bartosz L.; Bukowska, Danuta; Szkulmowski, Maciej; Krawiec, Krzysztof; Malukiewicz, Grazyna; Bieganowski, Lech; Wojtkowski, Maciej

2015-01-01

We compare four optical coherence tomography techniques for noninvasive visualization of microcapillary network in the human retina and murine cortex. We perform phantom studies to investigate contrast-to-noise ratio for angiographic images obtained with each of the algorithm. We show that the computationally simplest absolute intensity difference angiographic OCT algorithm that bases only on two cross-sectional intensity images may be successfully used in clinical study of healthy eyes and eyes with diabetic maculopathy and branch retinal vein occlusion. PMID:26309740

Postanaesthetic tear production and ocular irritation in cats.

PubMed

Peche, N; Köstlin, R; Reese, S; Pieper, K

2015-01-01

General anaesthesia significantly reduces tear production and normal values are not immediately re-established on ending anaesthesia. Therefore, adequate protection of the cornea has to be assured during the perianaesthetic period. There are various methods available, including taping of the eyelids and the application of eye ointments, gels and drops. In human medicine studies, different formulations were found to induce signs of ocular irritation. The aim of the present study was to determine tear production in cats after general anaesthesia, and to identify possible causes of irritation. Tear production was determined in 41 cats after general anaesthesia and eyes were examined for signs of irritation. Two different anaesthetic protocols were used. To protect the cornea, an ointment and gel were applied to the right and left eyes, respectively. Postoperatively, tear production was significantly reduced for 6 hours and 18 hours in the right and left eyes, respectively. Two hours after anaesthesia, blepharospasm of the right eye was observed in 92.7% (n = 38) of the cats. In contrast, the left eye was always held open. This study demonstrated that tear production in cats is significantly decreased both during and after anaesthesia. The degree of reduction was independent of the anaesthetic protocol. Both the eye ointment and gel proved effective in protecting the corneal surface. However, eye gel use is recommended because the eye ointment consistently caused an irritation comparable to the foreign-body sensation reported in humans.

Morphological and Hydrodynamic Correlations with Increasing Outflow Facility by Rho-Kinase Inhibitor Y-27632

PubMed Central

Yang, Chen-Yuan Charlie

2014-01-01

Abstract Rho-kinase inhibitors affect actomyosin cytoskeletal networks and have been shown to significantly increase outflow facility and lower intraocular pressure in various animal models and human eyes. This article summarizes common morphological changes in the trabecular meshwork induced by Rho-kinase inhibitors and specifically compares the morphological and hydrodynamic correlations with increased outflow facility by Rho-kinase inhibitor, Y-27632, in bovine, monkey, and human eyes under similar experimental conditions. Interspecies comparison has shown that morphological changes in the juxtacanalicular connective tissue (JCT) of these 3 species were different. However, these different morphological changes in the JCT, no matter if it's separation between the JCT and inner wall in bovine eyes, or separation between the JCT cells or between the JCT cells and their matrix in monkey eyes, or even no separation between the inner wall and the JCT but a more subtle expansion of the JCT in human eyes, appear to correlate with the increased percent change of outflow facility. More importantly, these different morphological changes all resulted in an increase in effective filtration area, which was positively correlated with increased outflow facility in all 3 species. These results suggest a link among changes in outflow facility, tissue architecture, and aqueous outflow pattern. Y-27632 increases outflow facility by redistributing aqueous outflow through a looser and larger area in the JCT. PMID:24460021

Pathological evaluation of postmortem human eyes implanted with a new single-piece hydrophobic acrylic lens.

PubMed

Izak, Andrea M; Werner, Liliana; Pandey, Suresh K; Apple, David J

2004-07-01

To report the pathological findings in 14 human cadaver eyes implanted with a single-piece AcrySof(Alcon Laboratories) posterior chamber intraocular lens (IOL). David J. Apple, MD Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Fourteen human autopsy eyes implanted with a single-piece AcrySof (SA30AL) IOL were evaluated. The eyes were sectioned at the equatorial plane, and the anterior segment containing the IOL in the capsular bag was evaluated from a posterior perspective (Miyake-Apple view) and from an anterior perspective (surgeon's view) after removal of cornea and iris. They were then processed through paraffin, sectioned, and stained with hematoxylin-eosin, periodic acid-Schiff, and Masson's trichrome and examined under light microscopy. All IOLs had symmetric in-the-bag fixation. Slight decentration was measured in 1 eye, which also had an anterior capsule tear. Grade 1 anterior capsule opacification was present in 9 eyes. No central posterior capsule opacification or posterior capsule folds were observed in any eye. Soemmering's ring formation was observed in 5 eyes. Zonular stretch caused by different degrees of capsular bag contraction was present in 4 eyes without decentration of the IOL. Analyses of pseudophakic cadaver eyes from the posterior (Miyake-Apple) view, complemented by microscopic analyses, proved useful in the evaluation of IOL-capsular bag interaction. These studies are more important in cases of newly introduced lens designs.

Comparative ocular anatomy of the western lowland gorilla.

PubMed

Knapp, Stefanie; McCulley, James P; Alvarado, Thomas P; Hogan, R Nick

2007-01-01

To examine the lowland gorilla (Gorilla gorilla gorilla) eye and determine similarities to and differences between the mountain gorilla (Gorilla gorilla beringei) and the human eye. In addition, we compare our findings of G. g. gorilla to previous reports on the eye of this subspecies. A 13-year-old deceased male lowland gorilla and a 34-year-old deceased female lowland gorilla were included in the study. Gross and microscopic examinations of the formalin-fixed right eyeball of each gorilla were carried out. Globe dimensions of G. g. gorilla were similar to G. g. beringei and to humans. The limbal conjunctival epithelium and the choroid were densely pigmented. However, the distribution of the conjunctival pigment ring was different to that of G. g. beringei and the melanocytes of the choroid were unusually round. There were deep crypts in the anterior border layer of the iris, and the epithelium of the pars plana was uniquely irregular. Vertical corneal diameter was observed to be equal or greater than horizontal diameter in G. g. gorilla, which is in contrast to humans and to previous findings for G. g. beringei. Corneal thickness was closer to that of humans than to G. g. beringei. Posterior lens capsule thickness was noticeably greater than that of humans. Although some variation between the ocular anatomy of G. g. gorilla and G. g. beringei does exist, the gross and microscopic findings closely resemble each other in these two subspecies. In addition, the eye of Gorilla appears remarkably similar to the human eye. However, comparison of measurements with those in humans is somewhat limited because formalin-fixation can introduce tissue shrinkage and artifact.

A new computerized diagnostic algorithm for quantitative evaluation of binocular misalignment in patients with strabismus

NASA Astrophysics Data System (ADS)

Nam, Kyoung Won; Kim, In Young; Kang, Ho Chul; Yang, Hee Kyung; Yoon, Chang Ki; Hwang, Jeong Min; Kim, Young Jae; Kim, Tae Yun; Kim, Kwang Gi

2012-10-01

Accurate measurement of binocular misalignment between both eyes is important for proper preoperative management, surgical planning, and postoperative evaluation of patients with strabismus. In this study, we proposed a new computerized diagnostic algorithm that can calculate the angle of binocular eye misalignment photographically by using a dedicated three-dimensional eye model mimicking the structure of the natural human eye. To evaluate the performance of the proposed algorithm, eight healthy volunteers and eight individuals with strabismus were recruited in this study, the horizontal deviation angle, vertical deviation angle, and angle of eye misalignment were calculated and the angular differences between the healthy and the strabismus groups were evaluated using the nonparametric Mann-Whitney test and the Pearson correlation test. The experimental results demonstrated a statistically significant difference between the healthy and strabismus groups (p = 0.015 < 0.05), but no statistically significant difference between the proposed method and the Krimsky test (p = 0.912 > 0.05). The measurements of the two methods were highly correlated (r = 0.969, p < 0.05). From the experimental results, we believe that the proposed diagnostic method has the potential to be a diagnostic tool that measures the physical disorder of the human eye to diagnose non-invasively the severity of strabismus.

Facial perception of conspecifics: chimpanzees (Pan troglodytes) preferentially attend to proper orientation and open eyes.

PubMed

Hirata, Satoshi; Fuwa, Koki; Sugama, Keiko; Kusunoki, Kiyo; Fujita, Shin

2010-09-01

This paper reports on the use of an eye-tracking technique to examine how chimpanzees look at facial photographs of conspecifics. Six chimpanzees viewed a sequence of pictures presented on a monitor while their eye movements were measured by an eye tracker. The pictures presented conspecific faces with open or closed eyes in an upright or inverted orientation in a frame. The results demonstrated that chimpanzees looked at the eyes, nose, and mouth more frequently than would be expected on the basis of random scanning of faces. More specifically, they looked at the eyes longer than they looked at the nose and mouth when photographs of upright faces with open eyes were presented, suggesting that particular attention to the eyes represents a spontaneous face-scanning strategy shared among monkeys, apes, and humans. In contrast to the results obtained for upright faces with open eyes, the viewing times for the eyes, nose, and mouth of inverted faces with open eyes did not differ from one another. The viewing times for the eyes, nose, and mouth of faces with closed eyes did not differ when faces with closed eyes were presented in either an upright or inverted orientation. These results suggest the possibility that open eyes play an important role in the configural processing of faces and that chimpanzees perceive and process open and closed eyes differently.

Visuomotor cerebellum in human and nonhuman primates.

PubMed

Voogd, Jan; Schraa-Tam, Caroline K L; van der Geest, Jos N; De Zeeuw, Chris I

2012-06-01

In this paper, we will review the anatomical components of the visuomotor cerebellum in human and, where possible, in non-human primates and discuss their function in relation to those of extracerebellar visuomotor regions with which they are connected. The floccular lobe, the dorsal paraflocculus, the oculomotor vermis, the uvula-nodulus, and the ansiform lobule are more or less independent components of the visuomotor cerebellum that are involved in different corticocerebellar and/or brain stem olivocerebellar loops. The floccular lobe and the oculomotor vermis share different mossy fiber inputs from the brain stem; the dorsal paraflocculus and the ansiform lobule receive corticopontine mossy fibers from postrolandic visual areas and the frontal eye fields, respectively. Of the visuomotor functions of the cerebellum, the vestibulo-ocular reflex is controlled by the floccular lobe; saccadic eye movements are controlled by the oculomotor vermis and ansiform lobule, while control of smooth pursuit involves all these cerebellar visuomotor regions. Functional imaging studies in humans further emphasize cerebellar involvement in visual reflexive eye movements and are discussed.

Non-vascular smooth muscle cells in the human choroid: distribution, development and further characterization

PubMed Central

May, Christian Albrecht

2005-01-01

To characterize further non-vascular smooth muscle cells (NVSMC) in the choroid of the human eye, extensive morphological studies were performed including a three-dimensional distribution of NVSMC in the adult human eye and their appearance during development. Whole mounts and sections through the choroid and sclera of eyes of 42 human donors (between the 13th week of gestation and 89 years of age) were stained with antibodies against smooth muscle actin and other markers for smooth muscle cells. On the basis of their morphological localization, three groups of NVSMC could be distinguished in the adult eyes: (a) a semicircular arrangement of NVSMC in the suprachoroid and inner sclera, around the entry of posterior ciliary arteries and nerves; (b) NVSMC parallel to the vessels in the posterior eye segment between the point of entry of the posterior ciliary arteries and the point of exit of the vortex veins; and (c) a dense plaque-like arrangement of NVSMC in the suprachoroid, overlying the foveal region. The last of these groups showed most pronounced interindividual differences. During development, the first NVSMC to be observed at the 20th week of gestation belonged to group b. A complete NVSMC network was first observed in a 6-year-old donor eye. All three groups stained positive for smoothelin, caldesmon and calponin in all localizations. The NVSMC show a distinct distribution that might reflect different aspects of their function in the choroid and suprachoroid. All cells could be histochemically characterized as truly contractile. PMID:16191166

The effects of metamaterial on electromagnetic fields absorption characteristics of human eye tissues.

PubMed

Gasmelseed, Akram; Yunus, Jasmy

2014-01-01

The interaction of a dipole antenna with a human eye model in the presence of a metamaterial is investigated in this paper. The finite difference time domain (FDTD) method with convolutional perfectly matched layer (CPML) formulation have been used. A three-dimensional anatomical model of the human eye with resolution of 1.25 mm × 1.25 mm × 1.25 mm was used in this study. The dipole antenna was driven by modulated Gaussian pulse and the numerical study is performed with dipole operating at 900 MHz. The analysis has been done by varying the size and value of electric permittivity of the metamaterial. By normalizing the peak SAR (1 g and 10 g) to 1 W for all examined cases, we observed how the SAR values are not affected by the different permittivity values with the size of the metamaterial kept fixed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Visual laterality in belugas (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) when viewing familiar and unfamiliar humans.

PubMed

Yeater, Deirdre B; Hill, Heather M; Baus, Natalie; Farnell, Heather; Kuczaj, Stan A

2014-11-01

Lateralization of cognitive processes and motor functions has been demonstrated in a number of species, including humans, elephants, and cetaceans. For example, bottlenose dolphins (Tursiops truncatus) have exhibited preferential eye use during a variety of cognitive tasks. The present study investigated the possibility of visual lateralization in 12 belugas (Delphinapterus leucas) and six Pacific white-sided dolphins (Lagenorhynchus obliquidens) located at two separate marine mammal facilities. During free swim periods, the belugas and Pacific white-sided dolphins were presented a familiar human, an unfamiliar human, or no human during 10-15 min sessions. Session videos were coded for gaze duration, eye presentation at approach, and eye preference while viewing each stimulus. Although we did not find any clear group level lateralization, we found individual left eye lateralized preferences related to social stimuli for most belugas and some Pacific white-sided dolphins. Differences in gaze durations were also observed. The majority of individual belugas had longer gaze durations for unfamiliar rather than familiar stimuli. These results suggest that lateralization occurs during visual processing of human stimuli in belugas and Pacific white-sided dolphins and that these species can distinguish between familiar and unfamiliar humans.

Human Stereopsis is not Limited by the Optics of the Well-focused Eye

PubMed Central

Vlaskamp, Björn N.S.; Yoon, Geunyoung; Banks, Martin S.

2011-01-01

Human stereopsis—the perception of depth from differences in the two eyes’ images—is very precise: Image differences smaller than a single photoreceptor can be converted into a perceived difference in depth. To better understand what determines this precision, we examined how the eyes’ optics affects stereo resolution. We did this by comparing performance with normal, well-focused optics and with optics improved by eliminating chromatic aberration and correcting higher-order aberrations. We first measured luminance contrast sensitivity in both eyes and showed that we had indeed improved optical quality significantly. We then measured stereo resolution in two ways: by finding the finest corrugation in depth that one can perceive, and by finding the smallest disparity one can perceive as different from zero. Our optical manipulation had no effect on stereo performance. We checked this by redoing the experiments at low contrast and again found no effect of improving optical quality. Thus, the resolution of human stereopsis is not limited by the optics of the well-focused eye. We discuss the implications of this remarkable finding. PMID:21734272

KMeyeDB: a graphical database of mutations in genes that cause eye diseases.

PubMed

Kawamura, Takashi; Ohtsubo, Masafumi; Mitsuyama, Susumu; Ohno-Nakamura, Saho; Shimizu, Nobuyoshi; Minoshima, Shinsei

2010-06-01

KMeyeDB (http://mutview.dmb.med.keio.ac.jp/) is a database of human gene mutations that cause eye diseases. We have substantially enriched the amount of data in the database, which now contains information about the mutations of 167 human genes causing eye-related diseases including retinitis pigmentosa, cone-rod dystrophy, night blindness, Oguchi disease, Stargardt disease, macular degeneration, Leber congenital amaurosis, corneal dystrophy, cataract, glaucoma, retinoblastoma, Bardet-Biedl syndrome, and Usher syndrome. KMeyeDB is operated using the database software MutationView, which deals with various characters of mutations, gene structure, protein functional domains, and polymerase chain reaction (PCR) primers, as well as clinical data for each case. Users can access the database using an ordinary Internet browser with smooth user-interface, without user registration. The results are displayed on the graphical windows together with statistical calculations. All mutations and associated data have been collected from published articles. Careful data analysis with KMeyeDB revealed many interesting features regarding the mutations in 167 genes that cause 326 different types of eye diseases. Some genes are involved in multiple types of eye diseases, whereas several eye diseases are caused by different mutations in one gene.

Eye Movements During Everyday Behavior Predict Personality Traits.

PubMed

Hoppe, Sabrina; Loetscher, Tobias; Morey, Stephanie A; Bulling, Andreas

2018-01-01

Besides allowing us to perceive our surroundings, eye movements are also a window into our mind and a rich source of information on who we are, how we feel, and what we do. Here we show that eye movements during an everyday task predict aspects of our personality. We tracked eye movements of 42 participants while they ran an errand on a university campus and subsequently assessed their personality traits using well-established questionnaires. Using a state-of-the-art machine learning method and a rich set of features encoding different eye movement characteristics, we were able to reliably predict four of the Big Five personality traits (neuroticism, extraversion, agreeableness, conscientiousness) as well as perceptual curiosity only from eye movements. Further analysis revealed new relations between previously neglected eye movement characteristics and personality. Our findings demonstrate a considerable influence of personality on everyday eye movement control, thereby complementing earlier studies in laboratory settings. Improving automatic recognition and interpretation of human social signals is an important endeavor, enabling innovative design of human-computer systems capable of sensing spontaneous natural user behavior to facilitate efficient interaction and personalization.

Protective ocular mechanisms in woodpeckers.

PubMed

Wygnanski-Jaffe, T; Murphy, C J; Smith, C; Kubai, M; Christopherson, P; Ethier, C R; Levin, A V

2007-01-01

Woodpeckers possess mechanisms protecting the eye from shaking/impact. Mechanisms available to woodpeckers but not humans may help explain some eye injuries in Shaken Baby syndrome (SBS). Gross dissection and histologic examination of eyes and orbits of seven woodpeckers. All birds showed restricted axial globe movement due to the tight fit within the orbit and fascial connections between the orbital rim and sclera. The sclera was reinforced with cartilage and bone, the optic nerve lacked redundancy, and the vitreous lacked attachments to the posterior pole retina. Woodpecker eyes differ from human infants by an inability of the globe to move axially in the orbit, the sclera to deform, and the vitreous to shear the retina. These findings support current hypotheses that abusive acceleration-deceleration-induced ocular injury in human infants may be related to translation of vitreous within the globe and the globe within the orbit. The woodpecker presents a natural model resistant to mechanical forces that have some similarity to SBS.

Human short-latency ocular vergence responses produced by interocular velocity differences

PubMed Central

Sheliga, B. M.; Quaia, C.; FitzGibbon, E. J.; Cumming, B. G.

2016-01-01

We studied human short-latency vergence eye movements to a novel stimulus that produces interocular velocity differences without a changing disparity signal. Sinusoidal luminance gratings moved in opposite directions (left vs. right; up vs. down) in the two eyes. The grating seen by each eye underwent ¼-wavelength shifts with each image update. This arrangement eliminated changing disparity cues, since the phase difference between the eyes alternated between 0° and 180°. We nevertheless observed robust short-latency vergence responses (VRs), whose sign was consistent with the interocular velocity differences (IOVDs), indicating that the IOVD cue in isolation can evoke short-latency VRs. The IOVD cue was effective only when the images seen by the two eyes overlapped in space. We observed equally robust VRs for opposite horizontal motions (left in one eye, right in the other) and opposite vertical motions (up in one eye, down in the other). Whereas the former are naturally generated by objects moving in depth, the latter are not part of our normal experience. To our knowledge, this is the first demonstration of a behavioral consequence of vertical IOVD. This may reflect the fact that some neurons in area MT are sensitive to these motion signals (Czuba, Huk, Cormack, & Kohn, 2014). VRs were the strongest for spatial frequencies in the range of 0.35–1 c/°, much higher than the optimal spatial frequencies for evoking ocular-following responses observed during frontoparallel motion. This suggests that the two motion signals are detected by different neuronal populations. We also produced IOVD using moving uncorrelated one-dimensional white-noise stimuli. In this case the most effective stimuli have low speed, as predicted if the drive originates in neurons tuned to high spatial frequencies (Sheliga, Quaia, FitzGibbon, & Cumming, 2016). PMID:27548089

Biomechanics of the Human Posterior Sclera: Age- and Glaucoma-Related Changes Measured Using Inflation Testing

PubMed Central

Coudrillier, Baptiste; Tian, Jing; Alexander, Stephen; Myers, Kristin M.; Quigley, Harry A.; Nguyen, Thao D.

2012-01-01

Purpose. The objective of this study was to measure the biomechanical response of the human posterior sclera in vitro and to estimate the effects of age and glaucoma. Methods. Scleral specimens from 22 donors with no history of glaucoma and 11 donors with a history of glaucoma were excised 3 mm posterior to the equator and affixed to an inflation chamber. Optic nerve cross-sections were graded to determine the presence of axon loss. The time-dependent inflation response was measured in a series of pressure-controlled load–unload tests to 30 mm Hg and creep tests to 15 and 30 mm Hg. Circumferential and meridional strains were computed from the digital image correlation displacements, and midposterior stresses were determined from pressure and deformed geometry. Results. Among normal specimens, older age was predictive of a stiffer response and a thinner sclera. In the age group 75 to 93, diagnosed glaucoma eyes with axon damage were thicker than normal eyes. Both damaged and undamaged glaucoma eyes had a different strain response in the peripapillary sclera characterized by a stiffer meridional response. Undamaged glaucoma eyes had slower circumferential creep rates in the peripapillary sclera than normal eyes. Glaucoma eyes were not different from normal eyes in stresses and strains in the midposterior sclera. Conclusions. The observed differences in the biomechanical response of normal and glaucoma sclera may represent baseline properties that contribute to axon damage, or may be characteristics that result from glaucomatous disease. PMID:22395883

The Processing of Human Emotional Faces by Pet and Lab Dogs: Evidence for Lateralization and Experience Effects

PubMed Central

Barber, Anjuli L. A.; Randi, Dania; Müller, Corsin A.; Huber, Ludwig

2016-01-01

From all non-human animals dogs are very likely the best decoders of human behavior. In addition to a high sensitivity to human attentive status and to ostensive cues, they are able to distinguish between individual human faces and even between human facial expressions. However, so far little is known about how they process human faces and to what extent this is influenced by experience. Here we present an eye-tracking study with dogs emanating from two different living environments and varying experience with humans: pet and lab dogs. The dogs were shown pictures of familiar and unfamiliar human faces expressing four different emotions. The results, extracted from several different eye-tracking measurements, revealed pronounced differences in the face processing of pet and lab dogs, thus indicating an influence of the amount of exposure to humans. In addition, there was some evidence for the influences of both, the familiarity and the emotional expression of the face, and strong evidence for a left gaze bias. These findings, together with recent evidence for the dog's ability to discriminate human facial expressions, indicate that dogs are sensitive to some emotions expressed in human faces. PMID:27074009

Course for undergraduate students: analysis of the retinal image quality of a human eye model

NASA Astrophysics Data System (ADS)

del Mar Pérez, Maria; Yebra, Ana; Fernández-Oliveras, Alicia; Ghinea, Razvan; Ionescu, Ana M.; Cardona, Juan C.

2014-07-01

In teaching of Vision Physics or Physiological Optics, the knowledge and analysis of the aberration that the human eye presents are of great interest, since this information allows a proper evaluation of the quality of the retinal image. The objective of the present work is that the students acquire the required competencies which will allow them to evaluate the optical quality of the human visual system for emmetropic and ammetropic eye, both with and without the optical compensation. For this purpose, an optical system corresponding to the Navarro-Escudero eye model, which allows calculating and evaluating the aberration of this eye model in different ammetropic conditions, was developed employing the OSLO LT software. The optical quality of the visual system will be assessed through determinations of the third and fifth order aberration coefficients, the impact diagram, wavefront analysis, calculation of the Point Spread Function and the Modulation Transfer Function for ammetropic individuals, with myopia or hyperopia, both with or without the optical compensation. This course is expected to be of great interest for student of Optics and Optometry Sciences, last courses of Physics or medical sciences related with human vision.

Novel quantitative pigmentation phenotyping enhances genetic association, epistasis, and prediction of human eye colour.

PubMed

Wollstein, Andreas; Walsh, Susan; Liu, Fan; Chakravarthy, Usha; Rahu, Mati; Seland, Johan H; Soubrane, Gisèle; Tomazzoli, Laura; Topouzis, Fotis; Vingerling, Johannes R; Vioque, Jesus; Böhringer, Stefan; Fletcher, Astrid E; Kayser, Manfred

2017-02-27

Success of genetic association and the prediction of phenotypic traits from DNA are known to depend on the accuracy of phenotype characterization, amongst other parameters. To overcome limitations in the characterization of human iris pigmentation, we introduce a fully automated approach that specifies the areal proportions proposed to represent differing pigmentation types, such as pheomelanin, eumelanin, and non-pigmented areas within the iris. We demonstrate the utility of this approach using high-resolution digital eye imagery and genotype data from 12 selected SNPs from over 3000 European samples of seven populations that are part of the EUREYE study. In comparison to previous quantification approaches, (1) we achieved an overall improvement in eye colour phenotyping, which provides a better separation of manually defined eye colour categories. (2) Single nucleotide polymorphisms (SNPs) known to be involved in human eye colour variation showed stronger associations with our approach. (3) We found new and confirmed previously noted SNP-SNP interactions. (4) We increased SNP-based prediction accuracy of quantitative eye colour. Our findings exemplify that precise quantification using the perceived biological basis of pigmentation leads to enhanced genetic association and prediction of eye colour. We expect our approach to deliver new pigmentation genes when applied to genome-wide association testing.

Novel quantitative pigmentation phenotyping enhances genetic association, epistasis, and prediction of human eye colour

PubMed Central

Wollstein, Andreas; Walsh, Susan; Liu, Fan; Chakravarthy, Usha; Rahu, Mati; Seland, Johan H.; Soubrane, Gisèle; Tomazzoli, Laura; Topouzis, Fotis; Vingerling, Johannes R.; Vioque, Jesus; Böhringer, Stefan; Fletcher, Astrid E.; Kayser, Manfred

2017-01-01

Success of genetic association and the prediction of phenotypic traits from DNA are known to depend on the accuracy of phenotype characterization, amongst other parameters. To overcome limitations in the characterization of human iris pigmentation, we introduce a fully automated approach that specifies the areal proportions proposed to represent differing pigmentation types, such as pheomelanin, eumelanin, and non-pigmented areas within the iris. We demonstrate the utility of this approach using high-resolution digital eye imagery and genotype data from 12 selected SNPs from over 3000 European samples of seven populations that are part of the EUREYE study. In comparison to previous quantification approaches, (1) we achieved an overall improvement in eye colour phenotyping, which provides a better separation of manually defined eye colour categories. (2) Single nucleotide polymorphisms (SNPs) known to be involved in human eye colour variation showed stronger associations with our approach. (3) We found new and confirmed previously noted SNP-SNP interactions. (4) We increased SNP-based prediction accuracy of quantitative eye colour. Our findings exemplify that precise quantification using the perceived biological basis of pigmentation leads to enhanced genetic association and prediction of eye colour. We expect our approach to deliver new pigmentation genes when applied to genome-wide association testing. PMID:28240252

Training for eye contact modulates gaze following in dogs.

PubMed

Wallis, Lisa J; Range, Friederike; Müller, Corsin A; Serisier, Samuel; Huber, Ludwig; Virányi, Zsófia

2015-08-01

Following human gaze in dogs and human infants can be considered a socially facilitated orientation response, which in object choice tasks is modulated by human-given ostensive cues. Despite their similarities to human infants, and extensive skills in reading human cues in foraging contexts, no evidence that dogs follow gaze into distant space has been found. We re-examined this question, and additionally whether dogs' propensity to follow gaze was affected by age and/or training to pay attention to humans. We tested a cross-sectional sample of 145 border collies aged 6 months to 14 years with different amounts of training over their lives. The dogs' gaze-following response in test and control conditions before and after training for initiating eye contact with the experimenter was compared with that of a second group of 13 border collies trained to touch a ball with their paw. Our results provide the first evidence that dogs can follow human gaze into distant space. Although we found no age effect on gaze following, the youngest and oldest age groups were more distractible, which resulted in a higher number of looks in the test and control conditions. Extensive lifelong formal training as well as short-term training for eye contact decreased dogs' tendency to follow gaze and increased their duration of gaze to the face. The reduction in gaze following after training for eye contact cannot be explained by fatigue or short-term habituation, as in the second group gaze following increased after a different training of the same length. Training for eye contact created a competing tendency to fixate the face, which prevented the dogs from following the directional cues. We conclude that following human gaze into distant space in dogs is modulated by training, which may explain why dogs perform poorly in comparison to other species in this task.

Eye Tracking and Head Movement Detection: A State-of-Art Survey

PubMed Central

2013-01-01

Eye-gaze detection and tracking have been an active research field in the past years as it adds convenience to a variety of applications. It is considered a significant untraditional method of human computer interaction. Head movement detection has also received researchers' attention and interest as it has been found to be a simple and effective interaction method. Both technologies are considered the easiest alternative interface methods. They serve a wide range of severely disabled people who are left with minimal motor abilities. For both eye tracking and head movement detection, several different approaches have been proposed and used to implement different algorithms for these technologies. Despite the amount of research done on both technologies, researchers are still trying to find robust methods to use effectively in various applications. This paper presents a state-of-art survey for eye tracking and head movement detection methods proposed in the literature. Examples of different fields of applications for both technologies, such as human-computer interaction, driving assistance systems, and assistive technologies are also investigated. PMID:27170851

Prediction of the thermal imaging minimum resolvable (circle) temperature difference with neural network application.

PubMed

Fang, Yi-Chin; Wu, Bo-Wen

2008-12-01

Thermal imaging is an important technology in both national defense and the private sector. An advantage of thermal imaging is its ability to be deployed while fully engaged in duties, not limited by weather or the brightness of indoor or outdoor conditions. However, in an outdoor environment, many factors, including atmospheric decay, target shape, great distance, fog, temperature out of range and diffraction limits can lead to bad image formation, which directly affects the accuracy of object recognition. The visual characteristics of the human eye mean that it has a much better capacity for picture recognition under normal conditions than artificial intelligence does. However, conditions of interference significantly reduce this capacity for picture recognition for instance, fatigue impairs human eyesight. Hence, psychological and physiological factors can affect the result when the human eye is adopted to measure MRTD (minimum resolvable temperature difference) and MRCTD (minimum resolvable circle temperature difference). This study explores thermal imaging recognition, and presents a method for effectively choosing the characteristic values and processing the images fully. Neural network technology is successfully applied to recognize thermal imaging and predict MRTD and MRCTD (Appendix A), exceeding thermal imaging recognition under fatigue and the limits of the human eye.

Implicit prosody mining based on the human eye image capture technology

NASA Astrophysics Data System (ADS)

Gao, Pei-pei; Liu, Feng

2013-08-01

The technology of eye tracker has become the main methods of analyzing the recognition issues in human-computer interaction. Human eye image capture is the key problem of the eye tracking. Based on further research, a new human-computer interaction method introduced to enrich the form of speech synthetic. We propose a method of Implicit Prosody mining based on the human eye image capture technology to extract the parameters from the image of human eyes when reading, control and drive prosody generation in speech synthesis, and establish prosodic model with high simulation accuracy. Duration model is key issues for prosody generation. For the duration model, this paper put forward a new idea for obtaining gaze duration of eyes when reading based on the eye image capture technology, and synchronous controlling this duration and pronunciation duration in speech synthesis. The movement of human eyes during reading is a comprehensive multi-factor interactive process, such as gaze, twitching and backsight. Therefore, how to extract the appropriate information from the image of human eyes need to be considered and the gaze regularity of eyes need to be obtained as references of modeling. Based on the analysis of current three kinds of eye movement control model and the characteristics of the Implicit Prosody reading, relative independence between speech processing system of text and eye movement control system was discussed. It was proved that under the same text familiarity condition, gaze duration of eyes when reading and internal voice pronunciation duration are synchronous. The eye gaze duration model based on the Chinese language level prosodic structure was presented to change previous methods of machine learning and probability forecasting, obtain readers' real internal reading rhythm and to synthesize voice with personalized rhythm. This research will enrich human-computer interactive form, and will be practical significance and application prospect in terms of disabled assisted speech interaction. Experiments show that Implicit Prosody mining based on the human eye image capture technology makes the synthesized speech has more flexible expressions.

The analysis of the influence of fractal structure of stimuli on fractal dynamics in fixational eye movements and EEG signal

NASA Astrophysics Data System (ADS)

Namazi, Hamidreza; Kulish, Vladimir V.; Akrami, Amin

2016-05-01

One of the major challenges in vision research is to analyze the effect of visual stimuli on human vision. However, no relationship has been yet discovered between the structure of the visual stimulus, and the structure of fixational eye movements. This study reveals the plasticity of human fixational eye movements in relation to the ‘complex’ visual stimulus. We demonstrated that the fractal temporal structure of visual dynamics shifts towards the fractal dynamics of the visual stimulus (image). The results showed that images with higher complexity (higher fractality) cause fixational eye movements with lower fractality. Considering the brain, as the main part of nervous system that is engaged in eye movements, we analyzed the governed Electroencephalogram (EEG) signal during fixation. We have found out that there is a coupling between fractality of image, EEG and fixational eye movements. The capability observed in this research can be further investigated and applied for treatment of different vision disorders.

Primate social attention: Species differences and effects of individual experience in humans, great apes, and macaques

PubMed Central

Shepherd, Stephen V.; Hirata, Satoshi; Call, Josep

2018-01-01

When viewing social scenes, humans and nonhuman primates focus on particular features, such as the models’ eyes, mouth, and action targets. Previous studies reported that such viewing patterns vary significantly across individuals in humans, and also across closely-related primate species. However, the nature of these individual and species differences remains unclear, particularly among nonhuman primates. In large samples of human and nonhuman primates, we examined species differences and the effects of experience on patterns of gaze toward social movies. Experiment 1 examined the species differences across rhesus macaques, nonhuman apes (bonobos, chimpanzees, and orangutans), and humans while they viewed movies of various animals’ species-typical behaviors. We found that each species had distinct viewing patterns of the models’ faces, eyes, mouths, and action targets. Experiment 2 tested the effect of individuals’ experience on chimpanzee and human viewing patterns. We presented movies depicting natural behaviors of chimpanzees to three groups of chimpanzees (individuals from a zoo, a sanctuary, and a research institute) differing in their early social and physical experiences. We also presented the same movies to human adults and children differing in their expertise with chimpanzees (experts vs. novices) or movie-viewing generally (adults vs. preschoolers). Individuals varied within each species in their patterns of gaze toward models’ faces, eyes, mouths, and action targets depending on their unique individual experiences. We thus found that the viewing patterns for social stimuli are both individual- and species-specific in these closely-related primates. Such individual/species-specificities are likely related to both individual experience and species-typical temperament, suggesting that primate individuals acquire their unique attentional biases through both ontogeny and evolution. Such unique attentional biases may help them learn efficiently about their particular social environments. PMID:29474416

Primate social attention: Species differences and effects of individual experience in humans, great apes, and macaques.

PubMed

Kano, Fumihiro; Shepherd, Stephen V; Hirata, Satoshi; Call, Josep

2018-01-01

When viewing social scenes, humans and nonhuman primates focus on particular features, such as the models' eyes, mouth, and action targets. Previous studies reported that such viewing patterns vary significantly across individuals in humans, and also across closely-related primate species. However, the nature of these individual and species differences remains unclear, particularly among nonhuman primates. In large samples of human and nonhuman primates, we examined species differences and the effects of experience on patterns of gaze toward social movies. Experiment 1 examined the species differences across rhesus macaques, nonhuman apes (bonobos, chimpanzees, and orangutans), and humans while they viewed movies of various animals' species-typical behaviors. We found that each species had distinct viewing patterns of the models' faces, eyes, mouths, and action targets. Experiment 2 tested the effect of individuals' experience on chimpanzee and human viewing patterns. We presented movies depicting natural behaviors of chimpanzees to three groups of chimpanzees (individuals from a zoo, a sanctuary, and a research institute) differing in their early social and physical experiences. We also presented the same movies to human adults and children differing in their expertise with chimpanzees (experts vs. novices) or movie-viewing generally (adults vs. preschoolers). Individuals varied within each species in their patterns of gaze toward models' faces, eyes, mouths, and action targets depending on their unique individual experiences. We thus found that the viewing patterns for social stimuli are both individual- and species-specific in these closely-related primates. Such individual/species-specificities are likely related to both individual experience and species-typical temperament, suggesting that primate individuals acquire their unique attentional biases through both ontogeny and evolution. Such unique attentional biases may help them learn efficiently about their particular social environments.

Comparative Analysis of Gene Expression for Convergent Evolution of Camera Eye Between Octopus and Human

PubMed Central

Ogura, Atsushi; Ikeo, Kazuho; Gojobori, Takashi

2004-01-01

Although the camera eye of the octopus is very similar to that of humans, phylogenetic and embryological analyses have suggested that their camera eyes have been acquired independently. It has been known as a typical example of convergent evolution. To study the molecular basis of convergent evolution of camera eyes, we conducted a comparative analysis of gene expression in octopus and human camera eyes. We sequenced 16,432 ESTs of the octopus eye, leading to 1052 nonredundant genes that have matches in the protein database. Comparing these 1052 genes with 13,303 already-known ESTs of the human eye, 729 (69.3%) genes were commonly expressed between the human and octopus eyes. On the contrary, when we compared octopus eye ESTs with human connective tissue ESTs, the expression similarity was quite low. To trace the evolutionary changes that are potentially responsible for camera eye formation, we also compared octopus-eye ESTs with the completed genome sequences of other organisms. We found that 1019 out of the 1052 genes had already existed at the common ancestor of bilateria, and 875 genes were conserved between humans and octopuses. It suggests that a larger number of conserved genes and their similar gene expression may be responsible for the convergent evolution of the camera eye. PMID:15289475

Toward a digital camera to rival the human eye

NASA Astrophysics Data System (ADS)

Skorka, Orit; Joseph, Dileepan

2011-07-01

All things considered, electronic imaging systems do not rival the human visual system despite notable progress over 40 years since the invention of the CCD. This work presents a method that allows design engineers to evaluate the performance gap between a digital camera and the human eye. The method identifies limiting factors of the electronic systems by benchmarking against the human system. It considers power consumption, visual field, spatial resolution, temporal resolution, and properties related to signal and noise power. A figure of merit is defined as the performance gap of the weakest parameter. Experimental work done with observers and cadavers is reviewed to assess the parameters of the human eye, and assessment techniques are also covered for digital cameras. The method is applied to 24 modern image sensors of various types, where an ideal lens is assumed to complete a digital camera. Results indicate that dynamic range and dark limit are the most limiting factors. The substantial functional gap, from 1.6 to 4.5 orders of magnitude, between the human eye and digital cameras may arise from architectural differences between the human retina, arranged in a multiple-layer structure, and image sensors, mostly fabricated in planar technologies. Functionality of image sensors may be significantly improved by exploiting technologies that allow vertical stacking of active tiers.

Theoretical investigation of aberrations upon ametropic human eyes

NASA Astrophysics Data System (ADS)

Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Baker, Kevin

2003-11-01

The human eye aberrations are important for visual acuity and ophthalmic diagnostics and surgical procedures. Reported monochromatic aberration data of the normal 20/20 human eyes are scarce. There exist even fewer reports of the relation between ametropic conditions and aberrations. We theoretically investigate the monochromatic and chromatic aberrations of human eyes for refractive errors of -10 to +10 diopters. Schematic human eye models are employed using optical design software for axial, index, and refractive types of ametropia.

Accounting for direction and speed of eye motion in planning visually guided manual tracking.

PubMed

Leclercq, Guillaume; Blohm, Gunnar; Lefèvre, Philippe

2013-10-01

Accurate motor planning in a dynamic environment is a critical skill for humans because we are often required to react quickly and adequately to the visual motion of objects. Moreover, we are often in motion ourselves, and this complicates motor planning. Indeed, the retinal and spatial motions of an object are different because of the retinal motion component induced by self-motion. Many studies have investigated motion perception during smooth pursuit and concluded that eye velocity is partially taken into account by the brain. Here we investigate whether the eye velocity during ongoing smooth pursuit is taken into account for the planning of visually guided manual tracking. We had 10 human participants manually track a target while in steady-state smooth pursuit toward another target such that the difference between the retinal and spatial target motion directions could be large, depending on both the direction and the speed of the eye. We used a measure of initial arm movement direction to quantify whether motor planning occurred in retinal coordinates (not accounting for eye motion) or was spatially correct (incorporating eye velocity). Results showed that the eye velocity was nearly fully taken into account by the neuronal areas involved in the visuomotor velocity transformation (between 75% and 102%). In particular, these neuronal pathways accounted for the nonlinear effects due to the relative velocity between the target and the eye. In conclusion, the brain network transforming visual motion into a motor plan for manual tracking adequately uses extraretinal signals about eye velocity.

A dataset of stereoscopic images and ground-truth disparity mimicking human fixations in peripersonal space

PubMed Central

Canessa, Andrea; Gibaldi, Agostino; Chessa, Manuela; Fato, Marco; Solari, Fabio; Sabatini, Silvio P.

2017-01-01

Binocular stereopsis is the ability of a visual system, belonging to a live being or a machine, to interpret the different visual information deriving from two eyes/cameras for depth perception. From this perspective, the ground-truth information about three-dimensional visual space, which is hardly available, is an ideal tool both for evaluating human performance and for benchmarking machine vision algorithms. In the present work, we implemented a rendering methodology in which the camera pose mimics realistic eye pose for a fixating observer, thus including convergent eye geometry and cyclotorsion. The virtual environment we developed relies on highly accurate 3D virtual models, and its full controllability allows us to obtain the stereoscopic pairs together with the ground-truth depth and camera pose information. We thus created a stereoscopic dataset: GENUA PESTO—GENoa hUman Active fixation database: PEripersonal space STereoscopic images and grOund truth disparity. The dataset aims to provide a unified framework useful for a number of problems relevant to human and computer vision, from scene exploration and eye movement studies to 3D scene reconstruction. PMID:28350382

Neurophysiology and Neuroanatomy of Smooth Pursuit in Humans

ERIC Educational Resources Information Center

Lencer, Rebekka; Trillenberg, Peter

2008-01-01

Smooth pursuit eye movements enable us to focus our eyes on moving objects by utilizing well-established mechanisms of visual motion processing, sensorimotor transformation and cognition. Novel smooth pursuit tasks and quantitative measurement techniques can help unravel the different smooth pursuit components and complex neural systems involved…

Zoonotic helminths affecting the human eye

PubMed Central

2011-01-01

Nowaday, zoonoses are an important cause of human parasitic diseases worldwide and a major threat to the socio-economic development, mainly in developing countries. Importantly, zoonotic helminths that affect human eyes (HIE) may cause blindness with severe socio-economic consequences to human communities. These infections include nematodes, cestodes and trematodes, which may be transmitted by vectors (dirofilariasis, onchocerciasis, thelaziasis), food consumption (sparganosis, trichinellosis) and those acquired indirectly from the environment (ascariasis, echinococcosis, fascioliasis). Adult and/or larval stages of HIE may localize into human ocular tissues externally (i.e., lachrymal glands, eyelids, conjunctival sacs) or into the ocular globe (i.e., intravitreous retina, anterior and or posterior chamber) causing symptoms due to the parasitic localization in the eyes or to the immune reaction they elicit in the host. Unfortunately, data on HIE are scant and mostly limited to case reports from different countries. The biology and epidemiology of the most frequently reported HIE are discussed as well as clinical description of the diseases, diagnostic considerations and video clips on their presentation and surgical treatment. Homines amplius oculis, quam auribus credunt Seneca Ep 6,5 Men believe their eyes more than their ears PMID:21429191

Racioethnic Differences in Human Posterior Scleral and Optic Nerve Stump Deformation

PubMed Central

Tamimi, Ehab A.; Pyne, Jeffrey D.; Muli, Dominic K.; Axman, Katelyn F.; Howerton, Stephen J.; Davis, Matthew R.; Girkin, Christopher A.; Vande Geest, Jonathan P.

2017-01-01

Purpose The purpose of this study was to quantify the biomechanical response of human posterior ocular tissues from donors of various racioethnic groups to better understand how differences in these properties may play a role in the racioethnic health disparities known to exist in glaucoma. Methods Sequential digital image correlation (S-DIC) was used to measure the pressure-induced surface deformations of 23 normal human posterior poles from three racioethnic groups: African descent (AD), European descent (ED), and Hispanic ethnicity (HIS). Regional in-plane principal strains were compared across three zones: the optic nerve stump (ONS), the peripapillary (PP) sclera, and non-PP sclera. Results The PP scleral tensile strains were found to be lower for ED eyes compared with AD and HIS eyes at 15 mm Hg (P = 0.024 and 0.039, respectively). The mean compressive strains were significantly higher for AD eyes compared with ED eyes at 15 mm Hg (P = 0.018). We also found that the relationship between tensile strain and pressure was significant for those of ED and HIS eyes (P < 0.001 and P = 0.004, respectively), whereas it was not significant for those of AD (P = 0.392). Conclusions Our results suggest that, assuming glaucomatous nerve loss is caused by mechanical strains in the vicinity of the optic nerve head, the mechanism of increased glaucoma prevalence may be different in those of AD versus HIS. Our ONS strain analysis also suggested that it may be important to account for ONS geometry and material properties in future scleral biomechanical analysis. PMID:28846773

Morphologic analysis of artifacts in human fetal eyes confounding histopathologic investigations.

PubMed

Herwig, Martina C; Müller, Annette M; Holz, Frank G; Loeffler, Karin U

2011-04-25

Human fetal eyes are an excellent source for studies of the normal ocular development and for examining early ocular changes associated with various syndromes in the context of a pediatric pathologic or prenatal sonographic diagnosis. However, artifacts caused by different factors often render an exact interpretation difficult. In this study, the frequency and extent of artifacts in human fetal eyes were investigated with the aim of distinguishing more precisely these artifacts from real findings, allowing also for a more diligent forensic interpretation. The cohort included 341 fetal eyes, ranging in age from 8 to 38 weeks of gestation, that were investigated macroscopically and by light microscopy. In most specimens, artifacts such as pigment spillage and autolytic changes of the retina were noted. Nearly all specimens showed changes of the lens with remarkable similarities to cataractous lenses in adult eyes. Structural ocular changes associated with systemic syndromes were also observed and in most instances could be distinguished from artifacts. Morphologic changes in fetal eyes should be classified in artifacts caused by way of abortion, mechanical effects from the removal of the eyes, delayed fixation with autolysis, and the fixative itself and should be distinguished from genuine structural abnormalities associated with ocular or systemic disease. This classification can be fairly difficult and requires experience. In addition, lens artifacts are often misleading, and the diagnosis of a fetal cataract should not be made based on histopathologic examination alone.

Optical and Biometric Characteristics of Anisomyopia in Human Adults

PubMed Central

Tian, Yibin; Tarrant, Janice; Wildsoet, Christine F.

2011-01-01

Purpose To investigate the role of higher order optical aberrations and thus retinal image degradation in the development of myopia, through the characterization of anisomyopia in human adults in terms of their optical and biometric characteristics. Methods The following data were collected from both eyes of fifteen young adult anisometropic myopes and sixteen isometropic myopes: subjective and objective refractive errors, corneal power and shape, monochromatic optical aberrations, anterior chamber depth, lens thickness, vitreous chamber depth, and best corrected visual acuity. Monochromatic aberrations were analyzed in terms of their higher order components, and further analyzed in terms of 31 optical quality metrics. Interocular differences for the two groups (anisomyopes vs. isomyopes) were compared and the relationship between measured ocular parameters and refractive errors also analyzed across all eyes. Results As expected, anisomyopes and isomyopes differed significantly in terms of interocular differences in vitreous chamber depth, axial length and refractive error. However, interocular differences in other optical properties showed no significant intergroup differences. Overall, higher myopia was associated with deeper anterior and vitreous chambers, higher astigmatism, more prolate corneas, and more positive spherical aberration. Other measured optical and biometric parameters were not significantly correlated with spherical refractive error, although some optical quality metrics and corneal astigmatism were significantly correlated with refractive astigmatism. Conclusions An optical cause for anisomyopia related to increased higher order aberrations is not supported by our data. Corneal shape changes and increased astigmatism in more myopic eyes may be a by-product of the increased anterior chamber growth in these eyes; likewise, the increased positive spherical aberration in more myopic eyes may be a product of myopic eye growth. PMID:21797915

Intraspecific eye color variability in birds and mammals: a recent evolutionary event exclusive to humans and domestic animals.

PubMed

Negro, Juan J; Carmen Blázquez, M; Galván, Ismael

2017-01-01

Human populations and breeds of domestic animals are composed of individuals with a multiplicity of eye (= iris) colorations. Some wild birds and mammals may have intraspecific eye color variability, but this variation seems to be due to the developmental stage of the individual, its breeding status, and/or sexual dimorphism. In other words, eye colour tends to be a species-specific trait in wild animals, and the exceptions are species in which individuals of the same age group or gender all develop the same eye colour. Domestic animals, by definition, include bird and mammal species artificially selected by humans in the last few thousand years. Humans themselves may have acquired a diverse palette of eye colors, likewise in recent evolutionary time, in the Mesolithic or in the Upper Paleolithic. We posit two previously unrecognized hypotheses regarding eye color variation: 1) eye coloration in wild animals of every species tends to be a fixed trait. 2) Humans and domestic animal populations, on the contrary, have eyes of multiple colors. Sexual selection has been invoked for eye color variation in humans, but this selection mode does not easily apply in domestic animals, where matings are controlled by the human breeder. Eye coloration is polygenic in humans. We wish to investigate the genetics of eye color in other animals, as well as the ecological correlates. Investigating the origin and function of eye colors will shed light on the reason why some species may have either light-colored irises (e.g., white, yellow or light blue) or dark ones (dark red, brown or black). The causes behind the vast array of eye colors across taxa have never been thoroughly investigated, but it may well be that all Darwinian selection processes are at work: sexual selection in humans, artificial selection for domestic animals, and natural selection (mainly) for wild animals.

Human agency beliefs influence behaviour during virtual social interactions.

PubMed

Caruana, Nathan; Spirou, Dean; Brock, Jon

2017-01-01

In recent years, with the emergence of relatively inexpensive and accessible virtual reality technologies, it is now possible to deliver compelling and realistic simulations of human-to-human interaction. Neuroimaging studies have shown that, when participants believe they are interacting via a virtual interface with another human agent, they show different patterns of brain activity compared to when they know that their virtual partner is computer-controlled. The suggestion is that users adopt an "intentional stance" by attributing mental states to their virtual partner. However, it remains unclear how beliefs in the agency of a virtual partner influence participants' behaviour and subjective experience of the interaction. We investigated this issue in the context of a cooperative "joint attention" game in which participants interacted via an eye tracker with a virtual onscreen partner, directing each other's eye gaze to different screen locations. Half of the participants were correctly informed that their partner was controlled by a computer algorithm ("Computer" condition). The other half were misled into believing that the virtual character was controlled by a second participant in another room ("Human" condition). Those in the "Human" condition were slower to make eye contact with their partner and more likely to try and guide their partner before they had established mutual eye contact than participants in the "Computer" condition. They also responded more rapidly when their partner was guiding them, although the same effect was also found for a control condition in which they responded to an arrow cue. Results confirm the influence of human agency beliefs on behaviour in this virtual social interaction context. They further suggest that researchers and developers attempting to simulate social interactions should consider the impact of agency beliefs on user experience in other social contexts, and their effect on the achievement of the application's goals.

Lutein and its oxidized forms in eye structures throughout prenatal human development.

PubMed

Panova, Ina G; Yakovleva, Marina A; Tatikolov, Alexander S; Kononikhin, A S; Feldman, Tatiana B; Poltavtseva, Rimma A; Nikolaev, E N; Sukhikh, Gennady T; Ostrovsky, Mikhail A

2017-07-01

The presence of carotenoids in the vitreous body, retina, lens, retinal pigment epithelium together with choroid (hereinafter RPE), and ciliary body and iris together with choroidal stroma (hereinafter CBI) was studied throughout the second trimester of prenatal development of the human eye. It has been found that the vitreous body, retina, and RPE contain lutein and its oxidized forms. Zeaxanthin was not found in the tissues studied. The presence of lutein in the vitreous body is transient and no longer detected after 28 weeks of gestation. Lutein was not detected in the lens and CBI, but its oxidized forms were found. The presence of carotenoids in different tissues of the eye in the course of normal eye development and the antioxidant role of carotenoids are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Capsulorhexis ovaling and capsular bag stretch after rigid and foldable intraocular lens implantation: experimental study in pediatric human eyes.

PubMed

Pandey, Suresh K; Werner, Liliana; Wilson, M Edward; Izak, Andrea M; Apple, David J

2004-10-01

To compare the amount of capsulorhexis ovaling and capsular bag stretch produced by various intraocular lenses (IOLs) implanted in pediatric human eyes obtained post-mortem. David J. Apple, MD Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, Salt Lake City, Utah, USA. In this nonrandomized comparative study, 16 pediatric human eyes obtained postmortem were divided into 2 groups: Eight eyes were obtained from children younger than 2 years (Group A), and 8 eyes were obtained from children older than 2 years (Group B). All eyes were prepared according to the Miyake-Apple posterior video technique. Six types of rigid and foldable posterior chamber IOLs manufactured from poly(methyl methacrylate) (single-piece), silicone (plate and loop haptics), and hydrophobic acrylic (single-piece and 3-piece AcrySof, Alcon Laboratories) biomaterials were implanted. The capsulorhexis opening and capsular bag diameters were measured before IOL implantation and after in-the-bag IOL fixation with the haptics (or the main axis) at the 3 to 9 o'clock meridian. The percentage of ovaling of the capsulorhexis opening was calculated by noting the difference in the opening's horizontal diameter before and after IOL implantation. The percentage of capsular bag stretch was also calculated by noting the difference in the horizontal capsular bag diameter before and after IOL implantation. All IOLs produced ovaling of the capsulorhexis opening and stretching of the capsular bag parallel to the IOL haptics. There were significant differences in capsulorhexis ovaling and capsular bag stretch (P<.001, analysis of variance) between the 6 IOL types in each group of eyes. The postimplantation difference was significant only between the single-piece hydrophobic acrylic IOL (AcrySof) and the other IOLs. The single-piece hydrophobic acrylic IOL was associated with significantly less capsulorhexis ovaling and capsular bag stretch in both groups (mean 12.06% +/- 0.59% [SD] and 7.6% +/- 1.47%, respectively). Modern rigid and foldable IOLs designed for the adult population implanted in the capsular bag of infants and children produced variable degrees of capsulorhexis ovaling and capsular bag stretch. The Miyake-Apple posterior video technique confirmed the well-maintained configuration of the capsular bag (with minimal ovaling) after implantation of a single-piece hydrophobic acrylic IOL because of its flexible haptic design.

Combining EEG and eye tracking: identification, characterization, and correction of eye movement artifacts in electroencephalographic data

PubMed Central

Plöchl, Michael; Ossandón, José P.; König, Peter

2012-01-01

Eye movements introduce large artifacts to electroencephalographic recordings (EEG) and thus render data analysis difficult or even impossible. Trials contaminated by eye movement and blink artifacts have to be discarded, hence in standard EEG-paradigms subjects are required to fixate on the screen. To overcome this restriction, several correction methods including regression and blind source separation have been proposed. Yet, there is no automated standard procedure established. By simultaneously recording eye movements and 64-channel-EEG during a guided eye movement paradigm, we investigate and review the properties of eye movement artifacts, including corneo-retinal dipole changes, saccadic spike potentials and eyelid artifacts, and study their interrelations during different types of eye- and eyelid movements. In concordance with earlier studies our results confirm that these artifacts arise from different independent sources and that depending on electrode site, gaze direction, and choice of reference these sources contribute differently to the measured signal. We assess the respective implications for artifact correction methods and therefore compare the performance of two prominent approaches, namely linear regression and independent component analysis (ICA). We show and discuss that due to the independence of eye artifact sources, regression-based correction methods inevitably over- or under-correct individual artifact components, while ICA is in principle suited to address such mixtures of different types of artifacts. Finally, we propose an algorithm, which uses eye tracker information to objectively identify eye-artifact related ICA-components (ICs) in an automated manner. In the data presented here, the algorithm performed very similar to human experts when those were given both, the topographies of the ICs and their respective activations in a large amount of trials. Moreover it performed more reliable and almost twice as effective than human experts when those had to base their decision on IC topographies only. Furthermore, a receiver operating characteristic (ROC) analysis demonstrated an optimal balance of false positive and false negative at an area under curve (AUC) of more than 0.99. Removing the automatically detected ICs from the data resulted in removal or substantial suppression of ocular artifacts including microsaccadic spike potentials, while the relevant neural signal remained unaffected. In conclusion the present work aims at a better understanding of individual eye movement artifacts, their interrelations and the respective implications for eye artifact correction. Additionally, the proposed ICA-procedure provides a tool for optimized detection and correction of eye movement-related artifact components. PMID:23087632

Contrast and assimilation in motion perception and smooth pursuit eye movements.

PubMed

Spering, Miriam; Gegenfurtner, Karl R

2007-09-01

The analysis of visual motion serves many different functions ranging from object motion perception to the control of self-motion. The perception of visual motion and the oculomotor tracking of a moving object are known to be closely related and are assumed to be controlled by shared brain areas. We compared perceived velocity and the velocity of smooth pursuit eye movements in human observers in a paradigm that required the segmentation of target object motion from context motion. In each trial, a pursuit target and a visual context were independently perturbed simultaneously to briefly increase or decrease in speed. Observers had to accurately track the target and estimate target speed during the perturbation interval. Here we show that the same motion signals are processed in fundamentally different ways for perception and steady-state smooth pursuit eye movements. For the computation of perceived velocity, motion of the context was subtracted from target motion (motion contrast), whereas pursuit velocity was determined by the motion average (motion assimilation). We conclude that the human motion system uses these computations to optimally accomplish different functions: image segmentation for object motion perception and velocity estimation for the control of smooth pursuit eye movements.

A boussinesq model of natural convection in the human eye and the formation of Krukenberg's spindle.

PubMed

Heys, Jeffrey J; Barocas, Victor H

2002-03-01

The cornea of the human eye is cooled by the surrounding air and by evaporation of the tear film. The temperature difference between the cornea and the iris (at core body temperature) causes circulation of the aqueous humor in the anterior chamber of the eye. Others have suggested that the circulation pattern governs the shape of the Krukenberg spindle, a distinctive vertical band of pigment on the posterior cornea surface in some pathologies. We modeled aqueous humor flow the human eye, treating the humor as a Boussinesq fluid and setting the corneal temperature based on infrared surface temperature measurements. The model predicts convection currents in the anterior chamber with velocities comparable to those resulting from forced flow through the gap between the iris and lens. When paths of pigment particles are calculated based on the predicted flow field, the particles circulate throughout the anterior chamber but tend to be near the vertical centerline of the eye for a greatest period of time. Further, the particles are usually in close proximity to the cornea only when they are near the vertical centerline. We conclude that the convective flow pattern of aqueous humor is consistent with a vertical pigment spindle.

How dogs know when communication is intended for them.

PubMed

Kaminski, Juliane; Schulz, Linda; Tomasello, Michael

2012-03-01

Domestic dogs comprehend human gestural communication in a way that other animal species do not. But little is known about the specific cues they use to determine when human communication is intended for them. In a series of four studies, we confronted both adult dogs and young dog puppies with object choice tasks in which a human indicated one of two opaque cups by either pointing to it or gazing at it. We varied whether the communicator made eye contact with the dog in association with the gesture (or whether her back was turned or her eyes were directed at another recipient) and whether the communicator called the dog's name (or the name of another recipient). Results demonstrated the importance of eye contact in human-dog communication, and, to a lesser extent, the calling of the dog's name--with no difference between adult dogs and young puppies--which are precisely the communicative cues used by human infants for identifying communicative intent. Unlike human children, however, dogs did not seem to comprehend the human's communicative gesture when it was directed to another human, perhaps because dogs view all human communicative acts as directives for the recipient. © 2011 Blackwell Publishing Ltd.

Effect of a single 3-hour exposure to bright light on core body temperature and sleep in humans.

PubMed

Dijk, D J; Cajochen, C; Borbély, A A

1991-01-02

Seven human subjects were exposed to bright light (BL, approx. 2500 lux) and dim light (DL, approx. 6 lux) during 3 h prior to nocturnal sleep, in a cross-over design. At the end of the BL exposure period core body temperature was significantly higher than at the end of the DL exposure period. The difference in core body temperature persisted during the first 4 h of sleep. The latency to sleep onset was increased after BL exposure. Rapid-eye movement sleep (REMS) and slow-wave sleep (SWS; stage 3 + 4 of non-REMS) were not significantly changed. Eight subjects were exposed to BL from 20.30 to 23.30 h while their eyes were covered or uncovered. During BL exposure with uncovered eyes, core body temperature decreased significantly less than during exposure with covered eyes. We conclude that bright light immediately affects core body temperature and that this effect is mediated via the eyes.

Geometrical theory to predict eccentric photorefraction intensity profiles in the human eye

NASA Astrophysics Data System (ADS)

Roorda, Austin; Campbell, Melanie C. W.; Bobier, W. R.

1995-08-01

In eccentric photorefraction, light returning from the retina of the eye is photographed by a camera focused on the eye's pupil. We use a geometrical model of eccentric photorefraction to generate intensity profiles across the pupil image. The intensity profiles for three different monochromatic aberration functions induced in a single eye are predicted and show good agreement with the measured eccentric photorefraction intensity profiles. A directional reflection from the retina is incorporated into the calculation. Intensity profiles for symmetric and asymmetric aberrations are generated and measured. The latter profile shows a dependency on the source position and the meridian. The magnitude of the effect of thresholding on measured pattern extents is predicted. Monochromatic aberrations in human eyes will cause deviations in the eccentric photorefraction measurements from traditional crescents caused by defocus and may cause misdiagnoses of ametropia or anisometropia. Our results suggest that measuring refraction along the vertical meridian is preferred for screening studies with the eccentric photorefractor.

Eye tracking uncovered great apes' ability to anticipate that other individuals will act according to false beliefs.

PubMed

Kano, Fumihiro; Krupenye, Christopher; Hirata, Satoshi; Call, Josep

2017-01-01

Using a novel eye-tracking test, we recently showed that great apes anticipate that other individuals will act according to false beliefs. This finding suggests that, like humans, great apes understand others' false beliefs, at least in an implicit way. One key question raised by our study is why apes have passed our tests but not previous ones. In this article, we consider this question by detailing the development of our task. We considered 3 major differences in our task compared with the previous ones. First, we monitored apes' eye movements, and specifically their anticipatory looks, to measure their predictions about how agents will behave. Second, we adapted our design from an anticipatory-looking false belief test originally developed for human infants. Third, we developed novel test scenarios that were specifically designed to capture the attention of our ape participants. We then discuss how each difference may help explain differences in performance on our task and previous ones, and finally propose some directions for future studies.

Comparison of in vitro eye irritation potential by bovine corneal opacity and permeability (BCOP) assay to erythema scores in human eye sting test of surfactant-based formulations.

PubMed

Cater, Kathleen C; Harbell, John W

2008-01-01

The bovine corneal opacity and permeability (BCOP) assay can be used to predict relative eye irritation potential of surfactant-based personal care formulations relative to a corporate benchmark. The human eye sting test is typically used to evaluate product claims of no tears/no stinging for children's bath products. A preliminary investigation was conducted to test a hypothesis that the BCOP assay could be used as a prediction model for relative ranking of human eye irritation responses under conditions of a standard human eye sting test to surfactant-based formulations. BCOP assays and human eye sting tests were conducted on 4 commercial and 1 prototype body wash (BW) developed specifically for children or as mild bath products. In the human eye sting test, 10 mul of a 10% dosing solution is instilled into one eye of each panelist (n = 20), and the contralateral eye is dosed with sterile water as a control. Bulbar conjunctival erythema responses of each eye are graded at 30 seconds by an ophthalmologist. The BCOP assay permeability values (optical density at 490 nm [OD(490)]) for the 5 BWs ranged from 0.438 to 1.252 (i.e., least to most irritating). By comparison, the number of panelists exhibiting erythema responses (mild to moderately pink) ranged from 3 of 20 panelists for the least irritating BW to 10 of 20 panelists for the most irritating BW tested. The relative ranking of eye irritation potential of the 5 BWs in the BCOP assay compares favorably with the relative ranking of the BWs in the human eye sting test. Based on these findings, the permeability endpoint of the BCOP assay, as described for surfactant-based formulations, showed promise as a prediction model for relative ranking of conjunctival erythema responses in the human eye. Consequently, screening of prototype formulations in the BCOP assay would allow for formula optimization of mild bath products prior to investment in a human eye sting test.

Morphometric measurement of Schlemm's canal in normal human eye using anterior segment swept source optical coherence tomography

NASA Astrophysics Data System (ADS)

Shi, Guohua; Wang, Fei; Li, Xiqi; Lu, Jing; Ding, Zhihua; Sun, Xinghuai; Jiang, Chunhui; Zhang, Yudong

2012-01-01

We have used anterior segment swept source optical coherence tomography to measure Schlemm's canal (SC) morphometric values in the living human eye. Fifty healthy volunteers with 100 normal eyes were measured in the nasal and temporal side. Comparison with the published SC morphometric values of histologic sections proves the reliability of our results. The statistical results show that there are no significant differences between nasal and temporal SC with respect to their diameter, perimeter, and area in our study (diameter: t=0.122, p=0.903; perimeter: t=-0.003, p=0.998; area: t=-1.169, p=0.244); further, no significant differences in SC morphometric values are found between oculus sinister and oculus dexter (diameter: t=0.943, p=0.35; perimeter: t=1.346, p=0.18; area: t=1.501, p=0.135).

Fluid mechanics of the human eye: aqueous humour flow in the anterior chamber.

PubMed

Fitt, A D; Gonzalez, G

2006-01-01

We consider and compare the various different kinds of flow that may take place in the anterior chamber of a human eye. The physical mechanisms responsible for causing such flows may be classified as follows: (i) buoyancy-driven flow arising from the temperature difference between the anterior surface of the cornea and the iris, (ii) flow generated by the aqueous production of the ciliary body, (iii) flow generated by the interaction between buoyancy and gravity while sleeping while sleeping in a face-up position, (iv) flow generated by phakodenesis (lens tremor), (v) flow generated by Rapid Eye Movement (REM) during sleep. Each flow is studied using a traditional fluid mechanics/asymptotic analysis approach. We also assess the veracity of a hypothesis that was recently advanced [see Maurice, D.M., 1998. The Von Sallman Lecture 1996: An ophthalmological explanation of REM sleep. Exp. Eye. Res. 66, 139-145, for details] to suggest that, contrary to previous opinion, the purpose of REM during sleep is to ensure corneal respiration in the absence of the buoyant mixing that routinely takes place due to (i) above during waking conditions.

Mitochondrial DNA common deletion in the human eye: a relation with corneal aging.

PubMed

Gendron, Sébastien P; Mallet, Justin D; Bastien, Nathalie; Rochette, Patrick J

2012-01-01

The most frequent mitochondrial DNA (mtDNA) mutation is a 4977 bp deletion known as the common deletion (mtDNA(CD4977)). mtDNA(CD4977) is related to skin photo-aging and to chronological aging of cells with high-energy demands such as neurons and muscle cells. The human eye contains both sun-exposed (cornea, iris) and high-energy demand structures (retina). In this study, we employed a highly sensitive quantitative PCR technique to determine mtDNA(CD4977) occurrence in different structures of the human eye. We found that the cornea, the most anterior structure of the eye, contains the highest amount of mtDNA(CD4977) (2.6%, 0.25% and 0.06% for the cornea, iris and retina, respectively). Within the cornea, mtDNA(CD4977) is almost exclusively found in the stroma, the cellular layer conferring transparency and rigidity to the human cornea (8.59%, 0.13% and 0.05% in the stroma, endothelium and epithelium, respectively). Moreover, we show that mtDNA(CD4977) accumulates with age in the corneal stroma. Taken together, our results suggest that mtDNA(CD4977) is related to photo-aging rather than chronological aging in the human eye. Similar to the involvement of mtDNA(CD4977) in skin photo-aging phenotypes, we believe that the clinical manifestations of corneal aging, including clouding and stiffening, are associated with the accumulation of mtDNA(CD4977) in the corneal stroma. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Biochemical Measurements of Free Opsin in Macular Degeneration Eyes: Examining the 11-CIS Retinal Deficiency Hypothesis of Delayed Dark Adaptation (An American Ophthalmological Society Thesis).

PubMed

Hanneken, Anne; Neikirk, Thomas; Johnson, Jennifer; Kono, Masahiro

2017-08-01

To test the hypothesis that delayed dark adaptation in patients with macular degeneration is due to an excess of free unliganded opsin (apo-opsin) and a deficiency of the visual chromophore, 11 -cis retinal, in rod outer segments. A total of 50 human autopsy eyes were harvested from donors with and without macular degeneration within 2-24 hrs. postmortem. Protocols were developed which permitted dark adaptation of normal human eyes after death and enucleation. Biochemical methods of purifying rod outer segments were optimized and the concentration of rhodopsin and apo-opsin was measured with UV-visible scanning spectroscopy. The presence of apo-opsin was calculated by measuring the difference in the rhodopsin absorption spectra before and after the addition of 11 -cis retinal. A total of 20 normal eyes and 16 eyes from donors with early, intermediate and advanced stages of macular degeneration were included in the final analysis. Dark adaptation was achieved by harvesting whole globes in low light, transferring into dark (light-proof) canisters and dissecting the globes using infrared light and image converters for visualization. Apo-opsin was readily detected in positive controls after the addition of 11 -cis retinal. Normal autopsy eyes showed no evidence of apo-opsin. Eyes with macular degeneration also showed no evidence of apo-opsin, regardless of the severity of disease. Methods have been developed to study dark adaptation in human autopsy eyes. Eyes with age-related macular degeneration do not show a deficiency of 11 -cis retinal or an excess of apo-opsin within rod outer segments.

'Goats that stare at men'--revisited: do dwarf goats alter their behaviour in response to eye visibility and head direction of a human?

PubMed

Nawroth, Christian; von Borell, Eberhard; Langbein, Jan

2016-05-01

Being able to recognise when one is being observed by someone else is thought to be adaptive during cooperative or competitive events. In particular for prey species, this ability should be of use in the context of predation. A previous study reported that goats (Capra aegagrus hircus) alter their behaviour according to the body and head orientation of a human experimenter. During a food anticipation task, an experimenter remained in a particular posture for 30 s before delivering a reward, and the goats' active anticipation and standing alert behaviour were analysed. To further evaluate the specific mechanisms at work, we here present two additional test conditions. In particular, we investigated the effects of the eye visibility and head orientation of a human experimenter on the behaviour of the goats (N = 7). We found that the level of the subjects' active anticipatory behaviour was highest in the conditions where the experimenter was directing his head and body towards the goat ('Control' and 'Eyes closed' conditions), but the anticipatory behaviour was significantly decreased when the body ('Head only') or the head and body of the experimenter were directed away from the subject ('Back' condition). For standing alert, we found no significant differences between the three conditions in which the experimenter was directing his head towards the subject ('Control', 'Eyes closed' and 'Head only'). This lack of differences in the expression of standing alert suggests that goats evaluate the direction of a human's head as an important cue in their anticipatory behaviour. However, goats did not respond to the visibility of the experimenter's eyes alone.

Image-size differences worsen stereopsis independent of eye position

PubMed Central

Vlaskamp, Björn N. S.; Filippini, Heather R.; Banks, Martin S.

2010-01-01

With the eyes in forward gaze, stereo performance worsens when one eye’s image is larger than the other’s. Near, eccentric objects naturally create retinal images of different sizes. Does this mean that stereopsis exhibits deficits for such stimuli? Or does the visual system compensate for the predictable image-size differences? To answer this, we measured discrimination of a disparity-defined shape for different relative image sizes. We did so for different gaze directions, some compatible with the image-size difference and some not. Magnifications of 10–15% caused a clear worsening of stereo performance. The worsening was determined only by relative image size and not by eye position. This shows that no neural compensation for image-size differences accompanies eye-position changes, at least prior to disparity estimation. We also found that a local cross-correlation model for disparity estimation performs like humans in the same task, suggesting that the decrease in stereo performance due to image-size differences is a byproduct of the disparity-estimation method. Finally, we looked for compensation in an observer who has constantly different image sizes due to differing eye lengths. She performed best when the presented images were roughly the same size, indicating that she has compensated for the persistent image-size difference. PMID:19271927

Cue-dependent memory-based smooth-pursuit in normal human subjects: importance of extra-retinal mechanisms for initial pursuit.

PubMed

Ito, Norie; Barnes, Graham R; Fukushima, Junko; Fukushima, Kikuro; Warabi, Tateo

2013-08-01

Using a cue-dependent memory-based smooth-pursuit task previously applied to monkeys, we examined the effects of visual motion-memory on smooth-pursuit eye movements in normal human subjects and compared the results with those of the trained monkeys. These results were also compared with those during simple ramp-pursuit that did not require visual motion-memory. During memory-based pursuit, all subjects exhibited virtually no errors in either pursuit-direction or go/no-go selection. Tracking eye movements of humans and monkeys were similar in the two tasks, but tracking eye movements were different between the two tasks; latencies of the pursuit and corrective saccades were prolonged, initial pursuit eye velocity and acceleration were lower, peak velocities were lower, and time to reach peak velocities lengthened during memory-based pursuit. These characteristics were similar to anticipatory pursuit initiated by extra-retinal components during the initial extinction task of Barnes and Collins (J Neurophysiol 100:1135-1146, 2008b). We suggest that the differences between the two tasks reflect differences between the contribution of extra-retinal and retinal components. This interpretation is supported by two further studies: (1) during popping out of the correct spot to enhance retinal image-motion inputs during memory-based pursuit, pursuit eye velocities approached those during simple ramp-pursuit, and (2) during initial blanking of spot motion during memory-based pursuit, pursuit components appeared in the correct direction. Our results showed the importance of extra-retinal mechanisms for initial pursuit during memory-based pursuit, which include priming effects and extra-retinal drive components. Comparison with monkey studies on neuronal responses and model analysis suggested possible pathways for the extra-retinal mechanisms.

Comparison of parameters affecting GNP-loaded choroidal melanoma dosimetry; Monte Carlo study

NASA Astrophysics Data System (ADS)

Sharabiani, Marjan; Asadi, Somayeh; Barghi, Amir Rahnamai; Vaezzadeh, Mehdi

2018-04-01

The current study reports the results of tumor dosimetry in the presence of gold nanoparticles (GNPs) with different sizes and concentrations. Due to limited number of works carried out on the brachytherapy of choroidal melanoma in combination with GNPs, this study was performed to determine the optimum size and concentration for GNPs which contributes the highest dose deposition in tumor region, using two phantom test cases namely water phantom and a full Monte Carlo model of human eye. Both water and human eye phantoms were simulated with MCNP5 code. Tumor dosimetry was performed for a typical point photon source with an energy of 0.38 MeV as a high energy source and 103Pd brachytherapy source with an average energy of 0.021 MeV as a low energy source in water phantom and eye phantom respectively. Such a dosimetry was done for different sizes and concentrations of GNPs. For all of the diameters, increase in concentration of GNPs resulted in an increase in dose deposited in the region of interest. In a certain concentration, GNPs with larger diameters contributed more dose to the tumor region, which was more pronounced using eye phantom. 100 nm was reported as the optimum size in order to achieve the highest energy deposition within the target. This work investigated the optimum parameters affecting macroscopic dose enhancement in GNP-aided brachytherapy of choroidal melanoma. The current work also had implications on using low energy photon sources in the presence of GNPs to acquire the highest dose enhancement. This study is conducted through four different sizes and concentrations of GNPs. Considering the sensitivity of human eye tissue, in order to report the precise optimum parameters affecting radiosensitivity, a comprehensive study on a wide range of sizes and concentrations are required.

Mechanistic-based non-animal assessment of eye toxicity: Inflammatory profile of human keratinocytes cells after exposure to eye damage/irritant agents.

PubMed

da Silva, Artur Christian Garcia; Chialchia, Adrienny Rodrigues; de Ávila, Renato Ivan; Valadares, Marize Campos

2018-06-25

Eye toxicity is a mandatory parameter in human risk and safety evaluation for products including chemicals, pesticides, medicines and cosmetics. Historically, this endpoint has been evaluated using the Draize rabbit eye test, an in vivo model that was never formally validated. Due to advances in scientific knowledge, economic and ethical issues, non-animal methods based on mechanisms of toxicity are being developed and validated for increasing the capability of these models to predict eye toxicity. In this study, the Cytometric Bead Array (CBA) and ELISA assays were used to evaluate the inflammatory cytokine profile produced by HaCaT human keratinocytes after exposure to chemicals with different UN GHS eye toxicity classifications, aiming to stablish a correlation between inflammatory endpoints and eye toxicity (damage/irritation) potential. As a first step, cytotoxic profile of the chemicals, including 3 non-irritants and 10 eye toxicants (GHS Category 1, 2A and 2B), was evaluated after 24 h exposure using MTT assay and Inhibitory Concentration of 20% of cell viability (IC 20 ) was calculated for each chemical. Then, the cells were exposed to these chemicals at IC 20 for 24 h and supernatants and cell lysates were analyzed by CBA assay for quantification of the following cytokines: IL-6, IL-8, IL-10, IL-1β, TNF and IL-12p70. Regarding cytotoxicity evaluation, chemicals showed different cytotoxicity profiles and data demonstrated no correlation with their UN GHS classification. Among the cytokines evaluated, IL-1β production has changed after exposure and such alterations were confirmed by quantification employing ELISA method. The higher intracellular levels of IL-1β were found in GHS Category 1 chemicals, followed by Category 2A and 2B, while non irritants did not induce such increase. Thus, these findings show that IL-1β measurement, using HaCaT model, can be a considerable biomarker to identify chemicals according to their potential in promote eye toxicity, differentiating damage from irritation potential. Copyright © 2018. Published by Elsevier B.V.

Human rather than ape-like orbital morphology allows much greater lateral visual field expansion with eye abduction

PubMed Central

Denion, Eric; Hitier, Martin; Levieil, Eric; Mouriaux, Frédéric

2015-01-01

While convergent, the human orbit differs from that of non-human apes in that its lateral orbital margin is significantly more rearward. This rearward position does not obstruct the additional visual field gained through eye motion. This additional visual field is therefore considered to be wider in humans than in non-human apes. A mathematical model was designed to quantify this difference. The mathematical model is based on published computed tomography data in the human neuro-ocular plane (NOP) and on additional anatomical data from 100 human skulls and 120 non-human ape skulls (30 gibbons; 30 chimpanzees / bonobos; 30 orangutans; 30 gorillas). It is used to calculate temporal visual field eccentricity values in the NOP first in the primary position of gaze then for any eyeball rotation value in abduction up to 45° and any lateral orbital margin position between 85° and 115° relative to the sagittal plane. By varying the lateral orbital margin position, the human orbit can be made “non-human ape-like”. In the Pan-like orbit, the orbital margin position (98.7°) was closest to the human orbit (107.1°). This modest 8.4° difference resulted in a large 21.1° difference in maximum lateral visual field eccentricity with eyeball abduction (Pan-like: 115°; human: 136.1°). PMID:26190625

Human Visual System as a Double-Slit Single Photon Interference Sensor: A Comparison between Modellistic and Biophysical Tests

PubMed Central

Pizzi, Rita; Wang, Rui; Rossetti, Danilo

2016-01-01

This paper describes a computational approach to the theoretical problems involved in the Young's single-photon double-slit experiment, focusing on a simulation of this experiment in the absence of measuring devices. Specifically, the human visual system is used in place of a photomultiplier or similar apparatus. Beginning with the assumption that the human eye perceives light in the presence of very few photons, we measure human eye performance as a sensor in a double-slit one-photon-at-a-time experimental setup. To interpret the results, we implement a simulation algorithm and compare its results with those of human subjects under identical experimental conditions. In order to evaluate the perceptive parameters exactly, which vary depending on the light conditions and on the subject’s sensitivity, we first review the existing literature on the biophysics of the human eye in the presence of a dim light source, and then use the known values of the experimental variables to set the parameters of the computational simulation. The results of the simulation and their comparison with the experiment involving human subjects are reported and discussed. It is found that, while the computer simulation indicates that the human eye has the capacity to detect the corpuscular nature of photons under these conditions, this was not observed in practice. The possible reasons for the difference between theoretical prediction and experimental results are discussed. PMID:26816029

Microspheres and Nanotechnology for Drug Delivery.

PubMed

Jóhannesson, Gauti; Stefánsson, Einar; Loftsson, Thorsteinn

2016-01-01

Ocular drug delivery to the posterior segment of the eye can be accomplished by invasive drug injections into different tissues of the eye and noninvasive topical treatment. Invasive treatment involves the risks of surgical trauma and infection, and conventional topical treatments are ineffective in delivering drugs to the posterior segment of the eye. In recent years, nanotechnology has become an ever-increasing part of ocular drug delivery. In the following, we briefly review microspheres and nanotechnology for drug delivery to the eye, including different forms of nanotechnology such as nanoparticles, microparticles, liposomes, microemulsions and micromachines. The permeation barriers and anatomical considerations linked to ocular drug delivery are discussed and a theoretical overview on drug delivery through biological membranes is given. Finally, in vitro, in vivo and human studies of x03B3;-cyclodextrin nanoparticle eyedrop suspensions are discussed as an example of nanotechnology used for drug delivery to the eye. © 2016 S. Karger AG, Basel.

Corneal polarimetry after LASIK refractive surgery

NASA Astrophysics Data System (ADS)

Bueno, Juan M.; Berrio, Esther; Artal, Pablo

2006-01-01

Imaging polarimetry provides spatially resolved information on the polarization properties of a system. In the case of the living human eye, polarization could be related to the corneal biomechanical properties, which vary from the normal state as a result of surgery or pathologies. We have used an aberro-polariscope, which we recently developed, to determine and to compare the spatially resolved maps of polarization parameters across the pupil between normal healthy and post-LASIK eyes. The depolarization distribution is not uniform across the pupil, with post-surgery eyes presenting larger levels of depolarization. While retardation increases along the radius in normal eyes, this pattern becomes irregular after LASIK refractive surgery. The maps of slow axis also differ in normal and post-surgery eyes, with a larger disorder in post-LASIK eyes. Since these changes in polarization indicate subtle structural modifications of the cornea, this approach can be useful in a clinical environment to follow the biomechanical and optical changes of the cornea after refractive surgery or for the early diagnosis of different corneal pathologies.

Electrical Microstimulation of the Superior Colliculus in Strabismic Monkeys.

PubMed

Fleuriet, Jérome; Walton, Mark M G; Ono, Seiji; Mustari, Michael J

2016-06-01

Visually guided saccades are disconjugate in human and nonhuman strabismic primates. The superior colliculus (SC) is a region of the brain topographically organized in visual and motor maps where the saccade goal is spatially coded. The present study was designed to investigate if a site of stimulation on the topographic motor map was evoking similar or different saccade vectors for each eye. We used microelectrical stimulation (MS) of the SC in two strabismic (one esotrope and one exotrope) and two control macaques under binocular and monocular viewing conditions. We compared the saccade amplitudes and directions for each SC site and each condition independently of the fixating eye and then between each fixating eye. A comparison with disconjugacies of visually guided saccades was also performed. We observed different saccade vectors for the two eyes in strabismic monkeys, but conjugate saccades in normal monkeys. Evoked saccade vectors for the left eye when that eye was fixating the target were different from those of the right eye when it was fixating. The disconjugacies evoked by the MS were not identical but similar to those observed for visually guided saccades especially for the dominant eye. Our results suggest that, in strabismus, the saccade generator does not interpret activation of a single location of the SC as the same desired displacement for each eye. This finding is important for advancing understanding of the development of neural circuits in strabismus. French Abstract.

P gene as an inherited biomarker of human eye color.

PubMed

Rebbeck, Timothy R; Kanetsky, Peter A; Walker, Amy H; Holmes, Robin; Halpern, Allan C; Schuchter, Lynn M; Elder, David E; Guerry, DuPont

2002-08-01

Human pigmentation, including eye color, has been associated with skin cancer risk. The P gene is the human homologue to the mouse pink-eye dilution locus and is responsible for oculocutaneous albinism type 2 and other phenotypes that confer eye hypopigmentation. The P gene is located on chromosome 15q11.2-q12, which is also the location of a putative eye pigmentation gene (EYCL3) inferred to exist by linkage analysis. Therefore, the P gene is a strong candidate for determination of human eye color. Using a sample of 629 normally pigmented individuals, we found that individuals were less likely to have blue or gray eyes if they had P gene variants Arg305Trp (P = 0.002), Arg419Gln (P = 0.001), or the combination of both variants (P = 0.003). These results suggest that P gene, in part, determines normal phenotypic variation in human eye color and may therefore represent an inherited biomarker of cutaneous cancer risk.

Microstructure and network organization of the microvasculature in the human macula.

PubMed

Yu, Paula K; Balaratnasingam, Chandrakumar; Cringle, Stephen J; McAllister, Ian L; Provis, Jan; Yu, Dao-Yi

2010-12-01

To characterize the topography and cellular structure of the macular microvasculature using a recently developed technique of arterial cannulation, perfusion, fixation, and staining of human donor eyes. Sixteen human donor eyes were used. The central retinal artery was cannulated and perfused with Ringer's, then fixative, membrane permeabilizing, and selected labeling solutions. The eyes were immersion fixed, and the retina was flat mounted for confocal microscopy. The macular area, including the foveola, fovea, and parafovea, was sampled. The intracellular cytoskeleton of vascular endothelial and smooth muscle cells was studied in different orders of arterioles and venules and in the capillaries. To evaluate the degree of asymmetry within vascular networks, the distribution of generation numbers and the Horton-Strahler approach to vessel naming were compared. The distribution of the microvascular network in the macular region was complex but followed a general theme. The parafoveal region was supplied by dense vasculature with approximately nine closely arranged pairs of arterioles and venules. Each arteriole had abundant branches and a high degree of asymmetry (∼10 generations and 3.5 orders within 1.2-mm length). Only a few arterioles (average ∼2.9) supplied the terminal capillary ring. Very long spindle endothelial cells were seen in the superficial and deep capillaries. Significant heterogeneity of distribution and shape of the endothelial and smooth muscle cells was evident in different orders of the macular vasculature. The authors have demonstrated for the first time the cellular structure and topographic features of the macular microvasculature in human donor eyes.

Feature Selection in Classification of Eye Movements Using Electrooculography for Activity Recognition

PubMed Central

Mala, S.; Latha, K.

2014-01-01

Activity recognition is needed in different requisition, for example, reconnaissance system, patient monitoring, and human-computer interfaces. Feature selection plays an important role in activity recognition, data mining, and machine learning. In selecting subset of features, an efficient evolutionary algorithm Differential Evolution (DE), a very efficient optimizer, is used for finding informative features from eye movements using electrooculography (EOG). Many researchers use EOG signals in human-computer interactions with various computational intelligence methods to analyze eye movements. The proposed system involves analysis of EOG signals using clearness based features, minimum redundancy maximum relevance features, and Differential Evolution based features. This work concentrates more on the feature selection algorithm based on DE in order to improve the classification for faultless activity recognition. PMID:25574185

Feature selection in classification of eye movements using electrooculography for activity recognition.

PubMed

Mala, S; Latha, K

2014-01-01

Activity recognition is needed in different requisition, for example, reconnaissance system, patient monitoring, and human-computer interfaces. Feature selection plays an important role in activity recognition, data mining, and machine learning. In selecting subset of features, an efficient evolutionary algorithm Differential Evolution (DE), a very efficient optimizer, is used for finding informative features from eye movements using electrooculography (EOG). Many researchers use EOG signals in human-computer interactions with various computational intelligence methods to analyze eye movements. The proposed system involves analysis of EOG signals using clearness based features, minimum redundancy maximum relevance features, and Differential Evolution based features. This work concentrates more on the feature selection algorithm based on DE in order to improve the classification for faultless activity recognition.

Ask the Experts

ERIC Educational Resources Information Center

Science Teacher, 2005

2005-01-01

Two science questions are answered: (1) How can someone have one brown eye and one blue eye?, and (2) Why are magnets attracted to some metals, but not all metals? It is very rare that a human will have two irises of different colors. This condition, heterochromia, can be a normal variant or the result of an ocular disease. Heterochromia can…

Blue Eyes, Brown Eyes, Cornrows, and Curls: Building on Books to Explore Physical Diversity with Preschool Children

ERIC Educational Resources Information Center

Kemple, Kristen M.; Lopez, Maria

2009-01-01

Children notice physical characteristics of others and develop attitudes toward human diversity at a very young age. High-quality children's literature is a helpful springboard to encourage their awareness of differences and to develop their appreciation of uniqueness. Children's books can be an important avenue for shaping how children perceive…

Topographic analyses of shape of eyes with pathologic myopia by high-resolution three-dimensional magnetic resonance imaging.

PubMed

Moriyama, Muka; Ohno-Matsui, Kyoko; Hayashi, Kengo; Shimada, Noriaki; Yoshida, Takeshi; Tokoro, Takashi; Morita, Ikuo

2011-08-01

To analyze the topography of human eyes with pathologic myopia by high-resolution magnetic resonance imaging (MRI) with volume rendering of the acquired images. Observational case series. Eighty-six eyes of 44 patients with high myopia (refractive error ≥-8.00 diopters [D] or axial length >26.5 mm) were studied. Forty emmetropic eyes were examined as controls. The participants were examined with an MRI scanner (Signa HDxt 1.5T, GE Healthcare, Waukesha, WI), and T(2)-weighted cubes were obtained. Volume renderings of the images from high-resolution 3-dimensional (3D) data were done by computer workstation. The margins of globes were then identified semiautomatically by the signal intensity, and the tissues outside the globes were removed. The 3D topographic characteristic of the globes and the distribution of the 4 distinct shapes of globes according to the symmetry and the radius of curvature of the contour of the posterior segment: the barrel, cylindric, nasally distorted, and temporally distorted types. In 69.8% of the patients with bilateral high myopia, both eyes had the same ocular shape. The most protruded part of the globe existed along the central sagittal axis in 78.3% of eyes and was slightly inferior to the central axis in the remaining eyes. In 38 of 68 eyes (55.9%) with bilateral pathologic myopia, multiple protrusions were observed. The eyes with 2 protrusions were subdivided into those with nasal protrusions and those with temporal protrusions. The eyes with 3 protrusions were subdivided into nasal, temporal superior, and temporal inferior protrusions. The eyes with visual field defects that could not be explained by myopic fundus lesions significantly more frequently had a temporally distorted shape. Eyes with ≥2 protrusions had myopic chorioretinal atrophy significantly more frequently than eyes with ≤1 protrusion. Our results demonstrate that it is possible to obtain a complete topographic image of human eyes by high-resolution MRI with volume-rendering techniques. The results showed that there are different ocular shapes in eyes with pathologic myopia, and that the difference in the ocular shape is correlated with the development of vision-threatening conditions in eyes with pathologic myopia. The author(s) have no proprietary or commercial interest in any materials discussed in this article. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Initial eye movements during face identification are optimal and similar across cultures

PubMed Central

Or, Charles C.-F.; Peterson, Matthew F.; Eckstein, Miguel P.

2015-01-01

Culture influences not only human high-level cognitive processes but also low-level perceptual operations. Some perceptual operations, such as initial eye movements to faces, are critical for extraction of information supporting evolutionarily important tasks such as face identification. The extent of cultural effects on these crucial perceptual processes is unknown. Here, we report that the first gaze location for face identification was similar across East Asian and Western Caucasian cultural groups: Both fixated a featureless point between the eyes and the nose, with smaller between-group than within-group differences and with a small horizontal difference across cultures (8% of the interocular distance). We also show that individuals of both cultural groups initially fixated at a slightly higher point on Asian faces than on Caucasian faces. The initial fixations were found to be both fundamental in acquiring the majority of information for face identification and optimal, as accuracy deteriorated when observers held their gaze away from their preferred fixations. An ideal observer that integrated facial information with the human visual system's varying spatial resolution across the visual field showed a similar information distribution across faces of both races and predicted initial human fixations. The model consistently replicated the small vertical difference between human fixations to Asian and Caucasian faces but did not predict the small horizontal leftward bias of Caucasian observers. Together, the results suggest that initial eye movements during face identification may be driven by brain mechanisms aimed at maximizing accuracy, and less influenced by culture. The findings increase our understanding of the interplay between the brain's aims to optimally accomplish basic perceptual functions and to respond to sociocultural influences. PMID:26382003

Steering a Tractor by Means of an EMG-Based Human-Machine Interface

PubMed Central

Gomez-Gil, Jaime; San-Jose-Gonzalez, Israel; Nicolas-Alonso, Luis Fernando; Alonso-Garcia, Sergio

2011-01-01

An electromiographic (EMG)-based human-machine interface (HMI) is a communication pathway between a human and a machine that operates by means of the acquisition and processing of EMG signals. This article explores the use of EMG-based HMIs in the steering of farm tractors. An EPOC, a low-cost human-computer interface (HCI) from the Emotiv Company, was employed. This device, by means of 14 saline sensors, measures and processes EMG and electroencephalographic (EEG) signals from the scalp of the driver. In our tests, the HMI took into account only the detection of four trained muscular events on the driver’s scalp: eyes looking to the right and jaw opened, eyes looking to the right and jaw closed, eyes looking to the left and jaw opened, and eyes looking to the left and jaw closed. The EMG-based HMI guidance was compared with manual guidance and with autonomous GPS guidance. A driver tested these three guidance systems along three different trajectories: a straight line, a step, and a circumference. The accuracy of the EMG-based HMI guidance was lower than the accuracy obtained by manual guidance, which was lower in turn than the accuracy obtained by the autonomous GPS guidance; the computed standard deviations of error to the desired trajectory in the straight line were 16 cm, 9 cm, and 4 cm, respectively. Since the standard deviation between the manual guidance and the EMG-based HMI guidance differed only 7 cm, and this difference is not relevant in agricultural steering, it can be concluded that it is possible to steer a tractor by an EMG-based HMI with almost the same accuracy as with manual steering. PMID:22164006

Steering a tractor by means of an EMG-based human-machine interface.

PubMed

Gomez-Gil, Jaime; San-Jose-Gonzalez, Israel; Nicolas-Alonso, Luis Fernando; Alonso-Garcia, Sergio

2011-01-01

An electromiographic (EMG)-based human-machine interface (HMI) is a communication pathway between a human and a machine that operates by means of the acquisition and processing of EMG signals. This article explores the use of EMG-based HMIs in the steering of farm tractors. An EPOC, a low-cost human-computer interface (HCI) from the Emotiv Company, was employed. This device, by means of 14 saline sensors, measures and processes EMG and electroencephalographic (EEG) signals from the scalp of the driver. In our tests, the HMI took into account only the detection of four trained muscular events on the driver's scalp: eyes looking to the right and jaw opened, eyes looking to the right and jaw closed, eyes looking to the left and jaw opened, and eyes looking to the left and jaw closed. The EMG-based HMI guidance was compared with manual guidance and with autonomous GPS guidance. A driver tested these three guidance systems along three different trajectories: a straight line, a step, and a circumference. The accuracy of the EMG-based HMI guidance was lower than the accuracy obtained by manual guidance, which was lower in turn than the accuracy obtained by the autonomous GPS guidance; the computed standard deviations of error to the desired trajectory in the straight line were 16 cm, 9 cm, and 4 cm, respectively. Since the standard deviation between the manual guidance and the EMG-based HMI guidance differed only 7 cm, and this difference is not relevant in agricultural steering, it can be concluded that it is possible to steer a tractor by an EMG-based HMI with almost the same accuracy as with manual steering.

Numerical modeling of heat and mass transfer in the human eye under millimeter wave exposure.

PubMed

Karampatzakis, Andreas; Samaras, Theodoros

2013-05-01

Human exposure to millimeter wave (MMW) radiation is expected to increase in the next several years. In this work, we present a thermal model of the human eye under MMW illumination. The model takes into account the fluid dynamics of the aqueous humor and predicts a frequency-dependent reversal of its flow that also depends on the incident power density. The calculated maximum fluid velocity in the anterior chamber and the temperature rise at the corneal apex are reported for frequencies from 40 to 100 GHz and different values of incident power density. Copyright © 2013 Wiley Periodicals, Inc.

CHARACTERIZATION OF ANTERIOR SEGMENT OPHTHALMOLOGIC LESIONS IDENTIFIED IN FREE-RANGING DOLPHINS AND THOSE UNDER HUMAN CARE.

PubMed

Colitz, Carmen M H; Walsh, Michael T; McCulloch, Stephen D

2016-03-01

Cetaceans in the wild and under human care develop a variety of ocular lesions. Although they have echolocation, cetacean species have good sight, making ocular health an important part of overall health care. The cornea is the primary site of abnormalities in both populations. Typical lesions of cetaceans under human care are characterized in this retrospective review of cases. One hundred eighty animals (n = 360 eyes) were chosen from the author's ophthalmologic examination reports from different geographic areas; they included Atlantic bottlenose dolphins (Tursiops truncatus), Pacific bottle nose dolphins (Tursiopstruncatus gilli), Indopacific bottlenose dolphins (Steno bredanensis), Indopacific humpback dolphins (Sousa chinensis), and roughtooth dolphins (Steno bredanensis). These animals were examined at least once, although most were examined numerous times over many years; lesions were categorized and are described. Seventy-seven eyes from 47 animals were normal. Medial keratopathy was the most common lesion and identified in 180 eyes from 97 animals, with 83 affected bilaterally. Horizontal keratopathy was identified in 69 eyes from 41 animals, with 28 affected bilaterally. Axial keratopathy and nonspecific axial opacities were identified in 67 eyes from 44 animals, with 21 affected bilaterally. Seventy-eight eyes from 50 animals, with 28 affected bilaterally, had more than one type of corneal lesion. Cataracts were identified in 32 eyes from 19 animals, with 13 affected bilaterally. Traumatic injuries were also common and involved eyelids and cornea. Sixteen eyes from 11 animals were blind; five dolphins were blind bilaterally due to phthisis bulbi secondary to corneal perforation or severe trauma. None of the diseases had a sex predisposition; however, medial keratopathy was significantly more common as a bilateral presentation than as a unilateral presentation. Cetaceans under human care with impaired sight can use echolocation; however, ocular health should definitely be a priority in their overall health plan.

Human lamina cribrosa insertion and age.

PubMed

Sigal, Ian A; Flanagan, John G; Lathrop, Kira L; Tertinegg, Inka; Bilonick, Richard

2012-10-03

To test the hypothesis that in healthy human eyes the lamina cribrosa (LC) insertion into the pia mater increases with age. The optic nerve heads (ONHs) of donor eyes fixed at either 5 or 50 mm Hg of IOP were sectioned, stained, and imaged under bright- and dark-field conditions. A 3-dimensional (3D) model of each ONH was reconstructed. From the 3D models we measured the area of LC insertion into the peripapillary scleral flange and into the pia, and computed the total area of insertion and fraction of LC inserting into the pia. Linear mixed effect models were used to determine if the measurements were associated with age or IOP. We analyzed 21 eyes from 11 individuals between 47 and 91 years old. The LC inserted into the pia in all eyes. The fraction of LC inserting into the pia (2.2%-29.6%) had a significant decrease with age (P = 0.049), which resulted from a nonsignificant increase in the total area of LC insertion (P = 0.41) and a nonsignificant decrease in the area of LC insertion into the pia (P = 0.55). None of the measures was associated with fixation IOP (P values 0.44-0.81). Differences between fellow eyes were smaller than differences between unrelated eyes. The LC insertion into the pia mater is common in middle-aged and older eyes, and does not increase with age. The biomechanical and vascular implications of the LC insertion into the pia mater are not well understood and should be investigated further.

Human Lamina Cribrosa Insertion and Age

PubMed Central

Sigal, Ian A.; Flanagan, John G.; Lathrop, Kira L.; Tertinegg, Inka; Bilonick, Richard

2012-01-01

Purpose. To test the hypothesis that in healthy human eyes the lamina cribrosa (LC) insertion into the pia mater increases with age. Methods. The optic nerve heads (ONHs) of donor eyes fixed at either 5 or 50 mm Hg of IOP were sectioned, stained, and imaged under bright- and dark-field conditions. A 3-dimensional (3D) model of each ONH was reconstructed. From the 3D models we measured the area of LC insertion into the peripapillary scleral flange and into the pia, and computed the total area of insertion and fraction of LC inserting into the pia. Linear mixed effect models were used to determine if the measurements were associated with age or IOP. Results. We analyzed 21 eyes from 11 individuals between 47 and 91 years old. The LC inserted into the pia in all eyes. The fraction of LC inserting into the pia (2.2%–29.6%) had a significant decrease with age (P = 0.049), which resulted from a nonsignificant increase in the total area of LC insertion (P = 0.41) and a nonsignificant decrease in the area of LC insertion into the pia (P = 0.55). None of the measures was associated with fixation IOP (P values 0.44–0.81). Differences between fellow eyes were smaller than differences between unrelated eyes. Conclusions. The LC insertion into the pia mater is common in middle-aged and older eyes, and does not increase with age. The biomechanical and vascular implications of the LC insertion into the pia mater are not well understood and should be investigated further. PMID:22956611

Rabbit as an animal model for intravitreal pharmacokinetics: Clinical predictability and quality of the published data.

PubMed

Del Amo, Eva M; Urtti, Arto

2015-08-01

Intravitreal administration is the method of choice in drug delivery to the retina and/or choroid. Rabbit is the most commonly used animal species in intravitreal pharmacokinetics, but it has been criticized as being a poor model of human eye. The critique is based on some anatomical differences, properties of the vitreous humor, and observed differences in drug concentrations in the anterior chamber after intravitreal injections. We have systematically analyzed all published information on intravitreal pharmacokinetics in the rabbit and human eye. The analysis revealed major problems in the design of the pharmacokinetic studies. In this review we provide advice for study design. Overall, the pharmacokinetic parameters (clearance, volume of distribution, half-life) in the human and rabbit eye have good correlation and comparable absolute values. Therefore, reliable rabbit-to-man translation of intravitreal pharmacokinetics should be feasible. The relevant anatomical and physiological parameters in rabbit and man show only small differences. Furthermore, the claimed discrepancy between drug concentrations in the human and rabbit aqueous humor is not supported by the data analysis. Based on the available and properly conducted pharmacokinetic studies, the differences in the vitreous structure in rabbits and human patients do not lead to significant pharmacokinetic differences. This review is the first step towards inter-species translation of intravitreal pharmacokinetics. More information is still needed to dissect the roles of drug delivery systems, disease states, age and ocular manipulation on the intravitreal pharmacokinetics in rabbit and man. Anyway, the published data and the derived pharmacokinetic parameters indicate that the rabbit is a useful animal model in intravitreal pharmacokinetics. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Lack of oblique astigmatism in the chicken eye.

PubMed

Maier, Felix M; Howland, Howard C; Ohlendorf, Arne; Wahl, Siegfried; Schaeffel, Frank

2015-04-01

Primate eyes display considerable oblique off-axis astigmatism which could provide information on the sign of defocus that is needed for emmetropization. The pattern of peripheral astigmatism is not known in the chicken eye, a common model of myopia. Peripheral astigmatism was mapped out over the horizontal visual field in three chickens, 43 days old, and in three near emmetropic human subjects, average age 34.7years, using infrared photoretinoscopy. There were no differences in astigmatism between humans and chickens in the central visual field (chicks -0.35D, humans -0.65D, n.s.) but large differences in the periphery (i.e. astigmatism at 40° in the temporal visual field: humans -4.21D, chicks -0.63D, p<0.001, unpaired t-test). The lack of peripheral astigmatism in chicks was not due to differences in corneal shape. Perhaps related to their superior peripheral optics, we found that chickens had excellent visual performance also in the far periphery. Using an automated optokinetic nystagmus paradigm, no difference was observed in spatial visual performance with vision restricted to either the central 67° of the visual field or to the periphery beyond 67°. Accommodation was elicited by stimuli presented far out in the visual field. Transscleral images of single infrared LEDs showed no sign of peripheral astigmatism. The chick may be the first terrestrial vertebrate described to lack oblique astigmatism. Since corneal shape cannot account for the difference in astigmatism in humans and chicks, it must trace back to the design of the crystalline lens. The lack of peripheral astigmatism in chicks also excludes a role in emmetropization. Copyright © 2015 Elsevier Ltd. All rights reserved.

How the Human Eye Focuses.

ERIC Educational Resources Information Center

Koretz, Jane F.; Handelman, George H.

1988-01-01

Describes the decline in people's ability to focus their eyes as their age increases. Discusses probable causes of this effect including changes in the eye's geometry and biochemistry. Diagrammatically illustrates age related changes in the lens of the human eye. (CW)

A comparative study of different amniotic membrane orientations during extraocular muscle surgery in rabbits.

PubMed

Kassem, Rehab Rashad; El-Mofty, Randa Mohamed Abdel-Moneim; Khodeir, Mustafa Mahmoud; Hamza, Wael Mostafa

2018-03-01

To histopathologically compare the effect of different orientations of cryopreserved human amniotic membrane (AM) transplant during extraocular muscle surgery in rabbits. Fifty-two albino rabbit eyes underwent 4-mm resection of the superior rectus. Eyes were randomly divided into four groups. In Group C (Control group, 16 eyes) the muscle was not wrapped with amniotic membrane. In the three AM groups, cryopreserved AM was wrapped around the muscle, oriented with either its stroma (Group S, 15 eyes) or epithelium (Group E, nine eyes) towards the muscle, or folded on itself with the epithelium externally (Group F, 12 eyes). The rabbits were sacrificed and the eyes were enucleated 6 weeks after surgery. Histopathological examination was conducted for periamniotic, foreign body, scleral, and conjunctival inflammation, conjunctival vascularity, adhesions and muscle fibrosis. In all AM eyes, the AM was surrounded by periamniotic inflammation, with no adhesions detected between the muscle and surrounding tissues in the segment where the AM was present, but detected elsewhere. Adhesions were detected in all group C eyes. Foreign body inflammation was significantly less in Group C than in each of the AM groups (p < .05), but was insignificantly different among the three AM groups (p > .05). Scleral inflammation was absent in all specimens. No significant differences were noted among all groups in terms of conjunctival vascularity, conjunctival inflammation, or muscle fibrosis (p > .05). All AM orientations were equally effective in preventing the development of postoperative adhesions between the extraocular muscle and surrounding tissues.

Comparison of eye imaging pattern recognition using neural network

NASA Astrophysics Data System (ADS)

Bukhari, W. M.; Syed A., M.; Nasir, M. N. M.; Sulaima, M. F.; Yahaya, M. S.

2015-05-01

The beauty of eye recognition system that it is used in automatic identifying and verifies a human weather from digital images or video source. There are various behaviors of the eye such as the color of the iris, size of pupil and shape of the eye. This study represents the analysis, design and implementation of a system for recognition of eye imaging. All the eye images that had been captured from the webcam in RGB format must through several techniques before it can be input for the pattern and recognition processes. The result shows that the final value of weight and bias after complete training 6 eye images for one subject is memorized by the neural network system and be the reference value of the weight and bias for the testing part. The target classifies to 5 different types for 5 subjects. The eye images can recognize the subject based on the target that had been set earlier during the training process. When the values between new eye image and the eye image in the database are almost equal, it is considered the eye image is matched.

Polarimetric Glucose Sensing Using Brewster Reflection off of Eye Lens: Theoretical Analysis

NASA Technical Reports Server (NTRS)

Boeckle, Stefan; Rovati, Luigi; Ansari, Rafat R.

2002-01-01

An important task of in vivo polarimetric glucose sensing is to find an appropriate way to optically access the aqueous humor of the human eye. In this paper two different approaches are analyzed theoretically and applied to the eye model of Le Grand. First approach is the tangential path of Cote, et al. (G.L. Cot6, M.D. Fox, and R.B. Northrop: Noninvasive Optical Polarimetric Glucose Sensing Using a True Phase Measurement Technique. IEEE Transactions on Biomedical Engineering, vol. 39, no. 7, pp. 752-756, 1992.) and the second is a new scheme of this paper of applying Brewster reflection off the eye lens.

Communication Aid with Human Eyes Only

NASA Astrophysics Data System (ADS)

Arai, Kohei; Yajima, Kenro

A communication aid with human eyes only is proposed. A set of candidate character is displayed onto computer screen of relatively small and light Head Mount Display: HMD that is mounted on glasses of which user wears on. When user looks at a candidate character with his/hers left eye while right eye picture is taken with small and light web camera that also is mounted on the glasses. The proposed system can selects 81 characters with two layers of 9 by 9 character candidate image. Other than these there is another selective image including control keys and frequently use of sentences. By using image matching between previously acquired template image for each candidate character and the currently acquired image, the proposed system realizes that which character in the candidates is selected. By using blinking and fix one's eye on combine together, the proposed system recognizes that user determines the selected key from the candidates. The blinking detection method employs a morphologic filter to avoid misunderstanding of dark eye detection due to eyebrows and shadows. Thus user can input sentences. User also may edit the sentences and then the sentences are read with Text to Speech: TTS software tool. Thus the system allows support conversations between handicapped and disabled persons without voice and the others peoples because only the function required for conversation is human eyes. Also the proposed system can be used as an input system for wearable computing systems. Test results by the 6 different able persons show that the proposed system does work with acceptable speed, around 1.5 second / character.

Staining and peeling of the internal limiting membrane in the cat eye.

PubMed

Gandorfer, Arnd; Rohleder, Matthias; Charteris, David G; Sethi, Charanjit; Kampik, Anselm; Luthert, Philip

2005-11-01

To investigate the cat vitreomacular interface using trypan blue (TB) and indocyanine green (ICG) and to determine the validity of the cat model in terms of staining and peeling of the internal limiting membrane (ILM). Lensectomy and vitrectomy were performed in four eyes of two cats. The ILM of two eyes was stained with TB (0.15%). ILM peeling was performed in one eye. Two eyes were stained with ICG (0.5%). One eye was illuminated for 3 min. Light and transmission electron microscopy and confocal microscopy were performed. Clinically, both dyes stained the cat ILM similar to human ILM. TB staining resulted in a normal ultrastructure and antigenity of the retina. ILM peeling was associated with intraretinal bleeding. There were fragments of Müller cells adherent to the retinal side of the ILM, and Müller cell endfeet were ruptured and avulsed. ICG staining of the ILM followed by illumination caused severe inner retinal damage. ICG without illumination resulted in focal ILM detachments associated with tearing of Müller cell endfeet. The cat can be used as a model to study the effect of TB and ICG on the central area of the cat retina, as previous results from clinical and experimental postmortem settings in human eyes were confirmed in the current study. Peeling of the ILM as a sheet as performed in human macular surgery is not feasible. Differences in the ultrastructure of the ILM and a strong adhesion of the ILM to Müller cell endfeet may account for this observation.

Controlling a human-computer interface system with a novel classification method that uses electrooculography signals.

PubMed

Wu, Shang-Lin; Liao, Lun-De; Lu, Shao-Wei; Jiang, Wei-Ling; Chen, Shi-An; Lin, Chin-Teng

2013-08-01

Electrooculography (EOG) signals can be used to control human-computer interface (HCI) systems, if properly classified. The ability to measure and process these signals may help HCI users to overcome many of the physical limitations and inconveniences in daily life. However, there are currently no effective multidirectional classification methods for monitoring eye movements. Here, we describe a classification method used in a wireless EOG-based HCI device for detecting eye movements in eight directions. This device includes wireless EOG signal acquisition components, wet electrodes and an EOG signal classification algorithm. The EOG classification algorithm is based on extracting features from the electrical signals corresponding to eight directions of eye movement (up, down, left, right, up-left, down-left, up-right, and down-right) and blinking. The recognition and processing of these eight different features were achieved in real-life conditions, demonstrating that this device can reliably measure the features of EOG signals. This system and its classification procedure provide an effective method for identifying eye movements. Additionally, it may be applied to study eye functions in real-life conditions in the near future.

Multiconjugate adaptive optics applied to an anatomically accurate human eye model.

PubMed

Bedggood, P A; Ashman, R; Smith, G; Metha, A B

2006-09-04

Aberrations of both astronomical telescopes and the human eye can be successfully corrected with conventional adaptive optics. This produces diffraction-limited imagery over a limited field of view called the isoplanatic patch. A new technique, known as multiconjugate adaptive optics, has been developed recently in astronomy to increase the size of this patch. The key is to model atmospheric turbulence as several flat, discrete layers. A human eye, however, has several curved, aspheric surfaces and a gradient index lens, complicating the task of correcting aberrations over a wide field of view. Here we utilize a computer model to determine the degree to which this technology may be applied to generate high resolution, wide-field retinal images, and discuss the considerations necessary for optimal use with the eye. The Liou and Brennan schematic eye simulates the aspheric surfaces and gradient index lens of real human eyes. We show that the size of the isoplanatic patch of the human eye is significantly increased through multiconjugate adaptive optics.

Optical aberrations, retinal image quality and eye growth: Experimentation and modeling

NASA Astrophysics Data System (ADS)

Tian, Yibin

2007-12-01

Retinal image quality is important for normal eye growth. Optical aberrations are of interest for two reasons: first, they degrade retinal images; second, they might provide some cues to defocus. Higher than normal ocular aberrations have been previously associated with human myopia. However, these studies were cross-sectional in design, and only reported aberrations in terms of root mean square (RMS) errors of Zernike coefficients, a poor metric of optical quality. This dissertation presents results from investigations of ocular optical aberrations, retinal image quality and eye growth in chicks and humans. A number of techniques were utilized, including Shack-Hartmann aberrometry, high-frequency A-scan ultrasonography, ciliary nerve section (CNX), photorefractive keratectomy (PRK) as well as computer simulations and modeling. A technique to extract light scatter information from Shack-Hartmann images was also developed. The main findings of the dissertation are summarized below. In young chicks, most ocular aberrations decreased with growth in both normal and CNX eyes, and there were diurnal fluctuations in some aberrations. Modeling suggested active reduction in higher order aberrations (HOAs) during early development. Although CNX eyes manifested greater than normal HOAs, they showed near normal growth. Retinal image degradation varied greatly among individual eyes post-PRK in young chicks. Including light scatter information into analyses of retinal image quality better estimated the latter. Albino eyes showed more severe retinal image degradation than normal eyes, due to increased optical aberrations and light scatter, but their growth was similar to those of normal eyes, implying that they are relatively insensitive to retina image quality. Although the above results questioned the influence of optical aberrations on early ocular growth, some optical quality metrics, derived from optical aberrations data, could predict how much the eyes of young chicks subsequently elongated. The performance of some focus measures was very poor when non-defocus aberrations exceeded a certain level; presumably, these non-defocus aberrations might interfere with the eye's ability to interpret defocus. In anisomyopic human adults, more myopic eyes had larger anterior and vitreous chambers, greater astigmatism, and more positive spherical aberration. However, compared to isometropes, only interocular differences in spherical equivalent refractive errors were significantly increased.

Early light deprivation effects on human cone-driven retinal function.

PubMed

Esposito Veneruso, Paolo; Ziccardi, Lucia; Magli, Giulia; Parisi, Vincenzo; Falsini, Benedetto; Magli, Adriano

2017-03-01

To assess whether the early light deprivation induced by congenital cataract may influence the cone-driven retinal function in humans. Forty-one patients affected by congenital cataract (CC) who had undergone uncomplicated cataract extraction surgery and intraocular lens implant, and 14 healthy subjects (HS) were enrolled. All patients underwent complete ophthalmological and orthoptic evaluations and best-corrected visual acuity (BCVA) measurement; light-adapted full-field electroretinograms (ERG) and photopic negative responses (PhNR) were recorded to obtain a reliable measurement of the outer/inner retinal function and of the retinal ganglion cells' function respectively. Mean values of light-adapted ERG a- and b-wave and PhNR amplitude of CC eyes were significantly reduced and photopic ERG b-wave implicit time mean values were significantly delayed when compared to HS ones. When studying photopic ERG mean amplitudes at 5 ms, significant differences were found when comparing CC and control eyes. In CC eyes, statistically significant correlations were found between a- and b- wave amplitudes and PhNR amplitudes. No significant correlations were found between ERG parameters and BCVA, as well as between the age of CC patients at surgery and the time elapsed from lens extraction. No significant differences were found when functional parameters of bilateral and unilateral congenital cataract (uCC) eyes were compared, however uCC eyes showed significant differences when compared with contralateral healthy eyes. We found a significant impairment of cone-driven retinal responses in patients with a history of congenital cataract. These changes might result from the long-lasting effects of early light deprivation on the cone retinal pathways. Our findings support the relevance of retinal involvement in deficits induced by early light deprivation. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Electrical Microstimulation of the Superior Colliculus in Strabismic Monkeys

PubMed Central

Fleuriet, Jérome; Walton, Mark M. G.; Ono, Seiji; Mustari, Michael J.

2016-01-01

Purpose Visually guided saccades are disconjugate in human and nonhuman strabismic primates. The superior colliculus (SC) is a region of the brain topographically organized in visual and motor maps where the saccade goal is spatially coded. The present study was designed to investigate if a site of stimulation on the topographic motor map was evoking similar or different saccade vectors for each eye. Methods We used microelectrical stimulation (MS) of the SC in two strabismic (one esotrope and one exotrope) and two control macaques under binocular and monocular viewing conditions. We compared the saccade amplitudes and directions for each SC site and each condition independently of the fixating eye and then between each fixating eye. A comparison with disconjugacies of visually guided saccades was also performed. Results We observed different saccade vectors for the two eyes in strabismic monkeys, but conjugate saccades in normal monkeys. Evoked saccade vectors for the left eye when that eye was fixating the target were different from those of the right eye when it was fixating. The disconjugacies evoked by the MS were not identical but similar to those observed for visually guided saccades especially for the dominant eye. Conclusions Our results suggest that, in strabismus, the saccade generator does not interpret activation of a single location of the SC as the same desired displacement for each eye. This finding is important for advancing understanding of the development of neural circuits in strabismus. French Abstract PMID:27309621

The Convergent Evolution of Blue Iris Pigmentation in Primates Took Distinct Molecular Paths

PubMed Central

Meyer, Wynn K; Zhang, Sidi; Hayakawa, Sachiko; Imai, Hiroo; Przeworski, Molly

2013-01-01

How many distinct molecular paths lead to the same phenotype? One approach to this question has been to examine the genetic basis of convergent traits, which likely evolved repeatedly under a shared selective pressure. We investigated the convergent phenotype of blue iris pigmentation, which has arisen independently in four primate lineages: humans, blue-eyed black lemurs, Japanese macaques, and spider monkeys. Characterizing the phenotype across these species, we found that the variation within the blue-eyed subsets of each species occupies strongly overlapping regions of CIE L*a*b* color space. Yet whereas Japanese macaques and humans display continuous variation, the phenotypes of blue-eyed black lemurs and their sister species (whose irises are brown) occupy more clustered subspaces. Variation in an enhancer of OCA2 is primarily responsible for the phenotypic difference between humans with blue and brown irises. In the orthologous region, we found no variant that distinguishes the two lemur species or associates with quantitative phenotypic variation in Japanese macaques. Given the high similarity between the blue iris phenotypes in these species and that in humans, this finding implies that evolution has used different molecular paths to reach the same end. Am J Phys Anthropol 151:398–407, 2013.© 2013 Wiley Periodicals, Inc. PMID:23640739

Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo.

PubMed

Yamanari, Masahiro; Nagase, Satoko; Fukuda, Shinichi; Ishii, Kotaro; Tanaka, Ryosuke; Yasui, Takeshi; Oshika, Tetsuro; Miura, Masahiro; Yasuno, Yoshiaki

2014-05-01

The relationship between scleral birefringence and biometric parameters of human eyes in vivo is investigated. Scleral birefringence near the limbus of 21 healthy human eyes was measured using polarization-sensitive optical coherence tomography. Spherical equivalent refractive error, axial eye length, and intraocular pressure (IOP) were measured in all subjects. IOP and scleral birefringence of human eyes in vivo was found to have statistically significant correlations (r = -0.63, P = 0.002). The slope of linear regression was -2.4 × 10(-2) deg/μm/mmHg. Neither spherical equivalent refractive error nor axial eye length had significant correlations with scleral birefringence. To evaluate the direct influence of IOP to scleral birefringence, scleral birefringence of 16 ex vivo porcine eyes was measured under controlled IOP of 5-60 mmHg. In these ex vivo porcine eyes, the mean linear regression slope between controlled IOP and scleral birefringence was -9.9 × 10(-4) deg/μm/mmHg. In addition, porcine scleral collagen fibers were observed with second-harmonic-generation (SHG) microscopy. SHG images of porcine sclera, measured on the external surface at the superior side to the cornea, showed highly aligned collagen fibers parallel to the limbus. In conclusion, scleral birefringence of healthy human eyes was correlated with IOP, indicating that the ultrastructure of scleral collagen was correlated with IOP. It remains to show whether scleral collagen ultrastructure of human eyes is affected by IOP as a long-term effect.

Human pigmentation genes under environmental selection

PubMed Central

2012-01-01

Genome-wide association studies and comparative genomics have established major loci and specific polymorphisms affecting human skin, hair and eye color. Environmental changes have had an impact on selected pigmentation genes as populations have expanded into different regions of the globe. PMID:23110848

Non-mydriatic video ophthalmoscope to measure fast temporal changes of the human retina

NASA Astrophysics Data System (ADS)

Tornow, Ralf P.; Kolář, Radim; Odstrčilík, Jan

2015-07-01

The analysis of fast temporal changes of the human retina can be used to get insight to normal physiological behavior and to detect pathological deviations. This can be important for the early detection of glaucoma and other eye diseases. We developed a small, lightweight, USB powered video ophthalmoscope that allows taking video sequences of the human retina with at least 25 frames per second without dilating the pupil. Short sequences (about 10 s) of the optic nerve head (20° x 15°) are recorded from subjects and registered offline using two-stage process (phase correlation and Lucas-Kanade approach) to compensate for eye movements. From registered video sequences, different parameters can be calculated. Two applications are described here: measurement of (i) cardiac cycle induced pulsatile reflection changes and (ii) eye movements and fixation pattern. Cardiac cycle induced pulsatile reflection changes are caused by changing blood volume in the retina. Waveform and pulse parameters like amplitude and rise time can be measured in any selected areas within the retinal image. Fixation pattern ΔY(ΔX) can be assessed from eye movements during video acquisition. The eye movements ΔX[t], ΔY[t] are derived from image registration results with high temporal (40 ms) and spatial (1,86 arcmin) resolution. Parameters of pulsatile reflection changes and fixation pattern can be affected in beginning glaucoma and the method described here may support early detection of glaucoma and other eye disease.

High-speed adaptive optics line scan confocal retinal imaging for human eye.

PubMed

Lu, Jing; Gu, Boyu; Wang, Xiaolin; Zhang, Yuhua

2017-01-01

Continuous and rapid eye movement causes significant intraframe distortion in adaptive optics high resolution retinal imaging. To minimize this artifact, we developed a high speed adaptive optics line scan confocal retinal imaging system. A high speed line camera was employed to acquire retinal image and custom adaptive optics was developed to compensate the wave aberration of the human eye's optics. The spatial resolution and signal to noise ratio were assessed in model eye and in living human eye. The improvement of imaging fidelity was estimated by reduction of intra-frame distortion of retinal images acquired in the living human eyes with frame rates at 30 frames/second (FPS), 100 FPS, and 200 FPS. The device produced retinal image with cellular level resolution at 200 FPS with a digitization of 512×512 pixels/frame in the living human eye. Cone photoreceptors in the central fovea and rod photoreceptors near the fovea were resolved in three human subjects in normal chorioretinal health. Compared with retinal images acquired at 30 FPS, the intra-frame distortion in images taken at 200 FPS was reduced by 50.9% to 79.7%. We demonstrated the feasibility of acquiring high resolution retinal images in the living human eye at a speed that minimizes retinal motion artifact. This device may facilitate research involving subjects with nystagmus or unsteady fixation due to central vision loss.

Optical properties of the mouse eye

PubMed Central

Geng, Ying; Schery, Lee Anne; Sharma, Robin; Dubra, Alfredo; Ahmad, Kamran; Libby, Richard T.; Williams, David R.

2011-01-01

The Shack-Hartmann wavefront sensor (SHWS) spots upon which ocular aberration measurements depend have poor quality in mice due to light reflected from multiple retinal layers. We have designed and implemented a SHWS that can favor light from a specific retinal layer and measured monochromatic aberrations in 20 eyes from 10 anesthetized C57BL/6J mice. Using this instrument, we show that mice are myopic, not hyperopic as is frequently reported. We have also measured longitudinal chromatic aberration (LCA) of the mouse eye and found that it follows predictions of the water-filled schematic mouse eye. Results indicate that the optical quality of the mouse eye assessed by measurement of its aberrations is remarkably good, better for retinal imaging than the human eye. The dilated mouse eye has a much larger numerical aperture (NA) than that of the dilated human eye (0.5 NA vs. 0.2 NA), but it has a similar amount of root mean square (RMS) higher order aberrations compared to the dilated human eye. These measurements predict that adaptive optics based on this method of wavefront sensing will provide improvements in retinal image quality and potentially two times higher lateral resolution than that in the human eye. PMID:21483598

Gold internal standard correction for elemental imaging of soft tissue sections by LA-ICP-MS: element distribution in eye microstructures.

PubMed

Konz, Ioana; Fernández, Beatriz; Fernández, M Luisa; Pereiro, Rosario; González, Héctor; Alvarez, Lydia; Coca-Prados, Miguel; Sanz-Medel, Alfredo

2013-04-01

Laser ablation coupled to inductively coupled plasma mass spectrometry has been developed for the elemental imaging of Mg, Fe and Cu distribution in histological tissue sections of fixed eyes, embedded in paraffin, from human donors (cadavers). This work presents the development of a novel internal standard correction methodology based on the deposition of a homogeneous thin gold film on the tissue surface and the use of the (197)Au(+) signal as internal standard. Sample preparation (tissue section thickness) and laser conditions were carefully optimized, and internal normalisation using (197)Au(+) was compared with (13)C(+) correction for imaging applications. (24)Mg(+), (56)Fe(+) and (63)Cu(+) distributions were investigated in histological sections of the anterior segment of the eye (including the iris, ciliary body, cornea and trabecular meshwork) and were shown to be heterogeneously distributed along those tissue structures. Reproducibility was assessed by imaging different human eye sections from the same donor and from ten different eyes from adult normal donors, which showed that similar spatial maps were obtained and therefore demonstrate the analytical potential of using (197)Au(+) as internal standard. The proposed analytical approach could offer a robust tool with great practical interest for clinical studies, e.g. to investigate trace element distribution of metals and their alterations in ocular diseases.

[Analysis of an ophthalmic pathology cohort of human fetal eyes with regard to interesting findings].

PubMed

Herwig, M C; Müller, A M; Holz, F G; Loeffler, K U

2010-11-01

Information on the evaluation of prenatal ocular findings is sparse. This article provides an overview of the morphology in a cohort of human fetal eyes, with particular emphasis on interesting findings. The study investigated 216 eyes from 115 human fetuses. The majority of fetal eyes presented with a regular phenotype. Rarely, unexpected findings were discovered in fetuses with or without systemic malformations. Routine evaluation of fetal eyes reveals-albeit rarely-new aspects providing further knowledge and occasionally enabling the exact classification of syndromes.

Context effects on smooth pursuit and manual interception of a disappearing target.

PubMed

Kreyenmeier, Philipp; Fooken, Jolande; Spering, Miriam

2017-07-01

In our natural environment, we interact with moving objects that are surrounded by richly textured, dynamic visual contexts. Yet most laboratory studies on vision and movement show visual objects in front of uniform gray backgrounds. Context effects on eye movements have been widely studied, but it is less well known how visual contexts affect hand movements. Here we ask whether eye and hand movements integrate motion signals from target and context similarly or differently, and whether context effects on eye and hand change over time. We developed a track-intercept task requiring participants to track the initial launch of a moving object ("ball") with smooth pursuit eye movements. The ball disappeared after a brief presentation, and participants had to intercept it in a designated "hit zone." In two experiments ( n = 18 human observers each), the ball was shown in front of a uniform or a textured background that either was stationary or moved along with the target. Eye and hand movement latencies and speeds were similarly affected by the visual context, but eye and hand interception (eye position at time of interception, and hand interception timing error) did not differ significantly between context conditions. Eye and hand interception timing errors were strongly correlated on a trial-by-trial basis across all context conditions, highlighting the close relation between these responses in manual interception tasks. Our results indicate that visual contexts similarly affect eye and hand movements but that these effects may be short-lasting, affecting movement trajectories more than movement end points. NEW & NOTEWORTHY In a novel track-intercept paradigm, human observers tracked a briefly shown object moving across a textured, dynamic context and intercepted it with their finger after it had disappeared. Context motion significantly affected eye and hand movement latency and speed, but not interception accuracy; eye and hand position at interception were correlated on a trial-by-trial basis. Visual context effects may be short-lasting, affecting movement trajectories more than movement end points. Copyright © 2017 the American Physiological Society.

Multimodal instrument for high-sensitivity autofluorescence and spectral optical coherence tomography of the human eye fundus

PubMed Central

Komar, Katarzyna; Stremplewski, Patrycjusz; Motoczyńska, Marta; Szkulmowski, Maciej; Wojtkowski, Maciej

2013-01-01

In this paper we present a multimodal device for imaging fundus of human eye in vivo which combines functionality of autofluorescence by confocal SLO with Fourier domain OCT. Native fluorescence of human fundus was excited by modulated laser beam (λ = 473 nm, 20 MHz) and lock-in detection was applied resulting in improving sensitivity. The setup allows for acquisition of high resolution OCT and high contrast AF images using fluorescence excitation power of 50-65 μW without averaging consecutive images. Successful functioning of constructed device have been demonstrated for 8 healthy volunteers of different age ranging from 24 to 83 years old. PMID:24298426

An eye movement study for identification of suitable font characters for presentation on a computer screen.

PubMed

Banerjee, Jayeeta; Majumdar, Dhurjati; Majumdar, Deepti; Pal, Madhu Sudan

2010-06-01

We are experiencing a shifting of media: from the printed paper to the computer screen. This transition is modifying the process of how we read and understand a text. It is very difficult to conclude on suitability of font characters based upon subjective evaluation method only. Present study evaluates the effect of font type on human cognitive workload during perception of individual alphabets on a computer screen. Twenty six young subjects volunteered for this study. Here, subjects have been shown individual characters of different font types and their eye movements have been recorded. A binocular eye movement recorder was used for eye movement recording. The results showed that different eye movement parameters such as pupil diameter, number of fixations, fixation duration were less for font type Verdana. The present study recommends the use of font type Verdana for presentation of individual alphabets on various electronic displays in order to reduce cognitive workload.

Application of 3-Dimensional Printing Technology to Construct an Eye Model for Fundus Viewing Study

PubMed Central

Li, Xinhua; Gao, Zhishan; Yuan, Dongqing; Liu, Qinghuai

2014-01-01

Objective To construct a life-sized eye model using the three-dimensional (3D) printing technology for fundus viewing study of the viewing system. Methods We devised our schematic model eye based on Navarro's eye and redesigned some parameters because of the change of the corneal material and the implantation of intraocular lenses (IOLs). Optical performance of our schematic model eye was compared with Navarro's schematic eye and other two reported physical model eyes using the ZEMAX optical design software. With computer aided design (CAD) software, we designed the 3D digital model of the main structure of the physical model eye, which was used for three-dimensional (3D) printing. Together with the main printed structure, polymethyl methacrylate(PMMA) aspherical cornea, variable iris, and IOLs were assembled to a physical eye model. Angle scale bars were glued from posterior to periphery of the retina. Then we fabricated other three physical models with different states of ammetropia. Optical parameters of these physical eye models were measured to verify the 3D printing accuracy. Results In on-axis calculations, our schematic model eye possessed similar size of spot diagram compared with Navarro's and Bakaraju's model eye, much smaller than Arianpour's model eye. Moreover, the spherical aberration of our schematic eye was much less than other three model eyes. While in off- axis simulation, it possessed a bit higher coma and similar astigmatism, field curvature and distortion. The MTF curves showed that all the model eyes diminished in resolution with increasing field of view, and the diminished tendency of resolution of our physical eye model was similar to the Navarro's eye. The measured parameters of our eye models with different status of ametropia were in line with the theoretical value. Conclusions The schematic eye model we designed can well simulate the optical performance of the human eye, and the fabricated physical one can be used as a tool in fundus range viewing research. PMID:25393277

Application of 3-dimensional printing technology to construct an eye model for fundus viewing study.

PubMed

Xie, Ping; Hu, Zizhong; Zhang, Xiaojun; Li, Xinhua; Gao, Zhishan; Yuan, Dongqing; Liu, Qinghuai

2014-01-01

To construct a life-sized eye model using the three-dimensional (3D) printing technology for fundus viewing study of the viewing system. We devised our schematic model eye based on Navarro's eye and redesigned some parameters because of the change of the corneal material and the implantation of intraocular lenses (IOLs). Optical performance of our schematic model eye was compared with Navarro's schematic eye and other two reported physical model eyes using the ZEMAX optical design software. With computer aided design (CAD) software, we designed the 3D digital model of the main structure of the physical model eye, which was used for three-dimensional (3D) printing. Together with the main printed structure, polymethyl methacrylate(PMMA) aspherical cornea, variable iris, and IOLs were assembled to a physical eye model. Angle scale bars were glued from posterior to periphery of the retina. Then we fabricated other three physical models with different states of ammetropia. Optical parameters of these physical eye models were measured to verify the 3D printing accuracy. In on-axis calculations, our schematic model eye possessed similar size of spot diagram compared with Navarro's and Bakaraju's model eye, much smaller than Arianpour's model eye. Moreover, the spherical aberration of our schematic eye was much less than other three model eyes. While in off- axis simulation, it possessed a bit higher coma and similar astigmatism, field curvature and distortion. The MTF curves showed that all the model eyes diminished in resolution with increasing field of view, and the diminished tendency of resolution of our physical eye model was similar to the Navarro's eye. The measured parameters of our eye models with different status of ametropia were in line with the theoretical value. The schematic eye model we designed can well simulate the optical performance of the human eye, and the fabricated physical one can be used as a tool in fundus range viewing research.

Design of optical system for binocular fundus camera.

PubMed

Wu, Jun; Lou, Shiliang; Xiao, Zhitao; Geng, Lei; Zhang, Fang; Wang, Wen; Liu, Mengjia

2017-12-01

A non-mydriasis optical system for binocular fundus camera has been designed in this paper. It can capture two images of the same fundus retinal region from different angles at the same time, and can be used to achieve three-dimensional reconstruction of fundus. It is composed of imaging system and illumination system. In imaging system, Gullstrand Le Grand eye model is used to simulate normal human eye, and Schematic eye model is used to test the influence of ametropia in human eye on imaging quality. Annular aperture and black dot board are added into illumination system, so that the illumination system can eliminate stray light produced by corneal-reflected light and omentoscopic lens. Simulation results show that MTF of each visual field at the cut-off frequency of 90lp/mm is greater than 0.2, system distortion value is -2.7%, field curvature is less than 0.1 mm, radius of Airy disc is 3.25um. This system has a strong ability of chromatic aberration correction and focusing, and can image clearly for human fundus in which the range of diopters is from -10 D to +6 D(1 D = 1 m -1 ).

An eye tracking system for monitoring face scanning patterns reveals the enhancing effect of oxytocin on eye contact in common marmosets.

PubMed

Kotani, Manato; Shimono, Kohei; Yoneyama, Toshihiro; Nakako, Tomokazu; Matsumoto, Kenji; Ogi, Yuji; Konoike, Naho; Nakamura, Katsuki; Ikeda, Kazuhito

2017-09-01

Eye tracking systems are used to investigate eyes position and gaze patterns presumed as eye contact in humans. Eye contact is a useful biomarker of social communication and known to be deficient in patients with autism spectrum disorders (ASDs). Interestingly, the same eye tracking systems have been used to directly compare face scanning patterns in some non-human primates to those in human. Thus, eye tracking is expected to be a useful translational technique for investigating not only social attention and visual interest, but also the effects of psychiatric drugs, such as oxytocin, a neuropeptide that regulates social behavior. In this study, we report on a newly established method for eye tracking in common marmosets as unique New World primates that, like humans, use eye contact as a mean of communication. Our investigation was aimed at characterizing these primates face scanning patterns and evaluating the effects of oxytocin on their eye contact behavior. We found that normal common marmosets spend more time viewing the eyes region in common marmoset's picture than the mouth region or a scrambled picture. In oxytocin experiment, the change in eyes/face ratio was significantly greater in the oxytocin group than in the vehicle group. Moreover, oxytocin-induced increase in the change in eyes/face ratio was completely blocked by the oxytocin receptor antagonist L-368,899. These results indicate that eye tracking in common marmosets may be useful for evaluating drug candidates targeting psychiatric conditions, especially ASDs. Copyright © 2017 Elsevier Ltd. All rights reserved.

A 2D correlation Raman spectroscopy analysis of a human cataractous lens

NASA Astrophysics Data System (ADS)

Sacharz, Julia; Wesełucha-Birczyńska, Aleksandra; Paluszkiewicz, Czesława; Chaniecki, Piotr; Błażewicz, Marta

2016-11-01

This work is a continuation of our study of a cataractous human eye lens removed after phacoemulsification surgery. There are clear differences in the lens colors that allowed for distinguishing two opaque phases in the obtained biological material: the white- and yellow-phase. The Raman spectroscopy and 2D correlation spectroscopy method were used to trace a pathologically altered human cataract lens at a molecular level. Although the Raman spectra of these two phases are relatively similar, taking advantage of 2D correlation, and considering time as an external perturbation, the synchronous and asynchronous spectra were obtained showing completely different patterns. Prominent synchronous auto-peaks appear at 3340, 2920, 1736, 1665 and 1083 cm-1 for the white-, and at 2929 and 1670 cm-1 for the yellow phase. The white phase is characterized by intensive asynchronous peaks at -(2936, 3360), -(1650, 1674) and +(1620,1678). The modifications in the water contained in the white phase structure are ahead of the changes in the protein (CH3-groups), furthermore changes in β-conformation are asynchronous with respect to the α-structure. The yellow phase demonstrates asynchronous peaks: +(2857, 2928), +(1645,1673), +(1663, 1679), and +(1672,1707). These illustrate concomitant modifications in the β- and unordered conformation. Both forms of cataractous human eye lens, white- and yellow-phases, are degenerate forms of the eye lens proteins, both are arranged in a different way. The main differences are observed for the amide I, methyl, methylene and Osbnd H vibrational band region. The effect of Asp, Glu and Tyr amino acids in cataractous lens transformations was observed.

Using Eye Movement to Control a Computer: A Design for a Lightweight Electro-Oculogram Electrode Array and Computer Interface

PubMed Central

Iáñez, Eduardo; Azorin, Jose M.; Perez-Vidal, Carlos

2013-01-01

This paper describes a human-computer interface based on electro-oculography (EOG) that allows interaction with a computer using eye movement. The EOG registers the movement of the eye by measuring, through electrodes, the difference of potential between the cornea and the retina. A new pair of EOG glasses have been designed to improve the user's comfort and to remove the manual procedure of placing the EOG electrodes around the user's eye. The interface, which includes the EOG electrodes, uses a new processing algorithm that is able to detect the gaze direction and the blink of the eyes from the EOG signals. The system reliably enabled subjects to control the movement of a dot on a video screen. PMID:23843986

Spatial scale and distribution of neurovascular signals underlying decoding of orientation and eye of origin from fMRI data

PubMed Central

Harrison, Charlotte; Jackson, Jade; Oh, Seung-Mock; Zeringyte, Vaida

2016-01-01

Multivariate pattern analysis of functional magnetic resonance imaging (fMRI) data is widely used, yet the spatial scales and origin of neurovascular signals underlying such analyses remain unclear. We compared decoding performance for stimulus orientation and eye of origin from fMRI measurements in human visual cortex with predictions based on the columnar organization of each feature and estimated the spatial scales of patterns driving decoding. Both orientation and eye of origin could be decoded significantly above chance in early visual areas (V1–V3). Contrary to predictions based on a columnar origin of response biases, decoding performance for eye of origin in V2 and V3 was not significantly lower than that in V1, nor did decoding performance for orientation and eye of origin differ significantly. Instead, response biases for both features showed large-scale organization, evident as a radial bias for orientation, and a nasotemporal bias for eye preference. To determine whether these patterns could drive classification, we quantified the effect on classification performance of binning voxels according to visual field position. Consistent with large-scale biases driving classification, binning by polar angle yielded significantly better decoding performance for orientation than random binning in V1–V3. Similarly, binning by hemifield significantly improved decoding performance for eye of origin. Patterns of orientation and eye preference bias in V2 and V3 showed a substantial degree of spatial correlation with the corresponding patterns in V1, suggesting that response biases in these areas originate in V1. Together, these findings indicate that multivariate classification results need not reflect the underlying columnar organization of neuronal response selectivities in early visual areas. NEW & NOTEWORTHY Large-scale response biases can account for decoding of orientation and eye of origin in human early visual areas V1–V3. For eye of origin this pattern is a nasotemporal bias; for orientation it is a radial bias. Differences in decoding performance across areas and stimulus features are not well predicted by differences in columnar-scale organization of each feature. Large-scale biases in extrastriate areas are spatially correlated with those in V1, suggesting biases originate in primary visual cortex. PMID:27903637

SU-G-IeP4-09: Method of Human Eye Aberration Measurement Using Plenoptic Camera Over Large Field of View

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Yang; Wang, Ruixing; Ma, Haotong

Purpose: The measurement based on Shack-Hartmann wave-front sensor(WFS), obtaining both the high and low order wave-front aberrations simultaneously and accurately, has been applied in the detection of human eyes aberration in recent years. However, Its application is limited by the small field of view (FOV), slight eye movement leads the optical bacon image exceeds the lenslet array which result in uncertain detection error. To overcome difficulties of precise eye location, the capacity of detecting eye wave-front aberration over FOV much larger than simply a single conjugate Hartmann WFS accurately and simultaneously is demanded. Methods: Plenoptic camera’s lenslet array subdivides themore » aperture light-field in spatial frequency domain, capture the 4-D light-field information. Data recorded by plenoptic cameras can be used to extract the wave-front phases associated to the eyes aberration. The corresponding theoretical model and simulation system is built up in this article to discuss wave-front measurement performance when utilizing plenoptic camera as wave-front sensor. Results: The simulation results indicate that the plenoptic wave-front method can obtain both the high and low order eyes wave-front aberration with the same accuracy as conventional system in single visual angle detectionand over FOV much larger than simply a single conjugate Hartmann systems. Meanwhile, simulation results show that detection of eye aberrations wave-front in different visual angle can be achieved effectively and simultaneously by plenoptic method, by both point and extended optical beacon from the eye. Conclusion: Plenoptic wave-front method possesses the feasibility in eye aberrations wave-front detection. With larger FOV, the method can effectively reduce the detection error brought by imprecise eye location and simplify the eye aberrations wave-front detection system comparing with which based on Shack-Hartmann WFS. Unique advantage of the plenoptic method lies in obtaining wave-front in different visual angle simultaneously, which provides an approach in building up 3-D model of eye refractor tomographically. Funded by the key Laboratory of High Power Laser and Physics, CAS Research Project of National University of Defense Technology No. JC13-07-01; National Natural Science Foundation of China No. 61205144.« less

The Advanced Human Eye Model (AHEM): a personal binocular eye modeling system inclusive of refraction, diffraction, and scatter.

PubMed

Donnelly, William

2008-11-01

To present a commercially available software tool for creating eye models to assist the development of ophthalmic optics and instrumentation, simulate ailments or surgery-induced changes, explore vision research questions, and provide assistance to clinicians in planning treatment or analyzing clinical outcomes. A commercially available eye modeling system was developed, the Advanced Human Eye Model (AHEM). Two mainstream optical software engines, ZEMAX (ZEMAX Development Corp) and ASAP (Breault Research Organization), were used to construct a similar software eye model and compared. The method of using the AHEM is described and various eye modeling scenarios are created. These scenarios consist of retinal imaging of targets and sources; optimization capability; spectacles, contact lens, and intraocular lens insertion and correction; Zernike surface deformation on the cornea; cataract simulation and scattering; a gradient index lens; a binocular mode; a retinal implant; system import/export; and ray path exploration. Similarity of the two different optical software engines showed validity to the mechanism of the AHEM. Metrics and graphical data are generated from the various modeling scenarios particular to their input specifications. The AHEM is a user-friendly commercially available software tool from Breault Research Organization, which can assist the design of ophthalmic optics and instrumentation, simulate ailments or refractive surgery-induced changes, answer vision research questions, or assist clinicians in planning treatment or analyzing clinical outcomes.

Micrometric Control of the Optics of the Human Eye: Environment or Genes?

PubMed

Tabernero, Juan; Hervella, Lucía; Benito, Antonio; Colodro-Conde, Lucía; Ordoñana, Juan R; Ruiz-Sanchez, Marcos; Marín, José María; Artal, Pablo

2017-04-01

The human eye has typically more optical aberrations than conventional artificial optical systems. While the lower order modes (defocus and astigmatism) are well studied, our purpose is to explore the influence of genes versus the environment on the higher order aberrations of the optical components of the eye. We have performed a classical twin study in a sample from the Region of Murcia (Spain). Optical aberrations using a Hartmann-Shack sensor (AOnEye Voptica SL, Murcia, Spain) and corneal aberrations (using corneal topography data) were measured in 138 eyes corresponding to 69 twins; 36 monozygotic (MZ) and 33 dizygotic (DZ) pairs (age 55 years, SD 7 years). Intraclass correlation coefficients (ICCs) were used to estimate how strongly aberrations of twins resemble each other, and genetic models were fitted to quantify heritability in the selected phenotypes. Genes had a significant influence in the variance of most of the higher order aberration terms (heritability from 40% to 70%). This genetic influence was observed similarly in both cornea and complete eye aberrations. Additionally, the compensation factor of spherical aberration in the eye (i.e., how much corneal spherical aberration was compensated by internal spherical aberration) was found under genetic influence (heritability of 68%). There is a significant genetic contribution to the variance of aberrations of the eye, not only at macroscopic levels, as in myopia or astigmatism, but also at microscopic levels, where a few micrometers changes in surface topography can produce a large difference in the value of the optical aberrations.

Biobanking of Human Retinas: The Next Big Leap for Eye Banks?

PubMed Central

Lužnik, Zala; Parekh, Mohit; Bertolin, Marina; Griffoni, Carlo; Ponzin, Diego

2015-01-01

Summary Retinal degenerative diseases are one of the main clinical causes of incurable and severe visional impairment. Thus, extensive research effort is put into the development of new causal therapeutic options. Promisingly, a number of studies showed regenerative capacity in specific retinal regions (the ciliary epithelium, retinal pigmented epithelium, iris, and Müller glia cells). However, most recent research studies are based on animal models or in vitro cultured cells, probably because of the limited availability of human posterior eye tissues (vitreous, retina, and choroid). To address this, we showed in our previous reports that eye banks with large numbers of globes collected yearly could set up biorepositories/biobanks where these precious tissues are isolated, quality controlled, and finally stored for scientists and clinicians wanting to access human tissues and test their own hypotheses. These precious human posterior eye tissues could be used for further research purposes, epidemiological studies, and target validation of newly developed drugs. In addition, this could be a promising and challenging option to retrieve potential retinal stem and progenitor cells from different parts of the retina and could be a breakthrough in the future delivery of ex vivo prepared customized (histocompatible) retinal tissue on scaffolds for transplantation purposes. In this Perspective, we will consider how the biorepositories could influence the future strategies for retinal stem cell therapies. Significance Retinal degenerative diseases are one of the main causes of severe vision impairment and regenerative medicine is attracting much attention as a potential therapy. Although highly desirable, the reactivation and proliferation of endogenous stem cells in vivo is not sufficient to generate enough cells to restore visual function after retinal injury. Thus, the replacement of exogenously derived normal donor cells is a promising solution. The challenge is to develop therapies with sufficient amounts of cells being harvested or expanded from donor tissues. Eye banks could overcome this issue by harvesting endogenous adult retinal stem cells from different donors. PMID:26032747

Effects of intraocular lenses with different diopters on chromatic aberrations in human eye models.

PubMed

Song, Hui; Yuan, Xiaoyong; Tang, Xin

2016-01-11

In this study, the effects of intraocular lenses (IOLs) with different diopters (D) on chromatic aberration were investigated in human eye models, and the influences of the central thickness of IOLs on chromatic aberration were compared. A Liou-Brennan-based IOL eye model was constructed using ZEMAX optical design software. Spherical IOLs with different diopters (AR40e, AMO Company, USA) were implanted; modulation transfer function (MTF) values at 3 mm of pupil diameter and from 0 to out-of-focus blur were collected and graphed. MTF values, measured at 555 nm of monochromatic light under each spatial frequency, were significantly higher than the values measured at 470 to 650 nm of polychromatic light. The influences of chromatic aberration on MTF values decreased with the increase in IOL diopter when the spatial frequency was ≤12 c/d, while increased effects were observed when the spatial frequency was ≥15 c/d. The MTF values of each IOL eye model were significantly lower than the MTF values of the Liou-Brennan eye models when measured at 555 nm of monochromatic light and at 470 to 650 nm of polychromatic light. The MTF values were also found to be increased with the increase in IOL diopter. With higher diopters of IOLs, the central thickness increased accordingly, which could have created increased chromatic aberration and decreased the retinal image quality. To improve the postoperative visual quality, IOLs with lower chromatic aberration should be selected for patients with short axial lengths.

Adaptive optics with a magnetic deformable mirror: applications in the human eye

NASA Astrophysics Data System (ADS)

Fernandez, Enrique J.; Vabre, Laurent; Hermann, Boris; Unterhuber, Angelika; Povazay, Boris; Drexler, Wolfgang

2006-10-01

A novel deformable mirror using 52 independent magnetic actuators (MIRAO 52, Imagine Eyes) is presented and characterized for ophthalmic applications. The capabilities of the device to reproduce different surfaces, in particular Zernike polynomials up to the fifth order, are investigated in detail. The study of the influence functions of the deformable mirror reveals a significant linear response with the applied voltage. The correcting device also presents a high fidelity in the generation of surfaces. The ranges of production of Zernike polynomials fully cover those typically found in the human eye, even for the cases of highly aberrated eyes. Data from keratoconic eyes are confronted with the obtained ranges, showing that the deformable mirror is able to compensate for these strong aberrations. Ocular aberration correction with polychromatic light, using a near Gaussian spectrum of 130 nm full width at half maximum centered at 800 nm, in five subjects is accomplished by simultaneously using the deformable mirror and an achromatizing lens, in order to compensate for the monochromatic and chromatic aberrations, respectively. Results from living eyes, including one exhibiting 4.66 D of myopia and a near pathologic cornea with notable high order aberrations, show a practically perfect aberration correction. Benefits and applications of simultaneous monochromatic and chromatic aberration correction are finally discussed in the context of retinal imaging and vision.

Adaptive Optics Analysis of Visual Benefit with Higher-order Aberrations Correction of Human Eye - Poster Paper

NASA Astrophysics Data System (ADS)

Xue, Lixia; Dai, Yun; Rao, Xuejun; Wang, Cheng; Hu, Yiyun; Liu, Qian; Jiang, Wenhan

2008-01-01

Higher-order aberrations correction can improve visual performance of human eye to some extent. To evaluate how much visual benefit can be obtained with higher-order aberrations correction we developed an adaptive optics vision simulator (AOVS). Dynamic real time optimized modal compensation was used to implement various customized higher-order ocular aberrations correction strategies. The experimental results indicate that higher-order aberrations correction can improve visual performance of human eye comparing with only lower-order aberration correction but the improvement degree and higher-order aberration correction strategy are different from each individual. Some subjects can acquire great visual benefit when higher-order aberrations were corrected but some subjects acquire little visual benefit even though all higher-order aberrations were corrected. Therefore, relative to general lower-order aberrations correction strategy, customized higher-order aberrations correction strategy is needed to obtain optimal visual improvement for each individual. AOVS provides an effective tool for higher-order ocular aberrations optometry for customized ocular aberrations correction.

Intraocular distribution of melanin in human, monkey, rabbit, minipig and dog eyes.

PubMed

Durairaj, Chandrasekar; Chastain, James E; Kompella, Uday B

2012-05-01

The purpose of this study was to quantify the melanin pigment content in sclera, choroid-RPE, and retina, three tissues encountered during transscleral drug delivery to the vitreous, in human, rabbit, monkey, minipig, and dog models. Strain differences were assessed in NZW × NZR F1 and Dutch belted rabbits and Yucatan and Gottingen minipigs. The choroid-RPE and retina tissues were divided into central (posterior pole area) and peripheral (away from posterior pole) regions while the sclera was analyzed without such division. Melanin content in the tissues was analyzed using a colorimetric assay. In all species the rank order for pigment content was: choroid-RPE >retina ≥ sclera, except in humans, where scleral melanin levels were higher than retina and central choroid. The melanin content in a given tissue differed between species. Further, while the peripheral tissue pigment levels tended to be generally higher compared to the central regions, these differences were significant in human in the case of choroid-RPE and in human, monkey, and dogs in the case of retina. Strain difference was observed only in the central choroid-RPE region of rabbits (NZW × NZR F1 >Dutch Belted). Species, strain, and regional differences exist in the melanin pigment content in the tissues of the posterior segment of the eye, with Gottingen minipig being closest to humans among the animals assessed. These differences in melanin content might contribute to differences in drug binding, delivery, and toxicity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Randomised masked trial of the clinical safety and tolerability of MGO Manuka Honey eye cream for the management of blepharitis

PubMed Central

Craig, Jennifer P; Wang, Michael T M; Ganesalingam, Kalaivarny; Rupenthal, Ilva D; Swift, Simon; Loh, Chee Seang; Te Weehi, Leah; Cheung, Isabella M Y; Watters, Grant A

2017-01-01

Objective To assess the clinical safety and tolerability of a novel MGO Manuka Honey microemulsion (MHME) eye cream for the management of blepharitis in human subjects. Methods and analysis Twenty-five healthy subjects were enrolled in a prospective, randomised, paired-eye, investigator-masked trial. The MHME eye cream (Manuka Health New Zealand) was applied to the closed eyelids of one eye (randomised) overnight for 2 weeks. LogMAR visual acuity, eyelid irritation symptoms, ocular surface characteristics and tear film parameters were assessed at baseline, day 7 and day 14. Expression of markers of ocular surface inflammation (matrix metalloproteinase-9 and interleukin-6) and goblet cell function (MUC5AC) were quantified using impression cytology at baseline and day 14. Results There were no significant changes in visual acuity, eyelid irritation symptoms, ocular surface characteristics, tear film parameters and inflammatory marker expression during the 2-week treatment period in treated and control eyes (all p>0.05), and measurements did not differ significantly between eyes (all p>0.05). No major adverse events were reported. Two subjects experienced transient ocular stinging, presumably due to migration of the product into the eye, which resolved following aqueous irrigation. Conclusion The MHME eye cream application was found to be well tolerated in healthy human subjects and was not associated with changes in visual acuity, ocular surface characteristics, tear film parameters, expression of markers of inflammation or goblet cell function. The findings support future clinical efficacy trials in patients with blepharitis. Trial registration number ACTRN12616000540415 PMID:29354710

Real-Time Detection and Measurement of Eye Features from Color Images

PubMed Central

Borza, Diana; Darabant, Adrian Sergiu; Danescu, Radu

2016-01-01

The accurate extraction and measurement of eye features is crucial to a variety of domains, including human-computer interaction, biometry, and medical research. This paper presents a fast and accurate method for extracting multiple features around the eyes: the center of the pupil, the iris radius, and the external shape of the eye. These features are extracted using a multistage algorithm. On the first stage the pupil center is localized using a fast circular symmetry detector and the iris radius is computed using radial gradient projections, and on the second stage the external shape of the eye (of the eyelids) is determined through a Monte Carlo sampling framework based on both color and shape information. Extensive experiments performed on a different dataset demonstrate the effectiveness of our approach. In addition, this work provides eye annotation data for a publicly-available database. PMID:27438838

Mucin-type O-glycans in Tears of Normal Subjects and Patients with Non-Sjögren’s Dry Eye

PubMed Central

Guzman-Aranguez, Ana; Mantelli, Flavio; Argüeso, Pablo

2009-01-01

Purpose O-linked carbohydrates (O-glycans) contribute to the hydrophilic character of mucins in mucosal tissues. This study aimed to identify the repertoire of O-glycans in the tear film, and the glycosyltransferases associated with their biosynthesis, in normal subjects and patients with non-Sjögren’s dry eye. Methods Human tear fluid was collected from the inferior conjunctival fornix. O-glycans were released by hydrazinolysis, labeled with 2-aminobenzamide, and analyzed by fluorometric, high-performance liquid chromatography (HPLC) coupled with exoglycosidase digestions. O-glycan structures identified in tears were related to potential biosynthetic pathways in human conjunctival epithelium using a glycogene microarray database. Lectin-binding analyses were performed using agglutinins from Arachis hypogaea, Maackia amurensis, and Sambucus nigra. Results The O-glycan profile of human tears consisted primarily of core 1 (Galβ1-3GalNAcα1-Ser/Thr)-based structures. Mono-sialyl O-glycans represented approximately 66% of the glycan pool, being α2-6-sialyl core 1 the predominant O-glycan structure in human tears (48%). Four families of glycosyltranferases potentially related to the biosynthesis of these structures were identified in human conjunctiva. These included thirteen polypeptide-GalNAc-transferases (GALNT), the core 1 β-3-galactosyltransferase (T-synthase), three α2-6-sialyltransferases (ST6GalNAc), and two α2-3-sialyltransferases (ST3Gal). No significant differences in total amount of O-glycans were detected between tears of normal subjects and dry eye patients, by HPLC and lectin blot. Likewise, no differences in glycosyltransferase expression were found by glycogene microarray. Conclusions This study identifies the most common mucin-type O-glycans in human tears and their expected biosynthetic pathways in ocular surface epithelia. Patients with non-Sjögren’s dry eye show no alterations in composition and amount of O-glycans in the tear fluid. PMID:19407012

Intraocular lens based on double-liquid variable-focus lens.

PubMed

Peng, Runling; Li, Yifan; Hu, Shuilan; Wei, Maowei; Chen, Jiabi

2014-01-10

In this work, the crystalline lens in the Gullstrand-Le Grand human eye model is replaced by a double-liquid variable-focus lens, the structure data of which are based on theoretical analysis and experimental results. When the pseudoaphakic eye is built in Zemax, aspherical surfaces are introduced to the double-liquid variable-focus lens to reduce the axial spherical aberration existent in the system. After optimization, the zoom range of the pseudoaphakic eye greatly exceeds that of normal human eyes, and the spot size on an image plane basically reaches the normal human eye's limit of resolution.

Scanning mid-IR laser apparatus with eye tracking for refractive surgery

NASA Astrophysics Data System (ADS)

Telfair, William B.; Yoder, Paul R., Jr.; Bekker, Carsten; Hoffman, Hanna J.; Jensen, Eric F.

1999-06-01

A robust, real-time, dynamic eye tracker has been integrated with the short pulse mid-infrared laser scanning delivery system previously described. This system employs a Q- switched Nd:YAG laser pumped optical parametric oscillator operating at 2.94 micrometers. Previous ablation studies on human cadaver eyes and in-vivo cat eyes demonstrated very smooth ablations with extremely low damage levels similar to results with an excimer. A 4-month healing study with cats indicated no adverse healing effects. In order to treat human eyes, the tracker is required because the eyes move during the procedure due to both voluntary and involuntary motions such as breathing, heartbeat, drift, loss of fixation, saccades and microsaccades. Eye tracking techniques from the literature were compared. A limbus tracking system was best for this application. Temporal and spectral filtering techniques were implemented to reduce tracking errors, reject stray light, and increase signal to noise ratio. The expanded-capability system (IRVision AccuScan 2000 Laser System) has been tested in the lab on simulated eye targets, glass eyes, cadaver eyes, and live human subjects. Circular targets ranging from 10-mm to 14-mm diameter were successfully tracked. The tracker performed beyond expectations while the system performed myopic photorefractive keratectomy procedures on several legally blind human subjects.

An ocular biomechanic model for dynamic simulation of different eye movements.

PubMed

Iskander, J; Hossny, M; Nahavandi, S; Del Porto, L

2018-04-11

Simulating and analysing eye movement is useful for assessing visual system contribution to discomfort with respect to body movements, especially in virtual environments where simulation sickness might occur. It can also be used in the design of eye prosthesis or humanoid robot eye. In this paper, we present two biomechanic ocular models that are easily integrated into the available musculoskeletal models. The model was previously used to simulate eye-head coordination. The models are used to simulate and analyse eye movements. The proposed models are based on physiological and kinematic properties of the human eye. They incorporate an eye-globe, orbital suspension tissues and six muscles with their connective tissues (pulleys). Pulleys were incorporated in rectus and inferior oblique muscles. The two proposed models are the passive pulleys and the active pulleys models. Dynamic simulations of different eye movements, including fixation, saccade and smooth pursuit, are performed to validate both models. The resultant force-length curves of the models were similar to the experimental data. The simulation results show that the proposed models are suitable to generate eye movement simulations with results comparable to other musculoskeletal models. The maximum kinematic root mean square error (RMSE) is 5.68° and 4.35° for the passive and active pulley models, respectively. The analysis of the muscle forces showed realistic muscle activation with increased muscle synergy in the active pulley model. Copyright © 2018 Elsevier Ltd. All rights reserved.

Genetic variation in CD38 and breastfeeding experience interact to impact infants’ attention to social eye cues

PubMed Central

Krol, Kathleen M.; Monakhov, Mikhail; Lai, Poh San; Ebstein, Richard P.; Grossmann, Tobias

2015-01-01

Attending to emotional information conveyed by the eyes is an important social skill in humans. The current study examined this skill in early development by measuring attention to eyes while viewing emotional faces in 7-mo-old infants. In particular, we investigated individual differences in infant attention to eyes in the context of genetic variation (CD38 rs3796863 polymorphism) and experiential variation (exclusive breastfeeding duration) related to the oxytocin system. Our results revealed that, whereas infants at this age show a robust fear bias (increased attention to fearful eyes), their attention to angry and happy eyes varies as a function of exclusive breastfeeding experience and genetic variation in CD38. Specifically, extended exclusive breastfeeding duration selectively enhanced looking preference to happy eyes and decreased looking to angry eyes. Importantly, however, this interaction was impacted by CD38 variation, such that only the looking preferences of infants homozygous for the C allele of rs3796863 were affected by breastfeeding experience. This genotype has been associated with reduced release of oxytocin and higher rates of autism. In contrast, infants with the CA/AA genotype showed similar looking preferences regardless of breastfeeding exposure. Thus, differences in the sensitivity to emotional eyes may be linked to an interaction between the endogenous (CD38) and exogenous (breastfeeding) availability of oxytocin. These findings underline the importance of maternal care and the oxytocin system in contributing to the early development of responding to social eye cues. PMID:26371313

Effect of Phenylephrine on the Accommodative System

PubMed Central

Del Águila-Carrasco, Antonio J.; Bernal-Molina, Paula; Ferrer-Blasco, Teresa; López-Gil, Norberto; Montés-Micó, Robert

2016-01-01

Accommodation is controlled by the action of the ciliary muscle and mediated primarily by parasympathetic input through postganglionic fibers that originate from neurons in the ciliary and pterygopalatine ganglia. During accommodation the pupil constricts to increase the depth of focus of the eye and improve retinal image quality. Researchers have traditionally faced the challenge of measuring the accommodative properties of the eye through a small pupil and thus have relied on pharmacological agents to dilate the pupil. Achieving pupil dilation (mydriasis) without affecting the accommodative ability of the eye (cycloplegia) could be useful in many clinical and research contexts. Phenylephrine hydrochloride (PHCl) is a sympathomimetic agent that is used clinically to dilate the pupil. Nevertheless, first investigations suggested some loss of functional accommodation in the human eye after PHCl instillation. Subsequent studies, based on different measurement procedures, obtained contradictory conclusions, causing therefore an unexpected controversy that has been spread almost to the present days. This manuscript reviews and summarizes the main research studies that have been performed to analyze the effect of PHCl on the accommodative system and provides clear conclusions that could help clinicians know the real effects of PHCl on the accommodative system of the human eye. PMID:28053778

NEIBank: Genomics and bioinformatics resources for vision research

PubMed Central

Peterson, Katherine; Gao, James; Buchoff, Patee; Jaworski, Cynthia; Bowes-Rickman, Catherine; Ebright, Jessica N.; Hauser, Michael A.; Hoover, David

2008-01-01

NEIBank is an integrated resource for genomics and bioinformatics in vision research. It includes expressed sequence tag (EST) data and sequence-verified cDNA clones for multiple eye tissues of several species, web-based access to human eye-specific SAGE data through EyeSAGE, and comprehensive, annotated databases of known human eye disease genes and candidate disease gene loci. All expression- and disease-related data are integrated in EyeBrowse, an eye-centric genome browser. NEIBank provides a comprehensive overview of current knowledge of the transcriptional repertoires of eye tissues and their relation to pathology. PMID:18648525

Wavelength-dependent ultraviolet induction of cyclobutane pyrimidine dimers in the human cornea.

PubMed

Mallet, Justin D; Rochette, Patrick J

2013-08-01

Exposition to ultraviolet (UV) light is involved in the initiation and the progression of skin cancer. The genotoxicity of UV light is mainly attributed to the induction of cyclobutane pyrimidine dimers (CPDs), the most abundant DNA damage generated by all UV types (UVA, B and C). The human cornea is also exposed to the harmful UV radiations, but no UV-related neoplasm has been reported in this ocular structure. The probability that a specific DNA damage leads to a mutation and eventually to cellular transformation is influenced by its formation frequency. To shed light on the genotoxic effect of sunlight in the human eye, we have analyzed CPD induction in the cornea and the iris following irradiation of ex vivo human eyes with UVA, B or C. The extent of CPD induction was used to establish the penetrance of the different UV types in the human cornea. We show that UVB- and UVC-induced CPDs are concentrated in the corneal epithelium and do not penetrate deeply beyond this corneal layer. On the other hand, UVA wavelengths penetrate deeper and induce CPDs in the entire cornea and in the first layers of the iris. Taken together, our results are undoubtedly an important step towards better understanding the consequences of UV exposure to the human eye.

High-speed adaptive optics line scan confocal retinal imaging for human eye

PubMed Central

Wang, Xiaolin; Zhang, Yuhua

2017-01-01

Purpose Continuous and rapid eye movement causes significant intraframe distortion in adaptive optics high resolution retinal imaging. To minimize this artifact, we developed a high speed adaptive optics line scan confocal retinal imaging system. Methods A high speed line camera was employed to acquire retinal image and custom adaptive optics was developed to compensate the wave aberration of the human eye’s optics. The spatial resolution and signal to noise ratio were assessed in model eye and in living human eye. The improvement of imaging fidelity was estimated by reduction of intra-frame distortion of retinal images acquired in the living human eyes with frame rates at 30 frames/second (FPS), 100 FPS, and 200 FPS. Results The device produced retinal image with cellular level resolution at 200 FPS with a digitization of 512×512 pixels/frame in the living human eye. Cone photoreceptors in the central fovea and rod photoreceptors near the fovea were resolved in three human subjects in normal chorioretinal health. Compared with retinal images acquired at 30 FPS, the intra-frame distortion in images taken at 200 FPS was reduced by 50.9% to 79.7%. Conclusions We demonstrated the feasibility of acquiring high resolution retinal images in the living human eye at a speed that minimizes retinal motion artifact. This device may facilitate research involving subjects with nystagmus or unsteady fixation due to central vision loss. PMID:28257458

A Model of the Human Eye

ERIC Educational Resources Information Center

Colicchia, G.; Wiesner, H.; Waltner, C.; Zollman, D.

2008-01-01

We describe a model of the human eye that incorporates a variable converging lens. The model can be easily constructed by students with low-cost materials. It shows in a comprehensible way the functionality of the eye's optical system. Images of near and far objects can be focused. Also, the defects of near and farsighted eyes can be demonstrated.

Imaging the Human Aqueous Humor Outflow Pathway in Human Eyes by Three Dimensional Micro-Computed Tomography (3D micro-CT)

PubMed Central

Hann, Cheryl R.; Bentley, Michael D.; Vercnocke, Andrew; Ritman, Erik L.; Fautsch, Michael P.

2011-01-01

The site of outflow resistance leading to elevated intraocular pressure in primary open angle glaucoma is believed to be located in the region of Schlemm’s canal inner wall endothelium, its basement membrane and the adjacent juxtacanalicular tissue. Evidence also suggests collector channels and intrascleral vessels may have a role in intraocular pressure in both normal and glaucoma eyes. Traditional imaging modalities limit the ability to view both proximal and distal portions of the trabecular outflow pathway as a single unit. In this study, we examined the effectiveness of three-dimensional micro-computed tomography (3D micro-CT) as a potential method to view the trabecular outflow pathway. Two normal human eyes were used: one immersion fixed in 4% paraformaldehyde, and one with anterior chamber perfusion at 10 mmHg followed by perfusion fixation in 4% paraformaldehyde/2% glutaraldehyde. Both eyes were postfixed in 1% osmium tetroxide, and scanned with 3D micro-CT at 2 µm or 5 µm voxel resolution. In the immersion fixed eye, 24 collector channels were identified with an average orifice size of 27.5 ± 5 µm. In comparison, the perfusion fixed eye had 29 collector channels with a mean orifice size of 40.5 ± 13 µm. Collector channels were not evenly dispersed around the circumference of the eye. There was no significant difference in the length of Schlemm’s canal in the immersed versus the perfused eye (33.2 versus 35.1 mm). Structures, locations and size measurements identified by 3D micro-CT were confirmed by correlative light microscopy. These findings confirm 3D micro-CT can be used effectively for the non-invasive examination of the trabecular meshwork, Schlemm’s canal, collector channels and intrascleral vasculature that comprise the distal outflow pathway. This imaging modality will be useful for noninvasive study of the role of the trabecular outflow pathway as a whole unit. PMID:21187085

The eyes and vision of butterflies.

PubMed

Arikawa, Kentaro

2017-08-15

Butterflies use colour vision when searching for flowers. Unlike the trichromatic retinas of humans (blue, green and red cones; plus rods) and honeybees (ultraviolet, blue and green photoreceptors), butterfly retinas typically have six or more photoreceptor classes with distinct spectral sensitivities. The eyes of the Japanese yellow swallowtail (Papilio xuthus) contain ultraviolet, violet, blue, green, red and broad-band receptors, with each ommatidium housing nine photoreceptor cells in one of three fixed combinations. The Papilio eye is thus a random patchwork of three types of spectrally heterogeneous ommatidia. To determine whether Papilio use all of their receptors to see colours, we measured their ability to discriminate monochromatic lights of slightly different wavelengths. We found that Papilio can detect differences as small as 1-2 nm in three wavelength regions, rivalling human performance. We then used mathematical modelling to infer which photoreceptors are involved in wavelength discrimination. Our simulation indicated that the Papilio vision is tetrachromatic, employing the ultraviolet, blue, green and red receptors. The random array of three ommatidial types is a common feature in butterflies. To address the question of how the spectrally complex eyes of butterflies evolved, we studied their developmental process. We have found that the development of butterfly eyes shares its molecular logic with that of Drosophila: the three-way stochastic expression pattern of the transcription factor Spineless determines the fate of ommatidia, creating the random array in Papilio. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations.

PubMed

Thurtell, M J; Black, R A; Halmagyi, G M; Curthoys, I S; Aw, S T

1999-05-01

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations. The effect of vertical eye-in-head position on the compensatory eye rotation response to passive and active high acceleration yaw head rotations was examined in eight normal human subjects. The stimuli consisted of brief, low amplitude (15-25 degrees ), high acceleration (4,000-6,000 degrees /s2) yaw head rotations with respect to the trunk (peak velocity was 150-350 degrees /s). Eye and head rotations were recorded in three-dimensional space using the magnetic search coil technique. The input-output kinematics of the three-dimensional vestibuloocular reflex (VOR) were assessed by finding the difference between the inverted eye velocity vector and the head velocity vector (both referenced to a head-fixed coordinate system) as a time series. During passive head impulses, the head and eye velocity axes aligned well with each other for the first 47 ms after the onset of the stimulus, regardless of vertical eye-in-head position. After the initial 47-ms period, the degree of alignment of the eye and head velocity axes was modulated by vertical eye-in-head position. When fixation was on a target 20 degrees up, the eye and head velocity axes remained well aligned with each other. However, when fixation was on targets at 0 and 20 degrees down, the eye velocity axis tilted forward relative to the head velocity axis. During active head impulses, the axis tilt became apparent within 5 ms of the onset of the stimulus. When fixation was on a target at 0 degrees, the velocity axes remained well aligned with each other. When fixation was on a target 20 degrees up, the eye velocity axis tilted backward, when fixation was on a target 20 degrees down, the eye velocity axis tilted forward. The findings show that the VOR compensates very well for head motion in the early part of the response to unpredictable high acceleration stimuli-the eye position- dependence of the VOR does not become apparent until 47 ms after the onset of the stimulus. In contrast, the response to active high acceleration stimuli shows eye position-dependence from within 5 ms of the onset of the stimulus. A model using a VOR-Listing's law compromise strategy did not accurately predict the patterns observed in the data, raising questions about how the eye position-dependence of the VOR is generated. We suggest, in view of recent findings, that the phenomenon could arise due to the effects of fibromuscular pulleys on the functional pulling directions of the rectus muscles.

Study of the human postural control system during quiet standing using detrended fluctuation analysis

NASA Astrophysics Data System (ADS)

Teresa Blázquez, M.; Anguiano, Marta; de Saavedra, Fernando Arias; Lallena, Antonio M.; Carpena, Pedro

2009-05-01

The detrended fluctuation analysis is used to study the behavior of different time series obtained from the trajectory of the center of pressure, the output of the activity of the human postural control system. The results suggest that these trajectories present two different regimes in their scaling properties: persistent (for high frequencies, short-range time scale) to antipersistent (for low frequencies, long-range time scale) behaviors. The similitude between the results obtained for the measurements, done with both eyes open and eyes closed, indicate either that the visual system may be disregarded by the postural control system while maintaining the quiet standing, or that the control mechanisms associated with each type of information (visual, vestibular and somatosensory) cannot be disentangled with the type of analysis performed here.

Eye Movements During Everyday Behavior Predict Personality Traits

PubMed Central

Hoppe, Sabrina; Loetscher, Tobias; Morey, Stephanie A.; Bulling, Andreas

2018-01-01

Besides allowing us to perceive our surroundings, eye movements are also a window into our mind and a rich source of information on who we are, how we feel, and what we do. Here we show that eye movements during an everyday task predict aspects of our personality. We tracked eye movements of 42 participants while they ran an errand on a university campus and subsequently assessed their personality traits using well-established questionnaires. Using a state-of-the-art machine learning method and a rich set of features encoding different eye movement characteristics, we were able to reliably predict four of the Big Five personality traits (neuroticism, extraversion, agreeableness, conscientiousness) as well as perceptual curiosity only from eye movements. Further analysis revealed new relations between previously neglected eye movement characteristics and personality. Our findings demonstrate a considerable influence of personality on everyday eye movement control, thereby complementing earlier studies in laboratory settings. Improving automatic recognition and interpretation of human social signals is an important endeavor, enabling innovative design of human–computer systems capable of sensing spontaneous natural user behavior to facilitate efficient interaction and personalization. PMID:29713270

Speckle measuring instrument based on biological characteristics of the human eyes and speckle reduction with advanced electromagnetic micro-scanning mirror

NASA Astrophysics Data System (ADS)

Yuan, Yuan; Fang, Tao; Sun, Min Yuan; Gao, Wei Nan; Zhang, Shuo; Bi, Yong

2018-07-01

Laser speckle is a major issue for laser projection displays. In various techniques of speckle reduction, speckle is quantified with a speckle contrast value. However, the measured speckle contrast is poorly suited for the subjective speckle perception of a human observer. Here, we investigate the characteristics of human eyes and propose a simplified optical transfer function of human eyes. Accordingly, two human-eye-modeled speckle measuring sets are configured. Based on the experimental set, an advanced electromagnetic micro-scanning mirror (EM-MSM) is exploited; which is of 6.5 mm in diameter and its half angle is 7.8° for a horizontal scan and 6.53° for a vertical scan. Finally, we quantitatively show that images generated with an EM-MSM exhibit superior quality. By providing human-eye-modeled speckle measuring instruments and an EM-MSM for speckle reduction, it has a promising promotion to laser projector development.

Imaging shear stress distribution and evaluating the stress concentration factor of the human eye

NASA Astrophysics Data System (ADS)

Joseph Antony, S.

2015-03-01

Healthy eyes are vital for a better quality of human life. Historically, for man-made materials, scientists and engineers use stress concentration factors to characterise the effects of structural non-homogeneities on their mechanical strength. However, such information is scarce for the human eye. Here we present the shear stress distribution profiles of a healthy human cornea surface in vivo using photo-stress analysis tomography, which is a non-intrusive and non-X-ray based method. The corneal birefringent retardation measured here is comparable to that of previous studies. Using this, we derive eye stress concentration factors and the directional alignment of major principal stress on the surface of the cornea. Similar to thermometers being used for monitoring the general health in humans, this report provides a foundation to characterise the shear stress carrying capacity of the cornea, and a potential bench mark for validating theoretical modelling of stresses in the human eye in future.

Eye Movements in Darkness Modulate Self-Motion Perception.

PubMed

Clemens, Ivar Adrianus H; Selen, Luc P J; Pomante, Antonella; MacNeilage, Paul R; Medendorp, W Pieter

2017-01-01

During self-motion, humans typically move the eyes to maintain fixation on the stationary environment around them. These eye movements could in principle be used to estimate self-motion, but their impact on perception is unknown. We had participants judge self-motion during different eye-movement conditions in the absence of full-field optic flow. In a two-alternative forced choice task, participants indicated whether the second of two successive passive lateral whole-body translations was longer or shorter than the first. This task was used in two experiments. In the first ( n = 8), eye movements were constrained differently in the two translation intervals by presenting either a world-fixed or body-fixed fixation point or no fixation point at all (allowing free gaze). Results show that perceived translations were shorter with a body-fixed than a world-fixed fixation point. A linear model indicated that eye-movement signals received a weight of ∼25% for the self-motion percept. This model was independently validated in the trials without a fixation point (free gaze). In the second experiment ( n = 10), gaze was free during both translation intervals. Results show that the translation with the larger eye-movement excursion was judged more often to be larger than chance, based on an oculomotor choice probability analysis. We conclude that eye-movement signals influence self-motion perception, even in the absence of visual stimulation.

Eye Movements in Darkness Modulate Self-Motion Perception

PubMed Central

Pomante, Antonella

2017-01-01

Abstract During self-motion, humans typically move the eyes to maintain fixation on the stationary environment around them. These eye movements could in principle be used to estimate self-motion, but their impact on perception is unknown. We had participants judge self-motion during different eye-movement conditions in the absence of full-field optic flow. In a two-alternative forced choice task, participants indicated whether the second of two successive passive lateral whole-body translations was longer or shorter than the first. This task was used in two experiments. In the first (n = 8), eye movements were constrained differently in the two translation intervals by presenting either a world-fixed or body-fixed fixation point or no fixation point at all (allowing free gaze). Results show that perceived translations were shorter with a body-fixed than a world-fixed fixation point. A linear model indicated that eye-movement signals received a weight of ∼25% for the self-motion percept. This model was independently validated in the trials without a fixation point (free gaze). In the second experiment (n = 10), gaze was free during both translation intervals. Results show that the translation with the larger eye-movement excursion was judged more often to be larger than chance, based on an oculomotor choice probability analysis. We conclude that eye-movement signals influence self-motion perception, even in the absence of visual stimulation. PMID:28144623

PSF and MTF comparison of two different surface ablation techniques for laser visual correction

NASA Astrophysics Data System (ADS)

Cruz Félix, Angel Sinue; López Olazagasti, Estela; Rosales, Marco A.; Ibarra, Jorge; Tepichín Rodríguez, Eduardo

2009-08-01

It is well known that the Zernike expansion of the wavefront aberrations has been extensively used to evaluate the performance of image forming optical systems. Recently, these techniques were adopted in the field of Ophthalmology to evaluate the objective performance of the human ocular system. We have been working in the characterization and evaluation of the performance of normal human eyes; i.e., eyes which do not require any refractive correction (20/20 visual acuity). These data provide us a reference model to analyze Pre- and Post-Operated results from eyes that have been subjected to laser refractive surgery. Two different ablation techniques are analyzed in this work. These techniques were designed to correct the typical refractive errors known as myopia, hyperopia, and presbyopia. When applied to the corneal surface, these techniques provide a focal shift and, in principle, an improvement of the visual performance. These features can be suitably described in terms of the PSF and MTF of the corresponding Pre- and Post-Operated wavefront aberrations. We show the preliminary results of our comparison.

Integrating the Advanced Human Eye Model (AHEM) and optical instrument models to model complete visual optical systems inclusive of the typical or atypical eye

NASA Astrophysics Data System (ADS)

Donnelly, William J., III

2012-06-01

PURPOSE: To present a commercially available optical modeling software tool to assist the development of optical instrumentation and systems that utilize and/or integrate with the human eye. METHODS: A commercially available flexible eye modeling system is presented, the Advanced Human Eye Model (AHEM). AHEM is a module that the engineer can use to perform rapid development and test scenarios on systems that integrate with the eye. Methods include merging modeled systems initially developed outside of AHEM and performing a series of wizard-type operations that relieve the user from requiring an optometric or ophthalmic background to produce a complete eye inclusive system. Scenarios consist of retinal imaging of targets and sources through integrated systems. Uses include, but are not limited to, optimization, telescopes, microscopes, spectacles, contact and intraocular lenses, ocular aberrations, cataract simulation and scattering, and twin eye model (binocular) systems. RESULTS: Metrics, graphical data, and exportable CAD geometry are generated from the various modeling scenarios.

Technical vision for robots

NASA Astrophysics Data System (ADS)

1985-01-01

A new invention by scientists who have copied the structure of a human eye will help replace a human telescope-watching astronomer with a robot. It will be possible to provide technical vision not only for robot astronomers but also for their industrial fellow robots. So far, an artificial eye with dimensions close to those of a human eye discerns only black-and-white images. But already the second model of the eye is to perceive colors as well. Polymers which are suited for the role of the coat of an eye, lens, and vitreous body were applied. The retina has been replaced with a bundle of the finest glass filaments through which light rays get onto photomultipliers. They can be positioned outside the artificial eye. The main thing is to prevent great losses in the light guide.

Extremely selective attention: eye-tracking studies of the dynamic allocation of attention to stimulus features in categorization.

PubMed

Blair, Mark R; Watson, Marcus R; Walshe, R Calen; Maj, Fillip

2009-09-01

Humans have an extremely flexible ability to categorize regularities in their environment, in part because of attentional systems that allow them to focus on important perceptual information. In formal theories of categorization, attention is typically modeled with weights that selectively bias the processing of stimulus features. These theories make differing predictions about the degree of flexibility with which attention can be deployed in response to stimulus properties. Results from 2 eye-tracking studies show that humans can rapidly learn to differently allocate attention to members of different categories. These results provide the first unequivocal demonstration of stimulus-responsive attention in a categorization task. Furthermore, the authors found clear temporal patterns in the shifting of attention within trials that follow from the informativeness of particular stimulus features. These data provide new insights into the attention processes involved in categorization. (c) 2009 APA, all rights reserved.

Fetal eye movements on magnetic resonance imaging.

PubMed

Woitek, Ramona; Kasprian, Gregor; Lindner, Christian; Stuhr, Fritz; Weber, Michael; Schöpf, Veronika; Brugger, Peter C; Asenbaum, Ulrika; Furtner, Julia; Bettelheim, Dieter; Seidl, Rainer; Prayer, Daniela

2013-01-01

Eye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed. Dynamic SSFP sequences were acquired in 72 singleton fetuses (17-40 GW, three age groups [17-23 GW, 24-32 GW, 33-40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid. In 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded. Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3-45%. In human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations.

Working sketch of an anatomically and optically equivalent physical model eye

NASA Astrophysics Data System (ADS)

Bakaraju, Ravi Chandra; Ehrmann, Klaus; Falk, Darrin; Papas, Eric B.; Ho, Arthur

2009-02-01

Our aim was to fabricate a bench-top physical model eye that closely replicates anatomical and optical properties of the average human eye, and to calibrate and standardize this model to suit normal viewing conditions and subsequently utilize it to understand the optical performance of corrective lens designs; especially multifocal soft contact lenses. Using available normative data on ocular biometrics and Zemax ray-tracing software as a tool, we modeled 25, 45 and 55 year-old average adult human eyes with discrete accommodation levels and pupil sizes. Specifications for the components were established following manufacturing tolerance analyses. The cornea was lathed from an optical material with refractive index of 1.376 @ 589 nm and the crystalline lenses were made of Boston RGP polymers with refractive indices of 1.423 (45 & 55yr) and 1.429 (25yr) @ 589 nm. These two materials served to model the equivalent crystalline lens of the different age-groups. A camera, the acting retina, was hosted on the motor-base having translatory and rotary functions to facilitate the simulation of different states of ametropia and peripheral refraction respectively. We report on the implementation of the first prototype and present some simulations of the optical performance of certain contact lenses with specific levels of ametropia, to demonstrate the potential use of such a physical model eye. On completion of development, calibration and standardization, optical quality assessment and performance predictions of different ophthalmic lenses can be studied in great detail. Optical performance with corrective lenses may be reliably simulated and predicted by customized combined computational and physical models giving insight into the merits and pitfalls of their designs

Mapping the emotional face. How individual face parts contribute to successful emotion recognition.

PubMed

Wegrzyn, Martin; Vogt, Maria; Kireclioglu, Berna; Schneider, Julia; Kissler, Johanna

2017-01-01

Which facial features allow human observers to successfully recognize expressions of emotion? While the eyes and mouth have been frequently shown to be of high importance, research on facial action units has made more precise predictions about the areas involved in displaying each emotion. The present research investigated on a fine-grained level, which physical features are most relied on when decoding facial expressions. In the experiment, individual faces expressing the basic emotions according to Ekman were hidden behind a mask of 48 tiles, which was sequentially uncovered. Participants were instructed to stop the sequence as soon as they recognized the facial expression and assign it the correct label. For each part of the face, its contribution to successful recognition was computed, allowing to visualize the importance of different face areas for each expression. Overall, observers were mostly relying on the eye and mouth regions when successfully recognizing an emotion. Furthermore, the difference in the importance of eyes and mouth allowed to group the expressions in a continuous space, ranging from sadness and fear (reliance on the eyes) to disgust and happiness (mouth). The face parts with highest diagnostic value for expression identification were typically located in areas corresponding to action units from the facial action coding system. A similarity analysis of the usefulness of different face parts for expression recognition demonstrated that faces cluster according to the emotion they express, rather than by low-level physical features. Also, expressions relying more on the eyes or mouth region were in close proximity in the constructed similarity space. These analyses help to better understand how human observers process expressions of emotion, by delineating the mapping from facial features to psychological representation.

Mapping the emotional face. How individual face parts contribute to successful emotion recognition

PubMed Central

Wegrzyn, Martin; Vogt, Maria; Kireclioglu, Berna; Schneider, Julia; Kissler, Johanna

2017-01-01

Which facial features allow human observers to successfully recognize expressions of emotion? While the eyes and mouth have been frequently shown to be of high importance, research on facial action units has made more precise predictions about the areas involved in displaying each emotion. The present research investigated on a fine-grained level, which physical features are most relied on when decoding facial expressions. In the experiment, individual faces expressing the basic emotions according to Ekman were hidden behind a mask of 48 tiles, which was sequentially uncovered. Participants were instructed to stop the sequence as soon as they recognized the facial expression and assign it the correct label. For each part of the face, its contribution to successful recognition was computed, allowing to visualize the importance of different face areas for each expression. Overall, observers were mostly relying on the eye and mouth regions when successfully recognizing an emotion. Furthermore, the difference in the importance of eyes and mouth allowed to group the expressions in a continuous space, ranging from sadness and fear (reliance on the eyes) to disgust and happiness (mouth). The face parts with highest diagnostic value for expression identification were typically located in areas corresponding to action units from the facial action coding system. A similarity analysis of the usefulness of different face parts for expression recognition demonstrated that faces cluster according to the emotion they express, rather than by low-level physical features. Also, expressions relying more on the eyes or mouth region were in close proximity in the constructed similarity space. These analyses help to better understand how human observers process expressions of emotion, by delineating the mapping from facial features to psychological representation. PMID:28493921

Eye Dominance Predicts fMRI Signals in Human Retinotopic Cortex

PubMed Central

Mendola, Janine D.; Conner, Ian P.

2009-01-01

There have been many attempts to define eye dominance in normal subjects, but limited consensus exists, and relevant physiological data is scarce. In this study, we consider two different behavioral methods for assignment of eye dominance, and how well they predict fMRI signals evoked by monocular stimulation. Sighting eye dominance was assessed with two standard tests, the Porta Test, and a ‘hole in hand’ variation of the Miles Test. Acuity dominance was tested with a standard eye chart and with a computerized test of grating acuity. We found limited agreement between the sighting and acuity methods for assigning dominance in our individual subjects. We then compared the fMRI response generated by dominant eye stimulation to that generated by non-dominant eye, according to both methods, in 7 normal subjects. The stimulus consisted of a high contrast hemifield stimulus alternating with no stimulus in a blocked paradigm. In separate scans, we used standard techniques to label the borders of visual areas V1, V2, V3, VP, V4, V3A, and MT. These regions of interest (ROIs) were used to analyze each visual area separately. We found that percent change in fMRI BOLD signal was stronger for the dominant eye as defined by the acuity method, and this effect was significant for areas located in the ventral occipital territory (V1v, V2v, VP, V4). In contrast, assigning dominance based on sighting produced no significant interocular BOLD differences. We conclude that interocular BOLD differences in normal subjects exist, and may be predicted by acuity measures. PMID:17194544

Directional asymmetries in human smooth pursuit eye movements.

PubMed

Ke, Sally R; Lam, Jessica; Pai, Dinesh K; Spering, Miriam

2013-06-27

Humans make smooth pursuit eye movements to bring the image of a moving object onto the fovea. Although pursuit accuracy is critical to prevent motion blur, the eye often falls behind the target. Previous studies suggest that pursuit accuracy differs between motion directions. Here, we systematically assess asymmetries in smooth pursuit. In experiment 1, binocular eye movements were recorded while observers (n = 20) tracked a small spot of light moving along one of four cardinal or diagonal axes across a featureless background. We analyzed pursuit latency, acceleration, peak velocity, gain, and catch-up saccade latency, number, and amplitude. In experiment 2 (n = 22), we examined the effects of spatial location and constrained stimulus motion within the upper or lower visual field. Pursuit was significantly faster (higher acceleration, peak velocity, and gain) and smoother (fewer and later catch-up saccades) in response to downward versus upward motion in both the upper and the lower visual fields. Pursuit was also more accurate and smoother in response to horizontal versus vertical motion. CONCLUSIONS. Our study is the first to report a consistent up-down asymmetry in human adults, regardless of visual field. Our findings suggest that pursuit asymmetries are adaptive responses to the requirements of the visual context: preferred motion directions (horizontal and downward) are more critical to our survival than nonpreferred ones.

The Connective Tissue Components of Optic Nerve Head Cupping in Monkey Experimental Glaucoma Part 1: Global Change

PubMed Central

Yang, Hongli; Ren, Ruojin; Lockwood, Howard; Williams, Galen; Libertiaux, Vincent; Downs, Crawford; Gardiner, Stuart K.; Burgoyne, Claude F.

2015-01-01

Purpose To characterize optic nerve head (ONH) connective tissue change within 21 monkey experimental glaucoma (EG) eyes, so as to identify its principal components. Methods Animals were imaged three to five times at baseline then every 2 weeks following chronic unilateral IOP elevation, and euthanized early through end-stage confocal scanning laser tomographic change. Optic nerve heads were serial-sectioned, three-dimensionally (3D) reconstructed, delineated, and quantified. Overall EG versus control eye differences were assessed by general estimating equations (GEE). Significant, animal-specific, EG eye change was required to exceed the maximum physiologic intereye differences in six healthy animals. Results Overall EG eye change was significant (P < 0.0026) and animal-specific EG eye change most frequent, for five phenomena (number of EG eyes and range of animal-specific change): posterior laminar deformation (21, −29 to −437 μm), laminar thickening (11, 20–73 μm) and thinning (3, −23 to −31 μm), scleral canal expansion (17, 20–139 μm), outward anterior (16, −16 to −124 μm) and posterior (17, −22 to −279 μm) laminar insertion migration, and peripapillary scleral bowing (11, 21–77 μm). Experimental glaucoma versus control eye laminar thickness differences were bimodal in behavior, being thickened in most EG eyes demonstrating the least deformation and less thickened or thinned in most EG eyes demonstrating the greatest deformation. Conclusions Our postmortem studies retrospectively identify five connective tissue components of ONH “cupping” in monkey EG which serve as targets for longitudinally staging and phenotyping ONH connective tissue alteration within all forms of monkey and human optic neuropathy. PMID:26641545

Priorities and trends in the study of proteins in eye research, 1924–2014

PubMed Central

Semba, Richard D.; Lam, Maggie; Sun, Kai; Zhang, Pingbo; Schaumberg, Debra A.; Ferrucci, Luigi; Ping, Peipei; Van Eyk, Jennifer E.

2015-01-01

Purpose To identify the proteins that are relevant to eye research and develop assays for the study of a set of these proteins. Experimental Design We conducted a bibliometric analysis by merging gene lists for human and mouse from the National Center for Biotechnology Information FTP site and combining them with PubMed references that were retrieved with the search terms “eye”[MeSH Terms] OR “eye”[All Fields] OR “eyes”[All Fields]. Results For human and mouse eye studies, respectively, the total number of publications was 13,525 and 23,895, and the total number of proteins was 4,050 and 4,717. For proteins in human and mouse eye studies, respectively, 88.7% and 81.7% had five or fewer citations. The top fifty most intensively studied proteins for human and mouse eye studies were generally in the areas of photoreceptors and phototransduction, inflammation and angiogenesis, neurodevelopment, lens transparency, and cell cycle and cellular processes. We proposed selected reaction monitoring assays that were developed in silico for the top fifty most intensively studied proteins in human and mouse eye research. Conclusions and clinical relevance We conclude that scientists engaged in eye research tend to focus on the same proteins. Newer resources and tools in proteomics can expand the investigations to lesser-known proteins of the eye. PMID:26123431

Assessment of the posterior segment of the cat eye by optical coherence tomography (OCT).

PubMed

Gekeler, Florian; Gmeiner, Helmut; Völker, Michael; Sachs, Helmut; Messias, Andre; Eule, Corinna; Bartz-Schmidt, Karl Ulrich; Zrenner, Eberhart; Shinoda, Kei

2007-01-01

To assess the feasibility of optical coherence tomography (OCT) for examining the cat ocular fundus, to provide normative data on retinal thickness in different fundus regions, and to demonstrate selected surgically induced vitreoretinal pathologies in the cat. Forty-five eyes of 28 healthy domestic cats and two eyes of domestic cats that had undergone subretinal implantation surgery for a visual prosthesis were examined. An optical coherence tomograph (Zeiss-Humphrey) was used to examine the anesthetized animals. At least five vertical and five horizontal scans in regular distribution were recorded for each cat including (1) the peripapillary region, (2) the area centralis, and (3) the peripheral retina. Thickness was measured manually at five locations in each scan. Retinal thickness was compared in the three above-mentioned fundus regions, between eyes and between vertical and horizontal scans. OCT was additionally performed in animals with retinal detachment and a subretinal visual prosthesis. OCT measurements required only minimal adjustments of human settings and yielded high quality images. In comparison to humans intraretinal layers were more difficult to differentiate. Retinal thickness was highest in the peripapillary region (245 +/- 21 microm), followed by the peripheral retina (204 +/- 11 microm) and the area centralis (182 +/- 11 microm; all P < 0.0001). There was no statistically significant difference between right and left eye or between vertical and horizontal scans. OCT demonstrated retinal detachment, an iatrogenic break and a subretinal prosthetic device in high detail. Retinal thickness was measurable with high precision; values compare well to older histologic studies. OCT bears significant advantages over histology in enabling one to repeat measurements in living animals and thus allowing longitudinal studies. Various vitreoretinal pathologies common in feline eyes are detectable and quantifiable by OCT.

Assessment of a new hydrophilic acrylic supplementary IOL for sulcus fixation in pseudophakic cadaver eyes

PubMed Central

Reiter, N; Werner, L; Guan, J; Li, J; Tsaousis, K T; Mamalis, N; Srinivasan, S

2017-01-01

Purpose Management of refractive errors after cataract surgery includes spectacles or contact lens, secondary laser vision correction, intraocular lens (IOL) exchange, or piggyback lens implantation. We evaluated for the first time a single-piece hydrophilic acrylic IOL designed for supplementary sulcus fixation in postmortem pseudophakic human eyes. Methods Pseudophakic human cadaver eyes were imaged by anterior segment optical coherence tomography (AS-OCT) to assess position of the primary IOL. Eyes were prepared as per the Miyake-Apple technique. The supplementary IOL (Medicontur A4 Addon IOL family) was then inserted into the ciliary sulcus. AS-OCT and photographs from anterior and posterior views were used to assess IOL centration, tilt, and interlenticular distance from the primary IOL. Results Data were obtained from 12 eyes having primary IOLs of varying materials and designs in the bag and representing different sizes of eyes and severity of Soemmering's ring formation. The A4 Addon IOL was successfully inserted into the ciliary sulcus and was well centered in all cases. Four cases of tilt were observed on AS-OCT: three with mild tilt due to pre-existing zonular dehiscence, and one due to a localized area of Soemmering's ring formation. Interlenticular distance ranged from 0.34 to 1.24 mm and was not dependent on severity of Soemmering's ring or type of primary IOL. Conclusions The A4 Addon IOL was designed for sulcus fixation as a supplementary lens, with a large diameter, a square-shaped optic, four smooth loop haptics, and a convex–concave optical surface. It exhibited appropriate centration and interlenticular distance with different primary in-the-bag IOLs. PMID:28106890

Dynamic sound localization in cats

PubMed Central

Ruhland, Janet L.; Jones, Amy E.

2015-01-01

Sound localization in cats and humans relies on head-centered acoustic cues. Studies have shown that humans are able to localize sounds during rapid head movements that are directed toward the target or other objects of interest. We studied whether cats are able to utilize similar dynamic acoustic cues to localize acoustic targets delivered during rapid eye-head gaze shifts. We trained cats with visual-auditory two-step tasks in which we presented a brief sound burst during saccadic eye-head gaze shifts toward a prior visual target. No consistent or significant differences in accuracy or precision were found between this dynamic task (2-step saccade) and the comparable static task (single saccade when the head is stable) in either horizontal or vertical direction. Cats appear to be able to process dynamic auditory cues and execute complex motor adjustments to accurately localize auditory targets during rapid eye-head gaze shifts. PMID:26063772

Computer vision syndrome (CVS) - Thermographic Analysis

NASA Astrophysics Data System (ADS)

Llamosa-Rincón, L. E.; Jaime-Díaz, J. M.; Ruiz-Cardona, D. F.

2017-01-01

The use of computers has reported an exponential growth in the last decades, the possibility of carrying out several tasks for both professional and leisure purposes has contributed to the great acceptance by the users. The consequences and impact of uninterrupted tasks with computers screens or displays on the visual health, have grabbed researcher’s attention. When spending long periods of time in front of a computer screen, human eyes are subjected to great efforts, which in turn triggers a set of symptoms known as Computer Vision Syndrome (CVS). Most common of them are: blurred vision, visual fatigue and Dry Eye Syndrome (DES) due to unappropriate lubrication of ocular surface when blinking decreases. An experimental protocol was de-signed and implemented to perform thermographic studies on healthy human eyes during exposure to dis-plays of computers, with the main purpose of comparing the existing differences in temperature variations of healthy ocular surfaces.

Consequences of Traumatic Brain Injury for Human Vergence Dynamics

PubMed Central

Tyler, Christopher W.; Likova, Lora T.; Mineff, Kristyo N.; Elsaid, Anas M.; Nicholas, Spero C.

2015-01-01

Purpose: Traumatic brain injury involving loss of consciousness has focal effects in the human brainstem, suggesting that it may have particular consequences for eye movement control. This hypothesis was investigated by measurements of vergence eye movement parameters. Methods: Disparity vergence eye movements were measured for a population of 123 normally sighted individuals, 26 of whom had suffered diffuse traumatic brain injury (dTBI) in the past, while the remainder served as controls. Vergence tracking responses were measured to sinusoidal disparity modulation of a random-dot field. Disparity vergence step responses were characterized in terms of their dynamic parameters separately for the convergence and divergence directions. Results: The control group showed notable differences between convergence and divergence dynamics. The dTBI group showed significantly abnormal vergence behavior on many of the dynamic parameters. Conclusion: The results support the hypothesis that occult injury to the oculomotor control system is a common residual outcome of dTBI. PMID:25691880

Design and Validation of an Infrared Badal Optometer for Laser Speckle (IBOLS)

PubMed Central

Teel, Danielle F. W.; Copland, R. James; Jacobs, Robert J.; Wells, Thad; Neal, Daniel R.; Thibos, Larry N.

2009-01-01

Purpose To validate the design of an infrared wavefront aberrometer with a Badal optometer employing the principle of laser speckle generated by a spinning disk and infrared light. The instrument was designed for subjective meridional refraction in infrared light by human patients. Methods Validation employed a model eye with known refractive error determined with an objective infrared wavefront aberrometer. The model eye was used to produce a speckle pattern on an artificial retina with controlled amounts of ametropia introduced with auxiliary ophthalmic lenses. A human observer performed the psychophysical task of observing the speckle pattern (with the aid of a video camera sensitive to infrared radiation) formed on the artificial retina. Refraction was performed by adjusting the vergence of incident light with the Badal optometer to nullify the motion of laser speckle. Validation of the method was performed for different levels of spherical ametropia and for various configurations of an astigmatic model eye. Results Subjective measurements of meridional refractive error over the range −4D to + 4D agreed with astigmatic refractive errors predicted by the power of the model eye in the meridian of motion of the spinning disk. Conclusions Use of a Badal optometer to control laser speckle is a valid method for determining subjective refractive error at infrared wavelengths. Such an instrument will be useful for comparing objective measures of refractive error obtained for the human eye with autorefractors and wavefront aberrometers that employ infrared radiation. PMID:18772719

Verification of the lack of correlation between age and longitudinal chromatic aberrations of the human eye from the visible to the infrared

PubMed Central

Nakajima, Masashi; Hiraoka, Takahiro; Hirohara, Yoko; Oshika, Tetsuro; Mihashi, Toshifumi

2015-01-01

Several researchers studied the longitudinal chromatic aberration (LCA) of the human eye and observed that it does not change due to age. We measured the LCA of 45 subjects’ normal right eyes at three distinct wavelengths (561, 690, and 840 nm) using a Hartmann–Shack wavefront aberrometer (HSWA) while consecutively switching between three light sources for wavefront sensing. We confirmed that the LCA of the human eye does not change due to age between 22 and 57 years. PMID:26203391

A Theoretical Analysis of a New Polarimetric Optical Scheme for Glucose Sensing in the Human Eye

NASA Technical Reports Server (NTRS)

Rovati, Luigi L.; Boeckle, Stefan; Ansari, Rafat R.; Salzman, Jack A. (Technical Monitor)

2002-01-01

The challenging task of in vivo polarimetric glucose sensing is the identification and selection of a scheme to optically access the aqueous humor of the human eye. In this short communication an earlier approach of Cote et al. is theoretically compared with our new optical scheme. Simulations of the new scheme using the eye model of Navarro, suggest that the new optical geometry can overcome the limitations of the previous approach for in vivo measurements of glucose in a human eye.

Human agency beliefs influence behaviour during virtual social interactions

PubMed Central

Brock, Jon

2017-01-01

In recent years, with the emergence of relatively inexpensive and accessible virtual reality technologies, it is now possible to deliver compelling and realistic simulations of human-to-human interaction. Neuroimaging studies have shown that, when participants believe they are interacting via a virtual interface with another human agent, they show different patterns of brain activity compared to when they know that their virtual partner is computer-controlled. The suggestion is that users adopt an “intentional stance” by attributing mental states to their virtual partner. However, it remains unclear how beliefs in the agency of a virtual partner influence participants’ behaviour and subjective experience of the interaction. We investigated this issue in the context of a cooperative “joint attention” game in which participants interacted via an eye tracker with a virtual onscreen partner, directing each other’s eye gaze to different screen locations. Half of the participants were correctly informed that their partner was controlled by a computer algorithm (“Computer” condition). The other half were misled into believing that the virtual character was controlled by a second participant in another room (“Human” condition). Those in the “Human” condition were slower to make eye contact with their partner and more likely to try and guide their partner before they had established mutual eye contact than participants in the “Computer” condition. They also responded more rapidly when their partner was guiding them, although the same effect was also found for a control condition in which they responded to an arrow cue. Results confirm the influence of human agency beliefs on behaviour in this virtual social interaction context. They further suggest that researchers and developers attempting to simulate social interactions should consider the impact of agency beliefs on user experience in other social contexts, and their effect on the achievement of the application’s goals. PMID:28948104

Interpretation of measurements of dynamic fluorescence of the eye

NASA Astrophysics Data System (ADS)

Schweitzer, Dietrich; Hammer, Martin; Jentsch, Susanne; Schenke, Stefan

2007-09-01

First pathological alterations occur at cellular level, most in metabolism. An indirect estimation of metabolic activity in cells is measurement of microcirculation. Measurements of tissue autofluorescence are potentially suited for direct investigation of cellular metabolism. Besides redox pairs of co-enzymes (NADH-NAD, FADH2-FAD) several other fluorophores are excited in tissue. In addition, a number of anatomical structures are simultaneously excited, when investigating the eye-ground. In this study, spectral and time resolved comparison was performed between purified substances, single ocular structures and in vivo measurements of the time-resolved autofluorescence at the human eye. In human eyes, the ageing pigment lipofuscin covers other fluorophores at the fundus in long - wave visible range. Applying lifetime measurements, weakly emitting fluorophores can be detected, when the lifetimes are different from the strongly emitting fluorophore. For this, the autofluorescence was excited at 468 nm and detected in two spectral ranges (500 nm-560 nm, 560 nm-700 nm). In tri-exponential fitting, the short lifetime corresponds to retinal pigment epithelium, the mean lifetime corresponds probably to neural retina and the long lifetime is caused by fluorescence of connective tissue.

Quantitative bioimaging of trace elements in the human lens by LA-ICP-MS.

PubMed

Konz, Ioana; Fernández, Beatriz; Fernández, M Luisa; Pereiro, Rosario; González-Iglesias, Héctor; Coca-Prados, Miguel; Sanz-Medel, Alfredo

2014-04-01

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for the quantitative imaging of Fe, Cu and Zn in cryostat sections of human eye lenses and for depth profiling analysis in bovine lenses. To ensure a tight temperature control throughout the experiments, a new Peltier-cooled laser ablation cell was employed. For quantification purposes, matrix-matched laboratory standards were prepared from a pool of human lenses from eye donors and spiked with standard solutions containing different concentrations of natural abundance Fe, Cu and Zn. A normalisation strategy was also carried out to correct matrix effects, lack of tissue homogeneity and/or instrumental drifts using a thin gold film deposited on the sample surface. Quantitative images of cryo-sections of human eye lenses analysed by LA-ICP-MS revealed a homogeneous distribution of Fe, Cu and Zn in the nuclear region and a slight increase in Fe concentration in the outer cell layer (i.e. lens epithelium) at the anterior pole. These results were assessed also by isotope dilution mass spectrometry, and Fe, Cu and Zn concentrations determined by ID-ICP-MS in digested samples of lenses and lens capsules.

Morphological study of the eye and adnexa in capuchin monkeys (Sapajus sp.)

PubMed Central

Silva, Danielle Nascimento; Oriá, Arianne Pontes; Araujo, Nayone Lantyer; Martins-Filho, Emanoel; Muramoto, Caterina; Libório, Fernanda de Azevedo

2017-01-01

The objective of this study was to describe the anatomic and histologic features of the Sapajus sp. eye, comparing similarities and differences of humans and other species of non-human primates for biomedical research purposes. Computed tomography (CT) of adnexa, eye and orbit live animal, as well as formolized pieces of the same structures of Sapajus sp. for anatomical and histological study were also performed. The anatomical description of the eye and adnexa was performed using the techniques of topographic dissection and exenteration. Histological fragments were fixated in buffered formalin 10%, processed by the routine paraffin inclusion technique, stained with hematoxylin-eosin and special stains. CT scan evaluation showed no differences between the live animal and the formolized head on identification of visual apparatus structures. Anatomic and histologic evaluation revealed rounded orbit, absence of the supraorbital foramen and frontal notch, little exposure of the sclera, with slight pigmentation of the exposed area and marked pigmentation at the sclerocorneal junction. Masson's Trichrome revealed the Meibomian glands, the corneal epithelium and Bowman's membrane; in the choroid, melanocytes and Bruch's membrane were observed; and in the retina, cones and rods as well as, optic nerve, the lamina cribrosa of the nerve fibers bundles. Toluidine blue highlighted the membranes: Bowman, Descemet and the endothelium; in the choroid: melanocytes; and in the retina: nuclear layers and retinal pigment epithelium. In view of the observed results Sapajus sp. is an important experimental model for research in the ophthalmology field, which has been shown due to the high similarity of its anatomical and histological structures with the human species. PMID:29206882

Why Don't We See in the Infrared?

NASA Astrophysics Data System (ADS)

Brecher, K.

1998-12-01

Solar radiation reaching the surface of the Earth includes a wide range of wavelengths and frequencies, with the peak of intensity including the infrared, visible and ultraviolet regions of the electromagnetic spectrum. In fact, the largest number of solar photons reaching our eyes arrives in the near infrared. Why, then, don't we see the world in the infrared? Many astronomy textbooks, both elementary and advanced, argue that the human eye has evolved to act as a kind of `solar Wien peak detector'. They note that if one uses the effective solar blackbody temperature of 5770 K, then, according to Wien's displacement law, the peak of the solar flux occurs at a wavelength of about 503 nm. Rods in the human eye peak in sensitivity at about 507 nm. Therefore, according to this line of reasoning, the human eye has evolved to avail itself of the Wien peak of the solar spectrum. (However, it should be noted that the peak sensitivity of the three different kinds of cones range from about 420 nm to about 560 nm). This astronomical argument is, at best, misleading. The solar blackbody spectrum, evaluated as a function of frequency, has a peak at about 340 THz. This is in the near infrared at a wavelength of about 884 nm. Since the human eye acts as an efficient quantum detector of photons, this is the appropriate solar radiation referent. Thus the Wien peak of the solar spectrum is not the reason that the eye's (scotopic) sensitivity peaks in the green. Many other factors contribute. Probably the most important are biochemical ones, which are constrained by available molecules such as rhodopsin that are useful for radiation to matter energy transfer. Physics also plays a role, because of absorption, scattering, refraction and diffraction. Other effects, including the Earth's atmospheric transmission and terrestrial surface reflectivities, may also matter.

The colours of humanity: the evolution of pigmentation in the human lineage.

PubMed

Jablonski, Nina G; Chaplin, George

2017-07-05

Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory. Functionally naked skin has been the physical interface between the physical environment and the human body for most of the history of the genus Homo , and hence skin coloration has been under intense natural selection. From an original condition of protective, dark, eumelanin-enriched coloration in early tropical-dwelling Homo and Homo sapiens , loss of melanin pigmentation occurred under natural selection as Homo sapiens dispersed into non-tropical latitudes of Africa and Eurasia. Genes responsible for skin, hair and eye coloration appear to have been affected significantly by population bottlenecks in the course of Homo sapiens dispersals. Because specific skin colour phenotypes can be created by different combinations of skin colour-associated genetic markers, loss of genetic variability due to genetic drift appears to have had negligible effects on the highly redundant genetic 'palette' for the skin colour. This does not appear to have been the case for hair and eye coloration, however, and these traits appear to have been more strongly influenced by genetic drift and, possibly, sexual selection.This article is part of the themed issue 'Animal coloration: production, perception, function and application'. © 2017 The Author(s).

Anisotropic responses to motion toward and away from the eye

NASA Technical Reports Server (NTRS)

Perrone, John A.

1986-01-01

When a rigid object moves toward the eye, it is usually perceived as being rigid. However, in the case of motion away from the eye, the motion and structure of the object are perceived nonveridically, with the percept tending to reflect the nonrigid transformations that are present in the retinal image. This difference in response to motion to and from the observer was quantified in an experiment using wire-frame computer-generated boxes which moved toward and away from the eye. Two theoretical systems are developed by which uniform three-dimensional velocity can be recovered from an expansion pattern of nonuniform velocity vectors. It is proposed that the human visual system uses two similar systems for processing motion in depth. The mechanism used for motion away from the eye produces perceptual errors because it is not suited to objects with a depth component.

Are the fluctuations in dynamic anterior surface aberrations of the human eye chaotic?

PubMed

Jayakumar, Varadharajan; Thapa, Damber; Hutchings, Natalie; Lakshminarayanan, Vasudevan

2013-12-15

The purpose of the study is to measure chaos in dynamic anterior surface aberrations and examine how it varies between the eyes of an individual. Noninvasive tear breakup time and dynamic corneal surface aberrations were measured for two open-eye intervals of 15 s. The maximal Lyapunov exponent (MLE) was calculated to test the nature of the fluctuations of the dynamic anterior surface aberrations. The average MLE for total higher-order aberration (HOA) was found to be small (+0.0102±0.0072) μm/s. No significant difference in MLE was found between the eyes for HOA (t-test; p=0.131). Data analysis was carried out for individual Zernike coefficients, including vertical prism as it gives a direct measure of the thickness of the tear film over time. The results show that the amount of chaos was small for each Zernike coefficient and not significantly correlated between the eyes.

Binocular summation for reflexive eye movements

PubMed Central

Quaia, Christian; Optican, Lance M.; Cumming, Bruce G.

2018-01-01

Psychophysical studies and our own subjective experience suggest that, in natural viewing conditions (i.e., at medium to high contrasts), monocularly and binocularly viewed scenes appear very similar, with the exception of the improved depth perception provided by stereopsis. This phenomenon is usually described as a lack of binocular summation. We show here that there is an exception to this rule: Ocular following eye movements induced by the sudden motion of a large stimulus, which we recorded from three human subjects, are much larger when both eyes see the moving stimulus, than when only one eye does. We further discovered that this binocular advantage is a function of the interocular correlation between the two monocular images: It is maximal when they are identical, and reduced when the two eyes are presented with different images. This is possible only if the neurons that underlie ocular following are sensitive to binocular disparity. PMID:29621384

DNA methyl transferases are differentially expressed in the human anterior eye segment.

PubMed

Bonnin, Nicolas; Belville, Corinne; Chiambaretta, Frédéric; Sapin, Vincent; Blanchon, Loïc

2014-08-01

DNA methylation is an epigenetic mark involved in the control of genes expression. Abnormal epigenetic events have been reported in human pathologies but weakly documented in eye diseases. The purpose of this study was to establish DNMT mRNA and protein expression levels in the anterior eye segment tissues and their related (primary or immortalized) cell cultures as a first step towards future in vivo and in vitro methylomic studies. Total mRNA was extracted from human cornea, conjunctiva, anterior lens capsule, trabeculum and related cell cultures (cornea epithelial, trabecular meshwork, keratocytes for primary cells; and HCE, Chang, B-3 for immortalized cells). cDNA was quantified by real-time PCR using specific primers for DNMT1, 2, 3A, 3B and 3L. Immunolocalization assays were carried out on human cornea using specific primary antibodies for DNMT1, 2 and 3A, 3B and 3L. All DNMT transcripts were detected in human cornea, conjunctiva, anterior lens capsule, trabeculum and related cells but showed statistically different expression patterns between tissues and cells. DNMT2 protein presented a specific and singular expression pattern in corneal endothelium. This study produced the first inventory of the expression patterns of DNMTs in human adult anterior eye segment. Our research highlights that DNA methylation cannot be ruled out as a way to bring new insights into well-known ocular diseases. In addition, future DNA methylation studies using various cells as experimental models need to be conducted with attention to approach the results analysis from a global tissue perspective. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

The Pattern of Sexual Interest of Female-to-Male Transsexual Persons With Gender Identity Disorder Does Not Resemble That of Biological Men: An Eye-Tracking Study.

PubMed

Tsujimura, Akira; Kiuchi, Hiroshi; Soda, Tetsuji; Takezawa, Kentaro; Fukuhara, Shinichiro; Takao, Tetsuya; Sekiguchi, Yuki; Iwasa, Atsushi; Nonomura, Norio; Miyagawa, Yasushi

2017-09-01

Very little has been elucidated about sexual interest in female-to-male (FtM) transsexual persons. To investigate the sexual interest of FtM transsexual persons vs that of men using an eye-tracking system. The study included 15 men and 13 FtM transsexual subjects who viewed three sexual videos (clip 1: sexy clothed young woman kissing the region of the male genitals covered by underwear; clip 2: naked actor and actress kissing and touching each other; and clip 3: heterosexual intercourse between a naked actor and actress) in which several regions were designated for eye-gaze analysis in each frame. The designation of each region was not visible to the participants. Visual attention was measured across each designated region according to gaze duration. For clip 1, there was a statistically significant sex difference in the viewing pattern between men and FtM transsexual subjects. Longest gaze time was for the eyes of the actress in men, whereas it was for non-human regions in FtM transsexual subjects. For clip 2, there also was a statistically significant sex difference. Longest gaze time was for the face of the actress in men, whereas it was for non-human regions in FtM transsexual subjects, and there was a significant difference between regions with longest gaze time. The most apparent difference was in the gaze time for the body of the actor: the percentage of time spent gazing at the body of the actor was 8.35% in FtM transsexual subjects, whereas it was only 0.03% in men. For clip 3, there were no statistically significant differences in viewing patterns between men and FtM transsexual subjects, although longest gaze time was for the face of the actress in men, whereas it was for non-human regions in FtM transsexual subjects. We suggest that the characteristics of sexual interest of FtM transsexual persons are not the same as those of biological men. Tsujimura A, Kiuchi H, Soda T, et al. The Pattern of Sexual Interest of Female-to-Male Transsexual Persons With Gender Identity Disorder Does Not Resemble That of Biological Men: An Eye-Tracking Study. Sex Med 2017;5:e169-e174. Copyright © 2017. Published by Elsevier Inc.

Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations

NASA Astrophysics Data System (ADS)

Nogueira, P.; Zankl, M.; Schlattl, H.; Vaz, P.

2011-11-01

The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation—the germinative cells—absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations.

PubMed

Nogueira, P; Zankl, M; Schlattl, H; Vaz, P

2011-11-07

The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

Cultural and Species Differences in Gazing Patterns for Marked and Decorated Objects: A Comparative Eye-Tracking Study

PubMed Central

Mühlenbeck, Cordelia; Jacobsen, Thomas; Pritsch, Carla; Liebal, Katja

2017-01-01

Objects from the Middle Paleolithic period colored with ochre and marked with incisions represent the beginning of non-utilitarian object manipulation in different species of the Homo genus. To investigate the visual effects caused by these markings, we compared humans who have different cultural backgrounds (Namibian hunter–gatherers and German city dwellers) to one species of non-human great apes (orangutans) with respect to their perceptions of markings on objects. We used eye-tracking to analyze their fixation patterns and the durations of their fixations on marked and unmarked stones and sticks. In an additional test, humans evaluated the objects regarding their aesthetic preferences. Our hypotheses were that colorful markings help an individual to structure the surrounding world by making certain features of the environment salient, and that aesthetic appreciation should be associated with this structuring. Our results showed that humans fixated on the marked objects longer and used them in the structural processing of the objects and their background, but did not consistently report finding them more beautiful. Orangutans, in contrast, did not distinguish between object and background in their visual processing and did not clearly fixate longer on the markings. Our results suggest that marking behavior is characteristic for humans and evolved as an attention-directing rather than aesthetic benefit. PMID:28167923

Chromatic and achromatic monocular deprivation produce separable changes of eye dominance in adults.

PubMed

Zhou, Jiawei; Reynaud, Alexandre; Kim, Yeon Jin; Mullen, Kathy T; Hess, Robert F

2017-11-29

Temporarily depriving one eye of its input, in whole or in part, results in a transient shift in eye dominance in human adults, with the patched eye becoming stronger and the unpatched eye weaker. However, little is known about the role of colour contrast in these behavioural changes. Here, we first show that the changes in eye dominance and contrast sensitivity induced by monocular eye patching affect colour and achromatic contrast sensitivity equally. We next use dichoptic movies, customized and filtered to stimulate the two eyes differentially. We show that a strong imbalance in achromatic contrast between the eyes, with no colour content, also produces similar, unselective shifts in eye dominance for both colour and achromatic contrast sensitivity. Interestingly, if this achromatic imbalance is paired with similar colour contrast in both eyes, the shift in eye dominance is selective, affecting achromatic but not chromatic contrast sensitivity and revealing a dissociation in eye dominance for colour and achromatic image content. On the other hand, a strong imbalance in chromatic contrast between the eyes, with no achromatic content, produces small, unselective changes in eye dominance, but if paired with similar achromatic contrast in both eyes, no changes occur. We conclude that perceptual changes in eye dominance are strongly driven by interocular imbalances in achromatic contrast, with colour contrast having a significant counter balancing effect. In the short term, eyes can have different dominances for achromatic and chromatic contrast, suggesting separate pathways at the site of these neuroplastic changes. © 2017 The Author(s).

The pink gene encodes the Drosophila orthologue of the human Hermansky-Pudlak syndrome 5 (HPS5) gene.

PubMed

Syrzycka, Monika; McEachern, Lori A; Kinneard, Jennifer; Prabhu, Kristel; Fitzpatrick, Kathleen; Schulze, Sandra; Rawls, John M; Lloyd, Vett K; Sinclair, Donald A R; Honda, Barry M

2007-06-01

Hermansky-Pudlak syndrome (HPS) consists of a set of human autosomal recessive disorders, with symptoms resulting from defects in genes required for protein trafficking in lysosome-related organelles such as melanosomes and platelet dense granules. A number of human HPS genes and rodent orthologues have been identified whose protein products are key components of 1 of 4 different protein complexes (AP-3 or BLOC-1, -2, and -3) that are key participants in the process. Drosophila melanogaster has been a key model organism in demonstrating the in vivo significance of many genes involved in protein trafficking pathways; for example, mutations in the "granule group" genes lead to changes in eye colour arising from improper protein trafficking to pigment granules in the developing eye. An examination of the chromosomal positioning of Drosophila HPS gene orthologues suggested that CG9770, the Drosophila HPS5 orthologue, might correspond to the pink locus. Here we confirm this gene assignment, making pink the first eye colour gene in flies to be identified as a BLOC complex gene.

The evolution of vision.

PubMed

Gehring, Walter J

2014-01-01

In this review, the evolution of vision is retraced from its putative origins in cyanobacteria to humans. Circadian oscillatory clocks, phototropism, and phototaxis require the capability to detect light. Photosensory proteins allow us to reconstruct molecular phylogenetic trees. The evolution of animal eyes leading from an ancestral prototype to highly complex image forming eyes can be deciphered on the basis of evolutionary developmental genetic experiments and comparative genomics. As all bilaterian animals share the same master control gene, Pax6, and the same retinal and pigment cell determination genes, we conclude that the different eye-types originated monophyletically and subsequently diversified by divergent, parallel, or convergent evolution. © 2012 Wiley Periodicals, Inc.

The Effects of Netarsudil Ophthalmic Solution on Aqueous Humor Dynamics in a Randomized Study in Humans.

PubMed

Kazemi, Arash; McLaren, Jay W; Kopczynski, Casey C; Heah, Theresa G; Novack, Gary D; Sit, Arthur J

2018-06-01

Netarsudil, an inhibitor of Rho kinase and a norepinephrine transporter, has been shown to lower elevated intraocular pressure (IOP) in controlled studies of patients with open-angle glaucoma and ocular hypertension, and in healthy volunteers. The mechanism of this ocular hypotensive effect in humans is unknown. The objective of this study was to evaluate the effect of netarsudil 0.02% on aqueous humor dynamics (AHD) parameters. In this double-masked, vehicle-controlled, paired-eye comparison study, 11 healthy volunteers received topical netarsudil ophthalmic solution 0.02% or its vehicle once daily for 7 days (morning dosing). The primary endpoints were the change in AHD parameters, compared between active and vehicle-treated eyes. In netarsudil-treated eyes, diurnal outflow facility increased from 0.27 ± 0.10 μL/min/mmHg to 0.33 ± 0.11 μL/min/mmHg (+22%; P = 0.02) after 7 days of treatment. In placebo-treated eyes, diurnal outflow facility did not significantly change (P = 0.94). The difference between netarsudil and placebo eyes in diurnal change of outflow facility was 0.08 μL/min/mmHg (P < 0.001). Diurnal episcleral venous pressure (EVP) in netarsudil-treated eyes decreased from 7.9 ± 1.2 mmHg to 7.2 ± 1.8 (-10%; P = 0.01). Diurnal EVP was not significantly different between netarsudil- and placebo-treated eyes. There was a trend toward decreasing aqueous humor flow rate (-15%; P = 0.08). No treatment changes were seen in uveoscleral outflow rate. Once-daily dosing of netarsudil ophthalmic solution 0.02% lowered IOP through increasing trabecular outflow facility and reducing EVP. This suggests a combination of mechanisms that affect both the proximal and distal outflow pathways.

Ranking fluctuating asymmetry in a dot figure and the significant impact of imagining a face.

PubMed

Neby, Magne; Ivar, Folstad

2013-01-01

Fluctuating asymmetry and averageness is correlated with our perception of beauty in human faces. Yet, whether deviations of centrality in the positioning of the eyes, the nose, and the mouth have different effects on our perception of asymmetry in a holistic human face, is still uncertain. In this study we aimed to test the relative effect of decentralising the horizontal position of three sets of paired dots representing eyes, nostrils, or mouth from the vertical midline of ambiguous dot figures, vaguely resembling a face. The figures were ranked according to perceived asymmetry by human observers. When associating the figures with non-facial objects (eg a butterfly), none of the figures' rank distribution differed from each other. However, when observers imagined the figures to represent a human face, the figure with the decentralised pair of dots representing the nostrils was significantly ranked as more asymmetric than the other figures. This result provides indications that the brain may deal with information about facial asymmetry and averageness heavily depending on the centrality of the nasal region.

Visual Positioning Indoors: Human Eyes vs. Smartphone Cameras

PubMed Central

Wu, Dewen; Chen, Ruizhi; Chen, Liang

2017-01-01

Artificial Intelligence (AI) technologies and their related applications are now developing at a rapid pace. Indoor positioning will be one of the core technologies that enable AI applications because people spend 80% of their time indoors. Humans can locate themselves related to a visually well-defined object, e.g., a door, based on their visual observations. Can a smartphone camera do a similar job when it points to an object? In this paper, a visual positioning solution was developed based on a single image captured from a smartphone camera pointing to a well-defined object. The smartphone camera simulates the process of human eyes for the purpose of relatively locating themselves against a well-defined object. Extensive experiments were conducted with five types of smartphones on three different indoor settings, including a meeting room, a library, and a reading room. Experimental results shown that the average positioning accuracy of the solution based on five smartphone cameras is 30.6 cm, while that for the human-observed solution with 300 samples from 10 different people is 73.1 cm. PMID:29144420

Visual Positioning Indoors: Human Eyes vs. Smartphone Cameras.

PubMed

Wu, Dewen; Chen, Ruizhi; Chen, Liang

2017-11-16

Artificial Intelligence (AI) technologies and their related applications are now developing at a rapid pace. Indoor positioning will be one of the core technologies that enable AI applications because people spend 80% of their time indoors. Humans can locate themselves related to a visually well-defined object, e.g., a door, based on their visual observations. Can a smartphone camera do a similar job when it points to an object? In this paper, a visual positioning solution was developed based on a single image captured from a smartphone camera pointing to a well-defined object. The smartphone camera simulates the process of human eyes for the purpose of relatively locating themselves against a well-defined object. Extensive experiments were conducted with five types of smartphones on three different indoor settings, including a meeting room, a library, and a reading room. Experimental results shown that the average positioning accuracy of the solution based on five smartphone cameras is 30.6 cm, while that for the human-observed solution with 300 samples from 10 different people is 73.1 cm.

A novel EOG/EEG hybrid human-machine interface adopting eye movements and ERPs: application to robot control.

PubMed

Ma, Jiaxin; Zhang, Yu; Cichocki, Andrzej; Matsuno, Fumitoshi

2015-03-01

This study presents a novel human-machine interface (HMI) based on both electrooculography (EOG) and electroencephalography (EEG). This hybrid interface works in two modes: an EOG mode recognizes eye movements such as blinks, and an EEG mode detects event related potentials (ERPs) like P300. While both eye movements and ERPs have been separately used for implementing assistive interfaces, which help patients with motor disabilities in performing daily tasks, the proposed hybrid interface integrates them together. In this way, both the eye movements and ERPs complement each other. Therefore, it can provide a better efficiency and a wider scope of application. In this study, we design a threshold algorithm that can recognize four kinds of eye movements including blink, wink, gaze, and frown. In addition, an oddball paradigm with stimuli of inverted faces is used to evoke multiple ERP components including P300, N170, and VPP. To verify the effectiveness of the proposed system, two different online experiments are carried out. One is to control a multifunctional humanoid robot, and the other is to control four mobile robots. In both experiments, the subjects can complete tasks effectively by using the proposed interface, whereas the best completion time is relatively short and very close to the one operated by hand.

Effect of monochromatic aberrations on photorefractive patterns

NASA Astrophysics Data System (ADS)

Campbell, Melanie C. W.; Bobier, W. R.; Roorda, A.

1995-08-01

Photorefractive methods have become popular in the measurement of refractive and accommodative states of infants and children owing to their photographic nature and rapid speed of measurement. As in the case of any method that measures the refractive state of the human eye, monochromatic aberrations will reduce the accuracy of the measurement. Monochromatic aberrations cannot be as easily predicted or controlled as chromatic aberrations during the measurement, and accordingly they will introduce measurement errors. This study defines this error or uncertainty by extending the existing paraxial optical analyses of coaxial and eccentric photorefraction. This new optical analysis predicts that, for the amounts of spherical aberration (SA) reported for the human eye, there will be a significant degree of measurement uncertainty introduced for all photorefractive methods. The dioptric amount of this uncertainty may exceed the maximum amount of SA present in the eye. The calculated effects on photorefractive measurement of a real eye with a mixture of spherical aberration and coma are shown to be significant. The ability, developed here, to predict photorefractive patterns corresponding to different amounts and types of monochromatic aberration may in the future lead to an extension of photorefractive methods to the dual measurement of refractive states and aberrations of individual eyes. aberration, retinal image quality,

Corollary discharge contributes to perceived eye location in monkeys

PubMed Central

Cavanaugh, James; FitzGibbon, Edmond J.; Wurtz, Robert H.

2013-01-01

Despite saccades changing the image on the retina several times per second, we still perceive a stable visual world. A possible mechanism underlying this stability is that an internal retinotopic map is updated with each saccade, with the location of objects being compared before and after the saccade. Psychophysical experiments have shown that humans derive such location information from a corollary discharge (CD) accompanying saccades. Such a CD has been identified in the monkey brain in a circuit extending from superior colliculus to frontal cortex. There is a missing piece, however. Perceptual localization is established only in humans and the CD circuit only in monkeys. We therefore extended measurement of perceptual localization to the monkey by adapting the target displacement detection task developed in humans. During saccades to targets, the target disappeared and then reappeared, sometimes at a different location. The monkeys reported the displacement direction. Detections of displacement were similar in monkeys and humans, but enhanced detection of displacement from blanking the target at the end of the saccade was observed only in humans, not in monkeys. Saccade amplitude varied across trials, but the monkey's estimates of target location did not follow that variation, indicating that eye location depended on an internal CD rather than external visual information. We conclude that monkeys use a CD to determine their new eye location after each saccade, just as humans do. PMID:23986562

Corollary discharge contributes to perceived eye location in monkeys.

PubMed

Joiner, Wilsaan M; Cavanaugh, James; FitzGibbon, Edmond J; Wurtz, Robert H

2013-11-01

Despite saccades changing the image on the retina several times per second, we still perceive a stable visual world. A possible mechanism underlying this stability is that an internal retinotopic map is updated with each saccade, with the location of objects being compared before and after the saccade. Psychophysical experiments have shown that humans derive such location information from a corollary discharge (CD) accompanying saccades. Such a CD has been identified in the monkey brain in a circuit extending from superior colliculus to frontal cortex. There is a missing piece, however. Perceptual localization is established only in humans and the CD circuit only in monkeys. We therefore extended measurement of perceptual localization to the monkey by adapting the target displacement detection task developed in humans. During saccades to targets, the target disappeared and then reappeared, sometimes at a different location. The monkeys reported the displacement direction. Detections of displacement were similar in monkeys and humans, but enhanced detection of displacement from blanking the target at the end of the saccade was observed only in humans, not in monkeys. Saccade amplitude varied across trials, but the monkey's estimates of target location did not follow that variation, indicating that eye location depended on an internal CD rather than external visual information. We conclude that monkeys use a CD to determine their new eye location after each saccade, just as humans do.

Gorillas with white sclera: A naturally occurring variation in a morphological trait linked to social cognitive functions.

PubMed

Mayhew, Jessica A; Gómez, Juan-Carlos

2015-08-01

Human eye morphology is considered unique among the primates in that humans possess larger width/height ratios (WHR), expose a greater amount of visible sclera (SSI; width of exposed eyeball/width of visible iris), and critically, have a white sclera due to a lack of pigmentation. White sclera in humans amplifies gaze direction, whereas the all-dark eyes of apes are hypothesized to conceal gaze from others. This study examines WHR and SSI in humans (N = 13) and gorillas (N = 85) engaged in direct and averted gazes and introduces a qualitative assessment of sclera color to evaluate variations in sclera pigmentation. The results confirm previous findings that humans possess a larger WHR than gorillas but indicate that humans and gorillas display similar amounts of visible sclera. Additionally, 72% (N = 124) of gorilla eyes in this sample deviated from the assumed all-dark eye condition. This questions whether gaze camouflage is the primary function of darkened sclera in non-human primates or whether other functional roles can be ascribed to the sclera, light or dark. We argue that white sclera evolved to amplify direct gazes in humans, which would have played a significant role in the development of ostensive communication, which is communication that both shows something and shows the intention to show something. We conclude that the horizontal elongation of the human eye, rather than sclera color, more reliably distinguishes human from great ape eyes, represented here by gorillas. © 2015 Wiley Periodicals, Inc.

Mouth and Voice: A Relationship between Visual and Auditory Preference in the Human Superior Temporal Sulcus

PubMed Central

2017-01-01

Cortex in and around the human posterior superior temporal sulcus (pSTS) is known to be critical for speech perception. The pSTS responds to both the visual modality (especially biological motion) and the auditory modality (especially human voices). Using fMRI in single subjects with no spatial smoothing, we show that visual and auditory selectivity are linked. Regions of the pSTS were identified that preferred visually presented moving mouths (presented in isolation or as part of a whole face) or moving eyes. Mouth-preferring regions responded strongly to voices and showed a significant preference for vocal compared with nonvocal sounds. In contrast, eye-preferring regions did not respond to either vocal or nonvocal sounds. The converse was also true: regions of the pSTS that showed a significant response to speech or preferred vocal to nonvocal sounds responded more strongly to visually presented mouths than eyes. These findings can be explained by environmental statistics. In natural environments, humans see visual mouth movements at the same time as they hear voices, while there is no auditory accompaniment to visual eye movements. The strength of a voxel's preference for visual mouth movements was strongly correlated with the magnitude of its auditory speech response and its preference for vocal sounds, suggesting that visual and auditory speech features are coded together in small populations of neurons within the pSTS. SIGNIFICANCE STATEMENT Humans interacting face to face make use of auditory cues from the talker's voice and visual cues from the talker's mouth to understand speech. The human posterior superior temporal sulcus (pSTS), a brain region known to be important for speech perception, is complex, with some regions responding to specific visual stimuli and others to specific auditory stimuli. Using BOLD fMRI, we show that the natural statistics of human speech, in which voices co-occur with mouth movements, are reflected in the neural architecture of the pSTS. Different pSTS regions prefer visually presented faces containing either a moving mouth or moving eyes, but only mouth-preferring regions respond strongly to voices. PMID:28179553

Mouth and Voice: A Relationship between Visual and Auditory Preference in the Human Superior Temporal Sulcus.

PubMed

Zhu, Lin L; Beauchamp, Michael S

2017-03-08

Cortex in and around the human posterior superior temporal sulcus (pSTS) is known to be critical for speech perception. The pSTS responds to both the visual modality (especially biological motion) and the auditory modality (especially human voices). Using fMRI in single subjects with no spatial smoothing, we show that visual and auditory selectivity are linked. Regions of the pSTS were identified that preferred visually presented moving mouths (presented in isolation or as part of a whole face) or moving eyes. Mouth-preferring regions responded strongly to voices and showed a significant preference for vocal compared with nonvocal sounds. In contrast, eye-preferring regions did not respond to either vocal or nonvocal sounds. The converse was also true: regions of the pSTS that showed a significant response to speech or preferred vocal to nonvocal sounds responded more strongly to visually presented mouths than eyes. These findings can be explained by environmental statistics. In natural environments, humans see visual mouth movements at the same time as they hear voices, while there is no auditory accompaniment to visual eye movements. The strength of a voxel's preference for visual mouth movements was strongly correlated with the magnitude of its auditory speech response and its preference for vocal sounds, suggesting that visual and auditory speech features are coded together in small populations of neurons within the pSTS. SIGNIFICANCE STATEMENT Humans interacting face to face make use of auditory cues from the talker's voice and visual cues from the talker's mouth to understand speech. The human posterior superior temporal sulcus (pSTS), a brain region known to be important for speech perception, is complex, with some regions responding to specific visual stimuli and others to specific auditory stimuli. Using BOLD fMRI, we show that the natural statistics of human speech, in which voices co-occur with mouth movements, are reflected in the neural architecture of the pSTS. Different pSTS regions prefer visually presented faces containing either a moving mouth or moving eyes, but only mouth-preferring regions respond strongly to voices. Copyright © 2017 the authors 0270-6474/17/372697-12$15.00/0.

Love, eye contact and the developmental origins of empathy v. psychopathy.

PubMed

Dadds, Mark R; Allen, Jennifer L; Oliver, Bonamy R; Faulkner, Nathan; Legge, Katherine; Moul, Caroline; Woolgar, Matthew; Scott, Stephen

2012-03-01

A propensity to attend to other people's emotions is a necessary condition for human empathy. To test our hypothesis that psychopathic disorder begins as a failure to attend to the eyes of attachment figures, using a `love' scenario in young children. Children with oppositional defiant disorder, assessed for callous-unemotional traits, and a control group were observed in a love interaction with mothers. Eye contact and affection were measured for each dyad. There was no group difference in affection and eye contact expressed by the mothers. Compared with controls, children with oppositional defiant disorder expressed lower levels of affection back towards their mothers; those with high levels of callous-unemotional traits showed significantly lower levels of affection than the children lacking these traits. As predicted, the former group showed low levels of eye contact toward their mothers. Low eye contact was not correlated with maternal coercive parenting or feelings toward the child, but was correlated with psychopathic fearlessness in their fathers. Impairments in eye contact are characteristic of children with callous-unemotional traits, and these impairments are independent of maternal behaviour.

The Simulating Social Mind: The Role of the Mirror Neuron System and Simulation in the Social and Communicative Deficits of Autism Spectrum Disorders

ERIC Educational Resources Information Center

Oberman, Lindsay M.; Ramachandran, Vilayanur S.

2007-01-01

The mechanism by which humans perceive others differs greatly from how humans perceive inanimate objects. Unlike inanimate objects, humans have the distinct property of being "like me" in the eyes of the observer. This allows us to use the same systems that process knowledge about self-performed actions, self-conceived thoughts, and…

FDTD analysis of temperature elevation in the lens of human and rabbit models due to near-field and far-field exposures at 2.45 GHz.

PubMed

Oizumi, Takuya; Laakso, Ilkka; Hirata, Akimasa; Fujiwara, Osamu; Watanabe, Soichi; Taki, Masao; Kojima, Masami; Sasaki, Hiroshi; Sasaki, Kazuyuki

2013-07-01

The eye is said to be one of the most sensitive organs to microwave heating. According to previous studies, the possibility of microwave-induced cataract formation has been experimentally investigated in rabbit and monkey eyes, but not for the human eye due to ethical reasons. In the present study, the temperature elevation in the lens, the skin around the eye and the core temperature of numerical human and rabbit models for far-field and near-field exposures at 2.45 GHz are investigated. The temperature elevations in the human and rabbit models were compared with the threshold temperatures for inducing cataracts, thermal pain in the skin and reversible health effects such as heat exhaustion or heat stroke. For plane-wave exposure, the core temperature elevation is shown to be essential both in the human and in the rabbit models as suggested in the international guidelines and standards. For localised exposure of the human eye, the temperature elevation of the skin was essential, and the lens temperature did not reach its threshold for thermal pain. On the other hand, the lens temperature elevation was found to be dominant for the rabbit eye.

Measuring Human Performance in Simulated Nuclear Power Plant Control Rooms Using Eye Tracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovesdi, Casey Robert; Rice, Brandon Charles; Bower, Gordon Ross

Control room modernization will be an important part of life extension for the existing light water reactor fleet. As part of modernization efforts, personnel will need to gain a full understanding of how control room technologies affect performance of human operators. Recent advances in technology enables the use of eye tracking technology to continuously measure an operator’s eye movement, which correlates with a variety of human performance constructs such as situation awareness and workload. This report describes eye tracking metrics in the context of how they will be used in nuclear power plant control room simulator studies.

Human-Computer Interface Controlled by Horizontal Directional Eye Movements and Voluntary Blinks Using AC EOG Signals

NASA Astrophysics Data System (ADS)

Kajiwara, Yusuke; Murata, Hiroaki; Kimura, Haruhiko; Abe, Koji

As a communication support tool for cases of amyotrophic lateral sclerosis (ALS), researches on eye gaze human-computer interfaces have been active. However, since voluntary and involuntary eye movements cannot be distinguished in the interfaces, their performance is still not sufficient for practical use. This paper presents a high performance human-computer interface system which unites high quality recognitions of horizontal directional eye movements and voluntary blinks. The experimental results have shown that the number of incorrect inputs is decreased by 35.1% in an existing system which equips recognitions of horizontal and vertical directional eye movements in addition to voluntary blinks and character inputs are speeded up by 17.4% from the existing system.

Determination of loss tangent of human tear film at 9.8 GHz

NASA Astrophysics Data System (ADS)

Bansal, Namita; Dhaliwal, A. S.; Mann, K. S.

2015-08-01

Basal (non-stimulated) tears that are produced by accessory lacrimal glands located in conjunctiva of human eye, form tear film which in turn keeps the eye moist and lubricate; nourishes the eye; protects the eye from dust, bacterial infection and shear forces generated during eye movements and blinking; and provides a refractive surface on the corneal epithelium. Film is known to contain water, mucin, lipids, lysozyme, glucose, urea, sodium etc. In present communication, loss tangent of human tear film has been determined at 9.8 GHz microwaves by employing cavity perturbation technique at a temperature of 37°C. The basal tears from a small population comprising six subjects were collected and average value of loss tangent is reported. Slater's technique was used to reduce the error caused in measuring the volume of sample. The determined values are useful to study the biological effects of microwaves on tear film as well as other parts of human eye such as eye lens and lens epithelial cells. To the best of author's knowledge, no such study is available in literature at any radio as well as microwave frequencies; therefore present determinations are first of its kind.

Visual optics: an engineering approach

NASA Astrophysics Data System (ADS)

Toadere, Florin

2010-11-01

The human eyes' visual system interprets the information from the visible light in order to build a representation of the world surrounding the body. It derives color by comparing the responses to light from the three types of photoreceptor cones in the eyes. These long medium and short cones are sensitive to blue, green and red portions of the visible spectrum. We simulate the color vision for the normal eyes. We see the effects of the dyes, filters, glasses and windows on color perception when the test image is illuminated with the D65 light sources. In addition to colors' perception, the human eyes can suffer from diseases and disorders. The eye can be seen as an optical instrument which has its own eye print. We present aspects of some nowadays methods and technologies which can capture and correct the human eyes' wavefront aberrations. We focus our attention to Siedel aberrations formula, Zenike polynomials, Shack-Hartmann Sensor, LASIK, interferograms fringes aberrations and Talbot effect.

Latent binocular function in amblyopia.

PubMed

Chadnova, Eva; Reynaud, Alexandre; Clavagnier, Simon; Hess, Robert F

2017-11-01

Recently, psychophysical studies have shown that humans with amblyopia do have binocular function that is not normally revealed due to dominant suppressive interactions under normal viewing conditions. Here we use magnetoencephalography (MEG) combined with dichoptic visual stimulation to investigate the underlying binocular function in humans with amblyopia for stimuli that, because of their temporal properties, would be expected to bypass suppressive effects and to reveal any underlying binocular function. We recorded contrast response functions in visual cortical area V1 of amblyopes and normal observers using a steady state visually evoked responses (SSVER) protocol. We used stimuli that were frequency-tagged at 4Hz and 6Hz that allowed identification of the responses from each eye and were of a sufficiently high temporal frequency (>3Hz) to bypass suppression. To characterize binocular function, we compared dichoptic masking between the two eyes in normal and amblyopic participants as well as interocular phase differences in the two groups. We observed that the primary visual cortex responds less to the stimulation of the amblyopic eye compared to the fellow eye. The pattern of interaction in the amblyopic visual system however was not significantly different between the amblyopic and fellow eyes. However, the amblyopic suppressive interactions were lower than those observed in the binocular system of our normal observers. Furthermore, we identified an interocular processing delay of approximately 20ms in our amblyopic group. To conclude, when suppression is greatly reduced, such as the case with our stimulation above 3Hz, the amblyopic visual system exhibits a lack of binocular interactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Viscoelastic properties of the posterior eye of normal subjects, patients with age-related macular degeneration, and pigs.

PubMed

Zhang, Zhen Huan; Pan, Meng Xin; Cai, Jia Tong; Weiland, James D; Chen, Kinon

2018-03-26

The purpose of this study is to measure, characterize, and compare the viscoelastic properties of the posterior eye of advanced dry age-related macular degeneration (AMD) patients, age-matched normal subjects, and pigs (3 groups). Ten horizontal and ten vertical strips of the macula retina and the underneath choroid and sclera were obtained for each group, respectively. They were examined by incremental stress-relaxation cycles in body-temperature saline. Mechanical response was characterized by the quasi-linear viscoelastic model. All the tissues were shown to be nonlinear viscoelastic. Stiffening and isotropization, increased relaxation, and softening and isotropization were found in AMD retina, choroid, and sclera, respectively, which are the mechanical features of the atherosclerotic process. The patients' medical records were in accordance with epidemiological studies indicating a relationship between the advanced AMD and atherosclerotic vascular disease (ASVD). Moreover, many differences were found between the viscoelastic properties of porcine and normal human retina, choroid, and sclera. The results suggest that AMD is associated with ASVD through a mechanism involving abnormal retinal, choroidal, and scleral mechanics similar to those seen in the atherosclerotic process. Moreover, researchers should be aware of mechanical differences when using porcine posterior eyes as a substitute for human posterior eyes. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

HUMAN EYE OPTICS: Determination of positions of optical elements of the human eye

NASA Astrophysics Data System (ADS)

Galetskii, S. O.; Cherezova, T. Yu

2009-02-01

An original method for noninvasive determining the positions of elements of intraocular optics is proposed. The analytic dependence of the measurement error on the optical-scheme parameters and the restriction in distance from the element being measured are determined within the framework of the method proposed. It is shown that the method can be efficiently used for determining the position of elements in the classical Gullstrand eye model and personalised eye models. The positions of six optical surfaces of the Gullstrand eye model and four optical surfaces of the personalised eye model can be determined with an error of less than 0.25 mm.

A pilot study: the efficacy of virgin coconut oil as ocular rewetting agent on rabbit eyes.

PubMed

Mutalib, Haliza Abdul; Kaur, Sharanjeet; Ghazali, Ahmad Rohi; Chinn Hooi, Ng; Safie, Nor Hasanah

2015-01-01

Purpose. An open-label pilot study of virgin coconut oil (VCO) was conducted to determine the safety of the agent as ocular rewetting eye drops on rabbits. Methods. Efficacy of the VCO was assessed by measuring NIBUT, anterior eye assessment, corneal staining, pH, and Schirmer value before instillation and at 30 min, 60 min, and two weeks after instillation. Friedman test was used to analyse any changes in all the measurable variables over the period of time. Results. Only conjunctival redness with instillation of saline agent showed significant difference over the period of time (P < 0.05). However, further statistical analysis had shown no significant difference at 30 min, 60 min, and two weeks compared to initial measurement (P > 0.05). There were no changes in the NIBUT, limbal redness, palpebral conjunctiva redness, corneal staining, pH, and Schirmer value over the period of time for each agent (P > 0.05). Conclusion. VCO acts as safe rewetting eye drops as it has shown no significant difference in the measurable parameter compared to commercial brand eye drops and saline. These study data suggest that VCO is safe to be used as ocular rewetting agent on human being.

What triggers catch-up saccades during visual tracking?

PubMed

de Brouwer, Sophie; Yuksel, Demet; Blohm, Gunnar; Missal, Marcus; Lefèvre, Philippe

2002-03-01

When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from one type of eye movement to the other are still poorly understood, even though they could bring a significant contribution to the understanding of how the CNS combines different kinds of control strategies to achieve a common motor and sensory goal. In this study, we investigated the oculomotor responses to a large range of different combinations of position error and velocity error during visual tracking of moving stimuli in humans. We found that the oculomotor system uses a prediction of the time at which the eye trajectory will cross the target, defined as the "eye crossing time" (T(XE)). The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e., to trigger catch-up saccades. On average, for T(XE) between 40 and 180 ms, no saccade is triggered and target tracking remains purely smooth. Conversely, when T(XE) becomes smaller than 40 ms or larger than 180 ms, a saccade is triggered after a short latency (around 125 ms).

Influence of the corneal optical zone on the point-spread function of the human eye

NASA Astrophysics Data System (ADS)

Rol, Pascal O.; Parel, Jean-Marie A.

1992-08-01

In refractive surgery, a number of surgical techniques have been developed to correct ametropia (refractive defaults) of the eye by changing the exterior shape of the cornea. Because the air-cornea interface makes up for about two thirds of the refractive power of the eye, a refractive correction can be obtained by a suitable reshaping of the cornea. Postoperatively, it is usually observed that the corneal region consists of two or more zones which are characterized by different optical parameters exhibiting in particular different focal distances. Under normal circumstances, only the central area of the cornea is involved in the formation of the retinal image. However, if part of the light entering the eye through peripheral portions of the cornea with refractive properties different from the central area can pass the pupil, an out-of-focus `ghost' image may be overlaid on the retina causing a blur. In such a case the resolution, and the contrast performance of the eye which is expected from a successful operation, may be reduced. This study is an attempt to quantify the vision blur as a function of the diameter of the central zone, i.e., the optical zone which is of importance for vision.

A Pilot Study: The Efficacy of Virgin Coconut Oil as Ocular Rewetting Agent on Rabbit Eyes

PubMed Central

Mutalib, Haliza Abdul; Kaur, Sharanjeet; Ghazali, Ahmad Rohi; Chinn Hooi, Ng; Safie, Nor Hasanah

2015-01-01

Purpose. An open-label pilot study of virgin coconut oil (VCO) was conducted to determine the safety of the agent as ocular rewetting eye drops on rabbits. Methods. Efficacy of the VCO was assessed by measuring NIBUT, anterior eye assessment, corneal staining, pH, and Schirmer value before instillation and at 30 min, 60 min, and two weeks after instillation. Friedman test was used to analyse any changes in all the measurable variables over the period of time. Results. Only conjunctival redness with instillation of saline agent showed significant difference over the period of time (P < 0.05). However, further statistical analysis had shown no significant difference at 30 min, 60 min, and two weeks compared to initial measurement (P > 0.05). There were no changes in the NIBUT, limbal redness, palpebral conjunctiva redness, corneal staining, pH, and Schirmer value over the period of time for each agent (P > 0.05). Conclusion. VCO acts as safe rewetting eye drops as it has shown no significant difference in the measurable parameter compared to commercial brand eye drops and saline. These study data suggest that VCO is safe to be used as ocular rewetting agent on human being. PMID:25802534

Driver fatigue detection based on eye state.

PubMed

Lin, Lizong; Huang, Chao; Ni, Xiaopeng; Wang, Jiawen; Zhang, Hao; Li, Xiao; Qian, Zhiqin

2015-01-01

Nowadays, more and more traffic accidents occur because of driver fatigue. In order to reduce and prevent it, in this study, a calculation method using PERCLOS (percentage of eye closure time) parameter characteristics based on machine vision was developed. It determined whether a driver's eyes were in a fatigue state according to the PERCLOS value. The overall workflow solutions included face detection and tracking, detection and location of the human eye, human eye tracking, eye state recognition, and driver fatigue testing. The key aspects of the detection system incorporated the detection and location of human eyes and driver fatigue testing. The simplified method of measuring the PERCLOS value of the driver was to calculate the ratio of the eyes being open and closed with the total number of frames for a given period. If the eyes were closed more than the set threshold in the total number of frames, the system would alert the driver. Through many experiments, it was shown that besides the simple detection algorithm, the rapid computing speed, and the high detection and recognition accuracies of the system, the system was demonstrated to be in accord with the real-time requirements of a driver fatigue detection system.

Eye Movements to Natural Images as a Function of Sex and Personality

PubMed Central

Mercer Moss, Felix Joseph; Baddeley, Roland; Canagarajah, Nishan

2012-01-01

Women and men are different. As humans are highly visual animals, these differences should be reflected in the pattern of eye movements they make when interacting with the world. We examined fixation distributions of 52 women and men while viewing 80 natural images and found systematic differences in their spatial and temporal characteristics. The most striking of these was that women looked away and usually below many objects of interest, particularly when rating images in terms of their potency. We also found reliable differences correlated with the images' semantic content, the observers' personality, and how the images were semantically evaluated. Information theoretic techniques showed that many of these differences increased with viewing time. These effects were not small: the fixations to a single action or romance film image allow the classification of the sex of an observer with 64% accuracy. While men and women may live in the same environment, what they see in this environment is reliably different. Our findings have important implications for both past and future eye movement research while confirming the significant role individual differences play in visual attention. PMID:23248740

Dog Breed Differences in Visual Communication with Humans.

PubMed

Konno, Akitsugu; Romero, Teresa; Inoue-Murayama, Miho; Saito, Atsuko; Hasegawa, Toshikazu

2016-01-01

Domestic dogs (Canis familiaris) have developed a close relationship with humans through the process of domestication. In human-dog interactions, eye contact is a key element of relationship initiation and maintenance. Previous studies have suggested that canine ability to produce human-directed communicative signals is influenced by domestication history, from wolves to dogs, as well as by recent breed selection for particular working purposes. To test the genetic basis for such abilities in purebred dogs, we examined gazing behavior towards humans using two types of behavioral experiments: the 'visual contact task' and the 'unsolvable task'. A total of 125 dogs participated in the study. Based on the genetic relatedness among breeds subjects were classified into five breed groups: Ancient, Herding, Hunting, Retriever-Mastiff and Working). We found that it took longer time for Ancient breeds to make an eye-contact with humans, and that they gazed at humans for shorter periods of time than any other breed group in the unsolvable situation. Our findings suggest that spontaneous gaze behavior towards humans is associated with genetic similarity to wolves rather than with recent selective pressure to create particular working breeds.

Estimation of the mechanical properties of the eye through the study of its vibrational modes.

PubMed

Aloy, M Á; Adsuara, J E; Cerdá-Durán, P; Obergaulinger, M; Esteve-Taboada, J J; Ferrer-Blasco, T; Montés-Micó, R

2017-01-01

Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz-10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.

Eye Lens Radiation Exposure in Greek Interventional Cardiology Article.

PubMed

Thrapsanioti, Zoi; Askounis, Panagiotis; Datseris, Ioannis; Diamanti, Ramza Anastasia; Papathanasiou, Miltiadis; Carinou, Eleftheria

2017-07-01

The lens of the eye is one of the radiosensitive tissues of the human body; if exposed to ionizing radiation can develop radiation-induced cataract at early ages. This study was held in Greece and included 44 Interventional Cardiologists (ICs) and an unexposed to radiation control group of 22 persons. Of the note, 26 ICs and the unexposed individuals underwent special eye examinations. The detected lens opacities were classified according to LOCS III protocol. Additionally, the lens doses of the ICs were measured using eye lens dosemeters. The mean dose to the lenses of the ICs per month was 0.83 ± 0.59 mSv for the left and 0.35 ± 0.38 mSv for the right eye, while the annual doses ranged between 0.7 and 11 mSv. Regarding the lens opacities, the two groups did not differ significantly in the prevalence of either nuclear or cortical lens opacities, whereas four ICs were detected with early stage subcapsular sclerosis. Though no statistically difference was observed in the cohort, the measured doses indicate that the eye doses received from the ICs can be significant. To minimize the radiation-induced risk at the eye lenses, the use of protective equipment and appropriate training on this issue is highly recommended. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Stiles-Crawford Effect: spot-size ratio departure in retinitis pigmentosa

NASA Astrophysics Data System (ADS)

Sharma, Nachieketa K.; Lakshminarayanan, Vasudevan

2016-04-01

The Stiles-Crawford effect of the first kind is the retina's compensative response to loss of luminance efficiency for oblique stimulation manifested as the spot-size ratio departure from the perfect power coupling for a normal human eye. In a retinitis pigmentosa eye (RP), the normal cone photoreceptor morphology is affected due to foveal cone loss and disrupted cone mosaic spatial arrangement with reduction in directional sensitivity. We show that the flattened Stiles-Crawford function (SCF) in a RP eye is due to a different spot-size ratio departure profile, that is, for the same loss of luminance efficiency, a RP eye has a smaller departure from perfect power coupling compared to a normal eye. Again, the difference in spot-size ratio departure increases from the centre towards the periphery, having zero value for axial entry and maximum value for maximum peripheral entry indicating dispersal of photoreceptor alignment which prevents the retina to go for a bigger compensative response as it lacks both in number and appropriate cone morphology to tackle the loss of luminance efficiency for oblique stimulation. The slope of departure profile also testifies to the flattened SCF for a RP eye. Moreover, the discrepancy in spot-size ratio departure between a normal and a RP eye is shown to have a direct bearing on the Stiles-Crawford diminution of visibility.

Chimpanzees and Humans Mimic Pupil-Size of Conspecifics

PubMed Central

Kret, Mariska E.; Tomonaga, Masaki; Matsuzawa, Tetsuro

2014-01-01

Group-living typically provides benefits to individual group members but also confers costs. To avoid incredulity and betrayal and allow trust and cooperation, individuals must understand the intentions and emotions of their group members. Humans attend to other's eyes and from gaze and pupil-size cues, infer information about the state of mind of the observed. In humans, pupil-size tends to mimic that of the observed. Here we tested whether pupil-mimicry exists in our closest relative, the chimpanzee (P. troglodytes). We conjectured that if pupil-mimicry has adaptive value, e.g. to promote swift communication of inner states and facilitate shared understanding and coordination, pupil-mimicry should emerge within but not across species. Pupillometry data was collected from human and chimpanzee subjects while they observed images of the eyes of both species with dilating/constricting pupils. Both species showed enhanced pupil-mimicry with members of their own species, with effects being strongest in humans and chimpanzee mothers. Pupil-mimicry may be deeply-rooted, but probably gained importance from the point in human evolution where the morphology of our eyes became more prominent. Humans' white sclera surrounding the iris, and the fine muscles around their eyes facilitate non-verbal communication via eye signals. PMID:25140998

Transcriptome analysis of Nautilus and pygmy squid developing eye provides insights in lens and eye evolution.

PubMed

Sousounis, Konstantinos; Ogura, Atsushi; Tsonis, Panagiotis A

2013-01-01

Coleoid cephalopods like squids have a camera-type eye similar to vertebrates. On the other hand, Nautilus (Nautiloids) has a pinhole eye that lacks lens and cornea. Since pygmy squid and Nautilus are closely related species they are excellent model organisms to study eye evolution. Having being able to collect Nautilus embryos, we employed next-generation RNA sequencing using Nautilus and pygmy squid developing eyes. Their transcriptomes were compared and analyzed. Enrichment analysis of Gene Ontology revealed that contigs related to nucleic acid binding were largely up-regulated in squid, while the ones related to metabolic processes and extracellular matrix-related genes were up-regulated in Nautilus. These differences are most likely correlated with the complexity of tissue organization in these species. Moreover, when the analysis focused on the eye-related contigs several interesting patterns emerged. First, contigs from both species related to eye tissue differentiation and morphogenesis as well as to cilia showed best hits with their Human counterparts, while contigs related to rabdomeric photoreceptors showed the best hit with their Drosophila counterparts. This bolsters the idea that eye morphogenesis genes have been generally conserved in evolution, and compliments other studies showing that genes involved in photoreceptor differentiation clearly follow the diversification of invertebrate (rabdomeric) and vertebrate (ciliated) photoreceptors. Interestingly some contigs showed as good a hit with Drosophila and Human homologues in Nautilus and squid samples. One of them, capt/CAP1, is known to be preferentially expressed in Drosophila developing eye and in vertebrate lens. Importantly our analysis also provided evidence of gene duplication and diversification of their function in both species. One of these genes is the Neurofibromatosis 1 (NF1/Nf1), which in mice has been implicated in lens formation, suggesting a hitherto unsuspected role in the evolution of the lens in molluscs.

Transcriptome Analysis of Nautilus and Pygmy Squid Developing Eye Provides Insights in Lens and Eye Evolution

PubMed Central

Sousounis, Konstantinos; Ogura, Atsushi; Tsonis, Panagiotis A.

2013-01-01

Coleoid cephalopods like squids have a camera-type eye similar to vertebrates. On the other hand, Nautilus (Nautiloids) has a pinhole eye that lacks lens and cornea. Since pygmy squid and Nautilus are closely related species they are excellent model organisms to study eye evolution. Having being able to collect Nautilus embryos, we employed next-generation RNA sequencing using Nautilus and pygmy squid developing eyes. Their transcriptomes were compared and analyzed. Enrichment analysis of Gene Ontology revealed that contigs related to nucleic acid binding were largely up-regulated in squid, while the ones related to metabolic processes and extracellular matrix-related genes were up-regulated in Nautilus. These differences are most likely correlated with the complexity of tissue organization in these species. Moreover, when the analysis focused on the eye-related contigs several interesting patterns emerged. First, contigs from both species related to eye tissue differentiation and morphogenesis as well as to cilia showed best hits with their Human counterparts, while contigs related to rabdomeric photoreceptors showed the best hit with their Drosophila counterparts. This bolsters the idea that eye morphogenesis genes have been generally conserved in evolution, and compliments other studies showing that genes involved in photoreceptor differentiation clearly follow the diversification of invertebrate (rabdomeric) and vertebrate (ciliated) photoreceptors. Interestingly some contigs showed as good a hit with Drosophila and Human homologues in Nautilus and squid samples. One of them, capt/CAP1, is known to be preferentially expressed in Drosophila developing eye and in vertebrate lens. Importantly our analysis also provided evidence of gene duplication and diversification of their function in both species. One of these genes is the Neurofibromatosis 1 (NF1/Nf1), which in mice has been implicated in lens formation, suggesting a hitherto unsuspected role in the evolution of the lens in molluscs. PMID:24205087

Human brain structure predicts individual differences in preconscious evaluation of facial dominance and trustworthiness

PubMed Central

Kanai, Ryota; Bahrami, Bahador; Rees, Geraint

2015-01-01

Social cues conveyed by the human face, such as eye gaze direction, are evaluated even before they are consciously perceived. While there is substantial individual variability in such evaluation, its neural basis is unknown. Here we asked whether individual differences in preconscious evaluation of social face traits were associated with local variability in brain structure. Adult human participants (n = 36) monocularly viewed faces varying in dominance and trustworthiness, which were suppressed from awareness by a dynamic noise pattern shown to the other eye. The time taken for faces to emerge from suppression and become visible (t2e) was used as a measure of potency in competing for visual awareness. Both dominant and untrustworthy faces resulted in slower t2e than neutral faces, with substantial individual variability in these effects. Individual differences in t2e were correlated with gray matter volume in right insula for dominant faces, and with gray matter volume in medial prefrontal cortex, right temporoparietal junction and bilateral fusiform face area for untrustworthy faces. Thus, individual differences in preconscious social processing can be predicted from local brain structure, and separable correlates for facial dominance and untrustworthiness suggest distinct mechanisms of preconscious processing. PMID:25193945

Computing retinal contour from optical biometry.

PubMed

Faria-Ribeiro, Miguel; López-Gil, Norberto; Navarro, Rafael; Lopes-Ferreira, Daniela; Jorge, Jorge; González-Méijome, Jose Manuel

2014-04-01

To describe a new methodology that derives horizontal posterior retinal contours from partial coherence interferometry (PCI) and ray tracing using the corneal topography. Corneal topography and PCI for seven horizontal visual field eccentricities correspondent to the central 60 degrees of the posterior pole were obtained in 55 myopic eyes. A semicustomized eye model based on the subject's corneal topography and the Navarro eye model was generated using Zemax-EE software. The model was used to compute the optical path length in the seven directions where PCI measurements were obtained. Vitreous chamber depth was computed using the PCI values obtained at each of those directions. Matlab software was developed to fit the best conic curve to the set of points previously obtained. We tested the limit in the accuracy of the methodology when the actual cornea of the subject is not used and for two different lens geometries. A standard eye model can induce an error in the retina sagitta estimation of the order of hundreds of micrometers in comparison with the semicustomized eye model. However, the use of a different lens model leads to an error of the order of tens of micrometers. The apical radius and conic constant of the average fit were -11.91 mm and -0.15, respectively. In general, a nasal-temporal asymmetry in the retina contour was found, showing mean larger values of vitreous chamber depth in the nasal side of the eye. The use of a semicustomized eye model, together with optical path length measured by PCI for different angles, can be used to predict the retinal contour within tenths of micrometers. This methodology can be useful in studies trying to understand the effect of peripheral retinal location on myopia progression as well as modeling the optics of the human eye for a wide field.

Further evidence for population specific differences in the effect of DNA markers and gender on eye colour prediction in forensics.

PubMed

Pośpiech, Ewelina; Karłowska-Pik, Joanna; Ziemkiewicz, Bartosz; Kukla, Magdalena; Skowron, Małgorzata; Wojas-Pelc, Anna; Branicki, Wojciech

2016-07-01

The genetics of eye colour has been extensively studied over the past few years, and the identified polymorphisms have been applied with marked success in the field of Forensic DNA Phenotyping. A picture that arises from evaluation of the currently available eye colour prediction markers shows that only the analysis of HERC2-OCA2 complex has similar effectiveness in different populations, while the predictive potential of other loci may vary significantly. Moreover, the role of gender in the explanation of human eye colour variation should not be neglected in some populations. In the present study, we re-investigated the data for 1020 Polish individuals and using neural networks and logistic regression methods explored predictive capacity of IrisPlex SNPs and gender in this population sample. In general, neural networks provided higher prediction accuracy comparing to logistic regression (AUC increase by 0.02-0.06). Four out of six IrisPlex SNPs were associated with eye colour in the studied population. HERC2 rs12913832, OCA2 rs1800407 and SLC24A4 rs12896399 were found to be the most important eye colour predictors (p < 0.007) while the effect of rs16891982 in SLC45A2 was less significant. Gender was found to be significantly associated with eye colour with males having ~1.5 higher odds for blue eye colour comparing to females (p = 0.002) and was ranked as the third most important factor in blue/non-blue eye colour determination. However, the implementation of gender into the developed prediction models had marginal and ambiguous impact on the overall accuracy of prediction confirming that the effect of gender on eye colour in this population is small. Our study indicated the advantage of neural networks in prediction modeling in forensics and provided additional evidence for population specific differences in the predictive importance of the IrisPlex SNPs and gender.

Dose conversion coefficients for photon exposure of the human eye lens.

PubMed

Behrens, R; Dietze, G

2011-01-21

In recent years, several papers dealing with the eye lens dose have been published, because epidemiological studies implied that the induction of cataracts occurs even at eye lens doses of less than 500 mGy. Different questions were addressed: Which personal dose equivalent quantity is appropriate for monitoring the dose to the eye lens? Is a new definition of the dose quantity H(p)(3) based on a cylinder phantom to represent the human head necessary? Are current conversion coefficients from fluence to equivalent dose to the lens sufficiently accurate? To investigate the latter question, a realistic model of the eye including the inner structure of the lens was developed. Using this eye model, conversion coefficients for electrons have already been presented. In this paper, the same eye model-with the addition of the whole body-was used to calculate conversion coefficients from fluence (and air kerma) to equivalent dose to the lens for photon radiation from 5 keV to 10 MeV. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are similar between 40 keV and 1 MeV and lower by up to a factor of 5 and 7 for photon energies at about 10 keV and 10 MeV, respectively. Above 1 MeV, the new values (calculated without kerma approximation) should be applied in pure photon radiation fields, while the values adopted by the ICRP in 1996 (calculated with kerma approximation) should be applied in case a significant contribution from secondary electrons originating outside the body is present.

Dose conversion coefficients for photon exposure of the human eye lens

NASA Astrophysics Data System (ADS)

Behrens, R.; Dietze, G.

2011-01-01

In recent years, several papers dealing with the eye lens dose have been published, because epidemiological studies implied that the induction of cataracts occurs even at eye lens doses of less than 500 mGy. Different questions were addressed: Which personal dose equivalent quantity is appropriate for monitoring the dose to the eye lens? Is a new definition of the dose quantity Hp(3) based on a cylinder phantom to represent the human head necessary? Are current conversion coefficients from fluence to equivalent dose to the lens sufficiently accurate? To investigate the latter question, a realistic model of the eye including the inner structure of the lens was developed. Using this eye model, conversion coefficients for electrons have already been presented. In this paper, the same eye model—with the addition of the whole body—was used to calculate conversion coefficients from fluence (and air kerma) to equivalent dose to the lens for photon radiation from 5 keV to 10 MeV. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are similar between 40 keV and 1 MeV and lower by up to a factor of 5 and 7 for photon energies at about 10 keV and 10 MeV, respectively. Above 1 MeV, the new values (calculated without kerma approximation) should be applied in pure photon radiation fields, while the values adopted by the ICRP in 1996 (calculated with kerma approximation) should be applied in case a significant contribution from secondary electrons originating outside the body is present.

ELECTRICAL STUDIES ON THE COMPOUND EYE OF LIGIA OCCIDENTALIS DANA (CRUSTACEA: ISOPODA)

PubMed Central

Ruck, Philip; Jahn, Theodore L.

1954-01-01

The ERG of the compound eye in freshly collected Ligia occidentalis, in response to high intensity light flashes of ⅛ second or longer duration, begins with a negative on-effect quickly followed by an early positive deflection, rapidly returns to the baseline during illumination, and ends with a positive off-effect. As the stimulus intensity is decreased the early positivity progressively decreases and the rapid return to the baseline is replaced by a slowing decline of the negative on-effect. Responses were recorded with one active electrode subcorneally situated in the illuminated eye, the reference electrode in the dark eye. The dark-adapted eye shows a facilitation of the amplitude and rates of rise and fall of the on-effect to a brief, high intensity light stimulus. This facilitation may persist for more than 2 minutes. Following light adaptation under conditions in which the human eye loses sensitivity by a factor of almost 40,000 the Ligia eye loses sensitivity by a factor of only 3. The flicker fusion frequency of the ERG may be as high as 120/second with a corneal illumination of 15,000 foot-candles. Bleeding an otherwise intact animal very rapidly results in a decline of amplitude, change of wave form, and loss of facilitation in the ERG. When the eye is deganglionated without bleeding the animal the isolated retina responds in the same manner as the intact eye. Histological examination of the Ligia receptor layer showed that each ommatidium contains three different retinula cell types, each of which may be responsible for a different aspect of the ERG. PMID:13174786

Three-dimensional ray tracing in spherical and elliptical generalized Luneburg lenses for application in the human eye lens.

PubMed

Gómez-Correa, J E; Coello, V; Garza-Rivera, A; Puente, N P; Chávez-Cerda, S

2016-03-10

Ray tracing in spherical Luneburg lenses has always been represented in 2D. All propagation planes in a 3D spherical Luneburg lens generate the same ray tracing, due to its radial symmetry. A geometry without radial symmetry generates a different ray tracing. For this reason, a new ray tracing method in 3D through spherical and elliptical Luneburg lenses using 2D methods is proposed. The physics of the propagation is shown here, which allows us to make a ray tracing associated with a vortex beam. A 3D ray tracing in a composite modified Luneburg lens that represents the human eye lens is also presented.

Teaching without Talking

ERIC Educational Resources Information Center

Hansen, Jacqueline

2010-01-01

A large part of human communication is nonverbal, and the messages sent by gestures, proximity, and eye contact can mean quite different things in different cultures. Because today's classrooms are culturally very diverse, teachers need detailed information about nonverbal information and how it varies among the students' cultures. (Contains 19…

The µ-opioid system promotes visual attention to faces and eyes.

PubMed

Chelnokova, Olga; Laeng, Bruno; Løseth, Guro; Eikemo, Marie; Willoch, Frode; Leknes, Siri

2016-12-01

Paying attention to others' faces and eyes is a cornerstone of human social behavior. The µ-opioid receptor (MOR) system, central to social reward-processing in rodents and primates, has been proposed to mediate the capacity for affiliative reward in humans. We assessed the role of the human MOR system in visual exploration of faces and eyes of conspecifics. Thirty healthy males received a novel, bidirectional battery of psychopharmacological treatment (an MOR agonist, a non-selective opioid antagonist, or placebo, on three separate days). Eye-movements were recorded while participants viewed facial photographs. We predicted that the MOR system would promote visual exploration of faces, and hypothesized that MOR agonism would increase, whereas antagonism decrease overt attention to the information-rich eye region. The expected linear effect of MOR manipulation on visual attention to the stimuli was observed, such that MOR agonism increased while antagonism decreased visual exploration of faces and overt attention to the eyes. The observed effects suggest that the human MOR system promotes overt visual attention to socially significant cues, in line with theories linking reward value to gaze control and target selection. Enhanced attention to others' faces and eyes represents a putative behavioral mechanism through which the human MOR system promotes social interest. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Oculomatic: High speed, reliable, and accurate open-source eye tracking for humans and non-human primates.

PubMed

Zimmermann, Jan; Vazquez, Yuriria; Glimcher, Paul W; Pesaran, Bijan; Louie, Kenway

2016-09-01

Video-based noninvasive eye trackers are an extremely useful tool for many areas of research. Many open-source eye trackers are available but current open-source systems are not designed to track eye movements with the temporal resolution required to investigate the mechanisms of oculomotor behavior. Commercial systems are available but employ closed source hardware and software and are relatively expensive, limiting wide-spread use. Here we present Oculomatic, an open-source software and modular hardware solution to eye tracking for use in humans and non-human primates. Oculomatic features high temporal resolution (up to 600Hz), real-time eye tracking with high spatial accuracy (<0.5°), and low system latency (∼1.8ms, 0.32ms STD) at a relatively low-cost. Oculomatic compares favorably to our existing scleral search-coil system while being fully non invasive. We propose that Oculomatic can support a wide range of research into the properties and neural mechanisms of oculomotor behavior. Copyright © 2016 Elsevier B.V. All rights reserved.

Using RGB displays to portray color realistic imagery to animal eyes

PubMed Central

Johnsen, Sönke

2017-01-01

Abstract RGB displays effectively simulate millions of colors in the eyes of humans by modulating the relative amount of light emitted by 3 differently colored juxtaposed lights (red, green, and blue). The relationship between the ratio of red, green, and blue light and the perceptual experience of that light has been well defined by psychophysical experiments in humans, but is unknown in animals. The perceptual experience of an animal looking at an RGB display of imagery designed for humans is likely to poorly represent an animal’s experience of the same stimulus in the real world. This is due, in part, to the fact that many animals have different numbers of photoreceptor classes than humans do and that their photoreceptor classes have peak sensitivities centered over different parts of the ultraviolet and visible spectrum. However, it is sometimes possible to generate videos that accurately mimic natural stimuli in the eyes of another animal, even if that animal’s sensitivity extends into the ultraviolet portion of the spectrum. How independently each RGB phosphor stimulates each of an animal’s photoreceptor classes determines the range of colors that can be simulated for that animal. What is required to determine optimal color rendering for another animal is a device capable of measuring absolute or relative quanta of light across the portion of the spectrum visible to the animal (i.e., a spectrometer), and data on the spectral sensitivities of the animal’s photoreceptor classes. In this article, we outline how to use such equipment and information to generate video stimuli that mimic, as closely as possible, an animal’s color perceptual experience of real-world objects. Key words: color vision, computer animation, perception, video playback, virtual reality. PMID:29491960

Effect of elemental compositions on Monte Carlo dose calculations in proton therapy of eye tumors

NASA Astrophysics Data System (ADS)

Rasouli, Fatemeh S.; Farhad Masoudi, S.; Keshazare, Shiva; Jette, David

2015-12-01

Recent studies in eye plaque brachytherapy have found considerable differences between the dosimetric results by using a water phantom, and a complete human eye model. Since the eye continues to be simulated as water-equivalent tissue in the proton therapy literature, a similar study for investigating such a difference in treating eye tumors by protons is indispensable. The present study inquires into this effect in proton therapy utilizing Monte Carlo simulations. A three-dimensional eye model with elemental compositions is simulated and used to examine the dose deposition to the phantom. The beam is planned to pass through a designed beam line to moderate the protons to the desired energies for ocular treatments. The results are compared with similar irradiation to a water phantom, as well as to a material with uniform density throughout the whole volume. Spread-out Bragg peaks (SOBPs) are created by adding pristine peaks to cover a typical tumor volume. Moreover, the corresponding beam parameters recommended by the ICRU are calculated, and the isodose curves are computed. The results show that the maximum dose deposited in ocular media is approximately 5-7% more than in the water phantom, and about 1-1.5% less than in the homogenized material of density 1.05 g cm-3. Furthermore, there is about a 0.2 mm shift in the Bragg peak due to the tissue composition difference between the models. It is found that using the weighted dose profiles optimized in a water phantom for the realistic eye model leads to a small disturbance of the SOBP plateau dose. In spite of the plaque brachytherapy results for treatment of eye tumors, it is found that the differences between the simplified models presented in this work, especially the phantom containing the homogenized material, are not clinically significant in proton therapy. Taking into account the intrinsic uncertainty of the patient dose calculation for protons, and practical problems corresponding to applying patient-specific eye modeling, we found that the results of using a generic phantom containing homogenized material for proton therapy of eye tumors can be satisfactory for designing the beam.

An optomechanical model eye for ophthalmological refractive studies.

PubMed

Arianpour, Ashkan; Tremblay, Eric J; Stamenov, Igor; Ford, Joseph E; Schanzlin, David J; Lo, Yuhwa

2013-02-01

To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery. Copyright 2013, SLACK Incorporated.

Efficient and robust pupil size and blink estimation from near-field video sequences for human-machine interaction.

PubMed

Chen, Siyuan; Epps, Julien

2014-12-01

Monitoring pupil and blink dynamics has applications in cognitive load measurement during human-machine interaction. However, accurate, efficient, and robust pupil size and blink estimation pose significant challenges to the efficacy of real-time applications due to the variability of eye images, hence to date, require manual intervention for fine tuning of parameters. In this paper, a novel self-tuning threshold method, which is applicable to any infrared-illuminated eye images without a tuning parameter, is proposed for segmenting the pupil from the background images recorded by a low cost webcam placed near the eye. A convex hull and a dual-ellipse fitting method are also proposed to select pupil boundary points and to detect the eyelid occlusion state. Experimental results on a realistic video dataset show that the measurement accuracy using the proposed methods is higher than that of widely used manually tuned parameter methods or fixed parameter methods. Importantly, it demonstrates convenience and robustness for an accurate and fast estimate of eye activity in the presence of variations due to different users, task types, load, and environments. Cognitive load measurement in human-machine interaction can benefit from this computationally efficient implementation without requiring a threshold calibration beforehand. Thus, one can envisage a mini IR camera embedded in a lightweight glasses frame, like Google Glass, for convenient applications of real-time adaptive aiding and task management in the future.

See You See Me: the Role of Eye Contact in Multimodal Human-Robot Interaction.

PubMed

Xu, Tian Linger; Zhang, Hui; Yu, Chen

2016-05-01

We focus on a fundamental looking behavior in human-robot interactions - gazing at each other's face. Eye contact and mutual gaze between two social partners are critical in smooth human-human interactions. Therefore, investigating at what moments and in what ways a robot should look at a human user's face as a response to the human's gaze behavior is an important topic. Toward this goal, we developed a gaze-contingent human-robot interaction system, which relied on momentary gaze behaviors from a human user to control an interacting robot in real time. Using this system, we conducted an experiment in which human participants interacted with the robot in a joint attention task. In the experiment, we systematically manipulated the robot's gaze toward the human partner's face in real time and then analyzed the human's gaze behavior as a response to the robot's gaze behavior. We found that more face looks from the robot led to more look-backs (to the robot's face) from human participants and consequently created more mutual gaze and eye contact between the two. Moreover, participants demonstrated more coordinated and synchronized multimodal behaviors between speech and gaze when more eye contact was successfully established and maintained.

Fight or flight? Dream content during sleepwalking/sleep terrors vs. rapid eye movement sleep behavior disorder.

PubMed

Uguccioni, Ginevra; Golmard, Jean-Louis; de Fontréaux, Alix Noël; Leu-Semenescu, Smaranda; Brion, Agnès; Arnulf, Isabelle

2013-05-01

Dreams enacted during sleepwalking or sleep terrors (SW/ST) may differ from those enacted during rapid eye movement sleep behavior disorder (RBD). Subjects completed aggression, depression, and anxiety questionnaires. The mentations associated with SW/ST and RBD behaviors were collected over their lifetime and on the morning after video polysomnography (PSG). The reports were analyzed for complexity, length, content, setting, bizarreness, and threat. Ninety-one percent of 32 subjects with SW/ST and 87.5% of 24 subjects with RBD remembered an enacted dream (121 dreams in a lifetime and 41 dreams recalled on the morning). These dreams were more complex and less bizarre, with a higher level of aggression in the RBD than in SW/ST subjects. In contrast, we found low aggression, anxiety, and depression scores during the daytime in both groups. As many as 70% of enacted dreams in SW/ST and 60% in RBD involved a threat, but there were more misfortunes and disasters in the SW/ST dreams and more human and animal aggressions in the RBD dreams. The response to these threats differed, as the sleepwalkers mostly fled from a disaster (and 25% fought back when attacked), while 75% of RBD subjects counterattacked when assaulted. The dreams setting included their bedrooms in 42% SW/ST dreams, though this finding was exceptional in the RBD dreams. Different threat simulations and modes of defense seem to play a role during dream-enacted behaviors (e.g., fleeing a disaster during SW/ST, counterattacking a human or animal assault during RBD), paralleling and exacerbating the differences observed between normal dreaming in nonrapid eye movement (NREM) vs rapid eye movement (REM) sleep. Copyright © 2013 Elsevier B.V. All rights reserved.

Foetal Testosterone, Social Relationships, and Restricted Interests in Children

ERIC Educational Resources Information Center

Knickmeyer, Rebecca; Baron-Cohen, Simon; Raggatt, Peter; Taylor, Kevin

2005-01-01

Background: Sex-differences exist in some areas of human social behaviour. In animals, foetal testosterone (fT) plays a central role in organising the brain and in later social behaviour. fT has also been implicated in language development, eye-contact, and spatial ability in humans. Methods: Fifty-eight children (35 male and 23 female), whose fT…

Variability in human cone topography assessed by adaptive optics scanning laser ophthalmoscopy

PubMed Central

Zhang, Tianjiao; Godara, Pooja; Blanco, Ernesto R.; Griffin, Russell L; Wang, Xiaolin; Curcio, Christine A.; Zhang, Yuhua

2015-01-01

Purpose To assess between- and within-individual variability of macular cone topography in the eyes of young adults. Design Observational case series. Methods Cone photoreceptors in 40 eyes of 20 subjects aged 19–29 years with normal maculae were imaged using a research adaptive optics scanning laser ophthalmoscope. Refractive errors ranged from −3.0 D to 0.63 D and differed by <0.50 D in fellow eyes. Cone density was assessed on a two-dimensional sampling grid over the central 2.4 mm × 2.4 mm. Between-individual variability was evaluated by coefficient of variation (CV). Within-individual variability was quantified by maximum difference and root-mean-square (RMS). Cones were cumulated over increasing eccentricity. Results Peak densities of foveal cones are 168,162 ± 23,529 cones/mm2 (mean ± SD) (CV = 0.14). The number of cones within the cone-dominated foveola (0.8–0.9 mm diameter) is 38,311 ± 2,319 (CV = 0.06). The RMS cone density difference between fellow eyes is 6.78%, and the maximum difference is 23.6%. Mixed model statistical analysis found no difference in the association between eccentricity and cone density in the superior/nasal (p=0.8503), superior/temporal (p=0.1551), inferior/nasal (p=0.8609), and inferior/temporal (p=0.6662) quadrants of fellow eyes. Conclusions New instrumentation imaged the smallest foveal cones, thus allowing accurate assignment of foveal centers and assessment of variability in macular cone density in a large sample of eyes. Though cone densities vary significantly in the fovea, the total number of foveolar cones are very similar both between- and within-subjects. Thus, the total number of foveolar cones may be an important measure of cone degeneration and loss. PMID:25935100

Comparative cyto-histological study of needle tip aspirates and entry sites after intravitreal injection using different needle types

PubMed Central

Lytvynchuk, Lyubomyr; Sergienko, Andrij; Savytska, Iryna; Albert, Réka; Glittenberg, Carl; Binder, Susanne; Petrovski, Goran

2017-01-01

A comparison of the cellular content of needle tip aspirates and entry sites after transconjunctival intravitreal injection (IVI) using different needle types was performed. White outbred rats and human cadaver eyes were used for IVI by hypodermic 27 gauge (G) and 30G needles, and spinal anesthesia Pencan 27G needles. Aspiration of vitreous for quantitative morphological and cell cultivation analysis, as well as cyto-histological analysis of aspirates and entry sites were carried out. The most common cells in the aspirates from all needle types were conjunctival epithelial-, ciliary body non-pigmented epithelial- and sclerocyte-like cells and granular proteins. Crystallized vitreous specimens were present in each aspirate. The entry sites of hypodermic needles showed marked trauma in all wall layers of rat and human eyes accompanied by cellular destruction and hemorrhages. Pencan 27G needle caused less tissue trauma with partial reposition of sclerocytes. Transconjunctival IVIs with hypodermic 27G and 30G, and Pencan 27G needles result in trauma of all layers of the eyeball. The possible consequences of cellular content being cut and injected into the eye, as well as the entry site wound shape deserve future consideration and improvements. PMID:28692684

Shielding Effect of Lead Glasses on Radiologists' Eye Lens Exposure in Interventional Procedures.

PubMed

Hu, Panpan; Kong, Yan; Chen, Bo; Liu, Qianqian; Zhuo, Weihai; Liu, Haikuan

2017-04-20

To study the shielding effect of radiologists' eye lens with lead glasses of different equivalent thicknesses and sizes in interventional radiology procedures. Using the human voxel phantom with a more accurate model of the eye and MCNPX software, eye lens doses of the radiologists who wearing different kinds of lead glasses were simulated, different beam projections were taken into consideration during the simulation. Measurements were also performed with the physical model to verify simulation results. Simulation results showed that the eye lens doses were reduced by a factor from 3 to 9 when wearing a 20 cm2-sized lead glasses with the equivalent thickness ranging from 0.1 to 1.0 mm Pb. The increase of dose reduction factor (DRF) was not significant whenever increase the lead equivalent of glasses of which larger than 0.35 mm. Furthermore, the DRF was proportional to the size of glass lens from 6 to 30 cm2 with the same lead equivalent. The simulation results were in well agreements with the measured ones. For more reasonable and effective protection of the eye lens of interventional radiologists, a pair of glasses with a lead equivalent of 0.5 mm Pb and large-sized (at least 27 cm2 per glass) lens are recommended. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Shifting the IGF-axis: An age-related decline in human tear IGF-1 correlates with clinical signs of dry eye.

PubMed

Patel, Roshni; Zhu, Meifang; Robertson, Danielle M

2018-06-01

The human corneal epithelium expresses both the insulin-like growth factor type 1 receptor (IGF-1R) and the IGF-1R/insulin receptor (INSR) hybrid. Despite the previous identification of IGF-1 in human tear fluid, little is known regarding the regulation of IGF-1 in tear fluid and its role in corneal epithelial homeostasis. In the present study, we investigated the impact of biological parameters on the concentration of human tear levels of IGF-1. Tear levels of IGF-1 were measured in 41 healthy, human volunteers without any reported symptoms of dry eye. All volunteers underwent standard biomicroscopic examination of the cornea and tear film. In a subgroup of volunteers, corneal staining with sodium fluorescein, tear film break up time and tear production using a Schirmer's test strip were measured to assess clinical signs of dry eye. Tears were collected from the inferior tear meniscus using glass microcapillary tubes and IGF-1 levels were measured using a solid phase sandwich ELISA. Tear levels of IGF-1 were highest in young adults and significantly decreased in older adults (P = 0.003). There were no differences in tear IGF-1 between males and females (P = 0.628). Tear IGF-1 levels were correlated with tear film break up time (R = 0.738) and tear production (R = 0.826). These data indicate that there is a progressive decline in tear IGF-1 due to aging that is associated with clinical signs of dry eye. This effect is likely due to age-related changes in the lacrimal gland. Copyright © 2018 Elsevier Ltd. All rights reserved.

Defining the Human Macula Transcriptome and Candidate Retinal Disease Genes UsingEyeSAGE

PubMed Central

Rickman, Catherine Bowes; Ebright, Jessica N.; Zavodni, Zachary J.; Yu, Ling; Wang, Tianyuan; Daiger, Stephen P.; Wistow, Graeme; Boon, Kathy; Hauser, Michael A.

2009-01-01

Purpose To develop large-scale, high-throughput annotation of the human macula transcriptome and to identify and prioritize candidate genes for inherited retinal dystrophies, based on ocular-expression profiles using serial analysis of gene expression (SAGE). Methods Two human retina and two retinal pigment epithelium (RPE)/choroid SAGE libraries made from matched macula or midperipheral retina and adjacent RPE/choroid of morphologically normal 28- to 66-year-old donors and a human central retina longSAGE library made from 41- to 66-year-old donors were generated. Their transcription profiles were entered into a relational database, EyeSAGE, including microarray expression profiles of retina and publicly available normal human tissue SAGE libraries. EyeSAGE was used to identify retina- and RPE-specific and -associated genes, and candidate genes for retina and RPE disease loci. Differential and/or cell-type specific expression was validated by quantitative and single-cell RT-PCR. Results Cone photoreceptor-associated gene expression was elevated in the macula transcription profiles. Analysis of the longSAGE retina tags enhanced tag-to-gene mapping and revealed alternatively spliced genes. Analysis of candidate gene expression tables for the identified Bardet-Biedl syndrome disease gene (BBS5) in the BBS5 disease region table yielded BBS5 as the top candidate. Compelling candidates for inherited retina diseases were identified. Conclusions The EyeSAGE database, combining three different gene-profiling platforms including the authors’ multidonor-derived retina/RPE SAGE libraries and existing single-donor retina/RPE libraries, is a powerful resource for definition of the retina and RPE transcriptomes. It can be used to identify retina-specific genes, including alternatively spliced transcripts and to prioritize candidate genes within mapped retinal disease regions. PMID:16723438

Defining the human macula transcriptome and candidate retinal disease genes using EyeSAGE.

PubMed

Bowes Rickman, Catherine; Ebright, Jessica N; Zavodni, Zachary J; Yu, Ling; Wang, Tianyuan; Daiger, Stephen P; Wistow, Graeme; Boon, Kathy; Hauser, Michael A

2006-06-01

To develop large-scale, high-throughput annotation of the human macula transcriptome and to identify and prioritize candidate genes for inherited retinal dystrophies, based on ocular-expression profiles using serial analysis of gene expression (SAGE). Two human retina and two retinal pigment epithelium (RPE)/choroid SAGE libraries made from matched macula or midperipheral retina and adjacent RPE/choroid of morphologically normal 28- to 66-year-old donors and a human central retina longSAGE library made from 41- to 66-year-old donors were generated. Their transcription profiles were entered into a relational database, EyeSAGE, including microarray expression profiles of retina and publicly available normal human tissue SAGE libraries. EyeSAGE was used to identify retina- and RPE-specific and -associated genes, and candidate genes for retina and RPE disease loci. Differential and/or cell-type specific expression was validated by quantitative and single-cell RT-PCR. Cone photoreceptor-associated gene expression was elevated in the macula transcription profiles. Analysis of the longSAGE retina tags enhanced tag-to-gene mapping and revealed alternatively spliced genes. Analysis of candidate gene expression tables for the identified Bardet-Biedl syndrome disease gene (BBS5) in the BBS5 disease region table yielded BBS5 as the top candidate. Compelling candidates for inherited retina diseases were identified. The EyeSAGE database, combining three different gene-profiling platforms including the authors' multidonor-derived retina/RPE SAGE libraries and existing single-donor retina/RPE libraries, is a powerful resource for definition of the retina and RPE transcriptomes. It can be used to identify retina-specific genes, including alternatively spliced transcripts and to prioritize candidate genes within mapped retinal disease regions.

Estimating Human Trabecular Meshwork Stiffness by Numerical Modeling and Advanced OCT Imaging.

PubMed

Wang, Ke; Johnstone, Murray A; Xin, Chen; Song, Shaozhen; Padilla, Steven; Vranka, Janice A; Acott, Ted S; Zhou, Kai; Schwaner, Stephen A; Wang, Ruikang K; Sulchek, Todd; Ethier, C Ross

2017-09-01

The purpose of this study was to estimate human trabecular meshwork (hTM) stiffness, thought to be elevated in glaucoma, using a novel indirect approach, and to compare results with direct en face atomic force microscopy (AFM) measurements. Postmortem human eyes were perfused to measure outflow facility and identify high- and low-flow regions (HF, LF) by tracer. Optical coherence tomography (OCT) images were obtained as Schlemm's canal luminal pressure was directly manipulated. TM stiffness was deduced by an inverse finite element modeling (FEM) approach. A series of AFM forcemaps was acquired along a line traversing the anterior angle on a radially cut flat-mount corneoscleral wedge with TM facing upward. The elastic modulus of normal hTM estimated by inverse FEM was 70 ± 20 kPa (mean ± SD), whereas glaucomatous hTM was slightly stiffer (98 ± 19 kPa). This trend was consistent with TM stiffnesses measured by AFM: normal hTM stiffness = 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa). None of these differences were statistically significant. TM in HF wedges was softer than that in LF wedges for both normal and glaucomatous eyes based on the inverse FEM approach but not by AFM. Outflow facility was significantly correlated with TM stiffness estimated by FEM in six human eyes (P = 0.018). TM stiffness is higher, but only modestly so, in glaucomatous patients. Outflow facility in both normal and glaucomatous human eyes appears to associate with TM stiffness. This evidence motivates further studies to investigate factors underlying TM biomechanical property regulation.

Expression of classical components of the renin-angiotensin system in the human eye.

PubMed

White, Andrew J R; Cheruvu, Sarat C; Sarris, Maria; Liyanage, Surabhi S; Lumbers, Eugenie; Chui, Jeanie; Wakefield, Denis; McCluskey, Peter J

2015-03-01

The purpose of this study was to determine the relative expression of clinically-relevant components of the renin-angiotensin system (RAS) in the adult human eye. We obtained 14 post-mortem enucleated human eyes from patients whom had no history of inflammatory ocular disease nor pre-mortem ocular infection. We determined the gene expression for prorenin, renin, prorenin receptor, angiotensin-converting enzyme, angiotensinogen and angiotensin II Type 1 receptor, on tissue sections and in cultured human primary retinal pigment epithelial and iris pigment epithelial (RPE/IPE) cell lines, using both qualitative and quantitative reverse transcription polymerase chain reaction (RT-PCR). Protein expression was studied using indirect immunofluorescence (IF). Almost all components of the classical RAS were found at high levels, at both the transcript and protein level, in the eyes' uvea and retina; and at lower levels in the cornea, conjunctiva and sclera. There was a much lower level of expression in the reference cultured RPE/IPE cells lines. This study describes the distribution of RAS in the normal adult human eye and demonstrates the existence of an independent ocular RAS, with uveal and retinal tissues showing the highest expression of RAS components. These preliminary findings provide scope for examination of additional components of this system in the human eye, as well as possible differential expression under pathological conditions. © The Author(s) 2014.

APPLICATION OF EYE TRACKING FOR MEASUREMENT AND EVALUATION IN HUMAN FACTORS STUDIES IN CONTROL ROOM MODERNIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovesdi, C.; Spielman, Z.; LeBlanc, K.

An important element of human factors engineering (HFE) pertains to measurement and evaluation (M&E). The role of HFE-M&E should be integrated throughout the entire control room modernization (CRM) process and be used for human-system performance evaluation and diagnostic purposes with resolving potential human engineering deficiencies (HEDs) and other human machine interface (HMI) design issues. NUREG-0711 describes how HFE in CRM should employ a hierarchical set of measures, particularly during integrated system validation (ISV), including plant performance, personnel task performance, situation awareness, cognitive workload, and anthropometric/ physiological factors. Historically, subjective measures have been primarily used since they are easier to collectmore » and do not require specialized equipment. However, there are pitfalls with relying solely on subjective measures in M&E such that negatively impact reliability, sensitivity, and objectivity. As part of comprehensively capturing a diverse set of measures that strengthen findings and inferences made of the benefits from emerging technologies like advanced displays, this paper discusses the value of using eye tracking as an objective method that can be used in M&E. A brief description of eye tracking technology and relevant eye tracking measures is provided. Additionally, technical considerations and the unique challenges with using eye tracking in full-scaled simulations are addressed. Finally, this paper shares preliminary findings regarding the use of a wearable eye tracking system in a full-scale simulator study. These findings should help guide future full-scale simulator studies using eye tracking as a methodology to evaluate human-system performance.« less

Comparisons of luminaires: Efficacies and system design

NASA Technical Reports Server (NTRS)

Albright, L. D.; Both, A. J.

1994-01-01

Lighting designs for architectural (aesthetic) purposes, vision and safety, and plant growth have many features in common but several crucial ones that are not. The human eye is very sensitive to the color (wavelength) of light, whereas plants are less so. There are morphological reactions, particularly to the red and blue portions of the light spectrum but, in general, plants appear to accept and use light for photosynthesis everywhere over the PAR region of the spectrum. In contrast, the human eye interprets light intensity on a logarithmic scale, making people insensitive to significant differences of light intensity. As a rough rule, light intensity must change by 30 to 50% for the human eye to recognize the difference. Plants respond much more linearly to light energy, at least at intensities below photosynthetic saturation. Thus, intensity differences not noticeable to the human eye can have significant effects on total plant growth and yield, and crop timing. These factors make luminaire selection and lighting system design particularly important when designing supplemental lighting systems for plant growth. Supplemental lighting for plant growth on the scale of commercial greenhouses is a relatively expensive undertaking. Light intensities are often much higher than required for task (vision) lighting, which increases both installation and operating costs. However, and especially in the northern regions of the United States (and Canada, Europe, etc.), supplemental lighting during winter may be necessary to produce certain crops (e.g., tomatoes) and very useful to achieve full plant growth potential and crop timing with most other greenhouse crops. Operating costs over the life of a luminaire typically will exceed the initial investment, making lighting efficacy a major consideration. This report reviews tests completed to evaluate the efficiencies of various commercially-available High-Pressure Sodium luminaires, and then describes the results of using a commercial lighting design computer program, Lumen-Micro, to explore how to place luminaires within greenhouses and plant growth chambers to achieve light (PAR) uniformity and relatively high lighting efficacies. Several suggestions are presented which could encourage systematic design of plant lighting systems.

Eye and head motion during head turns in spaceflight

NASA Technical Reports Server (NTRS)

Thornton, William E.; Uri, John J.; Moore, Thomas P.; Pool, Sam L.

1988-01-01

Eye-head motion was studied pre-, in- and postflight during single voluntary head turns. A transient increase in vestibulo-ocular reflex (VOR) gain occurred early in the flight, but later trended toward normal. This increased gain was produced by a relative increase in eye counterrotation velocity. Asymmetries in gain with right and left turns also occurred, caused by asymmetries in eye counterrotation velocities. These findings were remarkably similar to those from Soviet primate studies using gaze fixation targets, except the human study trended more rapidly toward normal. These findings differ substantially from those measuring VOR gain by head oscillation, in which no significant changes were found inflight. No visual disturbances were noted in either test condition or in normal activities. These head turn studies are the only ones to date documenting any functional change in VOR in weightlessness.

Lateralization of magnetic compass orientation in a migratory bird

NASA Astrophysics Data System (ADS)

Wiltschko, Wolfgang; Traudt, Joachim; Güntürkün, Onur; Prior, Helmut; Wiltschko, Roswitha

2002-10-01

Lateralization of brain functions, once believed to be a human characteristic, has now been found to be widespread among vertebrates. In birds, asymmetries of visual functions are well studied, with each hemisphere being specialized for different tasks. Here we report lateralized functions of the birds' visual system associated with magnetoperception, resulting in an extreme asymmetry of sensing the direction of the magnetic field. We found that captive migrants tested in cages with the magnetic field as the only available orientation cue were well oriented in their appropriate migratory direction when using their right eye only, but failed to show a significant directional preference when using their left eye. This implies that magnetoreception for compass orientation, assumed to take place in the eyes alongside the visual processes, is strongly lateralized, with a marked dominance of the right eye/left brain hemisphere.

The Science of Colour

ERIC Educational Resources Information Center

Edwards, S. J.

1975-01-01

Provides information on how humans see color including sensitivity of the eye, spatial effects, and temporal effects, and relative to the characteristics of the human eye explains how color is measured. (GS)

Fetal Eye Movements on Magnetic Resonance Imaging

PubMed Central

Woitek, Ramona; Kasprian, Gregor; Lindner, Christian; Stuhr, Fritz; Weber, Michael; Schöpf, Veronika; Brugger, Peter C.; Asenbaum, Ulrika; Furtner, Julia; Bettelheim, Dieter; Seidl, Rainer; Prayer, Daniela

2013-01-01

Objectives Eye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed. Methods Dynamic SSFP sequences were acquired in 72 singleton fetuses (17–40 GW, three age groups [17–23 GW, 24–32 GW, 33–40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid. Results In 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded. Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3–45%. Conclusions In human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations. PMID:24194885

Rapid, Accurate, and Non-Invasive Measurement of Zebrafish Axial Length and Other Eye Dimensions Using SD-OCT Allows Longitudinal Analysis of Myopia and Emmetropization

PubMed Central

Collery, Ross F.; Veth, Kerry N.; Dubis, Adam M.; Carroll, Joseph; Link, Brian A.

2014-01-01

Refractive errors in vision can be caused by aberrant axial length of the eye, irregular corneal shape, or lens abnormalities. Causes of eye length overgrowth include multiple genetic loci, and visual parameters. We evaluate zebrafish as a potential animal model for studies of the genetic, cellular, and signaling basis of emmetropization and myopia. Axial length and other eye dimensions of zebrafish were measured using spectral domain-optical coherence tomography (SD-OCT). We used ocular lens and body metrics to normalize and compare eye size and relative refractive error (difference between observed retinal radial length and controls) in wild-type and lrp2 zebrafish. Zebrafish were dark-reared to assess effects of visual deprivation on eye size. Two relative measurements, ocular axial length to body length and axial length to lens diameter, were found to accurately normalize comparisons of eye sizes between different sized fish (R2 = 0.9548, R2 = 0.9921). Ray-traced focal lengths of wild-type zebrafish lenses were equal to their retinal radii, while lrp2 eyes had longer retinal radii than focal lengths. Both genetic mutation (lrp2) and environmental manipulation (dark-rearing) caused elongated eye axes. lrp2 mutants had relative refractive errors of −0.327 compared to wild-types, and dark-reared wild-type fish had relative refractive errors of −0.132 compared to light-reared siblings. Therefore, zebrafish eye anatomy (axial length, lens radius, retinal radius) can be rapidly and accurately measured by SD-OCT, facilitating longitudinal studies of regulated eye growth and emmetropization. Specifically, genes homologous to human myopia candidates may be modified, inactivated or overexpressed in zebrafish, and myopia-sensitizing conditions used to probe gene-environment interactions. Our studies provide foundation for such investigations into genetic contributions that control eye size and impact refractive errors. PMID:25334040

Research on the liquid crystal adaptive optics system for human retinal imaging

NASA Astrophysics Data System (ADS)

Zhang, Lei; Tong, Shoufeng; Song, Yansong; Zhao, Xin

2013-12-01

The blood vessels only in Human eye retinal can be observed directly. Many diseases that are not obvious in their early symptom can be diagnosed through observing the changes of distal micro blood vessel. In order to obtain the high resolution human retinal images,an adaptive optical system for correcting the aberration of the human eye was designed by using the Shack-Hartmann wavefront sensor and the Liquid Crystal Spatial Light Modulator(LCLSM) .For a subject eye with 8m-1 (8D)myopia, the wavefront error is reduced to 0.084 λ PV and 0.12 λRMS after adaptive optics(AO) correction ,which has reached diffraction limit.The results show that the LCLSM based AO system has the ability of correcting the aberration of the human eye efficiently,and making the blurred photoreceptor cell to clearly image on a CCD camera.

Personal identification by eyes.

PubMed

Marinović, Dunja; Njirić, Sanja; Coklo, Miran; Muzić, Vedrana

2011-09-01

Identification of persons through the eyes is in the field of biometrical science. Many security systems are based on biometric methods of personal identification, to determine whether a person is presenting itself truly. The human eye contains an extremely large number of individual characteristics that make it particularly suitable for the process of identifying a person. Today, the eye is considered to be one of the most reliable body parts for human identification. Systems using iris recognition are among the most secure biometric systems.

Aqueous Angiography–Mediated Guidance of Trabecular Bypass Improves Angiographic Outflow in Human Enucleated Eyes

PubMed Central

Huang, Alex S.; Saraswathy, Sindhu; Dastiridou, Anna; Begian, Alan; Mohindroo, Chirayu; Tan, James C. H.; Francis, Brian A.; Hinton, David R.; Weinreb, Robert N.

2016-01-01

Purpose To assess the ability of trabecular micro-bypass stents to improve aqueous humor outflow (AHO) in regions initially devoid of AHO as assessed by aqueous angiography. Methods Enucleated human eyes (14 total from 7 males and 3 females [ages 52–84]) were obtained from an eye bank within 48 hours of death. Eyes were oriented by inferior oblique insertion, and aqueous angiography was performed with indocyanine green (ICG; 0.4%) or fluorescein (2.5%) at 10 mm Hg. With an angiographer, infrared and fluorescent images were acquired. Concurrent anterior segment optical coherence tomography (OCT) was performed, and fixable fluorescent dextrans were introduced into the eye for histologic analysis of angiographically positive and negative areas. Experimentally, some eyes (n = 11) first received ICG aqueous angiography to determine angiographic patterns. These eyes then underwent trabecular micro-bypass sham or stent placement in regions initially devoid of angiographic signal. This was followed by fluorescein aqueous angiography to query the effects. Results Aqueous angiography in human eyes yielded high-quality images with segmental patterns. Distally, angiographically positive but not negative areas demonstrated intrascleral lumens on OCT images. Aqueous angiography with fluorescent dextrans led to their trapping in AHO pathways. Trabecular bypass but not sham in regions initially devoid of ICG aqueous angiography led to increased aqueous angiography as assessed by fluorescein (P = 0.043). Conclusions Using sequential aqueous angiography in an enucleated human eye model system, regions initially without angiographic flow or signal could be recruited for AHO using a trabecular bypass stent. PMID:27588614

Identification of cornifelin and early growth response-1 gene as novel biomarkers for in vitro eye irritation using a 3D reconstructed human cornea model MCTT HCE™.

PubMed

Choi, Seunghye; Lee, Miri; Lee, Su-Hyon; Jung, Haeng-Sun; Kim, Seol-Yeong; Chung, Tae-Young; Choe, Tae-boo; Chun, Young-Jin; Lim, Kyung-Min

2015-09-01

Evaluation of the eye irritation is essential in the development of new cosmetic products. Draize rabbit eye irritation test has been widely used in which chemicals are directly applied to rabbit eye, and the symptoms and signs of eyes are scored. However, due to the invasive procedure, it causes substantial pain and discomfort to animals. Recently, we reported in vitro eye irritation test method using a 3D human corneal epithelial model (MCTT HCE™) which is reconstructed from remaining human tissues after a corneal transplantation. This model exhibited an excellent predictive capacity for 25 reference chemicals (sensitivity 100%, specificity 77% and accuracy 88% vs. GHS). To improve the test performance, we explored new biomarkers for the eye irritation through transcriptomic approach. Three surfactants were selected as model eye irritants that include sodium lauryl sulfate, benzalkonium chloride and triton X-100. After test chemicals were treated, we investigated differentially expressed genes through a whole-gene microarray (Affymetrix GeneChip(®) Human Gene 2.0 ST Array, 48,000 probes). As a result, we identified that mRNAs of cornifelin (CNFN), a constituent of the insoluble cornified cell envelope of stratified squamous epithelia, and early growth response-1 (EGR1), a nuclear transcriptional regulator, were significantly up-regulated by all three irritants. Up-regulation of CNFN and EGR1 was further confirmed by Q-RT-PCR, and immunohistochemistry revealed increased level of CNFN in irritant-treated tissues, supporting the relevance of CNFN and EGR1 as new biomarkers for eye irritation.

System for assisted mobility using eye movements based on electrooculography.

PubMed

Barea, Rafael; Boquete, Luciano; Mazo, Manuel; López, Elena

2002-12-01

This paper describes an eye-control method based on electrooculography (EOG) to develop a system for assisted mobility. One of its most important features is its modularity, making it adaptable to the particular needs of each user according to the type and degree of handicap involved. An eye model based on electroculographic signal is proposed and its validity is studied. Several human-machine interfaces (HMI) based on EOG are commented, focusing our study on guiding and controlling a wheelchair for disabled people, where the control is actually effected by eye movements within the socket. Different techniques and guidance strategies are then shown with comments on the advantages and disadvantages of each one. The system consists of a standard electric wheelchair with an on-board computer, sensors and a graphic user interface run by the computer. On the other hand, this eye-control method can be applied to handle graphical interfaces, where the eye is used as a mouse computer. Results obtained show that this control technique could be useful in multiple applications, such as mobility and communication aid for handicapped persons.

76 FR 33286 - Privacy Act of 1974; System of Records

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-08

... locations: Federal Housing Finance Agency, Office of Human Resources Management, 1700 G Street, NW... Human Resources Management, 1700 G Street, NW., Washington, DC 20552; 1625 Eye Street, NW., Washington...: Office of Human Resources Management, Federal Housing Finance Agency, 1625 Eye Street, NW., Washington...

Numerical analysis of specific absorption rate in the human head due to a 13.56 MHz RFID-based intra-ocular pressure measurement system

NASA Astrophysics Data System (ADS)

Hirtl, Rene; Schmid, Gernot

2013-09-01

A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues.

Preservation of Biological Activity of Plasma and Platelet-Derived Eye Drops After Their Different Time and Temperature Conditions of Storage.

PubMed

Anitua, Eduardo; de la Fuente, María; Riestra, Ana; Merayo-Lloves, Jesús; Muruzábal, Francisco; Orive, Gorka

2015-09-01

To analyze whether plasma rich in growth factors (PRGF) eye drops preserve their biological characteristics and activity after storage for 3 and 6 months at -20°C, at 4°C, and at room temperature for 72 hours, compared with fresh samples (t0). Blood from 6 healthy donors was harvested and centrifuged to obtain PRGF free of leukocytes. Resulting PRGF eye drops were stored for 3 and 6 months at -20°C. At each time, 2 aliquots were maintained at room temperature or at 4°C for 72 hours. Platelet-derived growth factor-AB, transforming growth factor-β1, vascular endothelial growth factor, epidermal growth factor, insulin-like growth factor-1, angiopoietin-1, and thrombospondin-1 were quantified at each time and temperature of storage. Also, the effect of PRGF eye drops on proliferation of primary human keratocytes was evaluated. All the analyzed growth factor levels remained constant at each time and storage condition. No differences were observed in the proliferative activity of keratocytes after treatment with PRGF eye drops at any studied time or temperature. Finally, there was no microbial contamination in any of the PRGF eye drops. The preservation of the PRGF eye drops at -20°C for up to 3 and 6 months does not mean reduction of the main growth factors and proteins implicated in ocular surface wound healing. Eye drop characteristics and in vitro biological activity were not affected by their usage and conservation for 72 hours at 4°C or at room temperature.

Transcriptomic analysis across nasal, temporal, and macular regions of human neural retina and RPE/choroid by RNA-Seq.

PubMed

Whitmore, S Scott; Wagner, Alex H; DeLuca, Adam P; Drack, Arlene V; Stone, Edwin M; Tucker, Budd A; Zeng, Shemin; Braun, Terry A; Mullins, Robert F; Scheetz, Todd E

2014-12-01

Proper spatial differentiation of retinal cell types is necessary for normal human vision. Many retinal diseases, such as Best disease and male germ cell associated kinase (MAK)-associated retinitis pigmentosa, preferentially affect distinct topographic regions of the retina. While much is known about the distribution of cell types in the retina, the distribution of molecular components across the posterior pole of the eye has not been well-studied. To investigate regional difference in molecular composition of ocular tissues, we assessed differential gene expression across the temporal, macular, and nasal retina and retinal pigment epithelium (RPE)/choroid of human eyes using RNA-Seq. RNA from temporal, macular, and nasal retina and RPE/choroid from four human donor eyes was extracted, poly-A selected, fragmented, and sequenced as 100 bp read pairs. Digital read files were mapped to the human genome and analyzed for differential expression using the Tuxedo software suite. Retina and RPE/choroid samples were clearly distinguishable at the transcriptome level. Numerous transcription factors were differentially expressed between regions of the retina and RPE/choroid. Photoreceptor-specific genes were enriched in the peripheral samples, while ganglion cell and amacrine cell genes were enriched in the macula. Within the RPE/choroid, RPE-specific genes were upregulated at the periphery while endothelium associated genes were upregulated in the macula. Consistent with previous studies, BEST1 expression was lower in macular than extramacular regions. The MAK gene was expressed at lower levels in macula than in extramacular regions, but did not exhibit a significant difference between nasal and temporal retina. The regional molecular distinction is greatest between macula and periphery and decreases between different peripheral regions within a tissue. Datasets such as these can be used to prioritize candidate genes for possible involvement in retinal diseases with regional phenotypes. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Transcriptomic analysis across nasal, temporal, and macular regions of human neural retina and RPE/choroid by RNA-Seq

PubMed Central

Whitmore, S. Scott; Wagner, Alex H.; DeLuca, Adam P.; Drack, Arlene V.; Stone, Edwin M.; Tucker, Budd A.; Zeng, Shemin; Braun, Terry A.; Mullins, Robert F.; Scheetz, Todd E.

2014-01-01

Proper spatial differentiation of retinal cell types is necessary for normal human vision. Many retinal diseases, such as Best disease and male germ cell associated kinase (MAK)-associated retinitis pigmentosa, preferentially affect distinct topographic regions of the retina. While much is known about the distribution of cell-types in the retina, the distribution of molecular components across the posterior pole of the eye has not been well-studied. To investigate regional difference in molecular composition of ocular tissues, we assessed differential gene expression across the temporal, macular, and nasal retina and retinal pigment epithelium (RPE)/choroid of human eyes using RNA-Seq. RNA from temporal, macular, and nasal retina and RPE/choroid from four human donor eyes was extracted, poly-A selected, fragmented, and sequenced as 100 bp read pairs. Digital read files were mapped to the human genome and analyzed for differential expression using the Tuxedo software suite. Retina and RPE/choroid samples were clearly distinguishable at the transcriptome level. Numerous transcription factors were differentially expressed between regions of the retina and RPE/choroid. Photoreceptor-specific genes were enriched in the peripheral samples, while ganglion cell and amacrine cell genes were enriched in the macula. Within the RPE/choroid, RPE-specific genes were upregulated at the periphery while endothelium associated genes were upregulated in the macula. Consistent with previous studies, BEST1 expression was lower in macular than extramacular regions. The MAK gene was expressed at lower levels in macula than in extramacular regions, but did not exhibit a significant difference between nasal and temporal retina. The regional molecular distinction is greatest between macula and periphery and decreases between different peripheral regions within a tissue. Datasets such as these can be used to prioritize candidate genes for possible involvement in retinal diseases with regional phenotypes. PMID:25446321

Designs and Algorithms to Map Eye Tracking Data with Dynamic Multielement Moving Objects.

PubMed

Kang, Ziho; Mandal, Saptarshi; Crutchfield, Jerry; Millan, Angel; McClung, Sarah N

2016-01-01

Design concepts and algorithms were developed to address the eye tracking analysis issues that arise when (1) participants interrogate dynamic multielement objects that can overlap on the display and (2) visual angle error of the eye trackers is incapable of providing exact eye fixation coordinates. These issues were addressed by (1) developing dynamic areas of interests (AOIs) in the form of either convex or rectangular shapes to represent the moving and shape-changing multielement objects, (2) introducing the concept of AOI gap tolerance (AGT) that controls the size of the AOIs to address the overlapping and visual angle error issues, and (3) finding a near optimal AGT value. The approach was tested in the context of air traffic control (ATC) operations where air traffic controller specialists (ATCSs) interrogated multiple moving aircraft on a radar display to detect and control the aircraft for the purpose of maintaining safe and expeditious air transportation. In addition, we show how eye tracking analysis results can differ based on how we define dynamic AOIs to determine eye fixations on moving objects. The results serve as a framework to more accurately analyze eye tracking data and to better support the analysis of human performance.

Designs and Algorithms to Map Eye Tracking Data with Dynamic Multielement Moving Objects

PubMed Central

Mandal, Saptarshi

2016-01-01

Design concepts and algorithms were developed to address the eye tracking analysis issues that arise when (1) participants interrogate dynamic multielement objects that can overlap on the display and (2) visual angle error of the eye trackers is incapable of providing exact eye fixation coordinates. These issues were addressed by (1) developing dynamic areas of interests (AOIs) in the form of either convex or rectangular shapes to represent the moving and shape-changing multielement objects, (2) introducing the concept of AOI gap tolerance (AGT) that controls the size of the AOIs to address the overlapping and visual angle error issues, and (3) finding a near optimal AGT value. The approach was tested in the context of air traffic control (ATC) operations where air traffic controller specialists (ATCSs) interrogated multiple moving aircraft on a radar display to detect and control the aircraft for the purpose of maintaining safe and expeditious air transportation. In addition, we show how eye tracking analysis results can differ based on how we define dynamic AOIs to determine eye fixations on moving objects. The results serve as a framework to more accurately analyze eye tracking data and to better support the analysis of human performance. PMID:27725830

Ethical Issues in Transnational Eye Banking.

PubMed

Martin, Dominique E; Kelly, Richard; Jones, Gary L A; Machin, Heather; Pollock, Graeme A

2017-02-01

To review ethical issues that may arise in the setting of transnational eye banking activities, such as when exporting or importing corneal tissue for transplantation. A principle-based normative analysis of potential common dilemmas in transnational eye banking activities was performed. Transnational activities in eye banking, like those in other fields involving procurement and use of medical products of human origin, may present a number of ethical issues for policy makers and professionals. Key ethical concerns include the potential impact of export or import activities on self-sufficiency of corneal tissue supply within exporting and importing countries; potential disclosure requirements when obtaining consent or authorization for ocular tissue donation when donations may be exported; and difficulties inherent in assuring equity in the allocation of tissues available for export and in establishing and respecting standards of safety and quality across different jurisdictions. Further analysis of specific ethical issues in eye banking is necessary to inform development of guidelines and other governance tools that will assist policy makers and professionals to support ethical practice.

Dose conversion coefficients for neutron exposure to the lens of the human eye.

PubMed

Manger, R P; Bellamy, M B; Eckerman, K F

2012-03-01

Dose conversion coefficients for the lens of the human eye have been calculated for neutron exposure at energies from 1 × 10(-9) to 20 MeV and several standard orientations: anterior-to-posterior, rotational and right lateral. MCNPX version 2.6.0, a Monte Carlo-based particle transport package, was used to determine the energy deposited in the lens of the eye. The human eyeball model was updated by partitioning the lens into sensitive and insensitive volumes as the anterior portion (sensitive volume) of the lens being more radiosensitive and prone to cataract formation. The updated eye model was used with the adult UF-ORNL mathematical phantom in the MCNPX transport calculations.

Holocamera for 3-D micrography of the alert human eye

NASA Astrophysics Data System (ADS)

Tokuda, A. R.; Auth, D. C.; Bruckner, A. P.

1980-07-01

A holocamera that safely records holograms of the full depth of the alert human eye with a spatial resolution of about 20 microns is described. A single-mode argon-ion laser generating 2 W at 5145 A serves as the illuminating source. Holographic exposure times of 0.3 msec are achieved by means of a fail-safe electromechanical shutter system. Integrated retinal irradiance levels are well under the American National Standards Institute safety standards. Reconstructed real images are projected directly onto the vidicon faceplate of a closed-circuit TV system, enabling convenient scanning in the x-y-z dimensions of the reconstructed eyeball. Serially reconstructed holograms of cataractous rabbit eyes and normal human eyes are presented.

Retinal image contrast obtained by a model eye with combined correction of chromatic and spherical aberrations

PubMed Central

Ohnuma, Kazuhiko; Kayanuma, Hiroyuki; Lawu, Tjundewo; Negishi, Kazuno; Yamaguchi, Takefumi; Noda, Toru

2011-01-01

Correcting spherical and chromatic aberrations in vitro in human eyes provides substantial visual acuity and contrast sensitivity improvements. We found the same improvement in the retinal images using a model eye with/without correction of longitudinal chromatic aberrations (LCAs) and spherical aberrations (SAs). The model eye included an intraocular lens (IOL) and artificial cornea with human ocular LCAs and average human SAs. The optotypes were illuminated using a D65 light source, and the images were obtained using two-dimensional luminance colorimeter. The contrast improvement from the SA correction was higher than the LCA correction, indicating the benefit of an aspheric achromatic IOL. PMID:21698008

Relative levels of motivation and asymmetries of viewing and detour task in guppies (Poecilia reticulata).

PubMed

Kaarthigeyan, J; Dharmaretnam, Meena

2005-04-15

Cerebral lateralisation once thought to be confined to humans has been reported for a range of vertebrate species now. We report here biases in visual perceptual processing in a teleost fish. Female guppy fish used the right eye preferentially to view a familiar stimulus. This bias reversed on being presented with a strange female guppy, the left eye being used more to view it. This pattern of viewing is probably associated with the right eye system, which is used to view a stimulus with an intention to approach it. The increase in the left eye use, to view a stranger may be associated with the role of the left eye in comparing the features of a strange conspecific. In the second experiment, lateralisation of viewing visual stimuli that could evoke different levels of motivation to biologically relevant stimuli was tested. It is known that female guppies prefer to approach orange coloured males. Lateralisation of detour response as well as eye use after detour to view a dull or an orange male stimulus was recorded in deprived female fish. There was a bias to detour to the left side; which was more significant for the orange than the dull male. Once the female guppies detoured the cage they preferentially used the left eye to view the male conspecific; this being significant for the deeply orange male. Thus, colouration of males evoking different levels motivation can be used to measure lateralisation in guppies.

Acute vitreoretinal trauma and inflammation after traumatic brain injury in mice.

PubMed

Evans, Lucy P; Newell, Elizabeth A; Mahajan, MaryAnn; Tsang, Stephen H; Ferguson, Polly J; Mahoney, Jolonda; Hue, Christopher D; Vogel, Edward W; Morrison, Barclay; Arancio, Ottavio; Nichols, Russell; Bassuk, Alexander G; Mahajan, Vinit B

2018-03-01

Limited attention has been given to ocular injuries associated with traumatic brain injury (TBI). The retina is an extension of the central nervous system and evaluation of ocular damage may offer a less-invasive approach to gauge TBI severity and response to treatment. We aim to characterize acute changes in the mouse eye after exposure to two different models of TBI to assess the utility of eye damage as a surrogate to brain injury. A model of blast TBI (bTBI) using a shock tube was compared to a lateral fluid percussion injury model (LFPI) using fluid pressure applied directly to the brain. Whole eyes were collected from mice 3 days post LFPI and 24 days post bTBI and were evaluated histologically using a hematoxylin and eosin stain. bTBI mice showed evidence of vitreous detachment in the posterior chamber in addition to vitreous hemorrhage with inflammatory cells. Subretinal hemorrhage, photoreceptor degeneration, and decreased cellularity in the retinal ganglion cell layer was also seen in bTBI mice. In contrast, eyes of LFPI mice showed evidence of anterior uveitis and subcapsular cataracts. We demonstrated that variations in the type of TBI can result in drastically different phenotypic changes within the eye. As such, molecular and phenotypic changes in the eye following TBI may provide valuable information regarding the mechanism, severity, and ongoing pathophysiology of brain injury. Because vitreous samples are easily obtained, molecular changes within the eye could be utilized as biomarkers of TBI in human patients.

Variations in Eyeball Diameters of the Healthy Adults

PubMed Central

Bekerman, Inessa; Gottlieb, Paul

2014-01-01

The purpose of the current research was to reevaluate the normative data on the eyeball diameters. Methods. In a prospective cohort study, the CT data of consecutive 250 adults with healthy eyes were collected and analyzed, and sagittal, transverse, and axial diameters of both eyeballs were measured. The data obtained from the left eye and from the right eye were compared. The correlation analysis was performed with the following variables: orbit size, gender, age, and ethnic background. Results. We did not find statistically significant differences correlated with gender of the patients and their age. The right eyeball was slightly smaller than the left one but this difference was statistically insignificant (P = 0.17). We did not find statistically significant differences of the eyeball sizes among the ethnicities we dealt with. Strong correlation was found between the transverse diameter and the width of the orbit (r = 0.88). Conclusion. The size of a human adult eye is approximately 24.2 mm (transverse) × 23.7 mm (sagittal) × 22.0–24.8 mm (axial) with no significant difference between sexes and age groups. In the transverse diameter, the eyeball size may vary from 21 mm to 27 mm. These data might be useful in ophthalmological, oculoplastic, and neurological practice. PMID:25431659

Variations in eyeball diameters of the healthy adults.

PubMed

Bekerman, Inessa; Gottlieb, Paul; Vaiman, Michael

2014-01-01

The purpose of the current research was to reevaluate the normative data on the eyeball diameters. Methods. In a prospective cohort study, the CT data of consecutive 250 adults with healthy eyes were collected and analyzed, and sagittal, transverse, and axial diameters of both eyeballs were measured. The data obtained from the left eye and from the right eye were compared. The correlation analysis was performed with the following variables: orbit size, gender, age, and ethnic background. Results. We did not find statistically significant differences correlated with gender of the patients and their age. The right eyeball was slightly smaller than the left one but this difference was statistically insignificant (P = 0.17). We did not find statistically significant differences of the eyeball sizes among the ethnicities we dealt with. Strong correlation was found between the transverse diameter and the width of the orbit (r = 0.88). Conclusion. The size of a human adult eye is approximately 24.2 mm (transverse) × 23.7 mm (sagittal) × 22.0-24.8 mm (axial) with no significant difference between sexes and age groups. In the transverse diameter, the eyeball size may vary from 21 mm to 27 mm. These data might be useful in ophthalmological, oculoplastic, and neurological practice.

Computational Model-Based Prediction of Human Episodic Memory Performance Based on Eye Movements

NASA Astrophysics Data System (ADS)

Sato, Naoyuki; Yamaguchi, Yoko

Subjects' episodic memory performance is not simply reflected by eye movements. We use a ‘theta phase coding’ model of the hippocampus to predict subjects' memory performance from their eye movements. Results demonstrate the ability of the model to predict subjects' memory performance. These studies provide a novel approach to computational modeling in the human-machine interface.

Workflows and individual differences during visually guided routine tasks in a road traffic management control room.

PubMed

Starke, Sandra D; Baber, Chris; Cooke, Neil J; Howes, Andrew

2017-05-01

Road traffic control rooms rely on human operators to monitor and interact with information presented on multiple displays. Past studies have found inconsistent use of available visual information sources in such settings across different domains. In this study, we aimed to broaden the understanding of observer behaviour in control rooms by analysing a case study in road traffic control. We conducted a field study in a live road traffic control room where five operators responded to incidents while wearing a mobile eye tracker. Using qualitative and quantitative approaches, we investigated the operators' workflow using ergonomics methods and quantified visual information sampling. We found that individuals showed differing preferences for viewing modalities and weighting of task components, with a strong coupling between eye and head movement. For the quantitative analysis of the eye tracking data, we propose a number of metrics which may prove useful to compare visual sampling behaviour across domains in future. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Adaptive Optics for the Human Eye

NASA Astrophysics Data System (ADS)

Williams, D. R.

2000-05-01

Adaptive optics can extend not only the resolution of ground-based telescopes, but also the human eye. Both static and dynamic aberrations in the cornea and lens of the normal eye limit its optical quality. Though it is possible to correct defocus and astigmatism with spectacle lenses, higher order aberrations remain. These aberrations blur vision and prevent us from seeing at the fundamental limits set by the retina and brain. They also limit the resolution of cameras to image the living retina, cameras that are a critical for the diagnosis and treatment of retinal disease. I will describe an adaptive optics system that measures the wave aberration of the eye in real time and compensates for it with a deformable mirror, endowing the human eye with unprecedented optical quality. This instrument provides fresh insight into the ultimate limits on human visual acuity, reveals for the first time images of the retinal cone mosaic responsible for color vision, and points the way to contact lenses and laser surgical methods that could enhance vision beyond what is currently possible today. Supported by the NSF Science and Technology Center for Adaptive Optics, the National Eye Institute, and Bausch and Lomb, Inc.

Application of adipose-derived stem cells on scleral contact lens carrier in an animal model of severe acute alkaline burn.

PubMed

Espandar, Ladan; Caldwell, Delmar; Watson, Richard; Blanco-Mezquita, Tomas; Zhang, Shijia; Bunnell, Bruce

2014-07-01

To evaluate the therapeutic effect of human adipose-derived stem cells (hASCs) overlaid on a scleral contact lens (SCL) carrier in a rabbit model of ocular alkaline burn. After inducing alkaline burn in 11 New Zealand white rabbits, hASCs cultured on SCLs were placed on the right eye of 5 rabbits, SCLs without cells were used in 5, and no treatment was applied in 1 eye. Each eye was examined and photographed for corneal vascularization, opacities, and epithelial defect in week 1, 2, and 4 after surgery. After 1 month, rabbits were killed and the corneas were removed and cut in half for electron and light microscopy examination. Human adipose-derived stem cells were attached to SCL surface and confluent easily. Human adipose-derived stem cells on SCL eyes showed smaller epithelial defect, less corneal opacity, corneal neovascularization relative to SCL eyes. Both groups showed no symblepharon. However, the cornea in the untreated eye was melted in 2 weeks and developed severe symblepharon. Human adipose-derived stem cells on SCL can reduce inflammation and corneal haziness in severe ocular alkaline burn injury in rabbits.

Application of Adipose-Derived Stem Cells on Scleral Contact Lens Carrier in an Animal Model of Severe Acute Alkaline Burn

PubMed Central

Espandar, Ladan; Caldwell, Delmar; Watson, Richard; Blanco-Mezquita, Tomas; Zhang, Shijia; Bunnell, Bruce

2015-01-01

Purpose To evaluate the therapeutic effect of human adipose-derived stem cells (hASCs) overlaid on a scleral contact lens (SCL) carrier in a rabbit model of ocular alkaline burn. Materials and Methods After inducing alkaline burn in 11 New Zealand white rabbits, hASCs cultured on SCLs were placed on the right eye of 5 rabbits, SCLs without cells were used in 5, and no treatment was applied in 1 eye. Each eye was examined and photographed for corneal vascularization, opacities, and epithelial defect in week 1, 2, and 4 after surgery. After 1 month, rabbits were killed and the corneas were removed and cut in half for electron and light microscopy examination. Results Human adipose-derived stem cells were attached to SCL surface and confluent easily. Human adipose-derived stem cells on SCL eyes showed smaller epithelial defect, less corneal opacity, corneal neovascularization relative to SCL eyes. Both groups showed no symblepharon. However, the cornea in the untreated eye was melted in 2 weeks and developed severe symblepharon. Conclusion Human adipose-derived stem cells on SCL can reduce inflammation and corneal haziness in severe ocular alkaline burn injury in rabbits. PMID:24901976

Estimation of the mechanical properties of the eye through the study of its vibrational modes

PubMed Central

2017-01-01

Measuring the eye’s mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz–10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young’s modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye. PMID:28922351

Low bandwidth eye tracker for scanning laser ophthalmoscopy

NASA Astrophysics Data System (ADS)

Harvey, Zachary G.; Dubra, Alfredo; Cahill, Nathan D.; Lopez Alarcon, Sonia

2012-02-01

The incorporation of adaptive optics to scanning ophthalmoscopes (AOSOs) has allowed for in vivo, noninvasive imaging of the human rod and cone photoreceptor mosaics. Light safety restrictions and power limitations of the current low-coherence light sources available for imaging result in each individual raw image having a low signal to noise ratio (SNR). To date, the only approach used to increase the SNR has been to collect large number of raw images (N >50), to register them to remove the distortions due to involuntary eye motion, and then to average them. The large amplitude of involuntary eye motion with respect to the AOSO field of view (FOV) dictates that an even larger number of images need to be collected at each retinal location to ensure adequate SNR over the feature of interest. Compensating for eye motion during image acquisition to keep the feature of interest within the FOV could reduce the number of raw frames required per retinal feature, therefore significantly reduce the imaging time, storage requirements, post-processing times and, more importantly, subject's exposure to light. In this paper, we present a particular implementation of an AOSO, termed the adaptive optics scanning light ophthalmoscope (AOSLO) equipped with a simple eye tracking system capable of compensating for eye drift by estimating the eye motion from the raw frames and by using a tip-tilt mirror to compensate for it in a closed-loop. Multiple control strategies were evaluated to minimize the image distortion introduced by the tracker itself. Also, linear, quadratic and Kalman filter motion prediction algorithms were implemented and tested and tested using both simulated motion (sinusoidal motion with varying frequencies) and human subjects. The residual displacement of the retinal features was used to compare the performance of the different correction strategies and prediction methods.

Interocular induction of illusory size perception.

PubMed

Song, Chen; Schwarzkopf, D Samuel; Rees, Geraint

2011-03-11

The perceived size of objects not only depends on their physical size but also on the surroundings in which they appear. For example, an object surrounded by small items looks larger than a physically identical object surrounded by big items (Ebbinghaus illusion), and a physically identical but distant object looks larger than an object that appears closer in space (Ponzo illusion). Activity in human primary visual cortex (V1) reflects the perceived rather than the physical size of objects, indicating an involvement of V1 in illusory size perception. Here we investigate the role of eye-specific signals in two common size illusions in order to provide further information about the mechanisms underlying illusory size perception. We devised stimuli so that an object and its spatial context associated with illusory size perception could be presented together to one eye or separately to two eyes. We found that the Ponzo illusion had an equivalent magnitude whether the objects and contexts were presented to the same or different eyes, indicating that it may be largely mediated by binocular neurons. In contrast, the Ebbinghaus illusion became much weaker when objects and their contexts were presented to different eyes, indicating important contributions to the illusion from monocular neurons early in the visual pathway. Our findings show that two well-known size illusions - the Ponzo illusion and the Ebbinghaus illusion - are mediated by different neuronal populations, and suggest that the underlying neural mechanisms associated with illusory size perception differ and can be dependent on monocular channels in the early visual pathway.

Parietal and superior frontal visuospatial maps activated by pointing and saccades

PubMed Central

Hagler, D.J.; Riecke, L.; Sereno, M.I.

2009-01-01

A recent study from our laboratory demonstrated that parietal cortex contains a map of visual space related to saccades and spatial attention and identified this area as the likely human homologue of the lateral intraparietal (LIP). A human homologue for the parietal reach region (PRR), thought to preferentially encode planned hand movements, has also been recently proposed. Both of these areas, originally identified in the macaque monkey, have been shown to encode space with eye-centered coordinates. Functional magnetic resonance imaging (fMRI) of humans was used to test the hypothesis that the putative human PRR contains a retinotopic map recruited by finger pointing but not saccades and to test more generally for differences in the visuospatial maps recruited by pointing and saccades. We identified multiple maps in both posterior parietal cortex and superior frontal cortex recruited for eye and hand movements, including maps not observed in previous mapping studies. Pointing and saccade maps were generally consistent within single subjects. We have developed new group analysis methods for phase-encoded data, which revealed subtle differences between pointing and saccades, including hemispheric asymmetries, but we did not find evidence of pointing-specific maps of visual space. PMID:17376706

Learning optimal eye movements to unusual faces

PubMed Central

Peterson, Matthew F.; Eckstein, Miguel P.

2014-01-01

Eye movements, which guide the fovea’s high resolution and computational power to relevant areas of the visual scene, are integral to efficient, successful completion of many visual tasks. How humans modify their eye movements through experience with their perceptual environments, and its functional role in learning new tasks, has not been fully investigated. Here, we used a face identification task where only the mouth discriminated exemplars to assess if, how, and when eye movement modulation may mediate learning. By interleaving trials of unconstrained eye movements with trials of forced fixation, we attempted to separate the contributions of eye movements and covert mechanisms to performance improvements. Without instruction, a majority of observers substantially increased accuracy and learned to direct their initial eye movements towards the optimal fixation point. The proximity of an observer’s default face identification eye movement behavior to the new optimal fixation point and the observer’s peripheral processing ability were predictive of performance gains and eye movement learning. After practice in a subsequent condition in which observers were directed to fixate different locations along the face, including the relevant mouth region, all observers learned to make eye movements to the optimal fixation point. In this fully learned state, augmented fixation strategy accounted for 43% of total efficiency improvements while covert mechanisms accounted for the remaining 57%. The findings suggest a critical role for eye movement planning to perceptual learning, and elucidate factors that can predict when and how well an observer can learn a new task with unusual exemplars. PMID:24291712

Impact of radiation protection means on the dose to the lens of the eye while handling radionuclides in nuclear medicine.

PubMed

Bruchmann, Iris; Szermerski, Bastian; Behrens, Rolf; Geworski, Lilli

2016-12-01

The human eye lens appears to be more radiosensitive than previously assumed. The reduction of the limit for the dose to the lens of the eye to 20 mSv per year has been passed in the current Euratom Directives (2013). Therefore, in this work the impact of laboratory glasses and X-ray protective goggles was investigated and reciprocal attenuation factors (i.e. transmission factors) for different nuclides (Tc-99m, I-131, Y-90, F-18 and Ga-68) were determined. The radionuclides in typical geometry (syringe, applicator) were positioned at a distance of 50 cm to the eyes of four Alderson-Head-Phantoms. Different dosemeters measuring H p (3) respective H p (0.07) were fixed to the eyes of the phantoms, either behind the glasses or without any protection means, respectively. The mean reciprocal attenuation factors were determined to be between unity for F-18 and I-131 using laboratory glasses (no attenuation effect) and < 0.01 for Y-90 using X-ray protective goggles. All other results were between these extremes. It has been shown, that prospective doses to the lens of the eye can be reduced significantly by using appropriate radiation protection means, especially for those dose-relevant beta radiation emitting nuclides such as Y-90. Copyright © 2015. Published by Elsevier GmbH.

76 FR 10041 - National Eye Institute; Notice of Closed Meeting

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2011-02-23

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2011-01-18

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Multiple levels of representation of reaching in the parieto-frontal network.

PubMed

Battaglia-Mayer, Alexandra; Caminiti, Roberto; Lacquaniti, Francesco; Zago, Myrka

2003-10-01

In daily life, hand and eye movements occur in different contexts. Hand movements can be made to a visual target shortly after its presentation, or after a longer delay; alternatively, they can be made to a memorized target location. In both instances, the hand can move in a visually structured scene under normal illumination, which allows visual monitoring of its trajectory, or in darkness. Across these conditions, movement can be directed to points in space already foveated, or to extrafoveal ones, thus requiring different forms of eye-hand coordination. The ability to adapt to these different contexts by providing successful answers to their demands probably resides in the high degree of flexibility of the operations that govern cognitive visuomotor behavior. The neurophysiological substrates of these processes include, among others, the context-dependent nature of neural activity, and a transitory, or task-dependent, affiliation of neurons to the assemblies underlying different forms of sensorimotor behavior. Moreover, the ability to make independent or combined eye and hand movements in the appropriate order and time sequence must reside in a process that encodes retinal-, eye- and hand-related inputs in a spatially congruent fashion. This process, in fact, requires exact knowledge of where the eye and the hand are at any given time, although we have no or little conscious experience of where they stay at any instant. How this information is reflected in the activity of cortical neurons remains a central question to understanding the mechanisms underlying the planning of eye-hand movement in the cerebral cortex. In the last 10 years, psychophysical analyses in humans, as well as neurophysiological studies in monkeys, have provided new insights on the mechanisms of different forms of oculo-manual actions. These studies have also offered preliminary hints as to the cortical substrates of eye-hand coordination. In this review, we will highlight some of the results obtained as well as some of the questions raised, focusing on the role of eye- and hand-tuning signals in cortical neural activity. This choice rests on the crucial role this information exerts in the specification of movement, and coordinate transformation.

Dog Breed Differences in Visual Communication with Humans

PubMed Central

Konno, Akitsugu; Romero, Teresa; Inoue-Murayama, Miho; Saito, Atsuko; Hasegawa, Toshikazu

2016-01-01

Domestic dogs (Canis familiaris) have developed a close relationship with humans through the process of domestication. In human-dog interactions, eye contact is a key element of relationship initiation and maintenance. Previous studies have suggested that canine ability to produce human-directed communicative signals is influenced by domestication history, from wolves to dogs, as well as by recent breed selection for particular working purposes. To test the genetic basis for such abilities in purebred dogs, we examined gazing behavior towards humans using two types of behavioral experiments: the ‘visual contact task’ and the ‘unsolvable task’. A total of 125 dogs participated in the study. Based on the genetic relatedness among breeds subjects were classified into five breed groups: Ancient, Herding, Hunting, Retriever-Mastiff and Working). We found that it took longer time for Ancient breeds to make an eye-contact with humans, and that they gazed at humans for shorter periods of time than any other breed group in the unsolvable situation. Our findings suggest that spontaneous gaze behavior towards humans is associated with genetic similarity to wolves rather than with recent selective pressure to create particular working breeds. PMID:27736990

Fast hierarchical knowledge-based approach for human face detection in color images

NASA Astrophysics Data System (ADS)

Jiang, Jun; Gong, Jie; Zhang, Guilin; Hu, Ruolan

2001-09-01

This paper presents a fast hierarchical knowledge-based approach for automatically detecting multi-scale upright faces in still color images. The approach consists of three levels. At the highest level, skin-like regions are determinated by skin model, which is based on the color attributes hue and saturation in HSV color space, as well color attributes red and green in normalized color space. In level 2, a new eye model is devised to select human face candidates in segmented skin-like regions. An important feature of the eye model is that it is independent of the scale of human face. So it is possible for finding human faces in different scale with scanning image only once, and it leads to reduction the computation time of face detection greatly. In level 3, a human face mosaic image model, which is consistent with physical structure features of human face well, is applied to judge whether there are face detects in human face candidate regions. This model includes edge and gray rules. Experiment results show that the approach has high robustness and fast speed. It has wide application perspective at human-computer interactions and visual telephone etc.

Human lacrimal gland mucins.

PubMed

Paulsen, Friedrich; Langer, Gesa; Hoffmann, Werner; Berry, Monica

2004-05-01

The objective of this study was to determine whether the lacrimal gland synthesizes mucins and whether they are changed with age or in cases of dry eye. Expression of mucins in human lacrimal glands was monitored by reverse transcription-polymerase chain reaction analysis. Furthermore, the presence and distribution of MUC1, -2, -4, -5AC, -5B, -6 and -7 in epithelia of the human lacrimal gland and its excretory duct system were assessed with antisera to mucin peptide cores. Thirty normal tissues from cadavers of different ages were tested, plus four with dry eye treated with artificial tears. Expression studies detected mRNAs for mucins MUC1, -4, -5AC, -5B, -6 and -7; whereas the MUC2 message was absent. The message for MUC4 was present in all four cases of dry eye, but only in six out of the 30 normal glands from individuals who did not receive artificial tears. MUC6 mRNA was detected only in about half of the investigated samples. Immunohistochemistry revealed membrane-bound MUC1 at the apical surface of acinar cells, absence of MUC2, MUC5AC associated with goblet cells of excretory ducts, MUC5B and -7 in the cytoplasm of acinar cells, and MUC7 also in epithelial cells of excretory ducts. MUC4 mucin was detected only in those individuals in which message was identified. In dry eyes, MUC5AC and -5B were localized in the same acinar cells; whereas MUC2 and MUC6 were not detectable. Dot-blot analysis clearly revealed increased amounts of MUC4, -5AC, and -5B in the glands of elderly women who received treatment for dry eyes. These results confirm that the human lacrimal gland synthesizes a spectrum of mucins; part of them might be correlated with age. Copyright 2004 Springer-Verlag

In vivo volumetric depth-resolved vasculature imaging of human limbus and sclera with 1 μm swept source phase-variance optical coherence angiography

NASA Astrophysics Data System (ADS)

Poddar, Raju; Zawadzki, Robert J.; Cortés, Dennis E.; Mannis, Mark J.; Werner, John S.

2015-06-01

We present in vivo volumetric depth-resolved vasculature images of the anterior segment of the human eye acquired with phase-variance based motion contrast using a high-speed (100 kHz, 105 A-scans/s) swept source optical coherence tomography system (SSOCT). High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. The human corneo-scleral junction and sclera were imaged with swept source phase-variance optical coherence angiography and compared with slit lamp images from the same eyes of normal subjects. Different features of the rich vascular system in the conjunctiva and episclera were visualized and described. This system can be used as a potential tool for ophthalmological research to determine changes in the outflow system, which may be helpful for identification of abnormalities that lead to glaucoma.

Dynamic Features for Iris Recognition.

PubMed

da Costa, R M; Gonzaga, A

2012-08-01

The human eye is sensitive to visible light. Increasing illumination on the eye causes the pupil of the eye to contract, while decreasing illumination causes the pupil to dilate. Visible light causes specular reflections inside the iris ring. On the other hand, the human retina is less sensitive to near infra-red (NIR) radiation in the wavelength range from 800 nm to 1400 nm, but iris detail can still be imaged with NIR illumination. In order to measure the dynamic movement of the human pupil and iris while keeping the light-induced reflexes from affecting the quality of the digitalized image, this paper describes a device based on the consensual reflex. This biological phenomenon contracts and dilates the two pupils synchronously when illuminating one of the eyes by visible light. In this paper, we propose to capture images of the pupil of one eye using NIR illumination while illuminating the other eye using a visible-light pulse. This new approach extracts iris features called "dynamic features (DFs)." This innovative methodology proposes the extraction of information about the way the human eye reacts to light, and to use such information for biometric recognition purposes. The results demonstrate that these features are discriminating features, and, even using the Euclidean distance measure, an average accuracy of recognition of 99.1% was obtained. The proposed methodology has the potential to be "fraud-proof," because these DFs can only be extracted from living irises.

Eye hyperdeviation in mouse cerebellar mutants is comparable to the gravity-dependent component of human downbeat nystagmus.

PubMed

Stahl, John S; Oommen, Brian S

2008-01-01

Humans with cerebellar degeneration commonly exhibit downbeat nystagmus (DBN). DBN has gravity-independent and -dependent components, and the latter has been proposed to reflect hyperactive tilt maculo-ocular reflexes (tilt-MOR). Mice with genetically determined cerebellar ataxia do not exhibit DBN, but they do exhibit tonic hyperdeviation of the eyes, which we have proposed to be the DBN equivalent. As such, the tilt-MOR might be predicted to be hyperactive in these mutant mice. We measured the tilt-MOR in 10 normal C57BL/6 mice and in 6 tottering, a mutant exhibiting ataxia and ocular motor abnormalities due to mutation of the P/Q calcium channel. Awake mice were placed in body orientations spanning 360 degrees about the pitch axis. The absolute, equilibrium vertical angular deviations of one eye were measured using infrared videooculography. In both strains, eye elevation varied quasi-sinusoidally with tilt angle in the range of 90 degrees nose-up to 90 degrees nose-down. Beyond this range the eye returned to a neutral position. Deviation over +/-30 degrees of tilt was an approximately linear function of the projection of the gravity vector into the animal's horizontal plane, and can thus be summarized by its slope (sensitivity). Sensitivity measured 14.9 degrees/g for C57BL/6 and 20.3 degrees/g for tottering, a statistically significant difference. Thus the pitch otolithic reflex of the ataxic mutants is hyperactive relative to controls and could explain tonic hyperdeviation of the eyes, consistent with the idea that the tonic hyperdeviation is analogous to DBN.

Statistical distribution of foveal transverse chromatic aberration, pupil centration, and angle psi in a population of young adult eyes

NASA Astrophysics Data System (ADS)

Rynders, Maurice; Lidkea, Bruce; Chisholm, William; Thibos, Larry N.

1995-10-01

Subjective transverse chromatic aberration (sTCA) manifest at the fovea was determined for a population of 85 young adults (19-38 years old) by means of a two-dimensional, two-color, vernier alignment technique. The statistical distribution of sTCA was well fitted by a bivariate Gaussian function with mean values that were not significantly different from zero in either the horizontal or the vertical direction. We conclude from this result that a hypothetical, average eye representing the population mean of human eyes with medium-sized pupils is free of foveal sTCA. However, the absolute magnitude of sTCA for any given individual was often significantly greater than zero and ranged from 0.05 to 2.67 arcmin for the red and the blue lights of a computer monitor (mean wavelengths, 605 and 497 nm, respectively). The statistical distribution of the absolute magnitude of sTCA was well described by a Rayleigh probability distribution with a mean of 0.8 arcmin. A simple device useful for population screening in a clinical setting was also tested and gave concordant results. Assuming that sTCA at the fovea is due to decentering of the pupil with respect to the visual axis, we infer from these results that the pupil is, on average, well centered in human eyes. The average magnitude of pupil decentration in individual eyes is less than 0.5 mm, which corresponds to psi =3 deg for the angle between the achromatic and the visual axes of the eye.

Amygdala lesions in rhesus macaques decrease attention to threat

PubMed Central

Dal Monte, Olga; Costa, Vincent D.; Noble, Pamela L.; Murray, Elisabeth A.; Averbeck, Bruno B.

2015-01-01

Evidence from animal and human studies has suggested that the amygdala plays a role in detecting threat and in directing attention to the eyes. Nevertheless, there has been no systematic investigation of whether the amygdala specifically facilitates attention to the eyes or whether other features can also drive attention via amygdala processing. The goal of the present study was to examine the effects of amygdala lesions in rhesus monkeys on attentional capture by specific facial features, as well as gaze patterns and changes in pupil dilation during free viewing. Here we show reduced attentional capture by threat stimuli, specifically the mouth, and reduced exploration of the eyes in free viewing in monkeys with amygdala lesions. Our findings support a role for the amygdala in detecting threat signals and in directing attention to the eye region of faces when freely viewing different expressions. PMID:26658670

Long-Range Correlation in alpha-Wave Predominant EEG in Human

NASA Astrophysics Data System (ADS)

Sharif, Asif; Chyan Lin, Der; Kwan, Hon; Borette, D. S.

2004-03-01

The background noise in the alpha-predominant EEG taken from eyes-open and eyes-closed neurophysiological states is studied. Scale-free characteristic is found in both cases using the wavelet approach developed by Simonsen and Nes [1]. The numerical results further show the scaling exponent during eyes-closed is consistently lower than eyes-open. We conjecture the origin of this difference is related to the temporal reconfiguration of the neural network in the brain. To further investigate the scaling structure of the EEG background noise, we extended the second order statistics to higher order moments using the EEG increment process. We found that the background fluctuation in the alpha-predominant EEG is predominantly monofractal. Preliminary results are given to support this finding and its implication in brain functioning is discussed. [1] A.H. Simonsen and O.M. Nes, Physical Review E, 58, 2779¡V2748 (1998).

Proposed new classification scheme for chemical injury to the human eye.

PubMed

Bagley, Daniel M; Casterton, Phillip L; Dressler, William E; Edelhauser, Henry F; Kruszewski, Francis H; McCulley, James P; Nussenblatt, Robert B; Osborne, Rosemarie; Rothenstein, Arthur; Stitzel, Katherine A; Thomas, Karluss; Ward, Sherry L

2006-07-01

Various ocular alkali burn classification schemes have been published and used to grade human chemical eye injuries for the purpose of identifying treatments and forecasting outcomes. The ILSI chemical eye injury classification scheme was developed for the additional purpose of collecting detailed human eye injury data to provide information on the mechanisms associated with chemical eye injuries. This information will have clinical application, as well as use in the development and validation of new methods to assess ocular toxicity. A panel of ophthalmic researchers proposed the new classification scheme based upon current knowledge of the mechanisms of eye injury, and their collective clinical and research experience. Additional ophthalmologists and researchers were surveyed to critique the scheme. The draft scheme was revised, and the proposed scheme represents the best consensus from at least 23 physicians and scientists. The new scheme classifies chemical eye injury into five categories based on clinical signs, symptoms, and expected outcomes. Diagnostic classification is based primarily on two clinical endpoints: (1) the extent (area) of injury at the limbus, and (2) the degree of injury (area and depth) to the cornea. The new classification scheme provides a uniform system for scoring eye injury across chemical classes, and provides enough detail for the clinician to collect data that will be relevant to identifying the mechanisms of ocular injury.

The isolated chicken eye test as a suitable in vitro method for determining the eye irritation potential of household cleaning products.

PubMed

Schutte, K; Prinsen, M K; McNamee, P M; Roggeband, R

2009-08-01

Eye irritation is an important endpoint in the safety evaluation of consumer products and their ingredients. Several in vitro methods have been developed and are used by different industry sectors to assess eye irritation. One such in vitro method in use for some time already is the isolated chicken eye test (ICE). This investigation focuses on assessing the ICE as a method to determine the eye irritation potential of household cleaning products, both for product safety assurance prior to marketing and for classification and labeling decisions. The ICE involves a single application of test substances onto the cornea of isolated chicken eyes. Endpoints are corneal swelling, corneal opacity and fluorescein retention. The ICE results were compared to historic LVET data in this study due to availability of such in vivo data and the ability to correlate LVET to human experience data on the outcome of accidental exposures to household cleaning products in general. The results of this study indicate that the ICE test is a useful in vitro method for evaluating the eye irritation/corrosion potential and establishing classification and labeling for household cleaning products. For new product formulations, it is best used as part of a weight-of-evidence approach and benchmarked against data from comparable formulations with known eye irritation/corrosion profiles and market experience.

Computing the stresses and deformations of the human eye components due to a high explosive detonation using fluid-structure interaction model.

PubMed

Karimi, Alireza; Razaghi, Reza; Navidbakhsh, Mahdi; Sera, Toshihiro; Kudo, Susumu

2016-05-01

In spite the fact that a very small human body surface area is comprised by the eye, its wounds due to detonation have recently been dramatically amplified. Although many efforts have been devoted to measure injury of the globe, there is still a lack of knowledge on the injury mechanism due to Primary Blast Wave (PBW). The goal of this study was to determine the stresses and deformations of the human eye components, including the cornea, aqueous, iris, ciliary body, lens, vitreous, retina, sclera, optic nerve, and muscles, attributed to PBW induced by trinitrotoluene (TNT) explosion via a Lagrangian-Eulerian computational coupling model. Magnetic Resonance Imaging (MRI) was employed to establish a Finite Element (FE) model of the human eye according to a normal human eye. The solid components of the eye were modelled as Lagrangian mesh, while an explosive TNT, air domain, and aqueous were modelled using Arbitrary Lagrangian-Eulerian (ALE) mesh. Nonlinear dynamic FE simulations were accomplished using the explicit FE code, namely LS-DYNA. In order to simulate the blast wave generation, propagation, and interaction with the eye, the ALE formulation with Jones-Wilkins-Lee (JWL) equation defining the explosive material were employed. The results revealed a peak stress of 135.70kPa brought about by detonation upsurge on the cornea at the distance of 25cm. The highest von Mises stresses were observed on the sclera (267.3kPa), whereas the lowest one was seen on the vitreous body (0.002kPa). The results also showed a relatively high resultant displacement for the macula as well as a high variation for the radius of curvature for the cornea and lens, which can result in both macular holes, optic nerve damage and, consequently, vision loss. These results may have implications not only for understanding the value of stresses and strains in the human eye components but also giving an outlook about the process of PBW triggers damage to the eye. Copyright © 2016 Elsevier Ltd. All rights reserved.

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LIMNOLOGICAL OPTOMETRY: EXAMINING EARTH'S EYE

EPA Science Inventory

In Thoreau's Walden, a lake is described as the landscape's most expressive feature and the earth's eye. Collectively, scientists are charged by society to assess, monitor, and remedy maladies of earth's eye in the same way optometrists maintain the health of the human eye. This ...

Complement factor H: spatial and temporal expression and localization in the eye.

PubMed

Mandal, Md Nawajes A; Ayyagari, Radha

2006-09-01

Complement factor H (CFH) is a component of the mammalian complement system, which regulates the alternative pathway of complement activation and protects the host cell from inappropriate complement activation. CFH is a key regulator of innate immunity, and CFH deficiency leads to membranoproliferative glomerulonephritis type II. A variation in human CFH, Y402H, has been shown to be associated with an increased risk for age-related macular degeneration. The authors describe studies on the spatial and temporal expression of the CFH gene and localization of this protein in ocular tissues to gain insight into its role in the eye. CFH expression in human and mouse tissues was studied by quantitative RT-PCR and Western blot analysis, and localization of CFH was studied by immunohistochemical analysis followed by fluorescence microscopy. In human and mouse, CFH expression was found to be similar to the highest level of expression in the liver. In ocular tissue, CFH was detected in the distalmost optic nerve (3 mm) cut from the scleral surface of the eyeball, sclera, RPE-choroid, retina, lens, and ciliary body. In mouse, Cfh expression was observed from early embryonic stages, and in the eye its expression increased with age. A significant level of CFH expression is maintained in different ocular tissues during development and aging. Sustained high levels of CFH expression in eye tissues suggest that this protein may play a role in protecting these tissues from indiscriminate complement activation and inflammatory insult.

Automated analysis of angle closure from anterior chamber angle images.

PubMed

Baskaran, Mani; Cheng, Jun; Perera, Shamira A; Tun, Tin A; Liu, Jiang; Aung, Tin

2014-10-21

To evaluate a novel software capable of automatically grading angle closure on EyeCam angle images in comparison with manual grading of images, with gonioscopy as the reference standard. In this hospital-based, prospective study, subjects underwent gonioscopy by a single observer, and EyeCam imaging by a different operator. The anterior chamber angle in a quadrant was classified as closed if the posterior trabecular meshwork could not be seen. An eye was classified as having angle closure if there were two or more quadrants of closure. Automated grading of the angle images was performed using customized software. Agreement between the methods was ascertained by κ statistic and comparison of area under receiver operating characteristic curves (AUC). One hundred forty subjects (140 eyes) were included, most of whom were Chinese (102/140, 72.9%) and women (72/140, 51.5%). Angle closure was detected in 61 eyes (43.6%) with gonioscopy in comparison with 59 eyes (42.1%, P = 0.73) using manual grading, and 67 eyes (47.9%, P = 0.24) with automated grading of EyeCam images. The agreement for angle closure diagnosis between gonioscopy and both manual (κ = 0.88; 95% confidence interval [CI), 0.81-0.96) and automated grading of EyeCam images was good (κ = 0.74; 95% CI, 0.63-0.85). The AUC for detecting eyes with gonioscopic angle closure was comparable for manual and automated grading (AUC 0.974 vs. 0.954, P = 0.31) of EyeCam images. Customized software for automated grading of EyeCam angle images was found to have good agreement with gonioscopy. Human observation of the EyeCam images may still be needed to avoid gross misclassification, especially in eyes with extensive angle closure. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Plant Light Measurement & Calculations.

ERIC Educational Resources Information Center

Hershey, David R.

1991-01-01

The differences between measuring light intensity for the human eye and for plant photosynthesis are discussed. Conversion factors needed to convert various units of light are provided. Photosynthetic efficiency and the electricity costs for plants to undergo photosynthesis using interior lighting are described. (KR)

Three-Dimensional Eye Tracking in a Surgical Scenario.

PubMed

Bogdanova, Rositsa; Boulanger, Pierre; Zheng, Bin

2015-10-01

Eye tracking has been widely used in studying the eye behavior of surgeons in the past decade. Most eye-tracking data are reported in a 2-dimensional (2D) fashion, and data for describing surgeons' behaviors on stereoperception are often missed. With the introduction of stereoscopes in laparoscopic procedures, there is an increasing need for studying the depth perception of surgeons under 3D image-guided surgery. We developed a new algorithm for the computation of convergence points in stereovision by measuring surgeons' interpupillary distance, the distance to the view target, and the difference between gaze locations of the 2 eyes. To test the feasibility of our new algorithm, we recruited 10 individuals to watch stereograms using binocular disparity and asked them to develop stereoperception using a cross-eyed viewing technique. Participants' eye motions were recorded by the Tobii eye tracker while they performed the trials. Convergence points between normal and stereo-viewing conditions were computed using the developed algorithm. All 10 participants were able to develop stereovision after a short period of training. During stereovision, participants' eye convergence points were 14 ± 1 cm in front of their eyes, which was significantly closer than the convergence points under the normal viewing condition (77 ± 20 cm). By applying our method of calculating convergence points using eye tracking, we were able to elicit the eye movement patterns of human operators between the normal and stereovision conditions. Knowledge from this study can be applied to the design of surgical visual systems, with the goal of improving surgical performance and patient safety. © The Author(s) 2015.

Glaucoma-related Changes in the Mechanical Properties and Collagen Micro-architecture of the Human Sclera

PubMed Central

Coudrillier, Baptiste; Pijanka, Jacek K.; Jefferys, Joan L.; Goel, Adhiraj; Quigley, Harry A.; Boote, Craig; Nguyen, Thao D.

2015-01-01

Objective The biomechanical behavior of the sclera determines the level of mechanical insult from intraocular pressure to the axons and tissues of the optic nerve head, as is of interest in glaucoma. In this study, we measure the collagen fiber structure and the strain response, and estimate the material properties of glaucomatous and normal human donor scleras. Methods Twenty-two posterior scleras from normal and diagnosed glaucoma donors were obtained from an eyebank. Optic nerve cross-sections were graded to determine the presence of axon loss. The specimens were subjected to pressure-controlled inflation testing. Full-field displacement maps were measured by digital image correlation (DIC) and spatially differentiated to compute surface strains. Maps of the collagen fiber structure across the posterior sclera of each inflated specimen were obtained using synchrotron wide-angle X-ray scattering (WAXS). Finite element (FE) models of the posterior scleras, incorporating a specimen-specific representation of the collagen structure, were constructed from the DIC-measured geometry. An inverse finite element analysis was developed to estimate the stiffness of the collagen fiber and inter-fiber matrix. Results The differences between glaucoma and non-glaucoma eyes were small in magnitude. Sectorial variations of degree of fiber alignment and peripapillary scleral strain significantly differed between normal and diagnosed glaucoma specimens. Meridional strains were on average larger in diagnosed glaucoma eyes compared with normal specimens. Non-glaucoma specimens had on average the lowest matrix and fiber stiffness, followed by undamaged glaucoma eyes, and damaged glaucoma eyes but the differences in stiffness were not significant. Conclusion The observed biomechanical and microstructural changes could be the result of tissue remodeling occuring in glaucoma and are likely to alter the mechanical environment of the optic nerve head and contribute to axonal damage. PMID:26161963

Similar Hydrodynamic and Morphological Changes in the Aqueous Humor Outflow Pathway after Washout and Y27632 Treatment in Monkey Eyes

PubMed Central

Lu, Zhaozeng; Zhang, Yuyan; Freddo, Thomas F.; Gong, Haiyan

2011-01-01

Our previous studies in bovine eyes demonstrated that the structural correlate to the increase in outflow facility after either Rho-kinase inhibitor Y-27632 (Y27) treatment or washout appeared to be separation between the juxtacanalicular tissue (JCT) and inner wall (IW) of the aqueous plexus, the bovine equivalent of Schlemm's canal (SC). While these findings suggest that Y27 and washout may increase outflow facility through a similar mechanism, the anatomy of bovine outflow pathway differs considerably from both the human and monkey outflow pathway; however, only the human eye does not exhibit washout. In light of this, we compared the effects of Y27 and washout on outflow facility, hydrodynamic patterns of outflow, and the morphology of the IW and JCT in monkey eyes, given that their anatomy is closer to human eyes. Twelve freshly enucleated monkey eyes were used in this study. Eyes were perfused with Dulbecco's PBS containing 5.5 mM glucose (GPBS) to establish a baseline facility at 15 mmHg. Four eyes were perfused for a short-duration (30 min) as a control, 4 eyes for a long-duration (180 min) to induce washout, and 4 eyes with GPBS+50 μM Y27 for 30 min. All eyes were then perfused with fluorescent microspheres (0.5μm; 0.002%) to label the hydrodynamic patterns of outflow and then perfusion-fixed. Confocal images of frontal sections were taken along the IW of SC. The total length (TL) and the tracer decorated length (FL) of the IW were measured to calculate the average percent effective filtration length (PEFL=FL/TL). Sections with SC were examined by light and electron microscopy. The TL of the IW and the length exhibiting separation (SL) in the JCT were measured to calculate the average percent separation length (PSL= SL/TL). Outflow facility increased 149.2% (p<0.01) from baseline after washout during long-duration perfusion, and 114.9% (p=0.004) after Y27 treatment, but did not change significantly after short-duration perfusion in control eyes (p=0.46). Distribution of the tracer labeling appeared punctate along the IW of control eyes, while a more uniform pattern was observed after washout and Y27 treatment. PEFL in washout (83.4±2.1%) and Y27 treated eyes (82.5±1.6%) was 3.4-fold larger compared to controls (24.2±4.2%, P<0.001). The JCT appeared distended with loss of connections between JCT cells and between JCT cells and their extracelluar matrix in eyes with washout or after Y-27 treatment. PSL in the JCT was 2.3-fold larger in washout eyes (77.4±3.3%) and 2.2-fold larger in Y27 treated eyes (75.2±5.3%) versus controls (33.5±5.3%, p=0.001). Significant positive correlations were found between outflow facility and PEFL, facility and PSL and between PEFL and PSL. Our data demonstrated that similar hydrodynamic and morphological changes occurred in the aqueous humor outflow pathway of monkey eyes after induction of washout and Y27 treatment. Both Y27 and washout increase outflow facility by redistributing aqueous outflow through a larger area in the JCT. These hydrodynamic changes are likely driven by morphologic changes associated with a decrease in cell-cell and cell-matrix connections in the JCT. PMID:21669200

Construction of special eye models for investigation of chromatic and higher-order aberrations of eyes.

PubMed

Zhai, Yi; Wang, Yan; Wang, Zhaoqi; Liu, Yongji; Zhang, Lin; He, Yuanqing; Chang, Shengjiang

2014-01-01

An achromatic element eliminating only longitudinal chromatic aberration (LCA) while maintaining transverse chromatic aberration (TCA) is established for the eye model, which involves the angle formed by the visual and optical axis. To investigate the impacts of higher-order aberrations on vision, the actual data of higher-order aberrations of human eyes with three typical levels are introduced into the eye model along visual axis. Moreover, three kinds of individual eye models are established to investigate the impacts of higher-order aberrations, chromatic aberration (LCA+TCA), LCA and TCA on vision under the photopic condition, respectively. Results show that for most human eyes, the impact of chromatic aberration on vision is much stronger than that of higher-order aberrations, and the impact of LCA in chromatic aberration dominates. The impact of TCA is approximately equal to that of normal level higher-order aberrations and it can be ignored when LCA exists.

Dose conversion coefficients for neutron exposure to the lens of the human eye

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manger, Ryan P; Bellamy, Michael B; Eckerman, Keith F

Dose conversion coefficients for the lens of the human eye have been calculated for neutron exposure at energies from 1 x 10{sup -9} to 20 MeV and several standard orientations: anterior-to-posterior, rotational and right lateral. MCNPX version 2.6.0, a Monte Carlo-based particle transport package, was used to determine the energy deposited in the lens of the eye. The human eyeball model was updated by partitioning the lens into sensitive and insensitive volumes as the anterior portion (sensitive volume) of the lens being more radiosensitive and prone to cataract formation. The updated eye model was used with the adult UF-ORNL mathematicalmore » phantom in the MCNPX transport calculations.« less

Defect window analysis by using SEM-contour based shape quantifying method for sub-20nm node production

NASA Astrophysics Data System (ADS)

Hibino, Daisuke; Hsu, Mingyi; Shindo, Hiroyuki; Izawa, Masayuki; Enomoto, Yuji; Lin, J. F.; Hu, J. R.

2013-04-01

The impact on yield loss due to systematic defect which remains after Optical Proximity Correction (OPC) modeling has increased, and achieving an acceptable yield has become more difficult in the leading technology beyond 20 nm node production. Furthermore Process-Window has become narrow because of the complexity of IC design and less process margin. In the past, the systematic defects have been inspected by human-eyes. However the judgment by human-eyes is sometime unstable and not accurate. Moreover an enormous amount of time and labor will have to be expended on the one-by-one judgment for several thousands of hot-spot defects. In order to overcome these difficulties and improve the yield and manufacturability, the automated system, which can quantify the shape difference with high accuracy and speed, is needed. Inspection points could be increased for getting higher yield, if the automated system achieves our goal. Defect Window Analysis (DWA) system by using high-precision-contour extraction from SEM image on real silicon and quantifying method which can calculate the difference between defect pattern and non-defect pattern automatically, which was developed by Hitachi High-Technologies, has been applied to the defect judgment instead of the judgment by human-eyes. The DWA result which describes process behavior might be feedback to design or OPC or mask. This new methodology and evaluation results will be presented in detail in this paper.

See You See Me: the Role of Eye Contact in Multimodal Human-Robot Interaction

PubMed Central

XU, TIAN (LINGER); ZHANG, HUI; YU, CHEN

2016-01-01

We focus on a fundamental looking behavior in human-robot interactions – gazing at each other’s face. Eye contact and mutual gaze between two social partners are critical in smooth human-human interactions. Therefore, investigating at what moments and in what ways a robot should look at a human user’s face as a response to the human’s gaze behavior is an important topic. Toward this goal, we developed a gaze-contingent human-robot interaction system, which relied on momentary gaze behaviors from a human user to control an interacting robot in real time. Using this system, we conducted an experiment in which human participants interacted with the robot in a joint attention task. In the experiment, we systematically manipulated the robot’s gaze toward the human partner’s face in real time and then analyzed the human’s gaze behavior as a response to the robot’s gaze behavior. We found that more face looks from the robot led to more look-backs (to the robot’s face) from human participants and consequently created more mutual gaze and eye contact between the two. Moreover, participants demonstrated more coordinated and synchronized multimodal behaviors between speech and gaze when more eye contact was successfully established and maintained. PMID:28966875

Common determinants of body size and eye size in chickens from an advanced intercross line.

PubMed

Prashar, Ankush; Hocking, Paul M; Erichsen, Jonathan T; Fan, Qiao; Saw, Seang Mei; Guggenheim, Jeremy A

2009-06-15

Myopia development is characterised by an increased axial eye length. Therefore, identifying factors that influence eye size may provide new insights into the aetiology of myopia. In humans, axial length is positively correlated to height and weight, and in mice, eye weight is positively correlated with body weight. The purpose of this study was to examine the relationship between eye size and body size in chickens from a genetic cross in which alleles with major effects on eye and body size were segregating. Chickens from a cross between a layer line (small body size and eye size) and a broiler line (large body and eye size) were interbred for 10 generations so that alleles for eye and body size would have the chance to segregate independently. At 3 weeks of age, 510 chicks were assessed using in vivo high resolution A-scan ultrasonography and keratometry. Equatorial eye diameter and eye weight were measured after enucleation. The variations in eye size parameters that could be explained by body weight (BW), body length (BL), head width (HW) and sex were examined using multiple linear regression. It was found that BW, BL and HW and sex together predicted 51-56% of the variation in eye weight, axial length, corneal radius, and equatorial eye diameter. By contrast, the same variables predicted only 22% of the variation in lens thickness. After adjusting for sex, the three body size parameters predicted 45-49% of the variation in eye weight, axial length, corneal radius, and eye diameter, but only 0.4% of the variation in lens thickness. In conclusion, about half of the variation in eye size in the chickens of this broiler-layer advanced intercross line is likely to be determined by pleiotropic genes that also influence body size. Thus, mapping the quantitative trait loci (QTL) that determine body size may be useful in understanding the genetic determination of eye size (a logical inference of this result is that the 20 or more genetic variants that have recently been shown to influence human height may also be found to influence axial eye length). Furthermore, adjusting for body size will be essential in mapping pure eye size QTL in this chicken population, and may also have value in mapping eye size QTL in humans.

77 FR 27784 - Announcement of National Eye Institute Participation in PA-11-347, “NINDS SBIR Technology...

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2012-05-11

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l-tyrosine induces melanocyte differentiation in novel pink-eyed dilution castaneus mouse mutant showing age-related pigmentation.

PubMed

Hirobe, Tomohisa; Ishikawa, Akira

2015-12-01

The mouse pink-eyed dilution (oculocutaneous albinism II; p/Oca2(p)) locus is known to control tyrosinase activity, melanin content, and melanosome development in melanocytes. Pink-eyed dilution castaneus (p(cas)/Oca2(p-cas)) is a novel mutant allele on mouse chromosome 7 that arose spontaneously in Indonesian wild mice, Mus musculus castaneus. Mice homozygous for Oca2(p-cas) usually exhibit pink eyes and beige-colored coat on nonagouti C57BL/6 (B6) background. Recently, a novel spontaneous mutation occurred in the progeny between this mutant and B6 mice. The eyes of this novel mutant progressively become black from pink and the coat becomes dark gray from beige with aging. The aim of this study is to clarify whatever differences exist in melanocyte proliferation and differentiation between the ordinary (pink-eyed) and novel (black-eyed) mutant using serum-free primary culture system. The characteristics of melanocyte proliferation and differentiation were investigated by serum-free primary culture system using melanocyte-proliferation medium (MDMD). The proliferation of melanoblasts in MDMD did not differ between the two mice. However, when the epidermal cell suspensions were cultured with MDMD supplemented with l-tyrosine (Tyr), the differentiation of black-eyed melanocytes was greatly induced in a concentration-dependent manner compared with pink-eyed melanocytes. Immunocytochemistry demonstrated that the expression of tyrosinase and tyrosinase-related protein-1 (Tyrp1) was greatly induced or stimulated both in pink-eyed and black-eyed melanocytes, whereas the expression of microphthalmia-associated transcription factor (Mitf) was stimulated only in black-eyed melanocytes. These results suggest that the age-related coat darkening in black-eyed mutant may be caused by the increased ability of melanocyte differentiation dependent on l-Tyr through the upregulation of tyrosinase, Tyrp1, and Mitf. This mutant mouse may be useful for animal model to clarify the mechanisms of age-related pigmentation in human skin, such as melasma and solar lentigines. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

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Multicolour LEDs in educational demonstrations of physics and optometry

NASA Astrophysics Data System (ADS)

Paulins, Paulis; Ozolinsh, Maris

2014-07-01

LED light sources are used to design experimental setup for university courses teaching human color vision. The setup allows to demonstrate various vision characteristics and to apply for student practical exercises to study eye spectral sensitivity in different spectral range using heterochromatic flicker photometry. Technique can be used in laboratory works for students to acquire knowledge in visual perception, basics of electronics and measuring, or it can be applied as fully computer control experiment. Besides studies of the eye spectral sensitivity students can practice in trichromatic color matching and other visual perception tasks

Double peacock eye optical element for extended focal depth imaging with ophthalmic applications.

PubMed

Romero, Lenny A; Millán, María S; Jaroszewicz, Zbigniew; Kolodziejczyk, Andrzej

2012-04-01

The aged human eye is commonly affected by presbyopia, and therefore, it gradually loses its capability to form images of objects placed at different distances. Extended depth of focus (EDOF) imaging elements can overcome this inability, despite the introduction of a certain amount of aberration. This paper evaluates the EDOF imaging performance of the so-called peacock eye phase diffractive element, which focuses an incident plane wave into a segment of the optical axis and explores the element's potential use for ophthalmic presbyopia compensation optics. Two designs of the element are analyzed: the single peacock eye, which produces one focal segment along the axis, and the double peacock eye, which is a spatially multiplexed element that produces two focal segments with partial overlapping along the axis. The performances of the peacock eye elements are compared with those of multifocal lenses through numerical simulations as well as optical experiments in the image space. The results demonstrate that the peacock eye elements form sharper images along the focal segment than the multifocal lenses and, therefore, are more suitable for presbyopia compensation. The extreme points of the depth of field in the object space, which represent the remote and the near object points, have been experimentally obtained for both the single and the double peacock eye optical elements. The double peacock eye element has better imaging quality for relatively short and intermediate distances than the single peacock eye, whereas the latter seems better for far distance vision.

Design and characterization of a tunable opto-mechatronic system to mimic the focusing and the regulation of illumination in the formation of images made by the human eye

NASA Astrophysics Data System (ADS)

Santiago-Alvarado, A.; Cruz-Félix, A.; Hernández Méndez, A.; Pérez-Maldonado, Y.; Domínguez-Osante, C.

2015-05-01

Tunable lenses have attracted much attention due to their potential applications in such areas like machine vision, laser projection, ophthalmology, etc. In this work we present the design of a tunable opto-mechatronic system capable of focusing and to regulate the entrance illumination that mimics the performance made by the iris and the crystalline lens of the human eye. A solid elastic lens made of PDMS has been used in order to mimic the crystalline lens and an automatic diaphragm has been used to mimic the iris of the human eye. Also, a characterization of such system has been performed with standard values of luminosity for the human eye have been taken into account to calibrate and to validate the entrance illumination levels to the overall optical system.

Imaging the Aqueous Humor Outflow Pathway in Human Eyes by Three-dimensional Micro-computed Tomography (3D micro-CT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

C Hann; M Bentley; A Vercnocke

2011-12-31

The site of outflow resistance leading to elevated intraocular pressure in primary open-angle glaucoma is believed to be located in the region of Schlemm's canal inner wall endothelium, its basement membrane and the adjacent juxtacanalicular tissue. Evidence also suggests collector channels and intrascleral vessels may have a role in intraocular pressure in both normal and glaucoma eyes. Traditional imaging modalities limit the ability to view both proximal and distal portions of the trabecular outflow pathway as a single unit. In this study, we examined the effectiveness of three-dimensional micro-computed tomography (3D micro-CT) as a potential method to view the trabecularmore » outflow pathway. Two normal human eyes were used: one immersion fixed in 4% paraformaldehyde and one with anterior chamber perfusion at 10 mmHg followed by perfusion fixation in 4% paraformaldehyde/2% glutaraldehyde. Both eyes were postfixed in 1% osmium tetroxide and scanned with 3D micro-CT at 2 {mu}m or 5 {mu}m voxel resolution. In the immersion fixed eye, 24 collector channels were identified with an average orifice size of 27.5 {+-} 5 {mu}m. In comparison, the perfusion fixed eye had 29 collector channels with a mean orifice size of 40.5 {+-} 13 {mu}m. Collector channels were not evenly dispersed around the circumference of the eye. There was no significant difference in the length of Schlemm's canal in the immersed versus the perfused eye (33.2 versus 35.1 mm). Structures, locations and size measurements identified by 3D micro-CT were confirmed by correlative light microscopy. These findings confirm 3D micro-CT can be used effectively for the non-invasive examination of the trabecular meshwork, Schlemm's canal, collector channels and intrascleral vasculature that comprise the distal outflow pathway. This imaging modality will be useful for non-invasive study of the role of the trabecular outflow pathway as a whole unit.« less

Eye gazing direction inspection based on image processing technique

NASA Astrophysics Data System (ADS)

Hao, Qun; Song, Yong

2005-02-01

According to the research result in neural biology, human eyes can obtain high resolution only at the center of view of field. In the research of Virtual Reality helmet, we design to detect the gazing direction of human eyes in real time and feed it back to the control system to improve the resolution of the graph at the center of field of view. In the case of current display instruments, this method can both give attention to the view field of virtual scene and resolution, and improve the immersion of virtual system greatly. Therefore, detecting the gazing direction of human eyes rapidly and exactly is the basis of realizing the design scheme of this novel VR helmet. In this paper, the conventional method of gazing direction detection that based on Purklinje spot is introduced firstly. In order to overcome the disadvantage of the method based on Purklinje spot, this paper proposed a method based on image processing to realize the detection and determination of the gazing direction. The locations of pupils and shapes of eye sockets change with the gazing directions. With the aid of these changes, analyzing the images of eyes captured by the cameras, gazing direction of human eyes can be determined finally. In this paper, experiments have been done to validate the efficiency of this method by analyzing the images. The algorithm can carry out the detection of gazing direction base on normal eye image directly, and it eliminates the need of special hardware. Experiment results show that the method is easy to implement and have high precision.

Two Variants in SLC24A5 Are Associated with “Tiger-Eye” Iris Pigmentation in Puerto Rican Paso Fino Horses

PubMed Central

Mack, Maura; Kowalski, Elizabeth; Grahn, Robert; Bras, Dineli; Penedo, Maria Cecilia T.; Bellone, Rebecca

2017-01-01

A unique eye color, called tiger-eye, segregates in the Puerto Rican Paso Fino (PRPF) horse breed and is characterized by a bright yellow, amber, or orange iris. Pedigree analysis identified a simple autosomal recessive mode of inheritance for this trait. A genome-wide association study (GWAS) with 24 individuals identified a locus on ECA 1 reaching genome-wide significance (Pcorrected = 1.32 × 10−5). This ECA1 locus harbors the candidate gene, Solute Carrier Family 24 (Sodium/Potassium/Calcium Exchanger), Member 5 (SLC24A5), with known roles in pigmentation in humans, mice, and zebrafish. Humans with compound heterozygous mutations in SLC24A5 have oculocutaneous albinism (OCA) type 6 (OCA6), which is characterized by dilute skin, hair, and eye pigmentation, as well as ocular anomalies. Twenty tiger-eye horses were homozygous for a nonsynonymous mutation in exon 2 (p.Phe91Tyr) of SLC24A5 (called here Tiger-eye 1), which is predicted to be deleterious to protein function. Additionally, eight of the remaining 12 tiger-eye horses heterozygous for the p.Phe91Tyr variant were also heterozygous for a 628 bp deletion encompassing all of exon 7 of SLC24A5 (c.875-340_1081+82del), which we will call here the Tiger-eye 2 allele. None of the 122 brown-eyed horses were homozygous for either tiger-eye-associated allele or were compound heterozygotes. Further, neither variant was detected in 196 horses from four related breeds not known to have the tiger-eye phenotype. Here, we propose that two mutations in SLC24A5 affect iris pigmentation in tiger-eye PRPF horses. Further, unlike OCA6 in humans, the Tiger-eye 1 mutation in its homozygous state or as a compound heterozygote (Tiger-eye 1/Tiger-eye 2) does not appear to cause ocular anomalies or a change in coat color in the PRPF horse. PMID:28655738

A new 3D reconstituted human corneal epithelium model as an alternative method for the eye irritation test.

PubMed

Jung, Kyoung-Mi; Lee, Su-Hyon; Ryu, Yang-Hwan; Jang, Won-Hee; Jung, Haeng-Sun; Han, Ju-Hee; Seok, Seung-Hyeok; Park, Jae-Hak; Son, Youngsook; Park, Young-Ho; Lim, Kyung-Min

2011-02-01

Many efforts are being made to develop new alternative in vitro test methods for the eye irritation test. Here we report a new reconstructed human corneal epithelial model (MCTT HCE model) prepared from primary-cultured human limbal epithelial cells as a new alternative in vitro eye irritation test method. In histological and immunohistochemical observation, MCTT HCE model displayed a morphology and biomarker expressions similar to intact human cornea. Moreover, the barrier function was well preserved as measured by high transepithelial electrical resistance, effective time-50 for Triton X-100, and corneal thickness. To employ the model as a new alternative method for eye irritation test, protocol refinement was performed and optimum assay condition was determined including treatment time, treatment volume, post-incubation time and rinsing method. Using the refined protocol, 25 reference chemicals with known eye irritation potentials were tested. With the viability cut-off value at 50%, chemicals were classified to irritant or non-irritant. When compared with GHS classification, the MCTT HCE model showed the accuracy of 88%, sensitivity of 100% and specificity of 77%. These results suggest that the MCTT HCE model might be useful as a new alternative eye irritation test method. Copyright © 2010 Elsevier Ltd. All rights reserved.

Application of a wide-field phantom eye for optical coherence tomography and reflectance imaging.

PubMed

Corcoran, Anthony; Muyo, Gonzalo; van Hemert, Jano; Gorman, Alistair; Harvey, Andrew R

2015-12-15

Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the design, manufacture and application of the first phantom eye that reproduces the off-axis optical characteristics of the human eye, and allows the performance assessment of wide-field ophthalmic devices. We base our design and manufacture on the wide-field schematic eye, [Navarro, R. J. Opt. Soc. Am. A , 1985, 2 .] as an accurate proxy to the human eye and enable assessment of ophthalmic imaging performance for a [Formula: see text] external FOV. We used multi-material 3D-printed retinal targets to assess imaging performance of the following ophthalmic instruments: the Optos 200Tx, Heidelberg Spectralis, Zeiss FF4 fundus camera and Optos OCT SLO and use the phantom to provide an insight into some of the challenges of wide-field OCT.

Application of a wide-field phantom eye for optical coherence tomography and reflectance imaging

NASA Astrophysics Data System (ADS)

Corcoran, Anthony; Muyo, Gonzalo; van Hemert, Jano; Gorman, Alistair; Harvey, Andrew R.

2015-12-01

Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the design, manufacture and application of the first phantom eye that reproduces the off-axis optical characteristics of the human eye, and allows the performance assessment of wide-field ophthalmic devices. We base our design and manufacture on the wide-field schematic eye, [Navarro, R. J. Opt. Soc. Am. A, 1985, 2.] as an accurate proxy to the human eye and enable assessment of ophthalmic imaging performance for a ? external FOV. We used multi-material 3D-printed retinal targets to assess imaging performance of the following ophthalmic instruments: the Optos 200Tx, Heidelberg Spectralis, Zeiss FF4 fundus camera and Optos OCT SLO and use the phantom to provide an insight into some of the challenges of wide-field OCT.

Numerical analysis of specific absorption rate in the human head due to a 13.56 MHz RFID-based intra-ocular pressure measurement system.

PubMed

Hirtl, Rene; Schmid, Gernot

2013-09-21

A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues.

Spatially resolved wavefront aberrations of ophthalmic progressive-power lenses in normal viewing conditions.

PubMed

Villegas, Eloy A; Artal, Pablo

2003-02-01

To measure the wavefront aberration at different locations in progressive-power lenses (PPL's) isolated and in situ (PPL's plus eye). A Hartmann-Shack wavefront sensor was used to measure progressive-power lenses and human eyes either independently or in combination. In each selected zone, the lens was placed and tilted accordingly to simulate natural viewing conditions. We measured 21 relevant locations across an isolated PPL (plano lens of power addition of 2 D). In six of the locations, the wavefront aberration of the eye plus PPL were obtained in two ways: (1) by direct measurement of the system and (2) by adding the individual wavefront aberrations of the eye and the lens for each appropriate zone. In every case, we obtained the wavefront aberration as Zernike polynomials expansions, the root mean square error, the point-spread function, and the Strehl ratio. Along the corridor of the PPL, third-order coma and trefoil, and astigmatism were the dominant aberrations. In areas of the PPL outside the corridor, astigmatism increased, whereas other aberrations remained similar to the lens center. Small differences were found between the direct and calculated methods used to obtain the wavefront aberration of the eye with the lens, and the possible sources of errors were discussed. In some lenses zones, the aberrations of the lens may be compensated by the particular aberrations of the eye, yielding improved optical performance over that present in the lens alone. We designed and built a wavefront sensor to perform spatially resolved aberration measurements in ophthalmic lenses, in particular in PPL's, either isolated or in combination with the eye. The aberrations appearing in the PPL were compared with those in normal aged eyes.

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2010-08-12

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A standard model eye with micro scale multilayer structure for ophthalmic optical coherence tomography equipment

NASA Astrophysics Data System (ADS)

Cao, Zhenggang; Ding, Zengqian; Hu, Zhixiong; Wen, Tao; Qiao, Wen; Liu, Wenli

2016-10-01

Optical coherence tomography (OCT) has been widely applied in diagnosis of eye diseases during the last 20 years. Differing from traditional two-dimension imaging technologies, OCT could also provide cross-sectional information of target tissues simultaneously and precisely. As well known, axial resolution is one of the most critical parameters impacting the OCT image quality, which determines whether an accurate diagnosis could be obtained. Therefore, it is important to evaluate the axial resolution of an OCT equipment. Phantoms always play an important role in the standardization and validation process. Here, a standard model eye with micro-scale multilayer structure was custom designed and manufactured. Mimicking a real human eye, analyzing the physical characteristic of layer structures of retina and cornea in-depth, appropriate materials were selected by testing the scattering coefficient of PDMS phantoms with difference concentration of TiO2 or BaSO4 particles. An artificial retina and cornea with multilayer-films which have a thickness of 10 to 60 micrometers for each layer were fabricated using spin coating technology. Considering key parameters of the standard model eye need to be traceable as well as accurate, the optical refractive index and layer structure thicknesses of phantoms were verified by utilizing Thickness Monitoring System. Consequently, a standard OCT model eye was obtained after the retinal or corneal phantom was embedded into a water-filled model eye which has been fabricated by 3D printing technology to simulate ocular dispersion and emmetropic refraction. The eye model was manufactured with a transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. By investigating with a research and a clinical OCT system respectively, the OCT model eye was demonstrated with similar physical properties as natural eye, and the multilayer film measurement provided an effective method to rapidly evaluate the axial resolution of ophthalmic OCT devices.

Differentiation between Vergence and Saccadic Functional Activity within the Human Frontal Eye Fields and Midbrain Revealed through fMRI

PubMed Central

Alkan, Yelda; Biswal, Bharat B.; Alvarez, Tara L.

2011-01-01

Purpose Eye movement research has traditionally studied solely saccade and/or vergence eye movements by isolating these systems within a laboratory setting. While the neural correlates of saccadic eye movements are established, few studies have quantified the functional activity of vergence eye movements using fMRI. This study mapped the neural substrates of vergence eye movements and compared them to saccades to elucidate the spatial commonality and differentiation between these systems. Methodology The stimulus was presented in a block design where the ‘off’ stimulus was a sustained fixation and the ‘on’ stimulus was random vergence or saccadic eye movements. Data were collected with a 3T scanner. A general linear model (GLM) was used in conjunction with cluster size to determine significantly active regions. A paired t-test of the GLM beta weight coefficients was computed between the saccade and vergence functional activities to test the hypothesis that vergence and saccadic stimulation would have spatial differentiation in addition to shared neural substrates. Results Segregated functional activation was observed within the frontal eye fields where a portion of the functional activity from the vergence task was located anterior to the saccadic functional activity (z>2.3; p<0.03). An area within the midbrain was significantly correlated with the experimental design for the vergence but not the saccade data set. Similar functional activation was observed within the following regions of interest: the supplementary eye field, dorsolateral prefrontal cortex, ventral lateral prefrontal cortex, lateral intraparietal area, cuneus, precuneus, anterior and posterior cingulates, and cerebellar vermis. The functional activity from these regions was not different between the vergence and saccade data sets assessed by analyzing the beta weights of the paired t-test (p>0.2). Conclusion Functional MRI can elucidate the differences between the vergence and saccade neural substrates within the frontal eye fields and midbrain. PMID:22073141

A Maternal Influence on Reading the Mind in the Eyes Mediated by Executive Function: Differential Parental Influences on Full and Half-Siblings

PubMed Central

Ragsdale, Gillian; Foley, Robert A.

2011-01-01

Background Parent-of-origin effects have been found to influence the mammalian brain and cognition and have been specifically implicated in the development of human social cognition and theory of mind. The experimental design in this study was developed to detect parent-of-origin effects on theory of mind, as measured by the ‘Reading the mind in the eyes’ (Eyes) task. Eyes scores were also entered into a principal components analysis with measures of empathy, social skills and executive function, in order to determine what aspect of theory of mind Eyes is measuring. Methodology/Principal Findings Maternal and paternal influences on Eyes scores were compared using correlations between pairs of full (70 pairs), maternal (25 pairs) and paternal siblings (15 pairs). Structural equation modelling supported a maternal influence on Eyes scores over the normal range but not low-scoring outliers, and also a sex-specific influence on males acting to decrease male Eyes scores. It was not possible to differentiate between genetic and environmental influences in this particular sample because maternal siblings tended to be raised together while paternal siblings were raised apart. The principal components analysis found Eyes was associated with measures of executive function, principally behavioural inhibition and attention, rather than empathy or social skills. Conclusions/Significance In conclusion, the results suggest a maternal influence on Eye scores in the normal range and a sex-specific influence acting to reduce scores in males. This influence may act via aspects of executive function such as behavioural inhibition and attention. There may be different influences acting to produce the lowest Eyes scores which implies that the heratibility and/or maternal influence on poor theory of mind skills may be qualitatively different to the influence on the normal range. PMID:21850264

Succinylcholine activation of human horizontal eye muscles.

PubMed

Lennerstrand, Gunnar; Bolzani, Roberto; Tian, Suna; Benassi, Mariagrazia; Fusari, Maurizio; Campos, Emilio; Schiavi, Costantino

2010-12-01

Succinylcholine (Sch) can induce contracture in slow, multiply innervated muscle fibres of the extraocular muscles in animals of different species. Slow muscle fibres also exist in human eye muscle but their physiological properties have not been studied. Isometric tension development was recorded in the lateral and medial rectus muscles in 12 patients operated under general anaesthesia. A strain gauge probe was attached with 5-0 silk sutures to the muscle tendon. Recordings were made in 12 eye muscles with the tendon attached to the globe and in four muscles detached from the globe. Muscle activation was produced by i.v. injection of Sch at a dose of 0.2-0.3 mg/kg bodyweight.   A single injection of Sch induced slow contractures lasting for several minutes. In the muscles attached to the globe, mean maximal isometric tension was 12.2 g in the lateral rectus and 12.8 g in the medial rectus. Similar tension was shown in the muscles detached from the globe. The contracture of eye muscles in response to Sch showed characteristics typical of slow muscle fibre activation in amphibian and avian muscle and confirmed the participation of slow fibre systems in ocular motor control. © 2009 The Authors. Journal compilation © 2009 Acta Ophthalmol.

Retinal axial focusing and multi-layer imaging with a liquid crystal adaptive optics camera

NASA Astrophysics Data System (ADS)

Liu, Rui-Xue; Zheng, Xian-Liang; Li, Da-Yu; Xia, Ming-Liang; Hu, Li-Fa; Cao, Zhao-Liang; Mu, Quan-Quan; Xuan, Li

2014-09-01

With the help of adaptive optics (AO) technology, cellular level imaging of living human retina can be achieved. Aiming to reduce distressing feelings and to avoid potential drug induced diseases, we attempted to image retina with dilated pupil and froze accommodation without drugs. An optimized liquid crystal adaptive optics camera was adopted for retinal imaging. A novel eye stared system was used for stimulating accommodation and fixating imaging area. Illumination sources and imaging camera kept linkage for focusing and imaging different layers. Four subjects with diverse degree of myopia were imaged. Based on the optical properties of the human eye, the eye stared system reduced the defocus to less than the typical ocular depth of focus. In this way, the illumination light can be projected on certain retina layer precisely. Since that the defocus had been compensated by the eye stared system, the adopted 512 × 512 liquid crystal spatial light modulator (LC-SLM) corrector provided the crucial spatial fidelity to fully compensate high-order aberrations. The Strehl ratio of a subject with -8 diopter myopia was improved to 0.78, which was nearly close to diffraction-limited imaging. By finely adjusting the axial displacement of illumination sources and imaging camera, cone photoreceptors, blood vessels and nerve fiber layer were clearly imaged successfully.

Experimental characterization of the imaging properties of multifocal intraocular lenses

NASA Astrophysics Data System (ADS)

Gobbi, Pier Giorgio; Fasce, Francesco; Bozza, Stefano; Brancato, Rosario

2003-07-01

Many different types of intraocular lenses (IOL) are currently available for implantation, both as crystalline lens replacements and as phakic refractive elements. Their optical design is increasingly sophisticated, including aspherical surface profiles and multi-zone multifocal structures, however a quantitative and comparative characterization of their imaging properties is lacking. Also a qualitative visualization of their properties would be very useful for patients in the lens choice process. To this end an experimental eye model has been developed to allow for simulated in-vivo testing of IOLs. The model cornea is made of PMMA with a dioptric power of 43 D, and it has an aspherical profile designed to minimize spherical aberration across the visible spectrum. The eye model has a variable iris and a mechanical support to accomodate IOLs, immersed in physiological solution. The eye length is variable and the retina is replaced by a glass plate. The image formed on this "retina" is optically conjugated to a CCD camera, with a suitable magnification in order to mimic the human fovea resolution, and displayed onto a monitor. With such an opto-mechanical eye model, two types of images have been used to characterize IOLs: letter charts and variable contrast gratings, in order to directly simulate human visual acuity and contrast sensitivity.

Effects of awakening and the use of topical dexamethasone and levofloxacin on the cytokine levels in tears following corneal transplantation.

PubMed

Fodor, Mariann; Petrovski, Goran; Pásztor, Dorottya; Gogolák, Péter; Rajnavölgyi, Éva; Berta, András

2014-01-01

To study the short-term effect of eye opening and use of topical dexamethasone phosphate 0.1% and levofloxacin 0.5% on the cytokine levels in human tears. Prospective experimental design was used for tear collection from eyes of 10 healthy controls and 20 patients four days after penetrating keratoplasty (PKP) at awakening and after instilling dexamethasone or levofloxacin. The concentrations of different cytokines were measured by cytometric bead array. At eye opening, IL-6 levels were higher in the PKP group as compared to the controls. Thirty minutes later, the released levels of IL-10, IL-13, IL-17, IFNγ, and CCL5 increased in controls, while CXCL8 decreased in both control and PKP groups. The release of the cytokines remained stable after 30 mins except for IFNγ, which showed a decrease in the controls following levofloxacin instillation. No short-term effects of the topically used dexamethasone and levofloxacin could be detected on the cytokine levels in controls and after PKP. Evidence of changes in the levels and time course of tear cytokines after awakening or eye opening could be established and the short-term confounding effects of dexamethasone and levofloxacin on the levels of released cytokines in human tears could be excluded.

Gold nanoparticle‐based brachytherapy enhancement in choroidal melanoma using a full Monte Carlo model of the human eye

PubMed Central

Vaez‐zadeh, Mehdi; Masoudi, S. Farhad; Rahmani, Faezeh; Knaup, Courtney; Meigooni, Ali S.

2015-01-01

The effects of gold nanoparticles (GNPs) in 125I brachytherapy dose enhancement on choroidal melanoma are examined using the Monte Carlo simulation technique. Usually, Monte Carlo ophthalmic brachytherapy dosimetry is performed in a water phantom. However, here, the compositions of human eye have been considered instead of water. Both human eye and water phantoms have been simulated with MCNP5 code. These simulations were performed for a fully loaded 16 mm COMS eye plaque containing 13 125I seeds. The dose delivered to the tumor and normal tissues have been calculated in both phantoms with and without GNPs. Normally, the radiation therapy of cancer patients is designed to deliver a required dose to the tumor while sparing the surrounding normal tissues. However, as the normal and cancerous cells absorbed dose in an almost identical fashion, the normal tissue absorbed radiation dose during the treatment time. The use of GNPs in combination with radiotherapy in the treatment of tumor decreases the absorbed dose by normal tissues. The results indicate that the dose to the tumor in an eyeball implanted with COMS plaque increases with increasing GNPs concentration inside the target. Therefore, the required irradiation time for the tumors in the eye is decreased by adding the GNPs prior to treatment. As a result, the dose to normal tissues decreases when the irradiation time is reduced. Furthermore, a comparison between the simulated data in an eye phantom made of water and eye phantom made of human eye composition, in the presence of GNPs, shows the significance of utilizing the composition of eye in ophthalmic brachytherapy dosimetry Also, defining the eye composition instead of water leads to more accurate calculations of GNPs radiation effects in ophthalmic brachytherapy dosimetry. PACS number: 87.53.Jw, 87.85.Rs, 87.10.Rt PMID:26699318

Resources for eye care at secondary and tertiary level government institutions in Saudi Arabia.

PubMed

Al Motowa, Saeed; Khandekar, Rajiv; Al-Towerki, Abdulelah

2014-01-01

To evaluate the number of healthcare personnel and equipment resources for eye care at government institutions in different administrative zones of the Kingdom of Saudi Arabia (KSA) and to recommend measures for increasing resources to address deficiencies. Data on resources (personnel and equipment) for eye care were collected from all governmental eye units in 2012. The data was regrouped by zones and administrative areas. The mid-2012 population projections were used to calculate the ophthalmologist to population ratio and optometrist to population ratio. The equipment available for eye care was reviewed. All 60 institutions in 13 administrative areas and five zones of KSA participated in this study. There were 407 ophthalmologists and 147 optometrists. The ophthalmologist to population ratio was 1:43,000 (1:12,900 in the northern zone to 1:80,300 in the western zone). By 2015, 700 ophthalmologists will be required, and by 2020, 1,100 ophthalmologists will be required. The optometrist to population ratio was 1:95,000 (1:34,100 in the northern zone to 1:146,700 in the western zone). Nearly 2,800 and 4,400 allied eye care personnel will be needed by 2015 and 2020. Diagnostic and treatment equipment such as lasers, electrophysiologic and ultrasound equipment, and fundus cameras were not available at all institutions. Data from the private sector need to be included to draw conclusions on the human resource index for eye care in the Kingdom. An unequal distribution of resources in different zones and administrative areas requires attention. Better utilization of available resources is recommended before fulfilling the demand for additional resources.

The adaptive nature of eye movements in linguistic tasks: how payoff and architecture shape speed-accuracy trade-offs.

PubMed

Lewis, Richard L; Shvartsman, Michael; Singh, Satinder

2013-07-01

We explore the idea that eye-movement strategies in reading are precisely adapted to the joint constraints of task structure, task payoff, and processing architecture. We present a model of saccadic control that separates a parametric control policy space from a parametric machine architecture, the latter based on a small set of assumptions derived from research on eye movements in reading (Engbert, Nuthmann, Richter, & Kliegl, 2005; Reichle, Warren, & McConnell, 2009). The eye-control model is embedded in a decision architecture (a machine and policy space) that is capable of performing a simple linguistic task integrating information across saccades. Model predictions are derived by jointly optimizing the control of eye movements and task decisions under payoffs that quantitatively express different desired speed-accuracy trade-offs. The model yields distinct eye-movement predictions for the same task under different payoffs, including single-fixation durations, frequency effects, accuracy effects, and list position effects, and their modulation by task payoff. The predictions are compared to-and found to accord with-eye-movement data obtained from human participants performing the same task under the same payoffs, but they are found not to accord as well when the assumptions concerning payoff optimization and processing architecture are varied. These results extend work on rational analysis of oculomotor control and adaptation of reading strategy (Bicknell & Levy, ; McConkie, Rayner, & Wilson, 1973; Norris, 2009; Wotschack, 2009) by providing evidence for adaptation at low levels of saccadic control that is shaped by quantitatively varying task demands and the dynamics of processing architecture. Copyright © 2013 Cognitive Science Society, Inc.

Aftereffects for Face Attributes with Different Natural Variability: Children Are More Adaptable than Adolescents

ERIC Educational Resources Information Center

Hills, Peter J.; Holland, Andrew M.; Lewis, Michael B.

2010-01-01

Adults can be adapted to a particular facial distortion in which both eyes are shifted symmetrically (Robbins, R., McKone, E., & Edwards, M. (2007). "Aftereffects for face attributes with different natural variability: Adapter position effects and neural models." "Journal of Experimental Psychology: Human Perception and Performance, 33," 570-592),…

Head-turning asymmetries during kissing and their association with lateral preference.

PubMed

Ocklenburg, Sebastian; Güntürkün, Onur

2009-01-01

A head-turning bias to the right side is one of the earliest functional asymmetries in human development and is already present during the final weeks of gestation. To test whether head-turning preference is related to other lateral preferences in adults, kissing behaviour of participants towards a symmetrical doll was observed to assess their spontaneous head-turning preference. Additionally, participants' individual handedness, footedness, and eye preference were determined using questionnaires. A significant difference in handedness and footedness, but not eye preference, was found between left- and right-kissers, with right-kissers showing a stronger right-sided bias than left-kissers. These results support the assumption that the head-turning bias in humans may be able to induce or enhance other asymmetries of perception and action.

Human amygdala activation during rapid eye movements of rapid eye movement sleep: an intracranial study.

PubMed

Corsi-Cabrera, María; Velasco, Francisco; Del Río-Portilla, Yolanda; Armony, Jorge L; Trejo-Martínez, David; Guevara, Miguel A; Velasco, Ana L

2016-10-01

The amygdaloid complex plays a crucial role in processing emotional signals and in the formation of emotional memories. Neuroimaging studies have shown human amygdala activation during rapid eye movement sleep (REM). Stereotactically implanted electrodes for presurgical evaluation in epileptic patients provide a unique opportunity to directly record amygdala activity. The present study analysed amygdala activity associated with REM sleep eye movements on the millisecond scale. We propose that phasic activation associated with rapid eye movements may provide the amygdala with endogenous excitation during REM sleep. Standard polysomnography and stereo-electroencephalograph (SEEG) were recorded simultaneously during spontaneous sleep in the left amygdala of four patients. Time-frequency analysis and absolute power of gamma activity were obtained for 250 ms time windows preceding and following eye movement onset in REM sleep, and in spontaneous waking eye movements in the dark. Absolute power of the 44-48 Hz band increased significantly during the 250 ms time window after REM sleep rapid eye movements onset, but not during waking eye movements. Transient activation of the amygdala provides physiological support for the proposed participation of the amygdala in emotional expression, in the emotional content of dreams and for the reactivation and consolidation of emotional memories during REM sleep, as well as for next-day emotional regulation, and its possible role in the bidirectional interaction between REM sleep and such sleep disorders as nightmares, anxiety and post-traumatic sleep disorder. These results provide unique, direct evidence of increased activation of the human amygdala time-locked to REM sleep rapid eye movements. © 2016 European Sleep Research Society.

Preliminary study of the safety and efficacy of medium-chain triglycerides for use as an intraocular tamponading agent in minipigs.

PubMed

Soler, Vincent J; Laurent, Camille; Sakr, Frédéric; Regnier, Alain; Tricoire, Cyrielle; Cases, Olivier; Kozyraki, Renata; Douet, Jean-Yves; Pagot-Mathis, Véronique

2017-08-01

To date, only silicone oils and gases have the appropriate characteristics for use in vitreo-retinal surgery as vitreous substitutes with intraocular tamponading properties. This preliminary study evaluated the safety and efficacy of medium-chain triglycerides (MCTs) for use as a tamponading agent in minipigs. In 15 minipigs, 15 right eyes underwent vitrectomies followed by injection of MCT tamponade (day 1). Two groups were defined. In Group A (ten eyes), the surgical procedure before MCT injection included induced rhegmatogenous retinal detachment (RRD), retina flattening, and retinopexy. In Group B (five eyes), MCT was injected without inducing RRD; in these eyes, MCT was removed on day 90. Pigs were sacrificed on day 45 (Group A) or 120 (Group B). Eyes were examined on days 1, 5, 15, and 45 in both groups and on days 90 and 120 in Group B. In Group B only, we performed bilateral electroretinography examinations on days 1 and 120, and histological examinations of MCTs and controlateral eyes were performed after sacrifice. In Group A eyes (n = 9; one eye was non-assessable), on day 45, the retina was flat in seven eyes and two RRD detachments were observed in insufficiently MCT-filled eyes. In Group B, electroretinography showed no significant differences between MCT eyes and controls on days 1 or 120. Histological analyses revealed no signs of retinal toxicity. This study showed that MCT tamponade seems to be effective and safe; however, additional studies are needed before it becomes commonly used as a tamponading agent in humans.

Human Commercial Models' Eye Colour Shows Negative Frequency-Dependent Selection.

PubMed

Forti, Isabela Rodrigues Nogueira; Young, Robert John

2016-01-01

In this study we investigated the eye colour of human commercial models registered in the UK (400 female and 400 male) and Brazil (400 female and 400 male) to test the hypothesis that model eye colour frequency was the result of negative frequency-dependent selection. The eye colours of the models were classified as: blue, brown or intermediate. Chi-square analyses of data for countries separated by sex showed that in the United Kingdom brown eyes and intermediate colours were significantly more frequent than expected in comparison to the general United Kingdom population (P<0.001). In Brazil, the most frequent eye colour brown was significantly less frequent than expected in comparison to the general Brazilian population. These results support the hypothesis that model eye colour is the result of negative frequency-dependent selection. This could be the result of people using eye colour as a marker of genetic diversity and finding rarer eye colours more attractive because of the potential advantage more genetically diverse offspring that could result from such a choice. Eye colour may be important because in comparison to many other physical traits (e.g., hair colour) it is hard to modify, hide or disguise, and it is highly polymorphic.

Effects of the holmium laser on the human cornea: a preliminary study

NASA Astrophysics Data System (ADS)

Mueller, Linda J.; Tassignon, Marie J.; Trau, Rene; Pels, Liesbeth; Vrensen, Gijs F.

1996-12-01

Treatment of peripheral post-mortem human corneas with the Holmium laser in a ring pattern resulted in opaque spots. One pair of treated eyes was immediately processed for light and electron microscopy and three other treated eyes were preserved for 4 days in medium in order to compare direct and short-term effects of the Holmium laser. Cross as well as frontal light microscopical sections of all eyes revealed interconnecting bands between the spots. At the ultrastructural level the anterior corneal tissue within these spots was characterized by coagulation of cells and collagen and shoed either a dramatic distorting effect on the epithelium in the eyes processed immediately or a single layer of flattened multi-nucleolated epithelial cells having more than one nucleolus per nucleus in the eyes stored in medium. Furthermore, the spots showed disturbed Bowman's layer, destroyed keratocytes and collagen fibrils which were either coagulated or organized chaotically. The interconnecting bands contained alternating normal and coagulated collagen fibers. The rest of the cornea outside the spots had a normal appearance. In corneas stored in medium, both keratocytes and epithelial cells over the entire cornea exhibited accumulations of cytoplasmic fibrils and glycogen particles. These phenomena were not observed in non-preserved corneas, suggesting that the differences are due to preservation and not due to the laser treatment. It is concluded that morphological changes occur mainly in the treated peripheral cornea whereas the central untreated cornea remains unaffected,indicating that the Holmium laser is a reliable instrument to treat hypermetropic patients.

A cell culture technique for human epiretinal membranes to describe cell behavior and membrane contraction in vitro.

PubMed

Wertheimer, Christian; Eibl-Lindner, Kirsten H; Compera, Denise; Kueres, Alexander; Wolf, Armin; Docheva, Denitsa; Priglinger, Siegfried G; Priglinger, Claudia; Schumann, Ricarda G

2017-11-01

To introduce a human cell culture technique for investigating in-vitro behavior of primary epiretinal cells and membrane contraction of fibrocellular tissue surgically removed from eyes with idiopathic macular pucker. Human epiretinal membranes were harvested from ten eyes with idiopathic macular pucker during standard vitrectomy. Specimens were fixed on cell culture plastic using small entomological pins to apply horizontal stress to the tissue, and then transferred to standard cell culture conditions. Cell behavior of 400 epiretinal cells from 10 epiretinal membranes was observed in time-lapse microscopy and analyzed in terms of cell migration, cell velocity, and membrane contraction. Immunocytochemistry was performed for cell type-specific antigens. Cell specific differences in migration behavior were observed comprising two phenotypes: (PT1) epiretinal cells moving fast, less directly, with small round phenotype and (PT2) epiretinal cells moving slowly, directly, with elongated large phenotype. No mitosis, no outgrowth and no migration onto the plastic were seen. Horizontal contraction measurements showed variation between specimens. Masses of epiretinal cells with a myofibroblast-like phenotype expressed cytoplasmatic α-SMA stress fibers and correlated with cell behavior characteristics (PT2). Fast moving epiretinal cells (PT1) were identified as microglia by immunostaining. This in-vitro technique using traction application allows for culturing surgically removed epiretinal membranes from eyes with idiopathic macular pucker, demonstrating cell behavior and membrane contraction of primary human epiretinal cells. Our findings emphasize the abundance of myofibroblasts, the presence of microglia and specific differences of cell behavior in these membranes. This technique has the potential to improve the understanding of pathologies at the vitreomacular interface and might be helpful in establishing anti-fibrotic treatment strategies.

Dynamic light scattering in ophthalmology: results of in vitro and in vivo experiments.

PubMed

Fankhauser, Franz

2006-01-01

To calibrate new dynamic light scattering (DLS) devices in defined solutions and post mortem porcine and human eyes. To examine all segments of the eye and to become familiar with the usage of the technique in living subjects. METHODS, DESIGN: Three new DLS devices for the usage in patients were developed. Mono-disperse solutions, poly-disperse solutions, gels, post mortem porcine and human eyes as well as healthy volunteers were studied. The detected signals were inverted into autocorrelation functions. We constructed three DLS devices appropriate for in vitro as well as in vivo examinations. In mono disperse solution precise disintegration rates could be calculated. In poly-disperse solutions, in gel and in the vitreous the results did not correlate with movements of individual particles but we could calculate characteristics of the complete scattering system. In vivo measurements demonstrated that DLS can be used in all human eye segments. DLS is a unique technique. With DLS the molecular composition of eye segments can be studied in living subjects. This can be used to understand the molecular basis of severe eye diseases. The presented data demonstrate that DLS delivers reproducible data from all eye segments. It is possible to study the molecular structures of eye segments in living subjects. The developed devices were proved successfully in vitro as well as in vivo. Limitations are the low specificity of DLS and its sensitivity to background noise. Now clinical studies are necessary to demonstrate potential diagnostic benefits of DLS in specific eye diseases.

Genes relacionados con microftalmia y anoftalmia hereditarias.

PubMed

Matías-Pérez, Diana; García-Montalvo, Iván Antonio; Zenteno, Juan Carlos

2017-01-01

Congenital eye malformations are the second most common cause of childhood blindness and are originated by disruption of the normal process of eye development during embryonic stage. Their etiology is variable, although monogenic causes are of great importance as they have a high risk of familial recurrence. Included among the most severe congenital eye abnormalities are microphthalmia, defined by an abnormally small eye, and anophthalmia, characterized by congenital absence of ocular structures. The currrent knowledge of the genes involved in human microphthalmia and anophthalmia in humans is revised in this work. Copyright: © 2017 SecretarÍa de Salud.

Interocular induction of illusory size perception

PubMed Central

2011-01-01

Background The perceived size of objects not only depends on their physical size but also on the surroundings in which they appear. For example, an object surrounded by small items looks larger than a physically identical object surrounded by big items (Ebbinghaus illusion), and a physically identical but distant object looks larger than an object that appears closer in space (Ponzo illusion). Activity in human primary visual cortex (V1) reflects the perceived rather than the physical size of objects, indicating an involvement of V1 in illusory size perception. Here we investigate the role of eye-specific signals in two common size illusions in order to provide further information about the mechanisms underlying illusory size perception. Results We devised stimuli so that an object and its spatial context associated with illusory size perception could be presented together to one eye or separately to two eyes. We found that the Ponzo illusion had an equivalent magnitude whether the objects and contexts were presented to the same or different eyes, indicating that it may be largely mediated by binocular neurons. In contrast, the Ebbinghaus illusion became much weaker when objects and their contexts were presented to different eyes, indicating important contributions to the illusion from monocular neurons early in the visual pathway. Conclusions Our findings show that two well-known size illusions - the Ponzo illusion and the Ebbinghaus illusion - are mediated by different neuronal populations, and suggest that the underlying neural mechanisms associated with illusory size perception differ and can be dependent on monocular channels in the early visual pathway. PMID:21396093

Dwarf Eye Disorder

ERIC Educational Resources Information Center

Science Teacher, 2005

2005-01-01

Johns Hopkins researchers at the Wilmer Eye Institute have discovered what appears to be the first human gene mutation that causes extreme farsightedness. The researchers report that nanophthalmos, Greek for "dwarf eye," is a rare, potentially blinding disorder caused by an alteration in a gene called MFRP that helps control eye growth and…

21 CFR 886.3320 - Eye sphere implant.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Eye sphere implant. 886.3320 Section 886.3320 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3320 Eye sphere implant. (a) Identification. An eye...

77 FR 12318 - National Eye Institute; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-29

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute... unwarranted invasion of personal privacy. Name of Committee: National Eye Institute Special Emphasis Panel; NEI Anterior Eye Disease. Date: March 19, 2012. Time: 1 p.m. to 2:30 p.m. Agenda: To review and...

75 FR 13769 - National Eye Institute; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-23

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute... unwarranted invasion of personal privacy. Name of Committee: National Eye Institute Special Emphasis Panel; National Eye Institute SBIR Special Emphasis Panel. Date: April 9, 2010. Time: 8:30 a.m. to 5 p.m. Agenda...

75 FR 20853 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-21

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute... unwarranted invasion of personal privacy. Name of Committee: National Eye Institute Special Emphasis Panel, Immunosuppression for Eye Diseases. Date: April 20, 2010. Time: 3 p.m. to 4 p.m. Agenda: To review and evaluate...

21 CFR 886.3320 - Eye sphere implant.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Eye sphere implant. 886.3320 Section 886.3320 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3320 Eye sphere implant. (a) Identification. An eye...

21 CFR 878.4440 - Eye pad.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Eye pad. 878.4440 Section 878.4440 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4440 Eye pad. (a) Identification. An eye pad is...

21 CFR 878.4440 - Eye pad.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Eye pad. 878.4440 Section 878.4440 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4440 Eye pad. (a) Identification. An eye pad is...

21 CFR 878.4440 - Eye pad.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Eye pad. 878.4440 Section 878.4440 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4440 Eye pad. (a) Identification. An eye pad is...

A multimodal interface to resolve the Midas-Touch problem in gaze controlled wheelchair.

PubMed

Meena, Yogesh Kumar; Cecotti, Hubert; Wong-Lin, KongFatt; Prasad, Girijesh

2017-07-01

Human-computer interaction (HCI) research has been playing an essential role in the field of rehabilitation. The usability of the gaze controlled powered wheelchair is limited due to Midas-Touch problem. In this work, we propose a multimodal graphical user interface (GUI) to control a powered wheelchair that aims to help upper-limb mobility impaired people in daily living activities. The GUI was designed to include a portable and low-cost eye-tracker and a soft-switch wherein the wheelchair can be controlled in three different ways: 1) with a touchpad 2) with an eye-tracker only, and 3) eye-tracker with soft-switch. The interface includes nine different commands (eight directions and stop) and integrated within a powered wheelchair system. We evaluated the performance of the multimodal interface in terms of lap-completion time, the number of commands, and the information transfer rate (ITR) with eight healthy participants. The analysis of the results showed that the eye-tracker with soft-switch provides superior performance with an ITR of 37.77 bits/min among the three different conditions (p<;0.05). Thus, the proposed system provides an effective and economical solution to the Midas-Touch problem and extended usability for the large population of disabled users.

An eye model for uncalibrated eye gaze estimation under variable head pose

NASA Astrophysics Data System (ADS)

Hnatow, Justin; Savakis, Andreas

2007-04-01

Gaze estimation is an important component of computer vision systems that monitor human activity for surveillance, human-computer interaction, and various other applications including iris recognition. Gaze estimation methods are particularly valuable when they are non-intrusive, do not require calibration, and generalize well across users. This paper presents a novel eye model that is employed for efficiently performing uncalibrated eye gaze estimation. The proposed eye model was constructed from a geometric simplification of the eye and anthropometric data about eye feature sizes in order to circumvent the requirement of calibration procedures for each individual user. The positions of the two eye corners and the midpupil, the distance between the two eye corners, and the radius of the eye sphere are required for gaze angle calculation. The locations of the eye corners and midpupil are estimated via processing following eye detection, and the remaining parameters are obtained from anthropometric data. This eye model is easily extended to estimating eye gaze under variable head pose. The eye model was tested on still images of subjects at frontal pose (0 °) and side pose (34 °). An upper bound of the model's performance was obtained by manually selecting the eye feature locations. The resulting average absolute error was 2.98 ° for frontal pose and 2.87 ° for side pose. The error was consistent across subjects, which indicates that good generalization was obtained. This level of performance compares well with other gaze estimation systems that utilize a calibration procedure to measure eye features.

The Nine-Step Minnesota Grading System for Eyebank Eyes With Age Related Macular Degeneration: A Systematic Approach to Study Disease Stages.

PubMed

Olsen, Timothy W; Liao, Albert; Robinson, Hershonna S; Palejwala, Neal V; Sprehe, Nicholas

2017-10-01

To refine the Minnesota Grading System (MGS) using definitions from the Age-Related Eye Disease Studies (AREDS) into a nine-step grading scale (MGS-9). A nine-step grading scale descriptive analysis using three key phenotypic features (total drusen area, increased, and decreased pigmentation) of human eyebank eyes that were graded according to definitions from the AREDS criteria in order to harmonize studies of disease progression for research involving human tissue. From 2005 through February 2017, we have analyzed 1159 human eyes, procured from two eyebanks. Each macula was imaged using high-resolution, stereoscopic color fundus photography with both direct- and transillumination. Fundus images were digitally overlaid with a grading template and triangulated for foveal centration. We documented and stratified risk for each globe by applying the AREDS nine-step grading scale to the key clinical features from the MGS-9. We found a good distribution within the MGS categories (1-9) with few level eight globes. Eyes were processed within 12.1 ± 6.3, hours from the time of death through imaging, dissection, and freezing or fixation. Applying the MGS-9 to 331 pairs (662 eyes were simultaneously graded), 84% were within one-grading step and 93% within two steps of the fellow eye. We also document reticular pseudodrusen, basal laminar drusen, and pattern dystrophy. The MGS nine-step grading scale enables researchers using human tissue to refine the risk assessment of donor tissue. This analysis will harmonize results among researchers when grading human tissue using MGS criteria. Most importantly, the MGS-9 links directly to the known risk for progression from the AREDS.

Eye Movements Affect Postural Control in Young and Older Females

PubMed Central

Thomas, Neil M.; Bampouras, Theodoros M.; Donovan, Tim; Dewhurst, Susan

2016-01-01

Visual information is used for postural stabilization in humans. However, little is known about how eye movements prevalent in everyday life interact with the postural control system in older individuals. Therefore, the present study assessed the effects of stationary gaze fixations, smooth pursuits, and saccadic eye movements, with combinations of absent, fixed and oscillating large-field visual backgrounds to generate different forms of retinal flow, on postural control in healthy young and older females. Participants were presented with computer generated visual stimuli, whilst postural sway and gaze fixations were simultaneously assessed with a force platform and eye tracking equipment, respectively. The results showed that fixed backgrounds and stationary gaze fixations attenuated postural sway. In contrast, oscillating backgrounds and smooth pursuits increased postural sway. There were no differences regarding saccades. There were also no differences in postural sway or gaze errors between age groups in any visual condition. The stabilizing effect of the fixed visual stimuli show how retinal flow and extraocular factors guide postural adjustments. The destabilizing effect of oscillating visual backgrounds and smooth pursuits may be related to more challenging conditions for determining body shifts from retinal flow, and more complex extraocular signals, respectively. Because the older participants matched the young group's performance in all conditions, decreases of posture and gaze control during stance may not be a direct consequence of healthy aging. Further research examining extraocular and retinal mechanisms of balance control and the effects of eye movements, during locomotion, is needed to better inform fall prevention interventions. PMID:27695412

Eye Movements Affect Postural Control in Young and Older Females.

PubMed

Thomas, Neil M; Bampouras, Theodoros M; Donovan, Tim; Dewhurst, Susan

2016-01-01

Visual information is used for postural stabilization in humans. However, little is known about how eye movements prevalent in everyday life interact with the postural control system in older individuals. Therefore, the present study assessed the effects of stationary gaze fixations, smooth pursuits, and saccadic eye movements, with combinations of absent, fixed and oscillating large-field visual backgrounds to generate different forms of retinal flow, on postural control in healthy young and older females. Participants were presented with computer generated visual stimuli, whilst postural sway and gaze fixations were simultaneously assessed with a force platform and eye tracking equipment, respectively. The results showed that fixed backgrounds and stationary gaze fixations attenuated postural sway. In contrast, oscillating backgrounds and smooth pursuits increased postural sway. There were no differences regarding saccades. There were also no differences in postural sway or gaze errors between age groups in any visual condition. The stabilizing effect of the fixed visual stimuli show how retinal flow and extraocular factors guide postural adjustments. The destabilizing effect of oscillating visual backgrounds and smooth pursuits may be related to more challenging conditions for determining body shifts from retinal flow, and more complex extraocular signals, respectively. Because the older participants matched the young group's performance in all conditions, decreases of posture and gaze control during stance may not be a direct consequence of healthy aging. Further research examining extraocular and retinal mechanisms of balance control and the effects of eye movements, during locomotion, is needed to better inform fall prevention interventions.

Social Attention in the Two Species of Pan: Bonobos Make More Eye Contact than Chimpanzees.

PubMed

Kano, Fumihiro; Hirata, Satoshi; Call, Josep

2015-01-01

Humans' two closest primate living relatives, bonobos and chimpanzees, differ behaviorally, cognitively, and emotionally in several ways despite their general similarities. While bonobos show more affiliative behaviors towards conspecifics, chimpanzees display more overt and severe aggression against conspecifics. From a cognitive standpoint, bonobos perform better in social coordination, gaze-following and food-related cooperation, while chimpanzees excel in tasks requiring extractive foraging skills. We hypothesized that attention and motivation play an important role in shaping the species differences in behavior, cognition, and emotion. Thus, we predicted that bonobos would pay more attention to the other individuals' face and eyes, as those are related to social affiliation and social coordination, while chimpanzees would pay more attention to the action target objects, as they are related to foraging. Using eye-tracking we examined the bonobos' and chimpanzees' spontaneous scanning of pictures that included eyes, mouth, face, genitals, and action target objects of conspecifics. Although bonobos and chimpanzees viewed those elements overall similarly, bonobos viewed the face and eyes longer than chimpanzees, whereas chimpanzees viewed the other elements, the mouth, action target objects and genitals, longer than bonobos. In a discriminant analysis, the individual variation in viewing patterns robustly predicted the species of individuals, thus clearly demonstrating species-specific viewing patterns. We suggest that such attentional and motivational differences between bonobos and chimpanzees could have partly contributed to shaping the species-specific behaviors, cognition, and emotion of these species, even in a relatively short period of evolutionary time.

Background matching and camouflage efficiency predict population density in four-eyed turtle (Sacalia quadriocellata).

PubMed

Xiao, Fanrong; Yang, Canchao; Shi, Haitao; Wang, Jichao; Sun, Liang; Lin, Liu

2016-10-01

Background matching is an important way to camouflage and is widespread among animals. In the field, however, few studies have addressed background matching, and there has been no reported camouflage efficiency in freshwater turtles. Background matching and camouflage efficiency of the four-eyed turtle, Sacalia quadriocellata, among three microhabitat sections of Hezonggou stream were investigated by measuring carapace components of CIE L*a*b* (International Commission on Illumination; lightness, red/green and yellow/blue) color space, and scoring camouflage efficiency through the use of humans as predators. The results showed that the color difference (ΔE), lightness difference (ΔL(*)), and chroma difference (Δa(*)b(*)) between carapace and the substrate background in midstream were significantly lower than that upstream and downstream, indicating that the four-eyed turtle carapace color most closely matched the substrate of midstream. In line with these findings, the camouflage efficiency was the best for the turtles that inhabit midstream. These results suggest that the four-eyed turtles may enhance camouflage efficiency by selecting microhabitat that best match their carapace color. This finding may explain the high population density of the four-eyed turtle in the midstream section of Hezonggou stream. To the best of our knowledge, this study is among the first to quantify camouflage of freshwater turtles in the wild, laying the groundwork to further study the function and mechanisms of turtle camouflage. Copyright © 2016. Published by Elsevier B.V.

Effects of light on brain and behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brainard, G.C.

1994-12-31

It is obvious that light entering the eye permits the sensory capacity of vision. The human species is highly dependent on visual perception of the environment and consequently, the scientific study of vision and visual mechanisms is a centuries old endeavor. Relatively new discoveries are now leading to an expanded understanding of the role of light entering the eye - in addition to supporting vision, light has various nonvisual biological effects. Over the past thirty years, animal studies have shown that environmental light is the primary stimulus for regulating circadian rhythms, seasonal cycles, and neuroendocrine responses. As with all photobiologicalmore » phenomena, the wavelength, intensity, timing and duration of a light stimulus is important in determining its regulatory influence on the circadian and neuroendocrine systems. Initially, the effects of light on rhythms and hormones were observed only in sub-human species. Research over the past decade, however, has confirmed that light entering the eyes of humans is a potent stimulus for controlling physiological rhythms. The aim of this paper is to examine three specific nonvisual responses in humans which are mediated by light entering the eye: light-induced melatonin suppression, light therapy for winter depression, and enhancement of nighttime performance. This will serve as a brief introduction to the growing database which demonstrates how light stimuli can influence physiology, mood and behavior in humans. Such information greatly expands our understanding of the human eye and will ultimately change our use of light in the human environment.« less

Effects of light on brain and behavior

NASA Technical Reports Server (NTRS)

Brainard, George C.

1994-01-01

It is obvious that light entering the eye permits the sensory capacity of vision. The human species is highly dependent on visual perception of the environment and consequently, the scientific study of vision and visual mechanisms is a centuries old endeavor. Relatively new discoveries are now leading to an expanded understanding of the role of light entering the eye in addition to supporting vision, light has various nonvisual biological effects. Over the past thirty years, animal studies have shown that environmental light is the primary stimulus for regulating circadian rhythms, seasonal cycles, and neuroendocrine responses. As with all photobiological phenomena, the wavelength, intensity, timing and duration of a light stimulus is important in determining its regulatory influence on the circadian and neuroendocrine systems. Initially, the effects of light on rhythms and hormones were observed only in sub-human species. Research over the past decade, however, has confirmed that light entering the eyes of humans is a potent stimulus for controlling physiological rhythms. The aim of this paper is to examine three specific nonvisual responses in humans which are mediated by light entering the eye: light-induced melatonin suppression, light therapy for winter depression, and enhancement of nighttime performance. This will serve as a brief introduction to the growing database which demonstrates how light stimuli can influence physiology, mood and behavior in humans. Such information greatly expands our understanding of the human eye and will ultimately change our use of light in the human environment.

Fluorescent scanning laser ophthalmoscopy for cellular resolution in vivo mouse retinal imaging: benefits and drawbacks of implementing adaptive optics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Goswami, Mayank; Pugh, Edward N.; Zawadzki, Robert J.

2016-03-01

Scanning Laser Ophthalmoscopy (SLO) is a very important imaging tool in ophthalmology research. By combing with Adaptive Optics (AO) technique, AO-SLO can correct for ocular aberrations resulting in cellular level resolution, allowing longitudinal studies of single cells morphology in the living eyes. The numerical aperture (NA) sets the optical resolution that can be achieve in the "classical" imaging systems. Mouse eye has more than twice NA of the human eye, thus offering theoretically higher resolution. However, in most SLO based imaging systems the imaging beam size at mouse pupil sets the NA of that instrument, while most of the AO-SLO systems use almost the full NA of the mouse eye. In this report, we first simulated the theoretical resolution that can be achieved in vivo for different imaging beam sizes (different NA), assumingtwo cases: no aberrations and aberrations based on published mouse ocular wavefront data. Then we imaged mouse retinas with our custom build SLO system using different beam sizes to compare these results with theory. Further experiments include comparison of the SLO and AO-SLO systems for imaging different type of fluorescently labeled cells (microglia, ganglion, photoreceptors, etc.). By comparing those results and taking into account systems complexity and ease of use, the benefits and drawbacks of two imaging systems will be discussed.

Relationship between saccadic eye movements and formation of the Krukenberg's spindle-a CFD study.

PubMed

Boushehrian, Hamidreza Hajiani; Abouali, Omid; Jafarpur, Khosrow; Ghaffarieh, Alireza; Ahmadi, Goodarz

2017-09-01

In this research, a series of numerical simulations for evaluating the effects of saccadic eye movement on the aqueous humour (AH) flow field and movement of pigment particles in the anterior chamber (AC) was performed. To predict the flow field of AH in the AC, the unsteady forms of continuity, momentum balance and conservation of energy equations were solved using the dynamic mesh technique for simulating the saccadic motions. Different orientations of the human eye including horizontal, vertical and angles of 10° and 20° were considered. The Lagrangian particle trajectory analysis approach was used to find the trajectories of pigment particles in the eye. Particular attention was given to the relation between the saccadic eye movement and potential formation of Krukenberg's spindle in the eye. The simulation results revealed that the natural convection flow was an effective mechanism for transferring pigment particles from the iris to near the cornea. In addition, the saccadic eye movement was the dominant mechanism for deposition of pigment particles on the cornea, which could lead to the formation of Krukenberg's spindle. The effect of amplitude of saccade motion angle in addition to the orientation of the eye on the formation of Krukenberg's spindle was investigated. © The authors 2016. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

Characterisation of the porcine eyeball as an in-vitro model for dry eye.

PubMed

Menduni, Francesco; Davies, Leon N; Madrid-Costa, D; Fratini, Antonio; Wolffsohn, James S

2018-02-01

To characterise the anatomical parameters of the porcine eye for potentially using it as a laboratory model of dry eye. Anterior chamber depth and angle, corneal curvature, shortest and longest diameter, endothelial cell density, and pachymetry were measured in sixty freshly enucleated porcine eyeballs. Corneal steepest meridian was 7.85±0.32mm, corneal flattest meridian was 8.28±0.32mm, shortest corneal diameter was 12.69±0.58mm, longest corneal diameter was 14.88±0.66mm and central corneal ultrasonic pachymetry was 1009±1μm. Anterior chamber angle was 28.83±4.16°, anterior chamber depth was 1.77±0.27mm, and central corneal thickness measured using OCT was 1248±144μm. Corneal endothelial cell density was 3250±172 cells/mm 2 . Combining different clinical techniques produced a pool of reproducible data on the porcine eye anatomy, which can be used by researchers to assess the viability of using the porcine eye as an in-vitro/ex-vivo model for dry eye. Due to the similar morphology with the human eye, porcine eyeballs may represent a useful and cost effective model to individually study important key factors in the development of dry eye, such as environmental and mechanical stresses. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Towards Quantum Experiments with Human Eye Detectors Based on Cloning via Stimulated Emission ?

NASA Astrophysics Data System (ADS)

De Martini, Francesco

2010-05-01

In a recent theoretical paper published in Physical Review Letters, Sekatsky, Brunner, Branciard, Gisin, Simon report an extended investigation on some properties of the human eye that affect its behavior as a quantum detector. We believe that the content of this work, albeit appealing at fist sight, is highly questionable simply because the human eye cannot be adopted as a sensing device within any quantum measurement apparatus. Furthermore, the criticism raised by these Authors against a real experiment on Micro—Macro entanglement recently published in Physical Review Letters (100, 253601, 2008) is found misleading and misses its target.

Sensing Passive Eye Response to Impact Induced Head Acceleration Using MEMS IMUs.

PubMed

Meng, Yuan; Bottenfield, Brent; Bolding, Mark; Liu, Lei; Adams, Mark L

2018-02-01

The eye may act as a surrogate for the brain in response to head acceleration during an impact. Passive eye movements in a dynamic system are sensed by microelectromechanical systems (MEMS) inertial measurement units (IMU) in this paper. The technique is validated using a three-dimensional printed scaled human skull model and on human volunteers by performing drop-and-impact experiments with ribbon-style flexible printed circuit board IMUs inserted in the eyes and reference IMUs on the heads. Data are captured by a microcontroller unit and processed using data fusion. Displacements are thus estimated and match the measured parameters. Relative accelerations and displacements of the eye to the head are computed indicating the influence of the concussion causing impacts.

The classical pink-eyed dilution mutation affects angiogenic responsiveness.

PubMed

Rogers, Michael S; Boyartchuk, Victor; Rohan, Richard M; Birsner, Amy E; Dietrich, William F; D'Amato, Robert J

2012-01-01

Angiogenesis is the process by which new blood vessels are formed from existing vessels. Mammalian populations, including humans and mice, harbor genetic variations that alter angiogenesis. Angiogenesis-regulating gene variants can result in increased susceptibility to multiple angiogenesis-dependent diseases in humans. Our efforts to dissect the complexity of the genetic diversity that regulates angiogenesis have used laboratory animals due to the availability of genome sequence for many species and the ability to perform high volume controlled breeding. Using the murine corneal micropocket assay, we have observed more than ten-fold difference in angiogenic responsiveness among various mouse strains. This degree of difference is observed with either bFGF or VEGF induced corneal neovascularization. Ongoing mapping studies have identified multiple loci that affect angiogenic responsiveness in several mouse models. In this study, we used F2 intercrosses between C57BL/6J and the 129 substrains 129P1/ReJ and 129P3/J, as well as the SJL/J strain, where we have identified new QTLs that affect angiogenic responsiveness. In the case of AngFq5, on chromosome 7, congenic animals were used to confirm the existence of this locus and subcongenic animals, combined with a haplotype-based mapping approach that identified the pink-eyed dilution mutation as a candidate polymorphism to explain AngFq5. The ability of mutations in the pink-eyed dilution gene to affect angiogenic response was demonstrated using the p-J allele at the same locus. Using this allele, we demonstrate that pink-eyed dilution mutations in Oca2 can affect both bFGF and VEGF-induced corneal angiogenesis.

The Importance of Postural Cues for Determining Eye Height in Immersive Virtual Reality

PubMed Central

Leyrer, Markus; Linkenauger, Sally A.; Bülthoff, Heinrich H.; Mohler, Betty J.

2015-01-01

In human perception, the ability to determine eye height is essential, because eye height is used to scale heights of objects, velocities, affordances and distances, all of which allow for successful environmental interaction. It is well understood that eye height is fundamental to determine many of these percepts. Yet, how eye height itself is provided is still largely unknown. While the information potentially specifying eye height in the real world is naturally coincident in an environment with a regular ground surface, these sources of information can be easily divergent in similar and common virtual reality scenarios. Thus, we conducted virtual reality experiments where we manipulated the virtual eye height in a distance perception task to investigate how eye height might be determined in such a scenario. We found that humans rely more on their postural cues for determining their eye height if there is a conflict between visual and postural information and little opportunity for perceptual-motor calibration is provided. This is demonstrated by the predictable variations in their distance estimates. Our results suggest that the eye height in such circumstances is informed by postural cues when estimating egocentric distances in virtual reality and consequently, does not depend on an internalized value for eye height. PMID:25993274

The importance of postural cues for determining eye height in immersive virtual reality.

PubMed

Leyrer, Markus; Linkenauger, Sally A; Bülthoff, Heinrich H; Mohler, Betty J

2015-01-01

In human perception, the ability to determine eye height is essential, because eye height is used to scale heights of objects, velocities, affordances and distances, all of which allow for successful environmental interaction. It is well understood that eye height is fundamental to determine many of these percepts. Yet, how eye height itself is provided is still largely unknown. While the information potentially specifying eye height in the real world is naturally coincident in an environment with a regular ground surface, these sources of information can be easily divergent in similar and common virtual reality scenarios. Thus, we conducted virtual reality experiments where we manipulated the virtual eye height in a distance perception task to investigate how eye height might be determined in such a scenario. We found that humans rely more on their postural cues for determining their eye height if there is a conflict between visual and postural information and little opportunity for perceptual-motor calibration is provided. This is demonstrated by the predictable variations in their distance estimates. Our results suggest that the eye height in such circumstances is informed by postural cues when estimating egocentric distances in virtual reality and consequently, does not depend on an internalized value for eye height.

Correlation peak analysis applied to a sequence of images using two different filters for eye tracking model

NASA Astrophysics Data System (ADS)

Patrón, Verónica A.; Álvarez Borrego, Josué; Coronel Beltrán, Ángel

2015-09-01

Eye tracking has many useful applications that range from biometrics to face recognition and human-computer interaction. The analysis of the characteristics of the eyes has become one of the methods to accomplish the location of the eyes and the tracking of the point of gaze. Characteristics such as the contrast between the iris and the sclera, the shape, and distribution of colors and dark/light zones in the area are the starting point for these analyses. In this work, the focus will be on the contrast between the iris and the sclera, performing a correlation in the frequency domain. The images are acquired with an ordinary camera, which with were taken images of thirty-one volunteers. The reference image is an image of the subjects looking to a point in front of them at 0° angle. Then sequences of images are taken with the subject looking at different angles. These images are processed in MATLAB, obtaining the maximum correlation peak for each image, using two different filters. Each filter were analyzed and then one was selected, which is the filter that gives the best performance in terms of the utility of the data, which is displayed in graphs that shows the decay of the correlation peak as the eye moves progressively at different angle. This data will be used to obtain a mathematical model or function that establishes a relationship between the angle of vision (AOV) and the maximum correlation peak (MCP). This model will be tested using different input images from other subject not contained in the initial database, being able to predict angle of vision using the maximum correlation peak data.

Objects predict fixations better than early saliency.

PubMed

Einhäuser, Wolfgang; Spain, Merrielle; Perona, Pietro

2008-11-20

Humans move their eyes while looking at scenes and pictures. Eye movements correlate with shifts in attention and are thought to be a consequence of optimal resource allocation for high-level tasks such as visual recognition. Models of attention, such as "saliency maps," are often built on the assumption that "early" features (color, contrast, orientation, motion, and so forth) drive attention directly. We explore an alternative hypothesis: Observers attend to "interesting" objects. To test this hypothesis, we measure the eye position of human observers while they inspect photographs of common natural scenes. Our observers perform different tasks: artistic evaluation, analysis of content, and search. Immediately after each presentation, our observers are asked to name objects they saw. Weighted with recall frequency, these objects predict fixations in individual images better than early saliency, irrespective of task. Also, saliency combined with object positions predicts which objects are frequently named. This suggests that early saliency has only an indirect effect on attention, acting through recognized objects. Consequently, rather than treating attention as mere preprocessing step for object recognition, models of both need to be integrated.

Wafer bonding process for building MEMS devices

NASA Astrophysics Data System (ADS)

Pabo, Eric F.; Meiler, Josef; Matthias, Thorsten

2014-06-01

The technology for the measurement of colour rendering and colour quality is not new, but many parameters related to this issue are currently changing. A number of standard methods were developed and are used by different specialty areas of the lighting industry. CIE 13.3 has been the accepted standard implemented by many users and used for many years. Light-emitting Diode (LED) technology moves at a rapid pace and, as this lighting source finds wider acceptance, it appears that traditional colour-rendering measurement methods produce inconsistent results. Practical application of various types of LEDs yielded results that challenged conventional thinking regarding colour measurement of light sources. Recent studies have shown that the anatomy and physiology of the human eye is more complex than formerly accepted. Therefore, the development of updated measurement methodology also forces a fresh look at functioning and colour perception of the human eye, especially with regard to LEDs. This paper includes a short description of the history and need for the measurement of colour rendering. Some of the traditional measurement methods are presented and inadequacies are discussed. The latest discoveries regarding the functioning of the human eye and the perception of colour, especially when LEDs are used as light sources, are discussed. The unique properties of LEDs when used in practical applications such as luminaires are highlighted.

Digital Quantification of Human Eye Color Highlights Genetic Association of Three New Loci

PubMed Central

Liu, Fan; Wollstein, Andreas; Hysi, Pirro G.; Ankra-Badu, Georgina A.; Spector, Timothy D.; Park, Daniel; Zhu, Gu; Larsson, Mats; Duffy, David L.; Montgomery, Grant W.; Mackey, David A.; Walsh, Susan; Lao, Oscar; Hofman, Albert; Rivadeneira, Fernando; Vingerling, Johannes R.; Uitterlinden, André G.; Martin, Nicholas G.; Hammond, Christopher J.; Kayser, Manfred

2010-01-01

Previous studies have successfully identified genetic variants in several genes associated with human iris (eye) color; however, they all used simplified categorical trait information. Here, we quantified continuous eye color variation into hue and saturation values using high-resolution digital full-eye photographs and conducted a genome-wide association study on 5,951 Dutch Europeans from the Rotterdam Study. Three new regions, 1q42.3, 17q25.3, and 21q22.13, were highlighted meeting the criterion for genome-wide statistically significant association. The latter two loci were replicated in 2,261 individuals from the UK and in 1,282 from Australia. The LYST gene at 1q42.3 and the DSCR9 gene at 21q22.13 serve as promising functional candidates. A model for predicting quantitative eye colors explained over 50% of trait variance in the Rotterdam Study. Over all our data exemplify that fine phenotyping is a useful strategy for finding genes involved in human complex traits. PMID:20463881

[Subretinal transplantation of human fetal lung fibroblasts expressed ciliary neurotrophic factor gene prevent photoreceptor degeneration in RCS rats].

PubMed

Huang, Qian; Xu, Ping; Xia, Xin; Hu, Hong-hui; Wang, Feng; Li, Hui-ming

2006-02-01

To investigate the efficacy of subretinal transplantation of CNTF gene transfected fibroblasts for preventing photoreceptor degeneration in RCS. The human fetal lung fibroblasts with high level expression of CNTF were established by liposome mediated gene transfer and MTX selection. A 5 microl of cell suspension, containing 1 x 10(5) cells, was injected through pars plana of ciliary body into the subretinal space of the right eye at postnatal 4-5 weeks, the left eye was left without injection or injected with PBS as controls. The both eyes were enucleated for histopathological examinations at 2, 4, 6, 8, 10, 12 and 15 weeks following transplantation. The level of CNTF protein (91,046.15 pg/ml) expressed in the transfected cells was determined by sandwich enzyme-linked immunosorbent assay (ELISA). The four of seven eyes examined by light microscopy and the ten of 14 eyes examined by electro microscopy showed rescue effect. The prolonged photoreceptor survival, reduction of apoptotic cells and debris were observed in transplanted eyes in comparison with untreated or sham-injected eyes. This study provides the first indication that transplanted human fibroblasts with high level expression of CNTF are able to rescue photoreceptor degeneration in RCS dystrophic rat retina.

Amylin competes for binding sites of CGRP in the chamber angle and uvea of monkey, cat, and pig eye.

PubMed

Alajuuma, Päivi; Oksala, Olli; Uusitalo, Hannu

2003-12-01

Calcitonin gene-related peptide (CGRP) binding sites have been identified previously in the eyes of monkey, cat, pig, and guinea pig. In this study, the ability of cat, human, and rat amylins to displace the binding of CGRP in the anterior part of the eye of monkey, cat, and pig was studied. The location and displacement of 125I-hCGRPalpha by amylins as concentrations of 1-1000 nM were studied in cryosections by autoradiography. In the monkey eye, cat and rat amylins were able to compete for the binding sites of CGRP in ciliary muscle and ciliary processes. In the cat eye, cat and human amylins clearly displaced CGRP binding from ciliary muscle, ciliary processes, iris, and chamber angle. Furthermore, rat amylin clearly displaced CGRP binding from ciliary muscle and ciliary processes. In the pig eye, cat, human, and rat amylins competed for the binding sites of CGRP in ciliary muscle, ciliary processes, iris, and limbal conjunctiva. Specific amylin receptors or the possible physiological role of amylin in the eye have not hitherto been reported. It seems, however, that amylin can bind to ocular CGRP receptors and thus probably plays a role in the regulation of the same functions as CGRP, (e.g., aqueous humor outflow).

Head Worn Display System for Equivalent Visual Operations

NASA Technical Reports Server (NTRS)

Cupero, Frank; Valimont, Brian; Wise, John; Best. Carl; DeMers, Bob

2009-01-01

Head-Worn Displays or so-called, near-to-eye displays have potentially significant advantages in terms of cost, overcoming cockpit space constraints, and for the display of spatially-integrated information. However, many technical issues need to be overcome before these technologies can be successfully introduced into commercial aircraft cockpits. The results of three activities are reported. First, the near-to-eye display design, technological, and human factors issues are described and a literature review is presented. Second, the results of a fixed-base piloted simulation, investigating the impact of near to eye displays on both operational and visual performance is reported. Straight-in approaches were flown in simulated visual and instrument conditions while using either a biocular or a monocular display placed on either the dominant or non-dominant eye. The pilot's flight performance, visual acuity, and ability to detect unsafe conditions on the runway were tested. The data generally supports a monocular design with minimal impact due to eye dominance. Finally, a method for head tracker system latency measurement is developed and used to compare two different devices.

Retinal adhesive force in living rabbit, cat, and monkey eyes. Normative data and enhancement by mannitol and acetazolamide.

PubMed

Kita, M; Marmor, M F

1992-05-01

Small retinal detachments (blebs) were made in living eyes by injecting balanced salt solution into the subretinal space with a micropipette. A second micropipette, inserted into the same bleb, measured subretinal pressure using a resistance servonulling system. The adhesive force was calculated from the pressure difference across the retina according to Laplace's law. The retinal adhesive force in rabbit, cat, and monkey eyes averaged 1.0, 1.8, and 1.4 x 10(2) dyne/cm, respectively. In rabbit eyes, 2 hr after intravenous administration of 15 mg/kg acetazolamide, the retinal adhesive force was increased to 133%. In monkeys, this dose of acetazolamide increased retinal adhesion to 144% of control values. Mannitol (2 g/kg) increased retinal adhesion in the monkey to 153% of control values 90 min after intravenous injection (compared with an increase of 145% in previous experiments in the rabbit). Because both mannitol and acetazolamide enhance retinal adhesiveness in living primate eyes, it seems likely that they will have a similar effect in humans that they may be clinically useful.

Truly simultaneous SS-OCT of the anterior and posterior human eye with full anterior chamber and 50° retinal field of views (Conference Presentation)

NASA Astrophysics Data System (ADS)

McNabb, Ryan P.; Viehland, Christian; Keller, Brenton; Vann, Robin R.; Izatt, Joseph A.; Kuo, Anthony N.

2017-02-01

Optical coherence tomography (OCT) has revolutionized clinical observation of the eye and is an indispensable part of the modern ophthalmic practice. Unlike many other ophthalmic imaging techniques, OCT provides three-dimensional information about the imaged eye. However, conventional clinical OCT systems image only the anterior or the posterior eye during a single acquisition. Newer OCT systems have begun to image both during the same acquisition but with compromises such as limited field of view in the posterior eye or requiring rapid switching between the anterior and posterior eye during the scan. We describe here the development and demonstration of an OCT system with truly simultaneous imaging of both the anterior and posterior eye capable of imaging the full anterior chamber width and 50° on the retina (macula, optic nerve, and arcades). The whole eye OCT system was developed using custom optics and optomechanics. Polarization was utilized to separate the imaging channels. We utilized a 200kHz swept-source laser (Axsun Technologies) centered at 1040±50nm of bandwidth. The clock signal generated by the laser was interpolated 4x to generate 5504 samples per laser sweep. With the whole eye OCT system, we simultaneously acquired anterior and posterior segments with repeated B-scans as well as three-dimensional volumes from seven healthy volunteers (other than refractive error). On three of these volunteers, whole eye OCT and partial coherence interferometry (LenStar PCI, Haag-Streit) were used to measure axial eye length. We measured a mean repeatability of ±47µm with whole eye OCT and a mean difference from PCI of -68µm.

The Method of Curvatures.

ERIC Educational Resources Information Center

Greenslade, Thomas B., Jr.; Miller, Franklin, Jr.

1981-01-01

Describes method for locating images in simple and complex systems of thin lenses and spherical mirrors. The method helps students to understand differences between real and virtual images. It is helpful in discussing the human eye and the correction of imperfect vision by the use of glasses. (Author/SK)

Human Eye Development Is Characterized by Coordinated Expression of Fibrillin Isoforms

PubMed Central

Hubmacher, Dirk; Reinhardt, Dieter P.; Plesec, Thomas; Schenke-Layland, Katja; Apte, Suneel S.

2014-01-01

Purpose. Mutations in human fibrillin-1 and -2, which are major constituents of tissue microfibrils, can affect multiple ocular components, including the ciliary zonule, lens, drainage apparatus, cornea, and retina. However, the expression pattern of the three human fibrillins and an integral microfibrillar component, MAGP1, during human eye development is not known. Methods. We analyzed sections from human eyes at gestational weeks (GWs) 6, 8, and 11 and at 1 and 3 years of age with antibodies specific for each human fibrillin isoform or MAGP1, using immunofluorescence microscopy. Results. During embryonic development, each fibrillin isoform was detected in vascular structures bridging the ciliary body and the developing lens, hyaloid vasculature, and retina. In addition, they were present in the developing corneal basement membranes and lens capsule. MAGP1 codistributed with the fibrillin isoforms. In contrast, the juvenile zonule was composed of fibrillin-1 microfibrils containing MAGP1, but fibrillin-2 was absent and fibrillin-3 was only sparsely detected. Conclusions. Fibrillin-1, -2, and, unique to humans, fibrillin-3 are found in various ocular structures during human embryonic eye development, whereas fibrillin-1 dominates the postnatal zonule. We speculate that vasculature spanning the ciliary body and lens, which elaborates fibrillin-2 and -3, may provide an initial scaffold for fibrillin assembly and zonule formation. PMID:25406291

Simulation and analysis of light scattering by multilamellar bodies present in the human eye

PubMed Central

Méndez-Aguilar, Emilia M.; Kelly-Pérez, Ismael; Berriel-Valdos, L. R.; Delgado-Atencio, José A.

2017-01-01

A modified computational model of the human eye was used to obtain and compare different probability density functions, radial profiles of light pattern distributions, and images of the point spread function formed in the human retina under the presence of different kinds of particles inside crystalline lenses suffering from cataracts. Specifically, this work uses simple particles without shells and multilamellar bodies (MLBs) with shells. The emergence of such particles alters the formation of images on the retina. Moreover, the MLBs change over time, which affects properties such as the refractive index of their shell. Hence, this work not only simulates the presence of such particles but also evaluates the incidence of particle parameters such as particle diameter, particle thickness, and shell refractive index, which are set based on reported experimental values. In addition, two wavelengths (400 nm and 700 nm) are used for light passing through the different layers of the computational model. The effects of these parameters on light scattering are analyzed using the simulation results. Further, in these results, the effects of light scattering on image formation can be seen when single particles, early-stage MLBs, or mature MLBs are incorporated in the model. Finally, it is found that particle diameter has the greatest impact on image formation. PMID:28663924

Do they see eye to eye? Management and employee perspectives of high-performance work systems and influence processes on service quality.

PubMed

Liao, Hui; Toya, Keiko; Lepak, David P; Hong, Ying

2009-03-01

Extant research on high-performance work systems (HPWSs) has primarily examined the effects of HPWSs on establishment or firm-level performance from a management perspective in manufacturing settings. The current study extends this literature by differentiating management and employee perspectives of HPWSs and examining how the two perspectives relate to employee individual performance in the service context. Data collected in three phases from multiple sources involving 292 managers, 830 employees, and 1,772 customers of 91 bank branches revealed significant differences between management and employee perspectives of HPWSs. There were also significant differences in employee perspectives of HPWSs among employees of different employment statuses and among employees of the same status. Further, employee perspective of HPWSs was positively related to individual general service performance through the mediation of employee human capital and perceived organizational support and was positively related to individual knowledge-intensive service performance through the mediation of employee human capital and psychological empowerment. At the same time, management perspective of HPWSs was related to employee human capital and both types of service performance. Finally, a branch's overall knowledge-intensive service performance was positively associated with customer overall satisfaction with the branch's service. (c) 2009 APA, all rights reserved.

Simulation and analysis of light scattering by multilamellar bodies present in the human eye.

PubMed

Méndez-Aguilar, Emilia M; Kelly-Pérez, Ismael; Berriel-Valdos, L R; Delgado-Atencio, José A

2017-06-01

A modified computational model of the human eye was used to obtain and compare different probability density functions, radial profiles of light pattern distributions, and images of the point spread function formed in the human retina under the presence of different kinds of particles inside crystalline lenses suffering from cataracts. Specifically, this work uses simple particles without shells and multilamellar bodies (MLBs) with shells. The emergence of such particles alters the formation of images on the retina. Moreover, the MLBs change over time, which affects properties such as the refractive index of their shell. Hence, this work not only simulates the presence of such particles but also evaluates the incidence of particle parameters such as particle diameter, particle thickness, and shell refractive index, which are set based on reported experimental values. In addition, two wavelengths (400 nm and 700 nm) are used for light passing through the different layers of the computational model. The effects of these parameters on light scattering are analyzed using the simulation results. Further, in these results, the effects of light scattering on image formation can be seen when single particles, early-stage MLBs, or mature MLBs are incorporated in the model. Finally, it is found that particle diameter has the greatest impact on image formation.

Effects of phencyclidine, secobarbital and diazepam on eye tracking in rhesus monkeys.

PubMed

Ando, K; Johanson, C E; Levy, D L; Yasillo, N J; Holzman, P S; Schuster, C R

1983-01-01

Rhesus monkeys were trained to track a moving disk using a procedure in which responses on a lever were reinforced with water delivery only when the disk, oscillating in a horizontal plane on a screen at a frequency of 0.4 Hz in a visual angle of 20 degrees, dimmed for a brief period. Pursuit eye movements were recorded by electrooculography (EOG). IM phencyclidine, secobarbital, and diazepam injections decreased the number of reinforced lever presses in a dose-related manner. Both secobarbital and diazepam produced episodic jerky-pursuit eye movements, while phencyclidine had no consistent effects on eye movements. Lever pressing was disrupted at doses which had little effect on the quality of smooth-pursuit eye movements in some monkeys. This separation was particularly pronounced with diazepam. The similarities of the drug effects on smooth-pursuit eye movements between the present study and human studies indicate that the present method using rhesus monkeys may be useful for predicting drug effects on eye tracking and oculomotor function in humans.

Simulation of Ametropic Human Eyes

NASA Astrophysics Data System (ADS)

Tan, Bo; Chen, Ying-Ling; Lewis, James W. L.

2004-11-01

The computational simulation of the performance of human eyes is complex because the optical parameters of the eye depend on many factors, including age, gender, race, refractive status (accommodation and near- or far-sightedness). This task is made more difficult by the inadequacy of the population statistical characteristics of these parameters. Previously we simulated ametropic (near- or far-sighted) eyes using three independent variables: the axial length of the eye, the corneal surface curvature, and the intraocular refractive index gradient. The prescription for the correction of an ametropic eye is determined by its second-order coefficients of the wavefront aberrations. These corrections are typically achieved using contact lens, spectacle lens, or laser surgery (LASIK). However, the higher order aberrations, which are not corrected and are likely complicated or enhanced by the lower-order correction, could be important for visual performance in a darkened environment. In this paper, we investigate the higher order wavefront aberrations of synthetic ametropic eyes and compare results with measured data published in the past decade. The behavior of three types of ametropes is discussed.

Bilateral symmetry in vision and influence of ocular surgical procedures on binocular vision: A topical review.

PubMed

Arba Mosquera, Samuel; Verma, Shwetabh

2016-01-01

We analyze the role of bilateral symmetry in enhancing binocular visual ability in human eyes, and further explore how efficiently bilateral symmetry is preserved in different ocular surgical procedures. The inclusion criterion for this review was strict relevance to the clinical questions under research. Enantiomorphism has been reported in lower order aberrations, higher order aberrations and cone directionality. When contrast differs in the two eyes, binocular acuity is better than monocular acuity of the eye that receives higher contrast. Anisometropia has an uncommon occurrence in large populations. Anisometropia seen in infancy and childhood is transitory and of little consequence for the visual acuity. Binocular summation of contrast signals declines with age, independent of inter-ocular differences. The symmetric associations between the right and left eye could be explained by the symmetry in pupil offset and visual axis which is always nasal in both eyes. Binocular summation mitigates poor visual performance under low luminance conditions and strong inter-ocular disparity detrimentally affects binocular summation. Considerable symmetry of response exists in fellow eyes of patients undergoing myopic PRK and LASIK, however the method to determine whether or not symmetry is maintained consist of comparing individual terms in a variety of ad hoc ways both before and after the refractive surgery, ignoring the fact that retinal image quality for any individual is based on the sum of all terms. The analysis of bilateral symmetry should be related to the patients' binocular vision status. The role of aberrations in monocular and binocular vision needs further investigation. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

40 CFR 721.1150 - Substituted polyglycidyl ben-zena-mine.

Code of Federal Regulations, 2011 CFR

2011-07-01

... following information: WARNING: CONTACT WITH SKIN AND EYES IS HARMFUL —Severe skin and eye irritant.... They have also caused allergic reactions in humans. —Prevent all contact with skin, eyes, and clothing... water. FIRST AID: —In case of eye contact, immediately flush with plenty of water and get immediate...

76 FR 24499 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-02

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: June 16, 2011. Open: 8:30 a.m. to 12 p.m. Agenda: Following opening...

78 FR 73867 - National Eye Institute; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-09

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute.... App.), notice is hereby given of a meeting of the National Advisory Eye Council. The meeting will be... Advisory Eye Council. Date: January 23, 2014. Open: 8:30 a.m. to 2:00 p.m. Agenda: Following opening...

75 FR 54642 - National Eye Institute; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-08

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute.... App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to the...: National Advisory Eye Council. Date: October 21, 2010. Open: 8:30 a.m. to 12 p.m. Agenda: Following opening...

76 FR 53687 - National Eye Institute Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-29

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: October 13, 2011. Open: 8:30 a.m. to 12 p.m. Agenda: Following opening...

77 FR 2076 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-13

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: February 2, 2012. Open: 8 a.m. to 12 p.m. Agenda: Following opening...

77 FR 31032 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-24

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: June 14, 2012. Open: 8:00 a.m. to 3:00 p.m. Agenda: Following opening...

40 CFR 156.70 - Precautionary statements for human hazards.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., dermal, inhalation toxicity) Irritation effects (skin and eye) Sensitizer (There are no categories of... or spray mist]. Do not get in eyes, on skin, or on clothing. [Front panel first aid statement required.] Corrosive, causes eye and skin damage [or skin irritation]. Do not get in eyes on skin, or on...

40 CFR 156.70 - Precautionary statements for human hazards.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., dermal, inhalation toxicity) Irritation effects (skin and eye) Sensitizer (There are no categories of... or spray mist]. Do not get in eyes, on skin, or on clothing. [Front panel first aid statement required.] Corrosive, causes eye and skin damage [or skin irritation]. Do not get in eyes on skin, or on...

77 FR 55852 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-11

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: October 4, 2012. Open: 8:30 a.m. to 2 p.m. Agenda: Following opening...

75 FR 26260 - National Eye Institute; Amended Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-11

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute; Amended Notice of Meeting Notice is hereby given of a change in the meeting of the National Eye Institute Special Emphasis Panel, April 20, 2010, 3 p.m., to April 20, 2010, 4 p.m., National Eye Institute, 5635...

75 FR 76474 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-08

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), notice is hereby given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: January 20, 2011. Open: 8:30 a.m. to 12 p.m. Agenda: Following opening...

77 FR 41406 - Evaluation of In Vitro Tests for Identifying Eye Injury Hazard Potential of Chemicals and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-13

... DEPARTMENT OF HEALTH AND HUMAN SERVICES Evaluation of In Vitro Tests for Identifying Eye Injury...-animal testing strategies proposed for identifying eye injury hazard potential of chemicals and products... Panel and submission of data from substances tested in in vitro tests for identifying eye injury hazard...

77 FR 73037 - National Eye Institute; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-07

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute....S.C. App.), Notice is Hereby Given of the National Advisory Eye Council. The meeting will be open to...: National Advisory Eye Council. Date: January 10, 2013. Open: 8:30 a.m. to 2:00 p.m. Agenda: Following...

75 FR 11551 - National Eye Institute; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-11

... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health National Eye Institute.... App.), notice is hereby given of a meeting of the National Advisory Eye Council. The meeting will be...: National Advisory Eye Council. Date: June 17, 2010. Closed: 8:30 a.m. to 11 a.m. Agenda: To review and...

A novel device for head gesture measurement system in combination with eye-controlled human machine interface

NASA Astrophysics Data System (ADS)

Lin, Chern-Sheng; Ho, Chien-Wa; Chang, Kai-Chieh; Hung, San-Shan; Shei, Hung-Jung; Yeh, Mau-Shiun

2006-06-01

This study describes the design and combination of an eye-controlled and a head-controlled human-machine interface system. This system is a highly effective human-machine interface, detecting head movement by changing positions and numbers of light sources on the head. When the users utilize the head-mounted display to browse a computer screen, the system will catch the images of the user's eyes with CCD cameras, which can also measure the angle and position of the light sources. In the eye-tracking system, the program in the computer will locate each center point of the pupils in the images, and record the information on moving traces and pupil diameters. In the head gesture measurement system, the user wears a double-source eyeglass frame, so the system catches images of the user's head by using a CCD camera in front of the user. The computer program will locate the center point of the head, transferring it to the screen coordinates, and then the user can control the cursor by head motions. We combine the eye-controlled and head-controlled human-machine interface system for the virtual reality applications.

Dissemination of information about the technologies of the Vision Research Lab through the World Wide Web

NASA Technical Reports Server (NTRS)

Dorais, Christopher M.

2004-01-01

The Vision Research Lab at NASA John Glenn Research Center is headed by Dr. Rafat Ansari. Dr. Ansari and other researchers have developed technologies that primarily use laser and fiber optics to non-invasively detect different ailments and diseases of the eye. One of my goals as a LERCIP intern and ACCESS scholar for the 2004 summer is to inform other NASA employees, researchers and the general public about these technologies through the development of a website. The website incorporates the theme that the eye is a window to the body. Thus by investigating the processes of the eye, we can better understand and diagnosis different ailments and diseases. These ailments occur in not only earth bound humans, but astronauts as well as a result of exposure to elevated levels of radiation and microgravity conditions. Thus the technologies being developed at the Vision Research Lab are invaluable to humans on Earth in addition to those astronauts in space. One of my first goals was to research the technologies being developed at the lab. The first several days were spent immersing myself in the various articles, journals and reports about the theories behind Dynamic Light Scattering, Laser Doppler Flowmetry, Autofluoresence, Raman Spectroscopy, Polarimetry and Oximetry. Interviews with the other researchers proved invaluable to help understand these theories as well gain hands on experience with the devices being developed using these technologies. The rest of the Vision Research Team and I sat down and discussed how the overall website should be presented. Combining this information with the knowledge of the theories and applications of the hardware being developed, I worked out different ideas to present this information. I quickly learned Paint Shop Pro 8 and FrontPage 2002, as well as using online tutorials and other resources to help design an effective website. The Vision Research Lab website incorporates the anatomy and physiology of the eye, different diseases that affect the eye and the technologies being develop at the lab to help diagnosis these diseases. It also includes background information on Dr. Ansari as well as other researchers involved in the lab and it includes segments on patents, awards and achievements. There are links to help viewers navigate to internal and external websites to further investigate different ideas and hrther understand the implications of these technologies at being developed.

Palisade Endings Are a Constant Feature in the Extraocular Muscles of Frontal-Eyed, But Not Lateral-Eyed, Animals.

PubMed

Blumer, Roland; Maurer-Gesek, Barbara; Gesslbauer, Bernhard; Blumer, Michael; Pechriggl, Elisabeth; Davis-López de Carrizosa, María A; Horn, Anja K; May, Paul J; Streicher, Johannes; de la Cruz, Rosa R; Pastor, Ángel M

2016-02-01

To test whether palisade endings are a general feature of mammalian extraocular muscles (EOMs). Thirteen species, some frontal-eyed (human, monkey, cat, and ferret), and others lateral-eyed (pig, sheep, calf, horse, rabbit, rat, mouse, gerbil, and guinea pig) were analyzed. Palisade endings were labeled by using different combinations of immunofluorescence techniques. Three-dimensional reconstructions of immunolabeled palisade endings were done. In all frontal-eyed species, palisade endings were a consistent feature in the rectus EOMs. Their total number was high and they exhibited an EOM-specific distribution. In particular, the number of palisade endings in the medial recti was significantly higher than in the other rectus muscles. In the lateral-eyed animals, palisade endings were infrequent and, when present, their total number was rather low. They were only found in ungulates (sheep, calf, pig, and horse) and in rabbit. In rodents (rat, guinea pig, mouse, and gerbil) palisade endings were found infrequently (e.g., rat) or were completely absent. Palisade endings in frontal-eyed species and in some lateral-eyed species (pig, sheep, calf, and horse) had a uniform morphology. They generally lacked α-bungarotoxin staining, with a few exceptions in primates. Palisade endings in other lateral-eyed species (rabbit and rat) exhibited a simplified morphology and bound α-bungarotoxin. Palisade endings are not a universal feature of mammalian EOMs. So, if they are proprioceptors, not all species require them. Because in frontal-eyed species, the medial rectus muscle has the highest number of palisade endings, they likely play a special role in convergence.

Palisade Endings Are a Constant Feature in the Extraocular Muscles of Frontal-Eyed, But Not Lateral-Eyed, Animals

PubMed Central

Blumer, Roland; Maurer-Gesek, Barbara; Gesslbauer, Bernhard; Blumer, Michael; Pechriggl, Elisabeth; Davis-López de Carrizosa, María A.; Horn, Anja K.; May, Paul J.; Streicher, Johannes; de la Cruz, Rosa R.; Pastor, Ángel M.

2016-01-01

Purpose To test whether palisade endings are a general feature of mammalian extraocular muscles (EOMs). Methods Thirteen species, some frontal-eyed (human, monkey, cat, and ferret), and others lateral-eyed (pig, sheep, calf, horse, rabbit, rat, mouse, gerbil, and guinea pig) were analyzed. Palisade endings were labeled by using different combinations of immunofluorescence techniques. Three-dimensional reconstructions of immunolabeled palisade endings were done. Results In all frontal-eyed species, palisade endings were a consistent feature in the rectus EOMs. Their total number was high and they exhibited an EOM-specific distribution. In particular, the number of palisade endings in the medial recti was significantly higher than in the other rectus muscles. In the lateral-eyed animals, palisade endings were infrequent and, when present, their total number was rather low. They were only found in ungulates (sheep, calf, pig, and horse) and in rabbit. In rodents (rat, guinea pig, mouse, and gerbil) palisade endings were found infrequently (e.g., rat) or were completely absent. Palisade endings in frontal-eyed species and in some lateral-eyed species (pig, sheep, calf, and horse) had a uniform morphology. They generally lacked α-bungarotoxin staining, with a few exceptions in primates. Palisade endings in other lateral-eyed species (rabbit and rat) exhibited a simplified morphology and bound α-bungarotoxin. Conclusions Palisade endings are not a universal feature of mammalian EOMs. So, if they are proprioceptors, not all species require them. Because in frontal-eyed species, the medial rectus muscle has the highest number of palisade endings, they likely play a special role in convergence. PMID:26830369

Evaluation of an eye-pointer interaction device for human-computer interaction.

PubMed

Cáceres, Enrique; Carrasco, Miguel; Ríos, Sebastián

2018-03-01

Advances in eye-tracking technology have led to better human-computer interaction, and involve controlling a computer without any kind of physical contact. This research describes the transformation of a commercial eye-tracker for use as an alternative peripheral device in human-computer interactions, implementing a pointer that only needs the eye movements of a user facing a computer screen, thus replacing the need to control the software by hand movements. The experiment was performed with 30 test individuals who used the prototype with a set of educational videogames. The results show that, although most of the test subjects would prefer a mouse to control the pointer, the prototype tested has an empirical precision similar to that of the mouse, either when trying to control its movements or when attempting to click on a point of the screen.

Ex vivo magnetic resonance imaging of crystalline lens dimensions in chicken.

PubMed

Tattersall, Rebecca J; Prashar, Ankush; Singh, Krish D; Tokarczuk, Pawel F; Erichsen, Jonathan T; Hocking, Paul M; Guggenheim, Jeremy A

2010-02-02

A reduction in the power of the crystalline lens during childhood is thought to be important in the emmetropization of the maturing eye. However, in humans and model organisms, little is known about the factors that determine the dimensions of the crystalline lens and in particular whether these different parameters (axial thickness, surface curvatures, equatorial diameter, and volume) are under a common source of control or regulated independently of other aspects of eye size and shape. Using chickens from a broiler-layer experimental cross as a model system, three-dimensional magnetic resonance imaging (MRI) scans were obtained at 115-microm isotropic resolution for one eye of 501 individuals aged 3-weeks old. After fixation with paraformaldehyde, the excised eyes were scanned overnight (16 h) in groups of 16 arranged in a 2x2x4 array. Lens dimensions were calculated from each image by fitting a three-dimensional mesh model to the lens, using the semi-automated analysis program mri3dX. The lens dimensions were compared to measures of eye and body size obtained in vivo using techniques that included keratometry and A-scan ultrasonography. A striking finding was that axial lens thickness measured using ex vivo MRI was only weakly correlated with lens thickness measured in vivo by ultrasonography (r=0.19, p<0.001). In addition, the MRI lens thickness estimates had a lower mean value and much higher variance. Indeed, about one-third of crystalline lenses showed a kidney-shaped appearance instead of the typical biconvex shape. Since repeat MRI scans of the same eye showed a high degree of reproducibility for the scanning and mri3dX analysis steps (the correlation in repeat lens thickness measurements was r=0.95, p<0.001) and a recent report has shown that paraformaldehyde fixation induces a loss of water from the human crystalline lens, it is likely that the tissue fixation step caused a variable degree of shrinkage and a change in shape to the lenses examined here. Despite this serious source of imprecision, we found significant correlations between lens volume and eye/body size (p<0.001) and between lens equatorial diameter and eye/body size (p<0.001) in these chickens. Our results suggest that certain aspects of lens size (specifically, lens volume and equatorial diameter) are controlled by factors that also regulate the size of the eye and body (presumably, predominantly genetic factors). However, since it has been shown previously that axial lens thickness is regulated almost independently of eye and body size, these results suggest that different systems might operate to control lens volume/diameter and lens thickness in normal chickens.

Ex vivo magnetic resonance imaging of crystalline lens dimensions in chicken

PubMed Central

Tattersall, Rebecca J.; Prashar, Ankush; Singh, Krish D.; Tokarczuk, Pawel F.; Erichsen, Jonathan T.; Hocking, Paul M.

2010-01-01

Purpose A reduction in the power of the crystalline lens during childhood is thought to be important in the emmetropization of the maturing eye. However, in humans and model organisms, little is known about the factors that determine the dimensions of the crystalline lens and in particular whether these different parameters (axial thickness, surface curvatures, equatorial diameter, and volume) are under a common source of control or regulated independently of other aspects of eye size and shape. Methods Using chickens from a broiler-layer experimental cross as a model system, three-dimensional magnetic resonance imaging (MRI) scans were obtained at 115-µm isotropic resolution for one eye of 501 individuals aged 3-weeks old. After fixation with paraformaldehyde, the excised eyes were scanned overnight (16 h) in groups of 16 arranged in a 2×2×4 array. Lens dimensions were calculated from each image by fitting a three-dimensional mesh model to the lens, using the semi-automated analysis program mri3dX. The lens dimensions were compared to measures of eye and body size obtained in vivo using techniques that included keratometry and A-scan ultrasonography. Results A striking finding was that axial lens thickness measured using ex vivo MRI was only weakly correlated with lens thickness measured in vivo by ultrasonography (r=0.19, p<0.001). In addition, the MRI lens thickness estimates had a lower mean value and much higher variance. Indeed, about one-third of crystalline lenses showed a kidney-shaped appearance instead of the typical biconvex shape. Since repeat MRI scans of the same eye showed a high degree of reproducibility for the scanning and mri3dX analysis steps (the correlation in repeat lens thickness measurements was r=0.95, p<0.001) and a recent report has shown that paraformaldehyde fixation induces a loss of water from the human crystalline lens, it is likely that the tissue fixation step caused a variable degree of shrinkage and a change in shape to the lenses examined here. Despite this serious source of imprecision, we found significant correlations between lens volume and eye/body size (p<0.001) and between lens equatorial diameter and eye/body size (p<0.001) in these chickens. Conclusions Our results suggest that certain aspects of lens size (specifically, lens volume and equatorial diameter) are controlled by factors that also regulate the size of the eye and body (presumably, predominantly genetic factors). However, since it has been shown previously that axial lens thickness is regulated almost independently of eye and body size, these results suggest that different systems might operate to control lens volume/diameter and lens thickness in normal chickens. PMID:20142845

The Development of Expert Face Processing: Are Infants Sensitive to Normal Differences in Second-Order Relational Information?

ERIC Educational Resources Information Center

Hayden, Angela; Bhatt, Ramesh S.; Reed, Andrea; Corbly, Christine R.; Joseph, Jane E.

2007-01-01

Sensitivity to second-order relational information (i.e., spatial relations among features such as the distance between eyes) is a vital part of achieving expertise with face processing. Prior research is unclear on whether infants are sensitive to second-order differences seen in typical human populations. In the current experiments, we examined…

39 CFR 265.6 - Availability of records.

Code of Federal Regulations, 2010 CFR

2010-07-01

... by the human eye, such as a computer print-out. On request, records will be provided in a different... investigation, or by an agency conducting a lawful national security intelligence investigation, information... authorized user of a postage meter or PC Postage product (postage evidencing systems) printing a specified...

Local synthesis of sex hormones: are there consequences for the ocular surface and dry eye?

PubMed

Gibson, Emma J; Stapleton, Fiona; Wolffsohn, James S; Golebiowski, Blanka

2017-12-01

Sex hormones are associated with the physiology and pathophysiology of almost all organs in the body, as well as most diseases. Interest in the associations between sex hormones and ocular tissues has increased in recent years. Androgens may have a positive effect on dry eye, whereas the effects of oestrogen on ocular conditions remain unclear. Intracrinology, the local synthesis and metabolism of hormones that is unique to humans, is of relevance to the eye and may help to explain why studies of the relationship between oestrogens and dry eye signs and symptoms are inconclusive. Knowledge of the pathways of hormone formation and metabolism is crucial to understanding the pathogenesis of ocular disease including dry eye. This review examines the mechanisms of steroidal sex hormone biosynthesis and reviews the significance of locally produced sex hormones, with a focus on ocular surface tissues. Much of the current literature is based on animal studies, which may not be transferable to humans due to the absence of intracrine production in animals. A large proportion of the human studies investigate systemic hormone levels rather than local levels. There is subsequently a need for additional studies to provide a better understanding of the local production of sex hormones within the human eye and ocular surface and to clarify the relationships between ocular levels of sex hormones and conditions including dry eye. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Colour vision experimental studies in teaching of optometry

NASA Astrophysics Data System (ADS)

Ozolinsh, Maris; Ikaunieks, Gatis; Fomins, Sergejs

2005-10-01

Following aspects related to human colour vision are included in experimental lessons for optometry students of University of Latvia. Characteristics of coloured stimuli (emitting and reflective), determination their coordinates in different colour spaces. Objective characteristics of transmitting of colour stimuli through the optical system of eye together with various types of appliances (lenses, prisms, Fresnel prisms). Psychophysical determination of mono- and polychromatic stimuli perception taking into account physiology of eye, retinal colour photoreceptor topography and spectral sensitivity, spatial and temporal characteristics of retinal receptive fields. Ergonomics of visual perception, influence of illumination and glare effects, testing of colour vision deficiencies.

Hypothesis on human eye perceiving optical spectrum rather than an image

NASA Astrophysics Data System (ADS)

Zheng, Yufeng; Szu, Harold

2015-05-01

It is a common knowledge that we see the world because our eyes can perceive an optical image. A digital camera seems a good example of simulating the eye imaging system. However, the signal sensing and imaging on human retina is very complicated. There are at least five layers (of neurons) along the signal pathway: photoreceptors (cones and rods), bipolar, horizontal, amacrine and ganglion cells. To sense an optical image, it seems that photoreceptors (as sensors) plus ganglion cells (converting to electrical signals for transmission) are good enough. Image sensing does not require ununiformed distribution of photoreceptors like fovea. There are some challenging questions, for example, why don't we feel the "blind spots" (never fibers exiting the eyes)? Similar situation happens to glaucoma patients who do not feel their vision loss until 50% or more nerves died. Now our hypothesis is that human retina initially senses optical (i.e., Fourier) spectrum rather than optical image. Due to the symmetric property of Fourier spectrum the signal loss from a blind spot or the dead nerves (for glaucoma patients) can be recovered. Eye logarithmic response to input light intensity much likes displaying Fourier magnitude. The optics and structures of human eyes satisfy the needs of optical Fourier spectrum sampling. It is unsure that where and how inverse Fourier transform is performed in human vision system to obtain an optical image. Phase retrieval technique in compressive sensing domain enables image reconstruction even without phase inputs. The spectrum-based imaging system can potentially tolerate up to 50% of bad sensors (pixels), adapt to large dynamic range (with logarithmic response), etc.

Effect of aberrations in human eye on contrast sensitivity function

NASA Astrophysics Data System (ADS)

Quan, Wei; Wang, Feng-lin; Wang, Zhao-qi

2011-06-01

The quantitative analysis of the effect of aberrations in human eye on vision has important clinical value in the correction of aberrations. The wave-front aberrations of human eyes were measured with the Hartmann-Shack wave-front sensor and modulation transfer function (MTF) was computed from the wave-front aberrations. Contrast sensitivity function (CSF) was obtained from MTF and the retinal aerial image modulation (AIM). It is shown that the 2nd, 3rd, 4th, 5th, 6th Zernike aberrations deteriorate contrast sensitivity function. When the 2nd, 3rd, 4th, 5th, 6th Zernike aberrations are corrected high contrast sensitivity function can be obtained.

Learning rational temporal eye movement strategies.

PubMed

Hoppe, David; Rothkopf, Constantin A

2016-07-19

During active behavior humans redirect their gaze several times every second within the visual environment. Where we look within static images is highly efficient, as quantified by computational models of human gaze shifts in visual search and face recognition tasks. However, when we shift gaze is mostly unknown despite its fundamental importance for survival in a dynamic world. It has been suggested that during naturalistic visuomotor behavior gaze deployment is coordinated with task-relevant events, often predictive of future events, and studies in sportsmen suggest that timing of eye movements is learned. Here we establish that humans efficiently learn to adjust the timing of eye movements in response to environmental regularities when monitoring locations in the visual scene to detect probabilistically occurring events. To detect the events humans adopt strategies that can be understood through a computational model that includes perceptual and acting uncertainties, a minimal processing time, and, crucially, the intrinsic costs of gaze behavior. Thus, subjects traded off event detection rate with behavioral costs of carrying out eye movements. Remarkably, based on this rational bounded actor model the time course of learning the gaze strategies is fully explained by an optimal Bayesian learner with humans' characteristic uncertainty in time estimation, the well-known scalar law of biological timing. Taken together, these findings establish that the human visual system is highly efficient in learning temporal regularities in the environment and that it can use these regularities to control the timing of eye movements to detect behaviorally relevant events.

Inhibition of copper-mediated aggregation of human γD-crystallin by Schiff bases.

PubMed

Chauhan, Priyanka; Muralidharan, Sai Brinda; Velappan, Anand Babu; Datta, Dhrubajyoti; Pratihar, Sanjay; Debnath, Joy; Ghosh, Kalyan Sundar

2017-06-01

Protein aggregation, due to the imbalance in the concentration of Cu 2+ and Zn 2+ ions is found to be allied with various physiological disorders. Copper is known to promote the oxidative damage of β/γ-crystallins in aged eye lens and causes their aggregation leading to cataract. Therefore, synthesis of a small-molecule 'chelator' for Cu 2+ with complementary antioxidant effect will find potential applications against aggregation of β/γ-crystallins. In this paper, we have reported the synthesis of different Schiff bases and studied their Cu 2+ complexation ability (using UV-Vis, FT-IR and ESI-MS) and antioxidant activity. Further based on their copper complexation efficiency, Schiff bases were used to inhibit Cu 2+ -mediated aggregation of recombinant human γD-crystallin (HGD) and β/γ-crystallins (isolated from cataractous human eye lens). Among these synthesized molecules, compound 8 at a concentration of 100 μM had shown ~95% inhibition of copper (100 μM)-induced aggregation. Compound 8 also showed a positive cooperative effect at a concentration of 5-15 μM on the inhibitory activity of human αA-crystallin (HAA) during Cu 2+ -induced aggregation of HGD. It eventually inhibited the aggregation process by additional ~20%. However, ~50% inhibition of copper-mediated aggregation of β/γ-crystallins (isolated from cataractous human eye lens) was recorded by compound 8 (100 μM). Although the reductive aminated products of the imines showed better antioxidant activity due to their lower copper complexing ability, they were found to be non-effective against Cu 2+ -mediated aggregation of HGD.

Pupillographic evaluation of the time course of atropine effects in the mouse eye.

PubMed

Schaeffel, Frank; Burkhardt, Eva

2005-03-01

The nonselective muscarinic antagonist atropine is currently the most potent drug against myopia development in both humans and animal models. However, the mechanism by which myopia is suppressed is still unknown, and the time course of its action is not well documented. Therefore, we have studied the duration of mydriasis in the mouse, a new model of myopia, after topical application of a single eye drop with different doses of atropine. The light-induced pupil response of the C57BL/6 (B6) wildtype strain was studied in alert mice that were restrained by grasping their necks. A video image-processing program detected the pupil and measured its diameter at 25 Hz sampling rate. To stimulate, an arrangement of green LEDs, which was attached to the recording video camera, could be flashed for 40 ms by pressing a key on the keyboard. A single drop of atropine solution (1, 0.5, or 0.1%) was instilled in one eye and the recovery of the pupil responses was followed for at least 150 h. Both eyes were measured. 1) Under the defined stimulation conditions, untreated wildtype mice displayed a pupil constriction of 23.7 +/- 2.4%. 2) All doses of atropine caused complete suppression of the pupil responses in the treated eyes within 1 min. 3) The pupil responses of the fellow eyes remained unaffected and were not different from those in untreated animals. 4) The recovery from mydriasis was very slow and did not show clear differences with dose. The extrapolated duration of complete recovery was about 10 d (0.1%: 217 h; 0.5%: 230 h; 1%: 294 h). Atropine caused a longlasting suppression of the pupil responses in the mouse eye. That the duration of recovery was not obviously dose-dependent suggests that all doses used in this study were saturating the receptors in the iris musculature.

Performing saccadic eye movements or blinking improves postural control.

PubMed

Rougier, Patrice; Garin, Mélanie

2007-07-01

To determine the relationship between eye movement and postural control on an undisturbed upright stance maintenance protocol, 15 young, healthy individuals were tested in various conditions. These conditions included imposed blinking patterns and horizontal and vertical saccadic eye movements. The directions taken by the center of pressure (CP) were recorded via a force platform on which the participants remained in an upright position. The CP trajectories were used to estimate, via a low-pass filter, the vertically projected movements of the center of gravity (CGv) and consequently the difference CP-CGv. An analysis of the frequency shows that regular bilateral blinking does not produce a significant change in postural control. In contrast, performing saccadic eye movements induces some reduced amplitude for both basic CGv and CP-CGv movements principally along the antero-posterior axis. The present result supports the theory that some ocular movements may modify postural control in the maintenance of the upright standing position in human participants.

Which Eye Tracker is Right for Your Research Performance Evaluation of Several Cost Variant Eye Trackers

DTIC Science & Technology

2016-09-19

REPORT TYPE 3. DATES COVERED (From - To) 21-10-16 Conference Proceedings 10/2015 – 03/2016 4. TITLE AND SUBTITLE Which eye tracker is right for...Force Research Laboratory 711th Human Performance Wing Airman Systems Directorate Warfighter Interface Division Applied Neuroscience Branch Wright...88ABW-2016-1334; Human Factors and Ergonomics Society 2016 Annual Meeting 19 – 23 Sept 2016 14. Though not often mentioned, the price point of many