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Sample records for acuity visual field

  1. Visual acuity test

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003396.htm Visual acuity test To use the sharing features on this page, please enable JavaScript. The visual acuity test is used to determine the smallest ...

  2. The neurology of visual acuity.

    PubMed

    Frisén, L

    1980-09-01

    A series of patients with well defined lesions of various parts of the visual pathways was studied in an attempt to iluminate the neuropathophysiology of visual acuity. Acuity was found to remain normal in all cases with unilateral retrochiasmal lesions, including those of the optic tract. Bilateral retrochiasmal lesions involving the foveal nerve fibres on both sides impaired acuity to the same degree in both eyes. Lateral chiasmal lesions regularly produced impaired acuity in the ipsilateral eye. Midchiasmal lesions commonly led to an impairment of visual acuity in both eyes, usually asymmetrically, and roughly proportionate to the severity of the visual field defect. Compression optic neuropathy was found to reduce acuity in rough proportion to the severity of compression. It was concluded that acuity remains normal as long as either the crossing or the non-crossing neural outflow from the retinal fovea remains intact: acuity fails only when both sets of nerve fibres are compromised. A properly executed acuity test seems to be a powerful tool for detecting such conditions. The lower limit of normal acuity should never be set below 1.0 or 20/20: even this level is clearly subnormal in many subjects.

  3. Use of optical coherence tomography to evaluate visual acuity and visual field changes in dengue fever.

    PubMed

    Rhee, Taek Kwan; Han, Jung Il

    2014-02-01

    Dengue fever is a viral disease that is transmitted by mosquitoes and affects humans. In rare cases, dengue fever can cause visual impairment, which usually occurs within 1 month after contracting dengue fever and ranges from mild blurring of vision to severe blindness. Visual impairment due to dengue fever can be detected through angiography, retinography, optical coherence tomography (OCT) imaging, electroretinography, event electroencephalography (visually evoked potentials), and visual field analysis. The purpose of this study is to report changes in the eye captured using fluorescein angiography, indocyanine green, and OCT in 3 cases of dengue fever visual impairment associated with consistent visual symptoms and similar retinochoroidopathic changes. The OCT results of the three patients with dengue fever showed thinning of the outer retinal layer and disruption of the inner segment/outer segment (IS/OS) junction. While thinning of the retina outer layer is an irreversible process, disruption of IS/OS junction is reported to be reversible. Follow-up examination of individuals with dengue fever and associated visual impairment should involve the use of OCT to evaluate visual acuity and visual field changes in patients with acute choroidal ischemia.

  4. Visual acuity and test performance.

    PubMed

    Heron, E; Zytkoskee, A

    1981-02-01

    Evaluation of scholastic achievement (American College Testing Service) test scores confirms previous reports that persons with poor visual acuity perform better on these tests than individuals with normal or superior acuity.

  5. Phenomenological model of visual acuity

    NASA Astrophysics Data System (ADS)

    Gómez-Pedrero, José A.; Alonso, José

    2016-12-01

    We propose in this work a model for describing visual acuity (V) as a function of defocus and pupil diameter. Although the model is mainly based on geometrical optics, it also incorporates nongeometrical effects phenomenologically. Compared to similar visual acuity models, the proposed one considers the effect of astigmatism and the variability of best corrected V among individuals; it also takes into account the accommodation and the "tolerance to defocus," the latter through a phenomenological parameter. We have fitted the model to the V data provided in the works of Holladay et al. and Peters, showing the ability of this model to accurately describe the variation of V against blur and pupil diameter. We have also performed a comparison between the proposed model and others previously published in the literature. The model is mainly intended for use in the design of ophthalmic compensations, but it can also be useful in other fields such as visual ergonomics, design of visual tests, and optical instrumentation.

  6. 38 CFR 4.76 - Visual acuity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Visual acuity. 4.76... DISABILITIES Disability Ratings The Organs of Special Sense § 4.76 Visual acuity. (a) Examination of visual acuity. Examination of visual acuity must include the central uncorrected and corrected visual acuity...

  7. Visual Acuity and the Eye.

    ERIC Educational Resources Information Center

    Beynon, J.

    1985-01-01

    Shows that visual acuity is a function of the structure of the eye and that its limit is set by the structure of the retina, emphasizing the role of lens aberrations and difraction on image quality. Also compares human vision with that of other vertebrates and insects. (JN)

  8. Preschool visual acuity screening tests.

    PubMed Central

    Friendly, D S

    1978-01-01

    The purpose of the study was to evaluate the relative merits of two screening tests used for visual acuity assessment of preschool children. The tests that were compared were the Good-Lite Company versions of the E-Test and of the STYCAR (Screening Test for Young Children and Retardates). The former is the most popular method for evaluating central acuity in young children in this nation; the STYCAR is a relatively new letter-matching-test developed in England, where it is widely employed. The E-Test poses left-right orientation problems which are eliminated by the symmetrical letters H, T, O and V utilized in the Letter-Matching-Test. Both visual acuity tests were administered on two separate occasions by personnel from the Prevention of Blindness Society of Metropolitan Washington to 633 preschool children in Washington, D.C. By random selection, 150 of the children received the E-Test at both sessions, 162 children received the Letter-Matching-Test at both sessions, 160 chilt athe the second session, and 161 children received the Letter-Matching-Test at the first session and the E-Test at the second session. The author medically examined the eyes of 408 of the 633 children without knowledge of which test had been initially administered. Statistical analysis of the data obtained from the study indicated that the Letter-Matching-Test was significantly better in terms of testability rates, group and individual instruction time, and performance time. The E-Test was more reliable in terms of test-retest acuity scores and was also more valid in terms of agreement between pass-fail results obtained at the first screening session and two levels of pass-fail refraction criteria. Images FIGURE 4 FIGURE 5 FIGURE 7 A FIGURE 7 B FIGURE 9 A FIGURE 9 B PMID:754379

  9. Prediction of Visual Acuity from Wavefront Aberrations

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B. (Inventor); Ahumada, Albert J. (Inventor)

    2013-01-01

    A method for generating a visual acuity metric, based on wavefront aberrations (WFAs), associated with a test subject and representing classes of imperfections, such as defocus, astigmatism, coma and spherical aberrations, of the subject's visual system. The metric allows choices of different image template, can predict acuity for different target probabilities, can incorporate different and possibly subject-specific neural transfer functions, can predict acuity for different subject templates, and incorporates a model of the optotype identification task.

  10. 38 CFR 4.76 - Visual acuity.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... distance and near vision using Snellen's test type or its equivalent. (b) Evaluation of visual acuity. (1) Evaluate central visual acuity on the basis of corrected distance vision with central fixation, even if a central scotoma is present. However, when the lens required to correct distance vision in the poorer...

  11. 38 CFR 4.76 - Visual acuity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... distance and near vision using Snellen's test type or its equivalent. (b) Evaluation of visual acuity. (1) Evaluate central visual acuity on the basis of corrected distance vision with central fixation, even if a central scotoma is present. However, when the lens required to correct distance vision in the poorer...

  12. 38 CFR 4.76 - Visual acuity.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... distance and near vision using Snellen's test type or its equivalent. (b) Evaluation of visual acuity. (1) Evaluate central visual acuity on the basis of corrected distance vision with central fixation, even if a central scotoma is present. However, when the lens required to correct distance vision in the poorer...

  13. 38 CFR 4.76 - Visual acuity.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... distance and near vision using Snellen's test type or its equivalent. (b) Evaluation of visual acuity. (1) Evaluate central visual acuity on the basis of corrected distance vision with central fixation, even if a central scotoma is present. However, when the lens required to correct distance vision in the poorer...

  14. Visual Acuity and Its Dependence Upon Receptor Density and Retinal Ganglion Cell Receptive Field Overlap.

    DTIC Science & Technology

    1981-11-01

    physiological basis of this effort was, in elegant detail, discovered in the visual system of the horseshoe crab by Hartline et al., (1954). Obviously...assamensis), and the crab -eating or cynamolgus (Macaca fasciculars). All were essentially identical in terms of the recordings from the eye. However, the

  15. Nonamblyopic eye visual acuity through Bangerter filters

    PubMed Central

    Rutstein, Robert P.; Foster, Nicole C.; Cotter, Susan A.; Kraker, Raymond T.; Lee, Dave H.; Melia, Michele; Quinn, Graham E.; Tamkins, Susanna M.; Wallace, David K.

    2011-01-01

    Purpose To describe the amount of visual acuity degradation induced by Bangerter filters in the better-seeing eye and to evaluate its stability over time in children with moderate amblyopia. Methods Visual acuity with and without a Bangerter filter was measured in the nonamblyopic eye of 186 children with moderate amblyopia who were then treated with either patching or with the Bangerter filters. A 0.2 filter was used for amblyopia of 20/80 and a 0.3 filter for amblyopia from 20/40 to 20/63. For the 89 children randomized to Bangerter filters, visual acuity was also measured in the nonamblyopic eye with and without the filters at both 6 weeks and 12 weeks after initiating treatment. Results Mean degradation in visual acuity of the nonamblyopic eye at baseline was 5.1 logMAR lines with the 0.2 filter and 4.8 logMAR lines with the 0.3 filter. The degradation with each filter did not always agree with the manufacturer’s specifications. Over time, the amount of degradation with the filters decreased. Conclusions The 0.2 and 0.3 Bangerter filters degrade nonamblyopic eye visual acuity sufficiently in amblyopic children. Because the amount of degradation decreases over time, it is recommended to periodically apply a new filter when using this type of amblyopia treatment. PMID:21419678

  16. Visual Acuity of Children: United States.

    ERIC Educational Resources Information Center

    Health Services and Mental Health Administration (DHEW), Bethesda, MD.

    National estimates based on the findings from the Health Examination Survey in 1963 to 1965 of uncorrected monocular and binocular visual-acuity levels of children were studied. A nationwide sample of 7,417 children was selected to represent the approximately 24 million noninstitutionalized American children between ages 6 and 11 years. Testing…

  17. Visual Acuity Assessment in Persons with Dementia. Research Report

    ERIC Educational Resources Information Center

    Morse, Alan R.; Teresi, Jeanne; Rosenthal, Bruce; Holmes, Douglas; Yatzkan, Elaine S.

    2004-01-01

    Most studies of vision in persons with Alzheimer's disease either exclude those with advanced dementia or are unable to assess their vision adequately, and therefore, improperly report these persons' visual acuity status. In this study, visual acuity was assessed using the ETDRS Snellen-type acuity chart and Teller Acuity Cards. The Teller Acuity…

  18. Visual Acuity During Treadmill Walking

    NASA Technical Reports Server (NTRS)

    Peters, B. T.; Brady, R.; vanEmmerik, R. E. A.; Bloomberg, Jacob J.

    2006-01-01

    An awareness of the physical world is essential for successful navigation through the environment. Vision is the means by which this awareness is made possible for most people. However, without adequate compensation, the movements of the body during walking could impair vision. Previous research has shown how the eyes, head and trunk movements are coordinated to provide the compensation necessary for clear vision, but the overall effectiveness of these coordinated movements is unknown. The goal of the research presented here was to provide a direct measure of visual performance during locomotion, while also investigating the degree to which coordinated head and body movements can be altered to facilitate the goal of seeing clearly.

  19. [The best corrected presenting distance visual acuity in forensic medicine].

    PubMed

    Liu, Rui-Jue

    2011-06-01

    At present the sight impairment evaluation in forensic medicine of China is based on the international classification of disease by WHO in 1973. The main measured indicator is "best corrected visual acuity". It is different from "presenting distance visual acuity" in some situations. In the new blindness and vision loss classification made by WHO in 2003, "presenting distance visual acuity" took the place of the "best corrected visual acuity". In the practice of forensic medicine, "presenting distance visual acuity" can not reflect the real visual acuity duo to the exaggeration or disguise of the wounded. We suggest to use "the best corrected presenting distance visual acuity" instead of "presenting distance visual acuity" in order to avoid the influences of the exaggeration or disguise of the wounded.

  20. 21 CFR 886.1150 - Visual acuity chart.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Visual acuity chart. 886.1150 Section 886.1150...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1150 Visual acuity chart. (a) Identification. A visual acuity chart is a device that is a chart, such as a Snellen chart with block letters...

  1. Visual acuity, color vision, and visual search performance at sea.

    PubMed

    Donderi, D C

    1994-03-01

    Visual acuity and color vision were tested during a search and rescue exercise at sea. Fifty-seven watchkeepers searched for orange and yellow life rafts during daylight and for lighted and unlighted life rafts at night with night vision goggles. There were 588 individual watches of one hour each. Measures of wind, waves, and weather were used as covariates. Daytime percentage detection was positively correlated with low-contrast visual acuity and negatively correlated with error scores on Dvorine pseudoisochromatic plates and the Farnsworth color test. Performance was better during the first half-hour of the watch. Efficiency calculations show that color vision selective screening at one standard deviation above the mean would increase daylight search performance by 10% and that one standard deviation visual acuity selection screening would increase performance by 12%. There was no relationship between either acuity or color vision and life raft detection using night vision goggles.

  2. Visual acuity estimation from simulated images

    NASA Astrophysics Data System (ADS)

    Duncan, William J.

    Simulated images can provide insight into the performance of optical systems, especially those with complicated features. Many modern solutions for presbyopia and cataracts feature sophisticated power geometries or diffractive elements. Some intraocular lenses (IOLs) arrive at multifocality through the use of a diffractive surface and multifocal contact lenses have a radially varying power profile. These type of elements induce simultaneous vision as well as affecting vision much differently than a monofocal ophthalmic appliance. With myriad multifocal ophthalmics available on the market it is difficult to compare or assess performance in ways that effect wearers of such appliances. Here we present software and algorithmic metrics that can be used to qualitatively and quantitatively compare ophthalmic element performance, with specific examples of bifocal intraocular lenses (IOLs) and multifocal contact lenses. We anticipate this study, methods, and results to serve as a starting point for more complex models of vision and visual acuity in a setting where modeling is advantageous. Generating simulated images of real- scene scenarios is useful for patients in assessing vision quality with a certain appliance. Visual acuity estimation can serve as an important tool for manufacturing and design of ophthalmic appliances.

  3. Bayesian model of Snellen visual acuity.

    PubMed

    Nestares, Oscar; Navarro, Rafael; Antona, Beatriz

    2003-07-01

    A Bayesian model of Snellen visual acuity (VA) has been developed that, as far as we know, is the first one that includes the three main stages of VA: (1) optical degradations, (2) neural image representation and contrast thresholding, and (3) character recognition. The retinal image of a Snellen test chart is obtained from experimental wave-aberration data. Then a subband image decomposition with a set of visual channels tuned to different spatial frequencies and orientations is applied to the retinal image, as in standard computational models of early cortical image representation. A neural threshold is applied to the contrast responses to include the effect of the neural contrast sensitivity. The resulting image representation is the base of a Bayesian pattern-recognition method robust to the presence of optical aberrations. The model is applied to images containing sets of letter optotypes at different scales, and the number of correct answers is obtained at each scale; the final output is the decimal Snellen VA. The model has no free parameters to adjust. The main input data are the eye's optical aberrations, and standard values are used for all other parameters, including the Stiles-Crawford effect, visual channels, and neural contrast threshold, when no subject specific values are available. When aberrations are large, Snellen VA involving pattern recognition differs from grating acuity, which is based on a simpler detection (or orientation-discrimination) task and hence is basically unaffected by phase distortions introduced by the optical transfer function. A preliminary test of the model in one subject produced close agreement between actual measurements and predicted VA values. Two examples are also included: (1) application of the method to the prediction of the VAin refractive-surgery patients and (2) simulation of the VA attainable by correcting ocular aberrations.

  4. Potential acuity meter for predicting visual acuity after Nd:YAG posterior capsulotomy

    SciTech Connect

    Smiddy, W.E.; Radulovic, D.; Yeo, J.H.; Stark, W.J.; Maumenee, A.E.

    1986-03-01

    We studied 30 patients with opacifications of the posterior capsule to determine if the potential acuity meter (PAM) could accurately predict final visual outcome after Nd:YAG discussion. The final visual acuity was within one line of the PAM prediction in 22 of 30 patients (73%), better by two or more lines in seven patients (23%), and worse in one patient (4%) by two lines. Although in thicker capsules the final acuity was occasionally better than the PAM prediction, the rates of false negative and false positive predictions were very low. Mild cystoid macular edema (3 patients), age-related macular degeneration (3 patients), intraocular lens status, and level of initial acuity did not diminish PAM accuracy. The PAM effectively predicts final visual acuity after YAG posterior capsulotomy, when used in a patient, unhurried manner.

  5. Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons.

    PubMed

    Veilleux, Carrie C; Kirk, E Christopher

    2009-04-01

    Studies of visual acuity in primates have shown that diurnal haplorhines have higher acuity (30-75 cycles per degree (c/deg)) than most other mammals. However, relatively little is known about visual acuity in non-haplorhine primates, and published estimates are only available for four strepsirrhine genera (Microcebus, Otolemur, Galago, and Lemur). We present here the first measurements of visual acuity in a cathemeral strepsirrhine species, the blue-eyed black lemur (Eulemur macaco flavifrons). Acuity in two subjects, a 3-year-old male and a 16-year-old female, was assessed behaviorally using a two-alternative forced choice discrimination task. Visual stimuli consisted of high contrast square wave gratings of seven spatial frequencies. Acuity threshold was determined using a 70% correct response criterion. Results indicate a maximum visual acuity of 5.1 c/deg for the female (1718 trials) and 3.8 c/deg for the male (846 trials). These values for E. macaco are slightly lower than those reported for diurnal Lemur catta, and are generally comparable to those reported for nocturnal Microcebus murinus and Otolemur crassicaudatus. To examine ecological sources of variation in primate visual acuity, we also calculated maximum theoretical acuity for Cheirogaleus medius (2.8 c/deg) and Tarsius syrichta (8.9 c/deg) using published data on retinal ganglion cell density and eye morphology. These data suggest that visual acuity in primates may be influenced by activity pattern, diet, and phylogenetic history. In particular, the relatively high acuity of T. syrichta and Galago senegalensis suggests that visual predation may be an important selective factor favoring high visual acuity in primates.

  6. Astronaut Frank Borman performing visual acuity tests in space

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Astronaut Frank Borman is seen performing visual acuity tests in space. Views include Borman looking at the camera as light shines through the capsule window (63712); Borman is using the visual acuity device and a portable mouth thermometer during his experiment (63713).

  7. Brief Report: Visual Acuity in Children with Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Albrecht, Matthew A.; Stuart, Geoffrey W.; Falkmer, Marita; Ordqvist, Anna; Leung, Denise; Foster, Jonathan K.; Falkmer, Torbjorn

    2014-01-01

    Recently, there has been heightened interest in suggestions of enhanced visual acuity in autism spectrum disorders (ASD) which was sparked by evidence that was later accepted to be methodologically flawed. However, a recent study that claimed children with ASD have enhanced visual acuity (Brosnan et al. in "J Autism Dev Disord"…

  8. Photovoltaic restoration of sight with high visual acuity.

    PubMed

    Lorach, Henri; Goetz, Georges; Smith, Richard; Lei, Xin; Mandel, Yossi; Kamins, Theodore; Mathieson, Keith; Huie, Philip; Harris, James; Sher, Alexander; Palanker, Daniel

    2015-05-01

    Patients with retinal degeneration lose sight due to the gradual demise of photoreceptors. Electrical stimulation of surviving retinal neurons provides an alternative route for the delivery of visual information. We demonstrate that subretinal implants with 70-μm-wide photovoltaic pixels provide highly localized stimulation of retinal neurons in rats. The electrical receptive fields recorded in retinal ganglion cells were similar in size to the natural visual receptive fields. Similarly to normal vision, the retinal response to prosthetic stimulation exhibited flicker fusion at high frequencies, adaptation to static images and nonlinear spatial summation. In rats with retinal degeneration, these photovoltaic arrays elicited retinal responses with a spatial resolution of 64 ± 11 μm, corresponding to half of the normal visual acuity in healthy rats. The ease of implantation of these wireless and modular arrays, combined with their high resolution, opens the door to the functional restoration of sight in patients blinded by retinal degeneration.

  9. Photovoltaic restoration of sight with high visual acuity

    PubMed Central

    Lorach, Henri; Goetz, Georges; Smith, Richard; Lei, Xin; Mandel, Yossi; Kamins, Theodore; Mathieson, Keith; Huie, Philip; Harris, James; Sher, Alexander; Palanker, Daniel

    2015-01-01

    Patients with retinal degeneration lose sight due to gradual demise of photoreceptors. Electrical stimulation of the surviving retinal neurons provides an alternative route for delivery of visual information. We demonstrate that subretinal arrays with 70 μm photovoltaic pixels provide highly localized stimulation, with electrical and visual receptive fields of comparable sizes in rat retinal ganglion cells. Similarly to normal vision, retinal response to prosthetic stimulation exhibits flicker fusion at high frequencies, adaptation to static images and non-linear spatial summation. In rats with retinal degeneration, these photovoltaic arrays provide spatial resolution of 64 ± 11 μm, corresponding to half of the normal visual acuity in pigmented rats. Ease of implantation of these wireless and modular arrays, combined with their high resolution opens the door to functional restoration of sight. PMID:25915832

  10. Changes in the clinical measurement of visual acuity

    NASA Astrophysics Data System (ADS)

    Bailey, I. L.; Jackson, A. J.

    2016-11-01

    In 1862, Hermann Snellen introduced his letter chart for the clinical measurement of visual acuity. His chart presented letters,or optotypes, arranged in a progressively diminishing size sequence, and the visual acuity was determined by the smallest letters that could read at a specified distance. Numerous modifications of the design of the optotypes, the progression of size and the chart layout were suggested, and in 1976, Bailey and Lovie published a set of design principles that made the visual task the same at all size levels, so that size become the only significant variable. This required the same number of letters at each size level, fixed spacing ratios and a logarithmic progression of size. This facilitates more precise quantification of visual acuity by giving credit for every letter read correctly, and this gives clinicians tighter confidence limits for determining changes or differences in visual acuity. However, optotype choices, and associated spacing arrangements can have significant effects on visual acuity scores as can viewing conditions and testing protocols. Computer based visual acuity tests are becoming more commonplace, there will be more variety in test charts and procedures which will create some problems for making comparisons between tests.

  11. Visual acuity in mammals: effects of eye size and ecology.

    PubMed

    Veilleux, Carrie C; Kirk, E Christopher

    2014-01-01

    Previous comparative research has attributed interspecific variation in eye size among mammals to selection related to visual acuity. Mammalian species have also been hypothesized to differ in visual acuity partly as a result of differences in ecology. While a number of prior studies have explored ecological and phylogenetic effects on eye shape, a broad comparative analysis of the relationships between visual acuity, eye size and ecology in mammals is currently lacking. Here we use phylogenetic comparative methods to explore these relationships in a taxonomically and ecologically diverse sample of 91 mammal species. These data confirm that axial eye length and visual acuity are significantly positively correlated in mammals. This relationship conforms to expectations based on theoretical optics and prior analyses of smaller comparative samples. Our data also demonstrate that higher visual acuity in mammals is associated with: (1) diurnality and (2) predatory habits once the effects of eye size and phylogeny have been statistically controlled. These results suggest that interspecific variation in mammalian visual acuity is the result of a complex interplay between phylogenetic history, visual anatomy and ecology.

  12. Predicting visual acuity from the structure of visual cortex

    PubMed Central

    Srinivasan, Shyam; Carlo, C. Nikoosh; Stevens, Charles F.

    2015-01-01

    Three decades ago, Rockel et al. proposed that neuronal surface densities (number of neurons under a square millimeter of surface) of primary visual cortices (V1s) in primates is 2.5 times higher than the neuronal density of V1s in nonprimates or many other cortical regions in primates and nonprimates. This claim has remained controversial and much debated. We replicated the study of Rockel et al. with attention to modern stereological precepts and show that indeed primate V1 is 2.5 times denser (number of neurons per square millimeter) than many other cortical regions and nonprimate V1s; we also show that V2 is 1.7 times as dense. As primate V1s are denser, they have more neurons and thus more pinwheels than similar-sized nonprimate V1s, which explains why primates have better visual acuity. PMID:26056277

  13. Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts As Visual Acuity Measurement Devices

    PubMed Central

    Livingstone, I. A. T.; Tarbert, C. M.; Giardini, M. E.; Bastawrous, A.; Middleton, D.; Hamilton, R.

    2016-01-01

    Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out

  14. Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts As Visual Acuity Measurement Devices.

    PubMed

    Livingstone, I A T; Tarbert, C M; Giardini, M E; Bastawrous, A; Middleton, D; Hamilton, R

    2016-01-01

    Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer's recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out

  15. Validation of a Manually Oscillating Chair for In-The-Field Assessment of Dynamic Visual Acuity on Crewmembers Within Hours of Returning From Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Kreutzberg, G. A.; Rosenberg, M. J. F.; Peters, B. T.; Reschke,M. F.

    2017-01-01

    Long-duration spaceflight results in sensorimotor adaptations, which cause functional deficits during gravitational transitions, such as landing on a planetary surface after long-duration microgravity exposure. Both the vestibular system and the central nervous system are affected by gravitational transitions. These systems are responsible for coordinating head and eye movements via the vestibulo-ocular reflex (VOR) and go through an adaptation period upon exposure to microgravity. Consequently, they must also re-adapt to Earth's gravitational environment upon landing. This re-adaptation causes decrements in gaze control and dynamic visual acuity, with crewmembers reporting oscillopsia and blurred vision caused by retinal slip, or the inability to keep an image focused on their retina. This is thought to drive motion sickness symptoms experienced by most crewmembers following landing. Retinal slip can be estimated by dynamic visual acuity (DVA); visual acuity while in motion. Previously, DVA has been assessed in the laboratory where subjects walked at 6.4 km/hr on a motorized treadmill. Using this method, Peters et al. (2011) found that DVA is worsened in astronauts by an average of 0.75 eye-chart lines one day after landing. However, it is believed that re-adaptation occurs quickly and that DVA might be worse immediately upon re-exposure to a gravitational environment. Since many crewmembers are unable to walk safely upon landing, it was necessary to develop a method for replicating the vertical head movements associated with walking. In addition, the use of a chair to imitate the head displacement caused by walking isolates eye-head interactions without allowing for trunk and lower-body compensation, as seen with treadmill walking (Mulavara & Bloomberg 2003). Therefore, a modality for assessing DVA in the field within a few hours of landing was developed. In this study, we validated the ability of a manually operated oscillating chair to reproduce the oscillatory

  16. Night vision goggle visual acuity assessment: results of an interagency test

    NASA Astrophysics Data System (ADS)

    Task, H. Lee

    2001-08-01

    There are several parameters that are used to characterize the quality of a night vision goggle (NVG) such as resolution, gain, field-of-view, visual acuity, etc. One of the primary parameters is visual acuity or resolution of the NVG. These two terms are often used interchangeably primarily because of the measurement methods employed. The objectives of this paper are to present: (1) an argument as to why NVG visual acuity and resolution should be considered as distinctly different parameters, (2) descriptions of different methods of measuring visual acuity and resolution, and (3) the results of a blind test by several agencies to measure the resolution of the same two NVGs (four oculars).

  17. Visual acuity in the short-tailed opossum (Monodelphis domestica).

    PubMed

    Dooley, J C; Nguyen, H M; Seelke, A M H; Krubitzer, L

    2012-10-25

    Monodelphis domestica (short-tailed opossum) is an emerging animal model for studies of neural development due to the extremely immature state of the nervous system at birth and its subsequent rapid growth to adulthood. Yet little is known about its normal sensory discrimination abilities. In the present investigation, visual acuity was determined in this species using the optokinetic test (OPT), which relies on involuntary head tracking of a moving stimulus and can be easily elicited using a rotating visual stimulus of varying spatial frequencies. Using this methodology, we determined that the acuity of Monodelphis is 0.58 cycles per degree (cpd), which is similar to the acuity of rats using the same methodology, and higher than in mice. However, acuity in the short-tailed opossum is lower than in other marsupials. This is in part due to the methodology used to determine acuity, but may also be due to differences in diel patterns, lifestyle and phylogeny. We demonstrate that for the short-tailed opossum, the OPT is a rapid and reliable method of determining a baseline acuity and can be used to study enhanced acuities due to cortical plasticity.

  18. Visual acuity in the short-tailed opossum (Monodelphis domestica)

    PubMed Central

    Dooley, James C.; Nguyen, Hoang; Seelke, Adele M. H.; Krubitzer, Leah

    2013-01-01

    Monodelphis domestica (short-tailed opossum) is an emerging animal model for studies of neural development due to the extremely immature state of the nervous system at birth and its subsequent rapid growth to adulthood. Yet little is known about its normal sensory discrimination abilities. In the present investigation, visual acuity was determined in this species using the optokinetic test (OPT), which relies on involuntary head tracking of a moving stimulus and can be easily elicited using a rotating visual stimulus of varying spatial frequencies. Using this methodology, we determined that the acuity of Monodelphis is 0.58 cycles per degree (cpd), which is similar to the acuity of rats using the same methodology, and higher than in mice. However, acuity in the short-tailed opossum is lower than in other marsupials. This is in part due to the methodology used to determine acuity, but may also be due to differences in diel patterns, lifestyle and phylogeny. We demonstrate that for the short-tailed opossum, the OPT is a rapid and reliable method of determining a baseline acuity and can be used to study enhanced acuities due to cortical plasticity. PMID:22871523

  19. Measuring Observers’ Visual Acuity Through Night Vision Goggles

    DTIC Science & Technology

    1998-01-01

    a two-alternative, forced-choice ( 2AFC ) method to determine visual acuity through NVGs as a function of night-time ambient illumination levels. A...computer executed the 2AFC (gap seen up or down), Step Program adapted from Simpson (1989). Based on the observerÕs last response, the program selected...threshold levels, NVG drift, good guessing in the 2AFC method, fatigue, eye strain, sinus headaches and so on. METHOD Psychometric Function of Acuity

  20. The Effect of Zeaxanthin on the Visual Acuity of Zebrafish.

    PubMed

    Saidi, Eric A; Davey, Pinakin Gunvant; Cameron, D Joshua

    2015-01-01

    Oral supplementation of carotenoids such as zeaxanthin or lutein which naturally occur in human retina have been shown to improve vision and prevent progression of damage to advanced AMD in some studies. The zebrafish eye shares many physiological similarities with the human eye and is increasingly being used as model for vision research. We hypothesized that injection of zeaxanthin into the zebrafish eye would improve the visual acuity of the zebrafish over time. Visual acuity, calculated in cycles per degree, was measured in adult zebrafish to establish a consistent baseline using the optokinetic response. Zeaxanthin dissolved into phosphate buffered saline (PBS) or PBS only was injected into the anterior chamber of the right and left eyes of the Zebrafish. Visual acuities were measured at 1 week and 3, 8 and 12 weeks post-injection to compare to baseline values. Repeated measures ANOVA was used to compare visual acuities between fish injected with PBS and zeaxanthin. A significant improvement in visual acuity, 14% better than before the injection (baseline levels), was observed one week after injection with zeaxanthin (p = 0.04). This improvement peaked at more than 30% for some fish a few weeks after the injection and improvement in vision persisted at 3 weeks after injection (p = 0.006). The enhanced visual function was not significantly better than baseline at 8 weeks (p = 0.19) and returned to baseline levels 12 weeks after the initial injection (p = 0.50). Zeaxanthin can improve visual acuity in zebrafish eyes. Further studies are required to develop a better understanding of the role zeaxanthin and other carotenoids play during normal visual function.

  1. Assessment of imaging with extended depth-of-field by means of the light sword lens in terms of visual acuity scale

    PubMed Central

    Kakarenko, Karol; Ducin, Izabela; Grabowiecki, Krzysztof; Jaroszewicz, Zbigniew; Kolodziejczyk, Andrzej; Mira-Agudelo, Alejandro; Petelczyc, Krzysztof; Składowska, Aleksandra; Sypek, Maciej

    2015-01-01

    We present outcomes of an imaging experiment using the refractive light sword lens (LSL) as a contact lens in an optical system that serves as a simplified model of the presbyopic eye. The results show that the LSL produces significant improvements in visual acuity of the simplified presbyopic eye model over a wide range of defocus. Therefore, this element can be an interesting alternative for the multifocal contact and intraocular lenses currently used in ophthalmology. The second part of the article discusses possible modifications of the LSL profile in order to render it more suitable for fabrication and ophthalmological applications. PMID:26137376

  2. Fresnel prisms and their effects on visual acuity and binocularity.

    PubMed Central

    Véronneau-Troutman, S

    1978-01-01

    1. The visual acuity with the Fresnel membrane prism is significantly less than that with the conventional prism of the same power for all prism powers from 12 delta through 30 delata at distance and from 15 delta through 30 delta at near. 2. The difference in the visual acuity between base up and base down, and between base in and base out, is not significantly different for either the Fresnel membrane prism or for the conventional prism. 3. For both Fresnel membrane prism and the conventional prism, the visual acuity when looking straight ahead. 4. Using Fresnel membrane prisms of the same power from different lots, the visual acuity varied significantly. The 30 delta prism caused the widest range in visual acuity. 5. When normal subjects are fitted with the higher powers of the Fresnel membrane prism, fusion and stereopsis are disrupted to such an extent that the use of this device to restore or to improve binocular vision in cases with large-angle deviations is seriously questioned. 6. Moreover, the disruption of fusion and stereopsis is abrupt and severe and does not parallel the decrease in visual acuity. The severely reduced ability to maintain fusion may be related to the optical aberrations, which, in turn, may be due to the molding process and the polyvinyl chloride molding material. 7. Through the flexibility of the membrane prism is a definite advantage, because of its proclivity to reduce visual acuity and increase aberrations its prescription for adults often must be limited to only one eye. 8. For the same reasons in the young child with binocular vision problems, the membrane prism presently available should be prescribed over both eyes only in powers less than 20 delta. When the membrane prism is to be used as a partial occluder (over one eye only), any power can be used. 9. The new Fresnel "hard" prism reduces visual acuity minimally and rarely disrupts binocularity, thus increasing the potential for prismotherapy to establish binocularity. This

  3. Dynamic visual acuity using "far" and "near" targets

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; Bloomberg, Jacob J.

    2005-01-01

    CONCLUSIONS: DVA may be useful for assessing the functional consequences of an impaired gaze stabilization mechanism or for testing the effectiveness of a rehabilitation paradigm. Because target distance influences the relative contributions of canal and otolith inputs, the ability to measure DVA at near and far viewing distances may also lead to tests that will independently assess canal and otolith function. OBJECTIVE: To present and test a methodology that uses dynamic visual acuity (DVA) to assess the efficacy of compensatory gaze mechanisms during a functionally relevant activity that differentially measures canal and otolith function. MATERIAL AND METHODS: The effect of treadmill walking at a velocity of 1.79 m/s on subjects' visual acuity was assessed at each of two viewing distances. A custom-written threshold determination program was used to display Landolt C optotypes on a laptop computer screen during a "far" (4 m) target condition and on a micro-display for a "near" (50 cm) target condition. The walking acuity scores for each target distance were normalized by subtracting a corresponding acuity measure obtained while standing still on the treadmill belt. RESULTS: As predicted by subjective reports of relative target motion, the decrease in visual acuity was significantly greater (p < 0.00001) for the near compared to the far condition.

  4. Malingering or simulation in ophthalmology-visual acuity

    PubMed Central

    Incesu, Ali Ihsan; Sobacı, Güngör

    2011-01-01

    Simulation can be defined as malingering, or sometimes functional visual loss (FVL). It manifests as either simulating an ophthalmic disease (positive simulation), or denial of ophthalmic disease (negative simulation). Conscious behavior and compensation or indemnity claims are prominent features of simulation. Since some authors suggest that this is a manifestation of underlying psychopathology, even conversion is included in this context. In today's world, every ophthalmologist can face with simulation of ophthalmic disease or disorder. In case of simulation suspect, the physician's responsibility is to prove the simulation considering the disease/disorder first, and simulation as an exclusion. In simulation examinations, the physician should be firm and smart to select appropriate test(s) to convince not only the subject, but also the judge in case of indemnity or compensation trials. Almost all ophthalmic sensory and motor functions including visual acuity, visual field, color vision and night vision can be the subject of simulation. Examiner must be skillful in selecting the most appropriate test. Apart from those in the literature, we included all kinds of simulation in ophthalmology. In addition, simulation examination techniques, such as, use of OCT (optical coherence tomography), frequency doubling perimetry (FDP), and modified polarization tests were also included. In this review, we made a thorough literature search, and added our experiences to give the readers up-to-date information on malingering or simulation in ophthalmology. PMID:22553721

  5. THE RELATION BETWEEN VISUAL ACUITY AND BRIGHTNESS DISCRIMINATION

    PubMed Central

    Hendley, Charles D.

    1948-01-01

    1. Visual acuity depends on the brightness contrast between test object and background; and conversely, brightness discrimination depends on the target size. Both functions vary with the brightness of the background. Measurements with rectangular targets of length-width ratio 2 were made over a range of sizes, contrasts, and brightnesses sufficient to determine the relations among these three variables. The rectangles were from 2' to 50' wide; the contrast fraction, ΔI/I, ranged from 0.01 to 40; the background brightness varied from 0.0001 to 2500 millilamberts. 2. When ΔI/I or visual acuity is plotted as a function of brightness the data do, in general, follow Hecht's equation. The departure from a simple photochemical theory which the larger targets show is probably due to changes in the functional retinal mosaic with changing brightness. 3. In general also, the relation between visual acuity and brightness, at selected contrasts, fits Hecht's derivation. At low contrasts, as the brightness is reduced a point is reached at which the test object becomes invisible at any size. 4. No simple relation emerges from the data relating visual acuity to contrast, at set levels of illumination. Over only a very short range are visual acuity and contrast directly related. At high contrasts, visual acuity reaches a maximum, whereas at low visual acuity, ΔI/I reaches a minimum which cannot be passed regardless of size. 5. The shape of the curves relating ΔI/I to brightness is not significantly altered by changing the exposure time. There is some evidence to show that a 3 second exposure of the target is equivalent to two looks of 0.2 second each. 6. In all these studies the thresholds were determined by a frequency of seeing method, and the data have been considered in terms of a quantum theory of threshold seeing. It was found that a threshold response involves between four and eight independent critical events, which are largely independent of size, brightness, and

  6. Heterogeneity of failure of visual acuity in Graves' disease.

    PubMed Central

    Sachdev, Y.; Chatterji, J. C.; Sharma, R. C.

    1979-01-01

    The eye manifestations of Graves' disease are usually mild and self-limiting. Occasionally they follow a progressive course leading to visual loss and total blindness. The ocular manifestations bear no relationship to the metabolic state and may appear before, during or after onset of thyrotoxicosis. Characteristically they become evident at about the time of onset of hypermetabolism. Various factors responsible for the failure of visual acuity are discussed with case illustrations. PMID:314108

  7. THE VISUAL ACUITY AND INTENSITY DISCRIMINATION OF DROSOPHILA

    PubMed Central

    Hecht, Selig; Wald, George

    1934-01-01

    Drosophila possesses an inherited reflex response to a moving visual pattern which can be used to measure its capacity for intensity discrimination and its visual acuity at different illuminations. It is found that these two properties of vision run approximately parallel courses as functions of the prevailing intensity. Visual acuity varies with the logarithm of the intensity in much the same sigmoid way as in man, the bee, and the fiddler crab. The resolving power is very poor at low illuminations and increases at high illuminations. The maximum visual acuity is 0.0018, which is 1/1000 of the maximum of the human eye and 1/10 that of the bee. The intensity discrimination of Drosophila is also extremely poor, even at its best. At low illuminations for two intensities to be recognized as different, the higher must be nearly 100 times the lower. This ratio decreases as the intensity increases, and reaches a minimum of 2.5 which is maintained at the highest intensities. The minimum value of ΔI/I for Drosophila is 1.5, which is to be compared with 0.25 for the bee and 0.006 for man. An explanation of the variation of visual acuity with illumination is given in terms of the variation in number of elements functional in the retinal mosaic at different intensities, this being dependent on the general statistical distribution of thresholds in the ommatidial population. Visual acuity is thus determined by the integral form of this distribution and corresponds to the total number of elements functional. The idea that intensity discrimination is determined by the differential form of this distribution—that is, that it depends on the rate of entrance of functional elements with intensity—is shown to be untenable in the light of the correspondence of the two visual functions. It is suggested that, like visual acuity, intensity discrimination may also have to be considered as a function of the total number of elements active at a given intensity. PMID:19872798

  8. Evaluation of visual acuity with Gen 3 night vision goggles

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur; Kaiser, Mary K.

    1994-01-01

    Using laboratory simulations, visual performance was measured at luminance and night vision imaging system (NVIS) radiance levels typically encountered in the natural nocturnal environment. Comparisons were made between visual performance with unaided vision and that observed with subjects using image intensification. An Amplified Night Vision Imaging System (ANVIS6) binocular image intensifier was used. Light levels available in the experiments (using video display technology and filters) were matched to those of reflecting objects illuminated by representative night-sky conditions (e.g., full moon, starlight). Results show that as expected, the precipitous decline in foveal acuity experienced with decreasing mesopic luminance levels is effectively shifted to much lower light levels by use of an image intensification system. The benefits of intensification are most pronounced foveally, but still observable at 20 deg eccentricity. Binocularity provides a small improvement in visual acuity under both intensified and unintensified conditions.

  9. Eye size and visual acuity influence vestibular anatomy in mammals.

    PubMed

    Kemp, Addison D; Christopher Kirk, E

    2014-04-01

    The semicircular canals of the inner ear detect head rotations and trigger compensatory movements that stabilize gaze and help maintain visual fixation. Mammals with large eyes and high visual acuity require precise gaze stabilization mechanisms because they experience diminished visual functionality at low thresholds of uncompensated motion. Because semicircular canal radius of curvature is a primary determinant of canal sensitivity, species with large canal radii are expected to be capable of more precise gaze stabilization than species with small canal radii. Here, we examine the relationship between mean semicircular canal radius of curvature, eye size, and visual acuity in a large sample of mammals. Our results demonstrate that eye size and visual acuity both explain a significant proportion of the variance in mean canal radius of curvature after statistically controlling for the effects of body mass and phylogeny. These findings suggest that variation in mean semicircular canal radius of curvature among mammals is partly the result of selection for improved gaze stabilization in species with large eyes and acute vision. Our results also provide a possible functional explanation for the small semicircular canal radii of fossorial mammals and plesiadapiforms.

  10. Effects of Horizontal Acceleration on Human Visual Acuity and Stereopsis

    PubMed Central

    Horng, Chi-Ting; Hsieh, Yih-Shou; Tsai, Ming-Ling; Chang, Wei-Kang; Yang, Tzu-Hung; Yauan, Chien-Han; Wang, Chih-Hung; Kuo, Wu-Hsien; Wu, Yi-Chang

    2015-01-01

    The effect of horizontal acceleration on human visual acuity and stereopsis is demonstrated in this study. Twenty participants (mean age 22.6 years) were enrolled in the experiment. Acceleration from two different directions was performed at the Taiwan High-Speed Rail Laboratory. Gx and Gy (< and >0.1 g) were produced on an accelerating platform where the subjects stood. The visual acuity and stereopsis of the right eye were measured before and during the acceleration. Acceleration <0.1 g in the X- or Y-axis did not affect dynamic vision and stereopsis. Vision decreased (mean from 0.02 logMAR to 0.25 logMAR) and stereopsis declined significantly (mean from 40 s to 60.2 s of arc) when Gx > 0.1 g. Visual acuity worsened (mean from 0.02 logMAR to 0.19 logMAR) and poor stereopsis was noted (mean from 40 s to 50.2 s of arc) when Gy > 0.1 g. The effect of acceleration from the X-axis on the visual system was higher than that from the Y-axis. During acceleration, most subjects complained of ocular strain when reading. To our knowledge, this study is the first to report the exact levels of visual function loss during Gx and Gy. PMID:25607601

  11. Effects of horizontal acceleration on human visual acuity and stereopsis.

    PubMed

    Horng, Chi-Ting; Hsieh, Yih-Shou; Tsai, Ming-Ling; Chang, Wei-Kang; Yang, Tzu-Hung; Yauan, Chien-Han; Wang, Chih-Hung; Kuo, Wu-Hsien; Wu, Yi-Chang

    2015-01-19

    The effect of horizontal acceleration on human visual acuity and stereopsis is demonstrated in this study. Twenty participants (mean age 22.6 years) were enrolled in the experiment. Acceleration from two different directions was performed at the Taiwan High-Speed Rail Laboratory. Gx and Gy (< and >0.1 g) were produced on an accelerating platform where the subjects stood. The visual acuity and stereopsis of the right eye were measured before and during the acceleration. Acceleration <0.1 g in the X- or Y-axis did not affect dynamic vision and stereopsis. Vision decreased (mean from 0.02 logMAR to 0.25 logMAR) and stereopsis declined significantly (mean from 40 s to 60.2 s of arc) when Gx > 0.1 g. Visual acuity worsened (mean from 0.02 logMAR to 0.19 logMAR) and poor stereopsis was noted (mean from 40 s to 50.2 s of arc) when Gy > 0.1 g. The effect of acceleration from the X-axis on the visual system was higher than that from the Y-axis. During acceleration, most subjects complained of ocular strain when reading. To our knowledge, this study is the first to report the exact levels of visual function loss during Gx and Gy.

  12. Dynamic Visual Acuity: a Functionally Relevant Research Tool

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; Brady, Rachel A.; Miller, Chris A.; Mulavara, Ajitkumar P.; Wood, Scott J.; Cohen, Helen S.; Bloomberg, Jacob J.

    2010-01-01

    Coordinated movements between the eyes and head are required to maintain a stable retinal image during head and body motion. The vestibulo-ocular reflex (VOR) plays a significant role in this gaze control system that functions well for most daily activities. However, certain environmental conditions or interruptions in normal VOR function can lead to inadequate ocular compensation, resulting in oscillopsia, or blurred vision. It is therefore possible to use acuity to determine when the environmental conditions, VOR function, or the combination of the two is not conductive for maintaining clear vision. Over several years we have designed and tested several tests of dynamic visual acuity (DVA). Early tests used the difference between standing and walking acuity to assess decrements in the gaze stabilization system after spaceflight. Supporting ground-based studies measured the responses from patients with bilateral vestibular dysfunction and explored the effects of visual target viewing distance and gait cycle events on walking acuity. Results from these studies show that DVA is affected by spaceflight, is degraded in patients with vestibular dysfunction, changes with target distance, and is not consistent across the gait cycle. We have recently expanded our research to include studies in which seated subjects are translated or rotated passively. Preliminary results from this work indicate that gaze stabilization ability may differ between similar active and passive conditions, may change with age, and can be affected by the location of the visual target with respect to the axis of motion. Use of DVA as a diagnostic tool is becoming more popular but the functional nature of the acuity outcome measure also makes it ideal for identifying conditions that could lead to degraded vision. By doing so, steps can be taken to alter the problematic environments to improve the man-machine interface and optimize performance.

  13. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider ...

  14. Quantitative assessment of visual acuity in projective head-mounted displays

    NASA Astrophysics Data System (ADS)

    Fidopiastis, Cali M.; Meyer, Catherine; Fuhrman, Christopher A.; Rolland, Jannick P.

    2003-09-01

    One issue of head mounted display design relates to the tradeoff between field of view (FOV) and resolution, which can lead to reduced visual acuity (VA). Essentially, an increase in FOV causes a decrease in visual acuity, for a given LCD display that has a fixed number of pixels. The effects of enhanced brightness on VA using two different types of retro-reflective material (cubed or beaded) were tested using a 52 deg. FOV projective helmet mounted display with VGA resolution. Three lighting conditions were also tested. Based on the display size, resolution, and FOV, we estimated a maximum visual acuity of 4.1 minutes of arc. In a counter-balanced between measures design, subjects' psychometric acuity functions were determined using a computer-generated 4AFC Landolt C test presented stereoscopically and probit analysis. The results confirmed that the maximum visual acuity possible within the setup was 4.1 arc minutes, the limit imposed by the microdisplay, and not the retroreflective material.

  15. Visual acuity with reversed-contrast charts: II. Clinical investigation.

    PubMed

    Westheimer, Gerald; Chu, Patricia; Huang, Wendy; Tran, Thuy; Dister, Robert

    2003-11-01

    Snellen visual acuity was measured in 106 patients ranging in age from 20 to 88 years in routine examinations in the general refraction clinic with two kinds of charts: the standard chart using black letters on a white background and a reversed-contrast display featuring white letters on a black background. The overall ratio of the white-on-black to the black-on-white Snellen fractions was 1.043. A scattergram relating this ratio to patient age revealed that the older the patient, the more the visual acuity was improved by switching to the reversed-contrast chart, with a regression line slope of 0.5 +/- 0.10. Impairment of the eye's optics, in particular by intraocular scatter causing a widening and flattening of the eye's point-spread function, explains these findings and suggests prognostic and therapeutic value of reversing the contrast polarity of displays.

  16. Influence of loupes and age on the near visual acuity of practicing dentists

    NASA Astrophysics Data System (ADS)

    Eichenberger, Martina; Perrin, Philippe; Neuhaus, Klaus W.; Bringolf, Ueli; Lussi, Adrian

    2011-03-01

    We evaluated the near visual acuity of 40 dentists and its improvement by using different magnification devices. The acuity was tested with miniaturized E-optotype tests on a negatoscope under the following conditions: 1. natural visual acuity, 300 mm; 2. single lens loupe, 2×, 250 mm; 3. Galilean loupe, 2.5×, 380 mm; and 4. Keplerian loupe, 4.3×, 400 mm. In part 1, the influence of the magnification devices was investigated for all dentists. The Keplerian loupe obtained the highest visual acuity (4.64), followed by the Galilean loupe (2.43), the single lens loupe (1.42), and natural visual acuity (1.19). For part 2, the dentists were classified according to their age (=40 years). The younger dentists' group achieved a significantly higher visual acuity with all magnification devices (p<0.001). For part 3, the dentists were grouped according to their natural visual acuity. The group with the higher natural visual acuity achieved significantly higher visual acuity with all magnification devices than did the group of dentists with the lower natural visual acuity (p<0.01). It can be concluded that near visual acuity varies highly between individuals and decreases during the lifetime. Independent of age or natural vision, visual acuity can be significantly improved by using magnification devices.

  17. Assessment of Visual Acuity in Relation to Central Nervous System Activation in Children with Mental Retardation.

    ERIC Educational Resources Information Center

    Jacobsen, Karl; Grottland, Havar; Flaten, Magne Arve

    2001-01-01

    Assessment of visual acuity, using Teller Acuity Cards, was combined with observations of behavioral state to indicate central nervous system activation in 24 individuals with mental retardation. Results indicate that forced-choice preferential-looking technique can be used to test visual acuity in this population unless the participant is drowsy.…

  18. Influence of intraocular lens subsurface nanoglistenings on functional visual acuity

    PubMed Central

    Miyata, Kazunori; Hayashidera, Takeshi; Iida, Masaharu; Takada, Keita; Minami, Keiichiro; Oshika, Tetsuro

    2017-01-01

    To investigate the influence of intraocular lens subsurface nanoglistenings (SSNGs) on functional visual acuity (FVA), thirty-nine eyes of 29 patients were examined in this study. The SSNG group comprised 19 eyes of 14 patients (75.7± 5.4 years, mean ± standard deviation), and the control group comprised 20 eyes of 15 patients (73.6 ± 6.5 years). The SSNGs were diagnosed on the basis of the typical whitish IOL appearance upon slit-lamp examination and results of densitometry regarding surface light scattering using Scheimpflug images. The FVA measurement system (AS-28; Kowa, Aichi, Japan) was used to examine changes in continuous visual acuity (VA) over time, and visual function parameters such as FVA, visual maintenance ratio (VMR), maximum VA, minimum VA, standard deviation of VA, and number of blinks were assessed. The results were compared between the SSNG and control groups, and correlations of FVA parameters with the intensity of surface light scattering, time after surgery, and age were also evaluated. There were significant differences in VMR (P = 0.035) and standard deviation of VAs (P = 0.031) between the two groups, although no significant differences were found in baseline VA, FVA, maximum VA, minimum VA, and number of blinks. None of the FVA parameters showed any significant correlations with the intensity of surface light scattering, time after surgery, or age. There is a possibility that VA is unstable during a continuous gazing task in patients with SSNGs. PMID:28328997

  19. Changes in brain morphology in albinism reflect reduced visual acuity.

    PubMed

    Bridge, Holly; von dem Hagen, Elisabeth A H; Davies, George; Chambers, Claire; Gouws, Andre; Hoffmann, Michael; Morland, Antony B

    2014-07-01

    Albinism, in humans and many animal species, has a major impact on the visual system, leading to reduced acuity, lack of binocular function and nystagmus. In addition to the lack of a foveal pit, there is a disruption to the routing of the nerve fibers crossing at the optic chiasm, resulting in excessive crossing of fibers to the contralateral hemisphere. However, very little is known about the effect of this misrouting on the structure of the post-chiasmatic visual pathway, and the occipital lobes in particular. Whole-brain analyses of cortical thickness in a large cohort of subjects with albinism showed an increase in cortical thickness, relative to control subjects, particularly in posterior V1, corresponding to the foveal representation. Furthermore, mean cortical thickness across entire V1 was significantly greater in these subjects compared to controls and negatively correlated with visual acuity in albinism. Additionally, the group with albinism showed decreased gyrification in the left ventral occipital lobe. While the increase in cortical thickness in V1, also found in congenitally blind subjects, has been interpreted to reflect a lack of pruning, the decreased gyrification in the ventral extrastriate cortex may reflect the reduced input to the foveal regions of the ventral visual stream.

  20. Theoretical and applied aspects of night vision goggle resolution and visual acuity assessment

    NASA Astrophysics Data System (ADS)

    Task, H. Lee; Pinkus, Alan R.

    2007-04-01

    The image quality of night vision goggles is often expressed in terms of visual acuity, resolution or modulation transfer function. The primary reason for providing a measure of image quality is the underlying assumption that the image quality metric correlates with the level of visual performance that one could expect when using the device, for example, target detection or target recognition performance. This paper provides a theoretical analysis of the relationships between these three image quality metrics: visual acuity, resolution and modulation transfer function. Results from laboratory and field studies were used to relate these metrics to visual performance. These results can also be applied to non-image intensifier based imaging systems such as a helmet-mounted display coupled to an imaging sensor.

  1. Improving Visual Acuity of Myopes through Operant Training: The Evaluation of Psychological and Physiological Mechanisms Facilitating Acuity Enhancement

    DTIC Science & Technology

    1988-12-01

    at far distances. High degrees of myopia are often accompanied by damage to the eye’s fundus and, when extreme, cannot be fully compensated by...refractively measured myopia . He attributed the improvement to experience in correct interpretation of a blurred visual image . Gibson (1953) proposed that...acuity is an alterable process. If acuity can be enhanced, it could benefit some of the nearly one billion individuals who have myopia or

  2. Recovery of visual acuity following the repair of pseudophakic retinal detachment.

    PubMed Central

    Isernhagen, R D; Wilkinson, C P

    1988-01-01

    Postoperative visual acuities were evaluated in a series of 100 pseudophakic eyes in which rhegmatogenous retinal detachments involved the macula and in which reattachment surgery was successful. Preoperative visual acuity and duration of macular detachment were directly and indirectly related to visual outcome, respectively. Eyes in which extracapsular surgery had been followed by posterior chamber lens implantation had significantly better postoperative visual acuities than cases in which older iris-fixation IOLs were placed following intracapsular procedures. PMID:2979019

  3. High and Low Contrast Visual Acuity Are Not Affected in Amyotrophic Lateral Sclerosis.

    PubMed

    Moss, Heather E; Samelson, Monica; Mohan, Girish; Jiang, Qin Li

    2016-01-01

    The afferent visual system may be affected by neuro-degeneration in amyotrophic lateral sclerosis (ALS) based on observations of visual function impairment and retinal inclusions on histopathology in ALS patients. To test the hypothesis that visual acuity is impaired in ALS, we compared three measures of visual acuity in ALS patients (n = 25) attending a multidisciplinary ALS clinic and age matched control subjects (n = 25). Bilateral monocular and binocular visual acuities were assessed using high contrast (black letters on white background) and low contrast (2.5%, 1.25% grey letters on white background) visual acuity charts under controlled lighting conditions following refraction. Binocular summation was calculated as the difference between binocular and best monocular acuity scores. There were no associations between binocular or monocular high contrast visual acuity or low contrast visual acuity and amyotrophic lateral sclerosis diagnosis (generalized estimating equation models accounting for age). Binocular summation was similar in both amyotrophic lateral sclerosis and control subjects. There was a small magnitude association between increased duration of ALS symptoms and reduced 1.25% low contrast visual acuity. This study does not confirm prior observations of impaired visual acuity in patients with amyotrophic lateral sclerosis and does not support this particular measure of visual function for use in broad scale assessment of visual pathway involvement in ALS patients.

  4. High and Low Contrast Visual Acuity Are Not Affected in Amyotrophic Lateral Sclerosis

    PubMed Central

    Samelson, Monica; Mohan, Girish; Jiang, Qin Li

    2016-01-01

    The afferent visual system may be affected by neuro-degeneration in amyotrophic lateral sclerosis (ALS) based on observations of visual function impairment and retinal inclusions on histopathology in ALS patients. To test the hypothesis that visual acuity is impaired in ALS, we compared three measures of visual acuity in ALS patients (n = 25) attending a multidisciplinary ALS clinic and age matched control subjects (n = 25). Bilateral monocular and binocular visual acuities were assessed using high contrast (black letters on white background) and low contrast (2.5%, 1.25% grey letters on white background) visual acuity charts under controlled lighting conditions following refraction. Binocular summation was calculated as the difference between binocular and best monocular acuity scores. There were no associations between binocular or monocular high contrast visual acuity or low contrast visual acuity and amyotrophic lateral sclerosis diagnosis (generalized estimating equation models accounting for age). Binocular summation was similar in both amyotrophic lateral sclerosis and control subjects. There was a small magnitude association between increased duration of ALS symptoms and reduced 1.25% low contrast visual acuity. This study does not confirm prior observations of impaired visual acuity in patients with amyotrophic lateral sclerosis and does not support this particular measure of visual function for use in broad scale assessment of visual pathway involvement in ALS patients. PMID:28033389

  5. Distinct eye movement patterns enhance dynamic visual acuity

    PubMed Central

    Palidis, Dimitrios J.; Wyder-Hodge, Pearson A.; Fooken, Jolande; Spering, Miriam

    2017-01-01

    Dynamic visual acuity (DVA) is the ability to resolve fine spatial detail in dynamic objects during head fixation, or in static objects during head or body rotation. This ability is important for many activities such as ball sports, and a close relation has been shown between DVA and sports expertise. DVA tasks involve eye movements, yet, it is unclear which aspects of eye movements contribute to successful performance. Here we examined the relation between DVA and the kinematics of smooth pursuit and saccadic eye movements in a cohort of 23 varsity baseball players. In a computerized dynamic-object DVA test, observers reported the location of the gap in a small Landolt-C ring moving at various speeds while eye movements were recorded. Smooth pursuit kinematics—eye latency, acceleration, velocity gain, position error—and the direction and amplitude of saccadic eye movements were linked to perceptual performance. Results reveal that distinct eye movement patterns—minimizing eye position error, tracking smoothly, and inhibiting reverse saccades—were related to dynamic visual acuity. The close link between eye movement quality and DVA performance has important implications for the development of perceptual training programs to improve DVA. PMID:28187157

  6. Visual Vestibular Interaction in the Dynamic Visual Acuity Test during Voluntary Head Rotation

    NASA Technical Reports Server (NTRS)

    Lee, Moo Hoon; Durnford, Simon; Crowley, John; Rupert, Angus

    1996-01-01

    Although intact vestibular function is essential in maintaining spatial orientation, no good screening tests of vestibular function are available to the aviation community. High frequency voluntary head rotation was selected as a vestibular stimulus to isolate the vestibulo-ocular reflex (VOR) from visual influence. A dynamic visual acuity test that incorporates voluntary head rotation was evaluated as a potential vestibular function screening tool. Twenty-seven normal subjects performed voluntary sinusoidal head rotation at frequencies from 0.7-4.0 Hz under three different visual conditions: visually-enhanced VOR, normal VOR, and visually suppressed VOR. Standardized Baily-Lovie chart letters were presented on a computer monitor in front of the subject, who then was asked to read the letters while rotating his head horizontally. The electro-oculogram and dynamic visual acuity score were recorded and analyzed. There were no significant differences in gain or phase shift among three visual conditions in the frequency range of 2.8 to 4.0 Hz. The dynamic visual acuity score shifted less than 0.3 logMAR at frequencies under 2.0 Hz. The dynamic visual acuity test at frequencies a round 2.0 Hz can be recommended for evaluating vestibular function.

  7. Visual acuity in an opportunistic raptor, the chimango caracara (Milvago chimango).

    PubMed

    Potier, Simon; Bonadonna, Francesco; Kelber, Almut; Duriez, Olivier

    2016-04-01

    Raptors are always considered to have an extraordinary resolving power of their eyes (high visual acuity). Nevertheless, raptors differ in their diet and foraging tactics, which could lead to large differences in visual acuity. The visual acuity of an opportunist bird of prey, the Chimango caracara (Mivalgo chimango) was estimated by operant conditioning. Three birds were trained to discriminate two stimuli, a positive grey uniform pattern and a negative grating pattern stimulus. The visual acuity range from 15.08 to 39.83 cycles/degrees. When compared to other birds, they have a higher visual acuity than non-raptorial birds, but they have the lowest visual acuity found in bird of prey so far. We discuss this result in the context of the ecology of the bird, with special focus on it is foraging tactic.

  8. Amblyopia and visual acuity in children with Down's syndrome

    PubMed Central

    Tsiaras, W.; Pueschel, S.; Keller, C.; Curran, R.; Giesswein, S.

    1999-01-01

    BACKGROUND/AIMS—Amblyopia in people with Down's syndrome has not been well investigated. This study was designed to determine the prevalence and associated conditions of amblyopia in a group of home reared children with Down's syndrome.
METHODS—All children in the study group underwent an evaluation of visual acuity. In addition, previous ophthalmological records were reviewed, and a subgroup of children was examined. For the purposes of this study, amblyopia was defined quantitatively as a difference of two Snellen acuity lines between eyes or if unilateral central steady maintained (CSM) vision and a clear fixation preference was observed. A high refractive error was defined as a spherical equivalent more than 3 dioptres and astigmatism more than 1.75 dioptres. Anisometropia was defined as a difference of at least 1.5 dioptres of sphere and/or 1.0 dioptre of cylinder between eyes. 68 children with Down's syndrome between the ages of 5 and 19 years were enrolled in the final study group.
RESULTS—Amblyopia was observed in 15 (22%) of 68 patients. An additional 16 (24%) patients had bilateral vision less than 20/50. Strabismus, high refractive errors, and anisometropia were the conditions most commonly associated with decreased vision and amblyopia
CONCLUSION—This study suggests that the prevalence of amblyopia is higher than previously reported. Fully 46% of these children with Down's syndrome had evidence of substantial visual deficits. These patients may be at higher risk for visual impairment and should be carefully examined for ophthalmological problems.

 PMID:10502568

  9. The Relationship between OCT-measured Central Retinal Thickness and Visual Acuity in Diabetic Macular Edema

    PubMed Central

    2008-01-01

    Objective To compare optical coherence tomography (OCT)-measured retinal thickness and visual acuity in eyes with diabetic macular edema (DME) both before and after macular laser photocoagulation. Design Cross-sectional and longitudinal study. Participants 210 subjects (251 eyes) with DME enrolled in a randomized clinical trial of laser techniques. Methods Retinal thickness was measured with OCT and visual acuity was measured with the electronic-ETDRS procedure. Main Outcome Measures OCT-measured center point thickness and visual acuity Results The correlation coefficients for visual acuity versus OCT center point thickness were 0.52 at baseline and 0.49, 0.36, and 0.38 at 3.5, 8, and 12 months post-laser photocoagulation. The slope of the best fit line to the baseline data was approximately 4.4 letters (95% C.I.: 3.5, 5.3) better visual acuity for every 100 microns decrease in center point thickness at baseline with no important difference at follow-up visits. Approximately one-third of the variation in visual acuity could be predicted by a linear regression model that incorporated OCT center point thickness, age, hemoglobin A1C, and severity of fluorescein leakage in the center and inner subfields. The correlation between change in visual acuity and change in OCT center point thickening 3.5 months after laser treatment was 0.44 with no important difference at the other follow-up times. A subset of eyes showed paradoxical improvements in visual acuity with increased center point thickening (7–17% at the three time points) or paradoxical worsening of visual acuity with a decrease in center point thickening (18%–26% at the three time points). Conclusions There is modest correlation between OCT-measured center point thickness and visual acuity, and modest correlation of changes in retinal thickening and visual acuity following focal laser treatment for DME. However, a wide range of visual acuity may be observed for a given degree of retinal edema and paradoxical

  10. Validation of the Total Visual Acuity Extraction Algorithm (TOVA) for Automated Extraction of Visual Acuity Data From Free Text, Unstructured Clinical Records

    PubMed Central

    Baughman, Douglas M.; Su, Grace L.; Tsui, Irena; Lee, Cecilia S.; Lee, Aaron Y.

    2017-01-01

    Purpose With increasing volumes of electronic health record data, algorithm-driven extraction may aid manual extraction. Visual acuity often is extracted manually in vision research. The total visual acuity extraction algorithm (TOVA) is presented and validated for automated extraction of visual acuity from free text, unstructured clinical notes. Methods Consecutive inpatient ophthalmology notes over an 8-year period from the University of Washington healthcare system in Seattle, WA were used for validation of TOVA. The total visual acuity extraction algorithm applied natural language processing to recognize Snellen visual acuity in free text notes and assign laterality. The best corrected measurement was determined for each eye and converted to logMAR. The algorithm was validated against manual extraction of a subset of notes. Results A total of 6266 clinical records were obtained giving 12,452 data points. In a subset of 644 validated notes, comparison of manually extracted data versus TOVA output showed 95% concordance. Interrater reliability testing gave κ statistics of 0.94 (95% confidence interval [CI], 0.89–0.99), 0.96 (95% CI, 0.94–0.98), 0.95 (95% CI, 0.92–0.98), and 0.94 (95% CI, 0.90–0.98) for acuity numerators, denominators, adjustments, and signs, respectively. Pearson correlation coefficient was 0.983. Linear regression showed an R2 of 0.966 (P < 0.0001). Conclusions The total visual acuity extraction algorithm is a novel tool for extraction of visual acuity from free text, unstructured clinical notes and provides an open source method of data extraction. Translational Relevance Automated visual acuity extraction through natural language processing can be a valuable tool for data extraction from free text ophthalmology notes. PMID:28299240

  11. Restoring Visual Acuity in Dynamic Conditions with a Vestibular Implant

    PubMed Central

    Guinand, Nils; Van de Berg, Raymond; Cavuscens, Samuel; Stokroos, Robert; Ranieri, Maurizio; Pelizzone, Marco; Kingma, Herman; Guyot, Jean-Philippe; Pérez Fornos, Angélica

    2016-01-01

    Vestibular implants are devices designed to rehabilitate patients with a bilateral vestibular loss (BVL). These patients lack a properly functioning vestibulo-ocular reflex (VOR), which impairs gaze stabilization abilities and results in an abnormal loss of visual acuity (VA) in dynamic situations (i.e., severely limiting the patient's ability to read signs or recognize faces while walking). We previously demonstrated that the VOR can be artificially restored in a group of BVL patients fitted with a prototype vestibular implant. This study was designed to investigate whether these promising results could be translated to a close-to-reality task, significantly improving VA abilities while walking. Six BVL patients previously implanted with a vestibular implant prototype participated in the experiments. VA was determined using Sloan letters displayed on a computer screen, in four conditions: (1) with the patient standing still without moving (static), (2) while the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned off (systemOFF), (3) while the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned on providing coherent motion information (systemONmotion), and (4) a “placebo” condition where the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned on providing reversed motion information (systemONsham). The analysis (one-way repeated measures analysis of variance) revealed a statistically significant effect of the test condition [F(3, 12) = 30.5, p < 0.001]. Significant decreases in VA were observed with the systemOFF condition when compared to the static condition (Tukey post-hoc p < 0.001). When the vestibular implant was turned on, delivering pertinent motion information (systemONmotion) the VA improved to close to normal values. The improvement disappeared in the placebo condition (systemONsham) and VA-values also dropped

  12. Dynamic Visual Acuity and Landing Sickness in Crewmembers Returning from Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.J.F; Peters, B.T.; Reschke, M. F.

    2016-01-01

    Long-term exposure to microgravity causes sensorimotor adaptations that result in functional deficits upon returning to a gravitational environment. At landing the vestibular system and the central nervous system, responsible for coordinating head and eye movements, are adapted to microgravity and must re-adapt to the gravitational environment. This re-adaptation causes decrements in gaze control and dynamic visual acuity, with astronauts reporting oscillopsia and blurred vision. Dynamic visual acuity (DVA) is assessed using an oscillating chair developed in the Neuroscience Laboratory at JSC. This chair is lightweight and easily portable for quick deployment in the field. The base of the chair is spring-loaded and allows for manual oscillation of the subject. Using a metronome, the chair is vertically oscillated plus or minus 2 cm at 2 Hz by an operator, to simulate walking. While the subject is being oscillated, they are asked to discern the direction of Landolt-C optotypes of varying sizes and record their direction using a gamepad. The visual acuity thresholds are determined using an algorithm that alters the size of the optotype based on the previous response of the subject using a forced-choice best parameter estimation that is able to rapidly converge on the threshold value. Visual acuity thresholds were determined both for static (seated) and dynamic (oscillating) conditions. Dynamic visual acuity is defined as the difference between the dynamic and static conditions. Dynamic visual acuity measures will be taken prior to flight (typically L-180, L-90, and L-60) and up to eight times after landing, including up to 3 times on R plus 0. Follow up measurements will be taken at R plus 1 (approximately 36 hours after landing). Long-duration International Space Station crewmembers will be tested once at the refueling stop in Europe and once again upon return to Johnson Space Center. In addition to DVA, subjective ratings of motion sickness will be recorded

  13. Visual Function and Visual Acuity in an Urban Adult Population.

    ERIC Educational Resources Information Center

    Katz, J.; Tielsch, J. M.

    1996-01-01

    A survey of 6,850 adults age 40 or over concerning the effects of poor vision found that difficulties with reading or other near-vision activities were the most common complaint. One-fourth reported limitations in activities because of poor vision. Factors associated with loss of visual function were general health status, educational level, and…

  14. Sensitivity of The Dynamic Visual Acuity Test To Sensorimotor Change

    NASA Technical Reports Server (NTRS)

    Cohen, Helen; Bloomberg, Jacob; Elizalde, Elizabeth; Fregia, Melody

    1999-01-01

    Post-flight astronauts, acutely post-vestibular nerve section patients, and patients with severe chronic bilateral vestibular deficits have oscillopsia caused by reduced vestibulocular reflex gains and decreased postural stability. Therefore, as previous work has shown, a test of dynamic visual acuity (DVA), in which the subject must read numbers from a computer screen while standing still or walking in place provides a composite measure of sensorimotor integration. This measure may be useful for determining the level of recovery, post-flight, post-operatively, or after vestibular rehabilitation. To determine the sensitivity of DVA to change in impaired populations we have tested patients with acoustic neuromas before and during the first post-operative week after resection of the tumors, and with bilaterally labyrinthine deficient subjects before and after six weeks of balance rehabilitation therapy.

  15. Evaluation of the degree of turbidity of cataract lens and its correlation with retinal visual acuity

    NASA Astrophysics Data System (ADS)

    Akchurin, Garif G.; Bakutkin, Valery V.; Zimnyakov, Dmitry A.; Radchenko, Elena Y.; Tuchin, Valery V.; Akchurin, Alexander G.

    1999-06-01

    Experimental in vitro studies of speckle-modulated laser field arising after transmission through different type of human cataractous lenses are presented. Computer analysis of digital imaging has allowed to determinate the degree of destruction of spatial coherence scattered laser beam and the angle of resolution of the retina using Retinal Analyzer of Vision (AROL-1) in diagnosis of cataract. Measurement of retinal visual acuity (RVA) in 135 patient with different types of cataract (senile, complicated, posterior capsular) before and after cataract extraction and also in vitro measurement of RVA with extracted cataractal lenses has shown that laser retinometer can be used for evaluating visual acuity within 0.3 - 1, practically for all types of cataracts.

  16. Photovoltaic restoration of sight with high visual acuity in rats with retinal degeneration

    NASA Astrophysics Data System (ADS)

    Palanker, D.; Goetz, G.; Lorach, H.; Mandel, Y.; Smith, R.; Boinagrov, D.; Lei, X.; Kamins, T.; Harris, J.; Mathieson, K.; Sher, A.

    2015-03-01

    Patients with retinal degeneration lose sight due to gradual demise of photoreceptors. Electrical stimulation of the surviving retinal neurons provides an alternative route for delivery of visual information. Subretinal photovoltaic arrays with 70μm pixels were used to convert pulsed near-IR light (880-915nm) into pulsed current to stimulate the nearby inner retinal neurons. Network-mediated responses of the retinal ganglion cells (RGCs) could be modulated by pulse width (1-20ms) and peak irradiance (0.5-10 mW/mm2). Similarly to normal vision, retinal response to prosthetic stimulation exhibited flicker fusion at high frequencies, adaptation to static images, and non-linear spatial summation. Spatial resolution was assessed in-vitro and in-vivo using alternating gratings with variable stripe width, projected with rapidly pulsed illumination (20-40Hz). In-vitro, average size of the electrical receptive fields in normal retina was 248+/-59μm - similar to their visible light RF size: 249+/-44μm. RGCs responded to grating stripes down to 67μm using photovoltaic stimulation in degenerate rat retina, and 28μm with visible light in normal retina. In-vivo, visual acuity in normally-sighted controls was 29+/-5μm/stripe, vs. 63+/-4μm/stripe in rats with subretinal photovoltaic arrays, corresponding to 20/250 acuity in human eye. With the enhanced acuity provided by eye movements and perceptual learning in human patients, visual acuity might exceed the 20/200 threshold of legal blindness. Ease of implantation and tiling of these wireless arrays to cover a large visual field, combined with their high resolution opens the door to highly functional restoration of sight.

  17. Visual Acuity of Radiologists: The Important but Forgotten Component of the Radiological Process.

    ERIC Educational Resources Information Center

    Good, Barbara C.

    This paper reports on a study of visual acuity among radiologists. Twenty-eight radiologists had their visual acuity tested by an optometrist. One week later, 70 medical school faculty radiologists were asked to respond to a printed questionnaire that elicited information about: (1) the date of the respondent's immediately previous examination;…

  18. Comparison of Dynamic Visual Acuity between Water Polo Players and Sedentary Students

    ERIC Educational Resources Information Center

    Quevedo-Junyent, Lluisa; Aznar-Casanova, Jose Antonio; Merindano-Encina, Dolores; Cardona, Genis; Sole-Forto, Joan

    2011-01-01

    In this study, we examined differences in dynamic visual acuity between elite and subelite water polo players and sedentary students. To measure dynamic visual acuity binocularly, we asked participants to indicate the orientation of a broken ring, similar to the Landolt C, which increased in size as it moved across a computer screen. Two different…

  19. 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".

  20. Believing is seeing: using mindlessness (mindfully) to improve visual acuity.

    PubMed

    Langer, Ellen; Djikic, Maja; Pirson, Michael; Madenci, Arin; Donohue, Rebecca

    2010-05-01

    These experiments show that vision can be improved by manipulating mind-sets. In Study 1, participants were primed with the mind-set that pilots have excellent vision. Vision improved for participants who experientially became pilots (by flying a realistic flight simulator) compared with control participants (who performed the same task in an ostensibly broken flight simulator). Participants in an eye-exercise condition (primed with the mind-set that improvement occurs with practice) and a motivation condition (primed with the mind-set "try and you will succeed") demonstrated visual improvement relative to the control group. In Study 2, participants were primed with the mind-set that athletes have better vision than nonathletes. Controlling for arousal, doing jumping jacks resulted in greater visual acuity than skipping (perceived to be a less athletic activity than jumping jacks). Study 3 took advantage of the mind-set primed by the traditional eye chart: Because letters get progressively smaller on successive lines, people expect that they will be able to read the first few lines only. When participants viewed a reversed chart and a shifted chart, they were able to see letters they could not see before. Thus, mind-set manipulation can counteract physiological limits imposed on vision.

  1. Night vision in barn owls: visual acuity and contrast sensitivity under dark adaptation.

    PubMed

    Orlowski, Julius; Harmening, Wolf; Wagner, Hermann

    2012-12-06

    Barn owls are effective nocturnal predators. We tested their visual performance at low light levels and determined visual acuity and contrast sensitivity of three barn owls by their behavior at stimulus luminances ranging from photopic to fully scotopic levels (23.5 to 1.5 × 10⁻⁶). Contrast sensitivity and visual acuity decreased only slightly from photopic to scotopic conditions. Peak grating acuity was at mesopic (4 × 10⁻² cd/m²) conditions. Barn owls retained a quarter of their maximal acuity when luminance decreased by 5.5 log units. We argue that the visual system of barn owls is designed to yield as much visual acuity under low light conditions as possible, thereby sacrificing resolution at photopic conditions.

  2. Visual acuity and quality of life in dry eye disease: Proceedings of the OCEAN group meeting.

    PubMed

    Benítez-Del-Castillo, José; Labetoulle, Marc; Baudouin, Christophe; Rolando, Maurizio; Akova, Yonca A; Aragona, Pasquale; Geerling, Gerd; Merayo-Lloves, Jesús; Messmer, Elisabeth M; Boboridis, Kostas

    2017-04-01

    Dry eye disease (DED) results in tear film instability and hyperosmolarity, inflammation of the ocular surface and, ultimately, visual disturbance that can significantly impact a patient's quality of life. The effects on visual acuity result in difficulties with driving, reading and computer use and negatively impact psychological health. These effects also extend to the workplace, with a loss of productivity and quality of work causing substantial economic losses. The effects of DED and the impact on vision experienced by patients may not be given sufficient importance by ophthalmologists. Functional visual acuity (FVA) is a measure of visual acuity after sustained eye opening without blinking for at least 10 s and mimics the sustained visual acuity of daily life. Measuring dynamic FVA allows the detection of impaired visual function in patients with DED who may display normal conventional visual acuity. There are currently several tests and methods that can be used to measure dynamic visual function: the SSC-350 FVA measurement system, assessment of best-corrected visual acuity decay using the interblink visual acuity decay test, serial measurements of ocular and corneal higher order aberrations, and measurement of dynamic vision quality using the Optical Quality Analysis System. Although the equipment for these methods may be too large or unaffordable for use in clinical practice, FVA testing is an important assessment for DED.

  3. Acuity-independent effects of visual deprivation on human visual cortex.

    PubMed

    Hou, Chuan; Pettet, Mark W; Norcia, Anthony M

    2014-07-29

    Visual development depends on sensory input during an early developmental critical period. Deviation of the pointing direction of the two eyes (strabismus) or chronic optical blur (anisometropia) separately and together can disrupt the formation of normal binocular interactions and the development of spatial processing, leading to a loss of stereopsis and visual acuity known as amblyopia. To shed new light on how these two different forms of visual deprivation affect the development of visual cortex, we used event-related potentials (ERPs) to study the temporal evolution of visual responses in patients who had experienced either strabismus or anisometropia early in life. To make a specific statement about the locus of deprivation effects, we took advantage of a stimulation paradigm in which we could measure deprivation effects that arise either before or after a configuration-specific response to illusory contours (ICs). Extraction of ICs is known to first occur in extrastriate visual areas. Our ERP measurements indicate that deprivation via strabismus affects both the early part of the evoked response that occurs before ICs are formed as well as the later IC-selective response. Importantly, these effects are found in the normal-acuity nonamblyopic eyes of strabismic amblyopes and in both eyes of strabismic patients without amblyopia. The nonamblyopic eyes of anisometropic amblyopes, by contrast, are normal. Our results indicate that beyond the well-known effects of strabismus on the development of normal binocularity, it also affects the early stages of monocular feature processing in an acuity-independent fashion.

  4. The Eye Phone Study: reliability and accuracy of assessing Snellen visual acuity using smartphone technology

    PubMed Central

    Perera, C; Chakrabarti, R; Islam, F M A; Crowston, J

    2015-01-01

    Purpose Smartphone-based Snellen visual acuity charts has become popularized; however, their accuracy has not been established. This study aimed to evaluate the equivalence of a smartphone-based visual acuity chart with a standard 6-m Snellen visual acuity (6SVA) chart. Methods First, a review of available Snellen chart applications on iPhone was performed to determine the most accurate application based on optotype size. Subsequently, a prospective comparative study was performed by measuring conventional 6SVA and then iPhone visual acuity using the ‘Snellen' application on an Apple iPhone 4. Results Eleven applications were identified, with accuracy of optotype size ranging from 4.4–39.9%. Eighty-eight patients from general medical and surgical wards in a tertiary hospital took part in the second part of the study. The mean difference in logMAR visual acuity between the two charts was 0.02 logMAR (95% limit of agreement −0.332, 0.372 logMAR). The largest mean difference in logMAR acuity was noted in the subgroup of patients with 6SVA worse than 6/18 (n=5), who had a mean difference of two Snellen visual acuity lines between the charts (0.276 logMAR). Conclusion We did not identify a Snellen visual acuity app at the time of study, which could predict a patients standard Snellen visual acuity within one line. There was considerable variability in the optotype accuracy of apps. Further validation is required for assessment of acuity in patients with severe vision impairment. PMID:25931170

  5. Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs.

    PubMed

    Hairol, Mohd Izzuddin; Formankiewicz, Monika A; Waugh, Sarah J

    2013-05-01

    Contrast-modulated (CM) stimuli are processed by spatial mechanisms that operate at larger spatial scales than those processing luminance-modulated (LM) stimuli and may be more prone to deficits in developing, amblyopic, and aging visual systems. Understanding neural mechanisms of contour interaction or crowding will help in detecting disorders of spatial vision. In this study, contour interaction effects on visual acuity for LM and CM C and bar stimuli are assessed in normal foveal vision. In Experiment 1, visual acuity is measured for all-LM and all-CM stimuli, at ~3.5× above their respective modulation thresholds. In Experiment 2, visual acuity is measured for Cs and bars of different type (LM C with CM bars and vice versa). Visual acuity is degraded for CM compared with LM Cs (0.46 ± 0.04 logMAR vs. 0.18 ± 0.04 logMAR). With nearby bars, CM acuity is degraded further (0.23 ± 0.01 logMAR or ~2 lines on an acuity chart), significantly more than LM acuity (0.11 ± 0.01 logMAR, ~1 line). Contour interaction for CM stimuli extends over greater distances (arcmin) than it does for LM stimuli, but extents are similar with respect to acuities (~3.5× the C gap width). Contour interaction is evident when the Cs and bars are defined differently: it is stronger when an LM C is flanked by CM bars (0.17 ± 0.03 logMAR) than when a CM C is flanked by LM bars (0.08 ± 0.02 logMAR). Our results suggest that contour interaction for foveally viewed acuity stimuli involves feature integration, such that the outputs of receptive fields representing Cs and bars are combined. Contour interaction operates at LM and CM representational stages, it can occur across stage, and it is enhanced at the CM stage. Greater contour interaction for CM Cs and bars could hold value for visual acuity testing and earlier diagnosis of conditions for which crowding is important, such as in amblyopia.

  6. The relationship between visual acuity and functioning and well-being among diabetics.

    PubMed

    Lee, P P; Whitcup, S M; Hays, R D; Spritzer, K; Javitt, J

    1995-08-01

    Given the enormous recent interest in functional capabilities related to vision, the goal of this study was to examine the relationship of standard clinical measures of vision (e.g. Snellen acuity) to functioning and well-being. The association between Snellen visual acuity, Amsler grid distortion and presence of diabetic retinopathy with self-reported functioning and well-being (SF-36) were examined in a sample of 327 diabetics from the Medical Outcomes Study (MOS). There was little or no correlation between Snellen visual acuity, Amsler grid distortion or diabetic retinopathy and functioning and well-being (i.e. SF-36 scales). Maximum product-moment correlation was 0.15 with worst eye visual acuity, 0.13 with best eye visual acuity, 0.08 with presence of retinopathy, and 0.10 with Amsler grid distortion. Analysis of variance revealed that visual acuity (both best and worst eye) was statistically related only to the physical function scale; no other exam measure was related to any other SF-36 scale score. Snellen visual acuity, Amsler distortion and diabetic retinopathy correlate weakly with patient self-reported functioning and well-being. Thus, the information provided by functioning and well-being measures is complementary to that of standard clinical measures of visual ability.

  7. Visual acuity loss and OCT changes as initial signs of leukaemia

    PubMed Central

    Ortiz, Jose M; Ruiz-Moreno, Jose M; Pozo-Martos, Paola; Montero, Javier A

    2010-01-01

    AIM To report two cases where decreased visual acuity was the first symptom of leukaemia and optical coherence tomography (OCT) allowed identification and localization of the retinal lesions. METHODS Retrospective, interventional, case reports. RESULTS One case of lymphoblastic acute leukaemia and chronic lymphoid leukaemia were diagnosed following decreased visual acuity. OCT showed macular serous detachment in the first case. The second case presented hypo fluorescent retinal infiltrates which appeared as hyper reflective lesions by OCT. Retinal changes disappeared and visual acuity was recovered following complete remission of the neoplasm. CONCLUSION OCT is a valuable, non invasive diagnostic tool permitting detection, localization and follow-up of ocular dissemination of neoplasms. PMID:22553573

  8. Age Differences in the Relationship between Visual Movement Imagery and Performance on Kinesthetic Acuity Tests.

    ERIC Educational Resources Information Center

    Livesey, David J.

    2002-01-01

    Investigated the relationship between Vividness of Movement Imagery Questionnaire scores and kinesthetic acuity--the sense of body position and movement--among 10- and 14-year-olds. Found that in the older group, those with high levels of visual movement imagery performed better on measures of kinesthetic acuity; no such effect was found for…

  9. Spatial visual acuity of the eagle Aquila audax: a behavioural, optical and anatomical investigation.

    PubMed

    Reymond, L

    1985-01-01

    Behavioural acuity of the wedge-tailed eagle was determined across a range of luminance. Maximum acuity is between 132 and 143 c/deg and with decreasing luminance acuity declines sharply. The maximum anatomical resolving power of the eagle's deep fovea was calculated as 140 c/deg. This calculation was based upon ophthalmoscopic measurement of posterior nodal distance and estimates of photoreceptor spacings made from fixed foveal tissue and corrected for shrinkage. Maximum behavioural acuity and anatomical resolving power correspond closely and approach the highest frequency (157 c/deg) transmitted by the minimum pupil diameter of the eye. These findings are discussed with reference to current theories of visual functioning.

  10. Influence of Motion Smear on Visual Acuity in Simulated Infantile Nystagmus

    PubMed Central

    Chung, Susana T. L.; LaFrance, Martin W.; Bedell, Harold E.

    2011-01-01

    Purpose In persons with infantile nystagmus (IN), visual acuity correlates with the duration of the foveation period of the nystagmus waveform, i.e., when the retinal image is on or near the fovea and moves with low velocity. In this study, we asked how acuity is affected by the non-foveating phases of the nystagmus waveform, when the velocity of retinal image motion is substantially higher. Methods Visual acuity was measured in three normal observers for high-contrast, 4-orientation Ts, presented during image motion that simulated either the whole jerk-IN waveform (whole-waveform) or only the foveation periods of the IN waveform (foveation-only). Simulated foveation durations ranged from 20 to 120 ms. For both motion waveforms, we displayed the acuity target for different number of cycles to examine if acuity benefits from multiple presentations of the stimulus. Results As expected, visual acuity improves with longer simulated foveation durations in both the whole-waveform and foveation-only conditions. Acuity is consistently better (by approximately 0.1 logMAR) in the foveation-only than the whole-waveform condition, indicating that the high-velocity image motion during the simulated IN waveform has a detrimental effect. This difference in acuity between the two waveform conditions increases with the number of cycles, apparently because summation occurs across cycles in the foveation-only condition but not in the whole-waveform condition. Conclusions In normal observers, visual acuity in the presence of a simulated nystagmus waveform is limited not only by the duration of the foveation periods, but also by the non-foveating phases of the waveform. However, because persons with IN report little or no motion smear in association with their nystagmus, it remains unclear whether the rapid retinal image motion during the non-foveating phases of the nystagmus waveform generates a similar degradation of visual acuity in IN. PMID:21200353

  11. Visual acuity in ray-finned fishes correlates with eye size and habitat.

    PubMed

    Caves, Eleanor M; Sutton, Tracey T; Johnsen, Sönke

    2017-02-09

    Visual acuity (the ability to resolve spatial detail) is highly variable across fishes. However, little is known about the evolutionary pressures underlying this variation. We reviewed published literature to create an acuity database for 159 species of ray-finned fishes (Actinopterygii). Within a subset of those species for which we had phylogenetic information and anatomically-measured acuity data (n=81), we examined relationships between acuity and both morphological (eye size and body size) and ecological (light level, water turbidity, habitat spatial complexity, and diet) variables. Acuity was significantly correlated with eye size (p<0.05); a weaker correlation with body size occurred via a correlation between eye and body size (p<0.001). Acuity decreased as light level decreased and turbidity increased; however, these decreases resulted from fishes in dark or murky environments having smaller eyes and bodies than those in bright or clear environments. We also found significantly lower acuity in horizon-dominated habitats than in featureless or complex habitats. Higher acuity in featureless habitats is likely due to species having absolutely larger eyes and bodies in that environment, though eye size relative to body size is not significantly different from that in complex environments. Controlling for relative eye size, we found that species in complex environments have even higher acuity than predicted. We found no relationship between visual acuity and diet. Our results show that eye size is a primary factor underlying variation in fish acuity. We additionally show that habitat type is an important ecological factor that correlates with acuity in certain species.

  12. Plasticity of Binocularity and Visual Acuity Are Differentially Limited by Nogo Receptor

    PubMed Central

    Stephany, Céleste-Élise; Chan, Leanne L.H.; Parivash, Sherveen N.; Dorton, Hilary M.; Piechowicz, Mariel

    2014-01-01

    The closure of developmental critical periods consolidates neural circuitry but also limits recovery from early abnormal sensory experience. Degrading vision by one eye throughout a critical period both perturbs ocular dominance (OD) in primary visual cortex and impairs visual acuity permanently. Yet understanding how binocularity and visual acuity interrelate has proven elusive. Here we demonstrate the plasticity of binocularity and acuity are separable and differentially regulated by the neuronal nogo receptor 1 (NgR1). Mice lacking NgR1 display developmental OD plasticity as adults and their visual acuity spontaneously improves after prolonged monocular deprivation. Restricting deletion of NgR1 to either cortical interneurons or a subclass of parvalbumin (PV)-positive interneurons alters intralaminar synaptic connectivity in visual cortex and prevents closure of the critical period for OD plasticity. However, loss of NgR1 in PV neurons does not rescue deficits in acuity induced by chronic visual deprivation. Thus, NgR1 functions with PV interneurons to limit plasticity of binocularity, but its expression is required more extensively within brain circuitry to limit improvement of visual acuity following chronic deprivation. PMID:25164659

  13. A single cohort prospective trial of the immediate effects of spinal manipulation on visual acuity

    PubMed Central

    Athaide, Michelle; Rego, Carol; Budgell, Brian

    2016-01-01

    Introduction: There is no high quality evidence on which to judge the generalizability of isolated reports of improvement in vision following manipulation. The current paucity of research results also precludes the thoughtful design of a controlled, prospective clinical study. Hence, the purpose of the current study was to test the feasibility of conducting a clinical trial of the acute effects of spinal manipulation on visual acuity. Methods: New adult patients presenting to a community based chiropractic clinic were recruited into a single cohort prospective trial to determine the immediate effects of cervical spinal manipulation on visual acuity. Results: The experimental protocol was well accepted by patients and caused minimal or no disruption of the clinic routine. By some measures, chiropractic treatment was accompanied by statistically significant improvements in visual acuity. Discussion: The results of this study indicate that it is quite feasible to conduct a prospective, community based clinical study of the acute effects of spinal manipulation on visual acuity. PMID:27069271

  14. The Effect of Signal-to-Noise Ratio on Visual Acuity Through Night Vision Goggles

    DTIC Science & Technology

    1991-02-01

    subjects in visuLal acuity performance with NVGs, it was concluded that further research should be conducted to examine the correlation between visual...the image intensifier tuho. Tile image intensifier tube is basically a light amplifier that is sensitive over tho spectral region of about 600nm to... excellent means of getting a sensitive measure of visual acuity. 2 Method 2.1 Subje;cts Twelve male volunteers participated in this study. ’he subjects

  15. Electrophysiological Correlates of Vernier Acuity in Human Visual Cortex.

    DTIC Science & Technology

    1984-04-28

    Ia ) VEPs evoked bj vernier offset stimuli couldbe used to estimate 7 LL- psychophysical threshold, b VEP amplitude was affected by interference lines...absolute accuracy. Relative estimate accuracy is judged by the criteria of the estimates being much less than the resolution acuity predicted by anato - mical

  16. A Comparison of Patched HOTV Visual Acuity and Photoscreening

    ERIC Educational Resources Information Center

    Leman, Rachel; Clausen, Michelle M.; Bates, Janice; Stark, Lee; Arnold, Koni K.; Arnold, Robert W.

    2006-01-01

    Early detection of significant vision problems in children is a high priority for pediatricians and school nurses. Routine vision screening is a necessary part of that detection and has traditionally involved acuity charts. However, photoscreening in which "red eye" is elicited to show whether each eye is focusing may outperform routine acuity…

  17. Contrast visual acuity in patients with retinitis pigmentosa assessed by a contrast sensitivity tester

    PubMed Central

    Oishi, Maho; Nakamura, Hajime; Hangai, Masanori; Oishi, Akio; Otani, Atsushi; Yoshimura, Nagahisa

    2012-01-01

    Purpose: To assess contrast visual acuity (CVA) in patients with retinitis pigmentosa (RP) and compare the result with standard visual acuity (VA), retinal thickness, status of inner segment/outer segment junction, and central visual field. Materials and Methods: Thirty-nine eyes of 39 patients with RP and 39 eyes of 39 healthy individuals were studied. To see the difference in CVA between RP patients and normal controls, only subjects with standard VA of 1.0 (20/20) or better were included. This was a cross-sectional study. CVA in various light conditions was measured with CAT-2000 and was compared between patients and controls. CVA of patients was further analyzed for association with other parameters including foveal retinal thickness, outer nuclear layer thickness, the status of inner segment/outer segment junction measured with optical coherence tomography (OCT), and visual field mean deviation (MD) measured with Humphrey field analyzer 10-2 program. Results: CVA impairment was evident in RP patients compared to controls (P < 0.01, in all measurement conditions). Multivariate analysis showed association of logarithm of the minimum angle of resolution (logMAR) with CVAs in several conditions. None of the OCT measurements was associated with CVA. When patients were divided into three groups based on MD, the most advanced group (MD worse than or equal to –20 dB) showed impairment of mesopic CVA (P < 0.05, under mesopic condition of 100% without glare, with glare, and 25% without glare). Conclusion: CVA impairment was confirmed in RP patients, especially in advanced cases. CVA measured with CAT-2000 may be a useful tool for assessing foveal function in RP patients. PMID:23202395

  18. Closed surfaces of constant visual acuity in symmetric dioptric power space.

    PubMed

    Rubin, A; Harris, W F

    2001-10-01

    This paper demonstrates a multivariate approach to understanding the complicated relations of visual acuity to refractive state or ametropia. Other approaches, as previously used, included graphical representations of lines or profiles of iso-oxyopia (Peters, 1961). But one limitation of Peters' method is that cylinder axis was ignored. However, here the relationship between visual acuity and refractive power will be represented by estimated closed surfaces of constant visual acuity in symmetric dioptric power space. At or near the common center (of several closed surfaces, for example) is the refractive compensation. Coming outwards from such a center, the visual acuity drops in all directions in the space. The primary purpose of this paper was to present estimated closed surfaces of constant visual acuity for several eyes. Various procedures were performed on several subjects including measurement of iris aperture diameter, subjective refraction, and autorefraction. Thereafter, an automated phoropter and either Jackson cross-cylinders or spheres were used to influence dioptric blur or defocus in the subjects. The visual stimulus was a computer-generated nondirectional or meridionally independent letter O. Ovoidal surfaces fit the measurements obtained (with Jackson cross-cylinders and spheres) better than ellipsoidal surfaces. The cross-section, in symmetric dioptric power space, at powers with the same nearest equivalent sphere as the refractive compensation is elliptical in many cases and reflects a dependence of visual acuity on cylinder axis. The surfaces differ when powers are changed so that one is moving away from (decompensation surfaces) or toward (accompensation surfaces) the refractive compensation. The multivariate and graphical methods used in this paper probably have implications for the direction of future research in a number of areas involving measures of vision function such as autorefraction, retinoscopy, subjective refraction, and visual

  19. Transcranial direct current stimulation improves visual acuity in amblyopic Long-Evans rats.

    PubMed

    Castaño-Castaño, S; Garcia-Moll, A; Morales-Navas, M; Fernandez, E; Sanchez-Santed, F; Nieto-Escamez, F

    2017-02-15

    Transcranial direct current stimulation (tDCS) has proved to increase brain cortex plasticity and different models of brain damage. In this work, we have analyzed the effects of tDCS in an experimental model of amblyopia using Long-Evans rats. Animals were monocularly deprived between 12 and 75 postnatal days and visual cortex contralateral to the deprived eye was stimulated using anodal tDCS during 8days (20min/day). The effects of tDCS treatment on the visual function were evaluated by using the optomotor reflex of the animals as a measure of visual acuity. Results obtained indicate that monocular occlusion during the critical period lead to a reduction of visual acuity in monocular and binocular conditions. Stimulation with anodal tDCS produced a nearly full recovery in visual acuity of amblyopic animals. However, same stimulation protocol in healthy control animals produced a decrease of binocular visual acuity. These data indicate that tDCS can reverse the effects of monocular deprivation on visual acuity, although it is essential to use this technique in a controlled way due to the possible adverse effects on healthy individuals.

  20. Visual acuity of the honey bee retina and the limits for feature detection

    PubMed Central

    Rigosi, Elisa; Wiederman, Steven D.; O’Carroll, David C.

    2017-01-01

    Visual abilities of the honey bee have been studied for more than 100 years, recently revealing unexpectedly sophisticated cognitive skills rivalling those of vertebrates. However, the physiological limits of the honey bee eye have been largely unaddressed and only studied in an unnatural, dark state. Using a bright display and intracellular recordings, we here systematically investigated the angular sensitivity across the light adapted eye of honey bee foragers. Angular sensitivity is a measure of photoreceptor receptive field size and thus small values indicate higher visual acuity. Our recordings reveal a fronto-ventral acute zone in which angular sensitivity falls below 1.9°, some 30% smaller than previously reported. By measuring receptor noise and responses to moving dark objects, we also obtained direct measures of the smallest features detectable by the retina. In the frontal eye, single photoreceptors respond to objects as small as 0.6° × 0.6°, with >99% reliability. This indicates that honey bee foragers possess significantly better resolution than previously reported or estimated behaviourally, and commonly assumed in modelling of bee acuity. PMID:28383025

  1. Effects of molting on the visual acuity of the blue crab, Callinectes sapidus.

    PubMed

    Baldwin, Jamie; Johnsen, Sönke

    2011-09-15

    In crustaceans with compound eyes, the corneal lens of each facet is part of the exoskeleton and thus shed during molting. Here we used an optomotor assay to evaluate the impact of molting on visual acuity (as measured by the minimum resolvable angle, α(min)) in the female blue crab, Callinectes sapidus. We found that visual acuity decreases substantially in the days prior to molting and is gradually recovered after molting. Four days prior to molting, α(min) was 1.8 deg (N=5), a value approximating the best possible acuity in this species. In the 24 h before ecdysis occurred, α(min) increased to 15.0 deg (N=12), corresponding to an eightfold drop in visual acuity. Within 6 days after molting, α(min) returned to the pre-molting value. Micrographs of C. sapidus eyes showed that a gap between the corneal lens and the crystalline cone first appeared approximately 5 days prior to shedding and increased in width as the process progressed. This separation was likely responsible for the loss of visual acuity observed in behavioral tests. In blue crabs, mating is limited to the period of the female's pubertal molt, and a reduction in acuity during this time may have an effect on the sensory cues used in female mate choice. The results described here may be broadly applicable to all arthropods that molt and have particular importance for crustaceans that molt multiple times in their lifetime or have mating cycles that are paired with molting.

  2. Measuring the Influence of Galilean Loupe System on Near Visual Acuity of Dentists under Simulated Clinical Conditions

    PubMed Central

    Urlic, Iris; Verzak, Željko; Vranic, Dubravka Negovetic

    2016-01-01

    Aim The purpose of this study was to compare near visual acuity of dentists without optical aids (VSC) with near visual acuity of those using the Galilean telescope system (VGA2) with magnification of x 2.5, and the distance of 350 mm in simulated clinical conditions. Methods The study included 46 dentists (visual acuity 1.0 without correction). A visual acuity testing was carried out using a miniaturized Snellen visual acuity chart which was placed in the cavity of molar teeth mounted in a phantom head in simulated clinical conditions. Near visual acuity for the vicinity was examined: 1) without correction at a distance of 300-400 mm (VSC); 2) with Galilean loupes with magnification of x2.5, focal length of 350mm. Results The distributions of near visual acuity recorded using VSC and VGA2, 5 systems were compared by the Wilcoxon Signed Rank test. The results obtained by Wilcoxon Signed Rank test pointed to a statistically significant difference in the distribution of recorded visual acuity between the VSC and VGA2 optical systems (W = - 403.5; p <0.001). Conclusion If using the VGA2, 5 systems, higher values of the near visual acuity were recorded and subsequently compared to near visual acuity without magnifying aids (VSC). PMID:27847397

  3. Quantitative visual psychophysics during the period of European enlightenment. The studies of the astronomer and mathematician Tobias Mayer (1723-1762) on visual acuity and colour perception.

    PubMed

    Grüsser, O J

    1989-02-01

    During the sixth decade of the 18th century, Tobias Mayer, Professor of Astronomy and Applied Mathematics (Economy) at the University of Göttingen, performed two investigations on quantitative visual psychophysics. He deduced a power law for the dependence of visual acuity on the intensity of light by which the stimulus pattern was illuminated. In his measurements he compared visual acuity determined with single black dots and visual acuity measured with gratings or checkerboard patterns; the latter he considered as the "real" measurement of visual acuity. Mayer also developed a three-dimensional hexaedric colour space from the definition of subtractive colour mixtures of three primary pigments (red, yellow, blue). This colour space can be considered as the predecessor of the later colour tables of Ostwald and Munsell. Mayer gave a simple quantitative description of each of the 819 hues in his colour space. Both psychophysical studies developed out of Mayer's interest in practical problems in astronomy and cartography. Mayer's main scientific merits were in the field of astronomy and mathematical geography. His psychophysical studies were performed in the spirit of enlightenment with the a priori assumption that the performance of the human perceptual machinery can be measured quantitatively and that the results are adequately expressed by mathematical rules. Mayer's achievements in the fields of mathematics, physics, astronomy and cartography were recently summarized by the extensive historical research of G.F. Forbes. In the present report a short biographical note precedes the description of Mayer's psychophysical studies.

  4. Out of sight, out of mind? Relations between visual acuity and cognition.

    PubMed

    La Fleur, Claire G; Salthouse, Timothy A

    2014-10-01

    Prior research has established significant relations between measures of sensory ability and cognitive function in adults of different ages, and several explanations for this relation have been proposed. One explanation is that sensory abilities restrict cognitive processing, a second is that cognitive abilities influence assessments of sensory ability, and a third is that both sensory function and cognition are affected by a common, potentially age-based, third factor. These explanations were investigated using mediation and moderation analyses, with near visual acuity as the sensory measure and scores on visual speed tests and auditory memory tests as the cognitive measures. Measures of visual acuity, speed, and memory were obtained from three moderately large samples, two cross-sectional (N = 380, N = 4,779) and one longitudinal (N = 2,258), with participants ranging from 18 to 90 years of age. The visual acuity and cognitive measures had different age trajectories, and the visual acuity-cognition relations were similar in each 5-year age band. The results suggest that the age-related differences and changes in near visual acuity are unlikely to contribute to the age-related differences and changes in speed and memory measures.

  5. Visual Acuity Testing: Feedback Affects Neither Outcome nor Reproducibility, but Leaves Participants Happier

    PubMed Central

    Bach, Michael; Schäfer, Kerstin

    2016-01-01

    Assessment of visual acuity is a well standardized procedure at least for expert opinions and clinical trials. It is often recommended not giving patients feedback on the correctness of their responses. As this viewpoint has not been quantitatively examined so far, we quantitatively assessed possible effects of feedback on visual acuity testing. In 40 normal participants we presented Landolt Cs in 8 orientations using the automated Freiburg Acuity Test (FrACT, acuity threshold was measured with an adaptive staircase procedure. In an ABCDDCBA scheme, trial-by-trial feedback was provided in 2 x 4 conditions: (A) no feedback, (B) acoustic signals indicating correctness, (C)visual indication of correct orientation, and (D) a combination of (B) and (C). After each run the participants judged comfort. Main outcome measures were absolute visual acuity (logMAR), its test-retest agreement (limits of agreement) and participants’ comfort estimates on a 5-step symmetric Likert scale. Feedback influenced acuity outcome significantly (p = 0.02), but with a tiny effect size: 0.02 logMAR poorer acuity for (D) compared to (A), even weaker effects for (B) and (C). Test-retest agreement was high (limits of agreement: ± 1.0 lines) and did not depend on feedback (p>0.5). The comfort ranking clearly differed, by 2 steps on the Likert scale: the condition (A)–no feedback–was on average “slightly uncomfortable”, the other three conditions were “slightly comfortable” (p<0.0001). Feedback affected neither reproducibility nor the acuity outcome to any relevant extent. The participants, however, reported markedly greater comfort with any kind of feedback. We conclude that systematic feedback (as implemented in FrACT) offers nothing but advantages for routine use. PMID:26824693

  6. Is acuity enough? Other considerations in clinical investigations of visual prostheses.

    PubMed

    Lepri, Bernard P

    2009-06-01

    Visual impairing eye diseases are the major frontier facing ophthalmic research today in light of our rapidly aging population. The visual skills necessary for improving the quality of daily function and life are inextricably linked to these impairing diseases. Both research and reimbursement programs are emphasizing outcome-based results. Is improvement in visual acuity alone enough to improve the function and quality of life of visually impaired persons? This perspective summarizes the types of effectiveness endpoints for clinical investigations of visual prostheses that go beyond visual acuity. The clinical investigation of visual prostheses should include visual function, functional vision and quality of life measures. Specifically, they encompass contrast sensitivity, orientation and mobility, activities of daily living and quality of life assessments. The perspective focuses on the design of clinical trials for visual prostheses and the methods of determining effectiveness above and beyond visual acuity that will yield outcomes that are measured by improved function in the visual world and quality of life. The visually impaired population is the primary consideration in this presentation with particular emphases on retinitis pigmentosa and age-related macular degeneration. Clinical trials for visual prostheses cannot be isolated from the need for medical rehabilitation in order to obtain measurements of effectiveness that produce outcomes/evidence-based success. This approach will facilitate improvement in daily function and quality of life of patients with diseases that cause chronic vision impairment.

  7. Bevacizumab injection in patients with age-related macular degeneration associated with poor initial visual acuity.

    PubMed

    El Matri, Leila; Bouraoui, Rym; Chebil, Ahmed; Kort, Fedra; Bouladi, Mejda; Limaiem, Rym; Landoulsi, Hana

    2012-01-01

    Purpose. To evaluate functional and anatomic effects of intravitreal bevacizumab in patients with neovascular AMD and initial low visual acuity. Methods. Retrospective case series of 38 eyes with neovascular AMD and initial visual acuity of 20/200 or less, treated with intravitreal bevacizumab injection. Results. Mean followup was 14.1 months ±  7.1 (range: 5 to 24 months). Mean logMAR vision at baseline was 1.38 logMAR ±  0.33, at 6 months was 1.14 logMAR ±  0.37 (P = 0.001) and at 12 months was 1.22 logMar ±  0.33 (P = 0.004). Mean baseline central retinal thickness was 431 μm ±  159.7 at 6 months was 293.43 μm  ±  122.79 (P = 10(-4)) and at 12 months was 293.1 μm  ±  130 (P = 0.004). Visual acuity improved in both patients with or without prior PDT treatment. Conclusions. Intravitreal bevacizumab injection may increase the chance of visual acuity gain in neovascular AMD even in cases with initial low visual acuity.

  8. Determine the effect of neck muscle fatigue on dynamic visual acuity in healthy young adults

    PubMed Central

    Al Saif, Amer A.; Al Senany, Samira

    2015-01-01

    [Purpose] The aim of this study was to determine whether neck muscle fatigue affects dynamic visual acuity in healthy young participants. [Subjects and Methods] This study was a double-blinded, prospective, randomized, controlled trial. Thirty healthy young subjects (ages 21 to 30 years) participated in the study. Participants were randomly divided into an experimental group (n=15) and a control group (n=15). The experimental group performed an exercise designed to induce neck muscle fatigue and the control group preformed non-fatiguing sham exercises. [Results] There were significant differences in mean dynamic visual acuity between the two groups (0.26±0.11 LogMar versus 0.003±0.02 LogMar). Subjects in the experimental group showed a significant decline in their dynamic visual acuity compared with the control group. Dynamic visual acuity strongly correlated with neck muscle fatigue (r = 0.79). No significant differences in joint position error were observed between the two groups and no significant correlations between joint position error and neck muscle fatigue were observed (r = 0.23). [Conclusion] The results of this study suggest that neck muscle fatigue negatively impacts dynamic visual acuity. Although not statistically significant, cervical spine proprioception as measured by the joint position error in the experimental group was diminished after fatigue. PMID:25642087

  9. Determine the effect of neck muscle fatigue on dynamic visual acuity in healthy young adults.

    PubMed

    Al Saif, Amer A; Al Senany, Samira

    2015-01-01

    [Purpose] The aim of this study was to determine whether neck muscle fatigue affects dynamic visual acuity in healthy young participants. [Subjects and Methods] This study was a double-blinded, prospective, randomized, controlled trial. Thirty healthy young subjects (ages 21 to 30 years) participated in the study. Participants were randomly divided into an experimental group (n=15) and a control group (n=15). The experimental group performed an exercise designed to induce neck muscle fatigue and the control group preformed non-fatiguing sham exercises. [Results] There were significant differences in mean dynamic visual acuity between the two groups (0.26±0.11 LogMar versus 0.003±0.02 LogMar). Subjects in the experimental group showed a significant decline in their dynamic visual acuity compared with the control group. Dynamic visual acuity strongly correlated with neck muscle fatigue (r = 0.79). No significant differences in joint position error were observed between the two groups and no significant correlations between joint position error and neck muscle fatigue were observed (r = 0.23). [Conclusion] The results of this study suggest that neck muscle fatigue negatively impacts dynamic visual acuity. Although not statistically significant, cervical spine proprioception as measured by the joint position error in the experimental group was diminished after fatigue.

  10. Compared optical performances of multifocal and monofocal intraocular lenses (contrast sensitivity and dynamic visual acuity)

    PubMed Central

    Williamson, W; Poirier, L; Coulon, P; Verin, P

    1994-01-01

    The functional results (contrast sensitivity and dynamic visual acuity) of 19 multifocal (3M design) and 14 all polymethylmethacrylate biconvex monofocal intraocular lenses (IOLs), 6 mm in optical diameter were compared. Best corrected visual acuity was > or = 8/10 (Monoyer chart) Parinaud 2 in all cases. Major differences of functional performance in favour of monofocal IOLs were found outside standard conditions of vision (low contrast and illumination levels). A significant difference in contrast sensitivity was found for each spatial frequency in favour of multifocal IOLs (0.0016 < p < 0.05). Mesopic vision was statistically higher in the monofocal IOL group (p = 0.0015). Moreover, dynamic visual acuity allowed accurate evaluation of the difference in performance between these two models of implant. In view of these results multifocal IOLs should be reserved for patients with normal psychosensitive adaptation; an ocular pathology that could alter contrast sensitivity or mesopic vision is a contraindication for multifocal IOLs. PMID:8199107

  11. Early non-visual experience influences proprioceptive-spatial discrimination acuity in adulthood.

    PubMed

    Fiehler, Katja; Reuschel, Johanna; Rösler, Frank

    2009-02-01

    The present study tested whether non-visual spatial experience affects later acuity of space perception. Congenitally blind adults who differed in the age acquired spatial knowledge via an orientation and mobility (O&M) training and matched sighted controls performed passive arm movements and judged the direction of the sensed movement. Proprioceptive-spatial discrimination acuity was assessed by an adaptive psychophysical procedure in two spatial coding conditions. In the egocentric coding condition, participants judged whether the hand trajectory felt left- or right-tilted in reference to a straight trajectory aligned to the transverse horizontal plane of the body midline axis. In the allocentric coding condition, they indicated whether the hand trajectory felt acute- or obtuse-angled in reference to a right angle. Proprioceptive-spatial acuity of congenitally blind participants significantly covaried with the age they attended an O&M training. The earlier the congenitally blind participants started the O&M training the more accurate was their space perception. Congenitally blind participants who underwent an O&M training after the age of 12 years showed poorer acuity than sighted controls. Congenitally blind participants with an earlier O&M training, however, approached the performance level of the sighted controls. The observed improvement in spatial acuity was more pronounced when judgements were given on the basis of an allocentric than an egocentric frame of reference. These findings suggest that proprioceptive-spatial acuity in adulthood depends on non-visual spatial experience during early development.

  12. Vestibular, Visual Acuity and Balance Outcomes in Children with Cochlear Implants: A Preliminary Report

    PubMed Central

    Janky, Kristen; Givens, Diane

    2016-01-01

    There is a high incidence of vestibular loss in children with cochlear implants (CCI). However, the relationship between vestibular loss and various outcomes is unknown in children. Objectives 1) determine if age-related changes in peripheral vestibular tests occur; 2) quantify peripheral vestibular function in children with normal hearing (CNH) and CCI; 3) determine if amount of vestibular loss predicts visual acuity and balance performance. Design Eleven CCI and 12 CNH completed the following tests of vestibular function: ocular and cervical vestibular evoked myogenic potential (VEMP) to assess utricle and saccule function, and the video head impulse test (vHIT) to assess semicircular canal function. The relationship between amount of vestibular loss and the following balance and visual acuity outcomes was assessed: dynamic gait index, single leg stance, the sensory organization test, and tests of visual acuity, including dynamic visual acuity and the gaze stabilization test. Results 1) There were no significant age-related changes in peripheral vestibular testing with the exception of the n23 cervical VEMP latency, which was moderately correlated with age; 2) CCI had significantly higher rates of vestibular loss for each test of canal and otolith function; 3) Amount of vestibular loss predicted performance on single leg stance, the dynamic gait index, some conditions of the sensory organization test, and the dynamic visual acuity test. Age was also a contributing factor for predicting the performance of almost all outcomes. Conclusions Preliminarily, children with vestibular loss do not recover naturally to levels of their healthy peers, particularly with activities that utilize vestibular input; they have poorer visual acuity and balance function. PMID:26182202

  13. Grating Visual Acuity Results in the Early Treatment for Retinopathy of Prematurity Study

    PubMed Central

    2015-01-01

    Objective To compare grating (resolution) visual acuity at 6 years of age in eyes that received early treatment (ET) for high-risk prethreshold retinopathy of prematurity (ROP) versus eyes that were managed conventionally (CM). Methods In a randomized clinical trial, infants with bilateral, high-risk prethreshold ROP (N=317) had one eye treated early at high-risk prethreshold disease and the other eye managed conventionally, and treated if ROP progressed to threshold severity. For asymmetric cases (N=84), the high-risk prethreshold eye was randomized to either ET or CM. Main Outcome Measures Grating visual acuity measured at 6 years of age by masked testers using Teller acuity cards. Results Monocular grating acuity results were obtained from 317 (86%) of 370 surviving children. Analysis of grating acuity results for all subjects with high-risk prethreshold ROP showed no statistically significant overall benefit for early treatment (18.1% vs 22.8% unfavorable outcome, P=0.08). When the 6-year grating acuity results were analyzed according to a clinical algorithm (high-risk Type 1 and high-risk Type 2 prethreshold ROP), a benefit was seen in Type 1 eyes (16.4% vs 25.2%, P=0.004) that were treated early, but not in Type 2 eyes (21.3% vs 15.9%, P=0.29). Conclusion Early treatment for eyes with Type 1 ROP improved grating acuity outcomes but early treatment for eyes with Type 2 ROP did not. Application to Clinical Medicine Type I eyes should be treated early; however, based on acuity results at age 6 years, Type 2 eyes should be cautiously monitored for progression to Type 1 ROP. Trial Registration NCT00027222 PMID:21746974

  14. Normal Visual Acuity and Electrophysiological Contrast Gain in Adults with High-Functioning Autism Spectrum Disorder

    PubMed Central

    Tebartz van Elst, Ludger; Bach, Michael; Blessing, Julia; Riedel, Andreas; Bubl, Emanuel

    2015-01-01

    A common neurodevelopmental disorder, autism spectrum disorder (ASD), is defined by specific patterns in social perception, social competence, communication, highly circumscribed interests, and a strong subjective need for behavioral routines. Furthermore, distinctive features of visual perception, such as markedly reduced eye contact and a tendency to focus more on small, visual items than on holistic perception, have long been recognized as typical ASD characteristics. Recent debate in the scientific community discusses whether the physiology of low-level visual perception might explain such higher visual abnormalities. While reports of this enhanced, “eagle-like” visual acuity contained methodological errors and could not be substantiated, several authors have reported alterations in even earlier stages of visual processing, such as contrast perception and motion perception at the occipital cortex level. Therefore, in this project, we have investigated the electrophysiology of very early visual processing by analyzing the pattern electroretinogram-based contrast gain, the background noise amplitude, and the psychophysical visual acuities of participants with high-functioning ASD and controls with equal education. Based on earlier findings, we hypothesized that alterations in early vision would be present in ASD participants. This study included 33 individuals with ASD (11 female) and 33 control individuals (12 female). The groups were matched in terms of age, gender, and education level. We found no evidence of altered electrophysiological retinal contrast processing or psychophysical measured visual acuities. There appears to be no evidence for abnormalities in retinal visual processing in ASD patients, at least with respect to contrast detection. PMID:26379525

  15. Posterior staphyloma in oculocutaneous albinism: another possible cause of reduced visual acuity.

    PubMed

    Lee, Susan; Schimmenti, Lisa A; King, Richard A; Brilliant, Murray; Anderson, Jennifer L; Schoonveld, Cheri; Summers, C Gail

    2015-12-01

    Posterior staphyloma is typically associated with myopic degeneration and has not been recognized as a cause of reduced visual acuity in albinism. We report 3 cases of posterior staphyloma, each with oculocutaneous albinism (OCA) defined by phenotype and genotype. Two cases are biological sisters with OCA type 2; one was myopic and the other was hyperopic. The third case involves a man with OCA associated with Hermansky-Pudlak syndrome (HPS-5). Staphyloma may be another cause of reduced visual acuity in albinism, particularly with increasing age. It may occur in association with myopia or hyperopia.

  16. Effect of Target Location on Dynamic Visual Acuity During Passive Horizontal Rotation

    NASA Technical Reports Server (NTRS)

    Appelbaum, Meghan; DeDios, Yiri; Kulecz, Walter; Peters, Brian; Wood, Scott

    2010-01-01

    The vestibulo-ocular reflex (VOR) generates eye rotation to compensate for potential retinal slip in the specific plane of head movement. Dynamic visual acuity (DVA) has been utilized as a functional measure of the VOR. The purpose of this study was to examine changes in accuracy and reaction time when performing a DVA task with targets offset from the plane of rotation, e.g. offset vertically during horizontal rotation. Visual acuity was measured in 12 healthy subjects as they moved a hand-held joystick to indicate the orientation of a computer-generated Landolt C "as quickly and accurately as possible." Acuity thresholds were established with optotypes presented centrally on a wall-mounted LCD screen at 1.3 m distance, first without motion (static condition) and then while oscillating at 0.8 Hz (DVA, peak velocity 60 deg/s). The effect of target location was then measured during horizontal rotation with the optotypes randomly presented in one of nine different locations on the screen (offset up to 10 deg). The optotype size (logMar 0, 0.2 or 0.4, corresponding to Snellen range 20/20 to 20/50) and presentation duration (150, 300 and 450 ms) were counter-balanced across five trials, each utilizing horizontal rotation at 0.8 Hz. Dynamic acuity was reduced relative to static acuity in 7 of 12 subjects by one step size. During the random target trials, both accuracy and reaction time improved proportional to optotype size. Accuracy and reaction time also improved between 150 ms and 300 ms presentation durations. The main finding was that both accuracy and reaction time varied as a function of target location, with greater performance decrements when acquiring vertical targets. We conclude that dynamic visual acuity varies with target location, with acuity optimized for targets in the plane of motion. Both reaction time and accuracy are functionally relevant DVA parameters of VOR function.

  17. Perceptual limit to display resolution of images as per visual acuity

    NASA Astrophysics Data System (ADS)

    Masaoka, Kenichiro; Niida, Takahiro; Murakami, Miya; Suzuki, Kenji; Sugawara, Masayuki; Nojiri, Yuji

    2008-02-01

    Achieving ultimate visual realness of natural images on a display requires high resolution, so that artifacts due to finite image resolution are undetectable. An image resolution of 30 cycles/degree (cpd) or one pixel/arc-minute is often used as the criterion for viewing conditions when assessing displayed image quality. It is reasoned that if the pixel size is smaller than the separable angle of normal vision (20/20), the pixel structure is invisible and doesn't negatively affect image quality. However, it is not clear whether 30 cpd resolution is adequate to prevent seeing artifacts, especially for observers with better than 20/20 vision. We conducted experiments to find the threshold resolution of natural images and its dependence on visual acuity. Three objects were used; each object was presented 60 times at 5 resolutions (19.5, 26, 39, 52, or 78 cpd) next to the same image at a resolution of 156 cpd. Forty-five observers with visual acuity of 20/20 or better were asked to make a forced-choice distinction between the image pair in regard to resolution. Each observer indicated which image of the pair appeared at a higher resolution. The results show that the mean resolution for 75% correct responses for each of the visual acuity groups increased from more than 30 cpd as visual acuity increased and reached a plateau at 40-50 cpd at -0.3 logMAR.

  18. Evaluation of vestibular and dynamic visual acuity in adults with congenital deafness.

    PubMed

    Nakajima, Yukinori; Kaga, Kimitaka; Takekoshi, Hideki; Sakuraba, Keisyoku

    2012-10-01

    This study compared vestibular and dynamic visual acuity in 19 adult athletes with deafness participating in Deaflympics to those of 25 young adults with normal hearing. Balance capability was evaluated using a one-leg standing test with eyes open and stabilometry. Caloric tests and vestibular evoked myogenic potential tests were conducted to test vestibular function. Visual function was evaluated using a dynamic visual acuity test. No significant difference was found between results of the one-leg standing test with eyes open and stabilometry with eyes open. Athletes with deafness performed better than normal hearing young adults with eyes closed. The caloric test indicated hypofunction of the lateral semicircular canal function in 5 of the 19 athletes with deafness. Balance-function tests showed normal results for both groups. The results for athletes with deafness on visual acuity were better than those of controls. Young Deaflympics athletes with deafness can adjust their balance function as well as or better than normal hearing young adults using dynamic visual acuity.

  19. Comparability of ophthalmic diagnoses by clinical and Reading Center examiners in the Visual Acuity Impairment Survey Pilot Study.

    PubMed

    Sperduto, R D; Hiller, R; Podgor, M J; Palmberg, P; Ferris, F L; Wentworth, D

    1986-12-01

    Technologic advances in ophthalmic equipment offer the possibility of replacing direct clinical examinations with Reading Center evaluations of data recorded in epidemiologic studies. Clinical and Reading Center examiners made independent ophthalmic diagnoses of 133 right and 132 left eyes of 138 adults in the Visual Acuity Impairment Survey Pilot Study, carried out in three US cities, Boston, Detroit, and Minneapolis, in August 1981-December 1982. The Reading Center diagnosed eye conditions using only photographic and visual field data collected at the time of the clinical examination. In the comparisons of clinical and Reading Center evaluations reported here, only eyes judged by the examiners to have pathology severe enough to reduce visual acuity to 6/9 or worse were classified as having pathology. (No visual acuity criterion was required for the diagnosis of glaucoma or diabetic retinopathy.) There was agreement in diagnostic assessments between clinical and Reading Center examiners in about 80% of eyes. The kappa statistic, which adjusts for chance agreement, was in the fair to good range: 0.60 for 133 right eyes and 0.62 for 132 left eyes. When the Reading Center examiners were provided with additional information on medical history, refractive error and best corrected visual acuity, the agreement between clinical and Reading Center assessments among the subset of eyes with 6/9 or worse vision again was in the fair to good range, with kappas of 0.61 for 45 right eyes and 0.68 for 48 left eyes. Inter-observer agreement between Reading Center examiners in diagnosing pathology was in the good to excellent range. Use of Reading Centers in future epidemiologic studies should be considered, but elimination of the clinical examinations is not recommended until modifications in the protocol described here have been made and shown to improve levels of agreement between clinical and Reading Center examiners.

  20. Association of Visual Acuity and Cognitive Impairment in Older Individuals: Fujiwara-kyo Eye Study.

    PubMed

    Mine, Masashi; Miyata, Kimie; Morikawa, Masayuki; Nishi, Tomo; Okamoto, Nozomi; Kawasaki, Ryo; Yamashita, Hidetoshi; Kurumatani, Norio; Ogata, Nahoko

    2016-01-01

    Both visual impairment and cognitive impairment are essential factors that determine the quality of life in the aged population. The aim of this study was to determine if a correlation existed between visual acuity and cognitive impairment in an elderly Japanese population. The Fujiwara-kyo Eye Study was a cross-sectional study of individuals aged ≥68 years who lived in Nara Prefecture of Japan. Participants underwent ophthalmological examinations and cognitive function test. A mild visual impairment was defined as having a best corrected visual acuity (BCVA) >0.2 logarithm of the minimum angle of resolution (logMAR) units in the better eye. Cognitive impairment was defined as having a Mini-Mental State Examination (MMSE) score of ≤23 points. A total to 2818 individuals completed the examinations. The mean age of the participants was 76.3 ± 4.8 years (mean ± standard deviation). The mean BCVA of the better eye was -0.02 ± 0.13 logMAR units and 6.6% subjects were classified as being mildly visually impaired. The mean MMSE score was 27.3 ± 2.3 and 5.7% subjects were classified as being cognitively impaired. The proportion of subjects with cognitive or moderate visual impairment increased with age, and there was a significant correlation between the visual acuity and MMSE score (r = -0.10, p < 0.0001). Subjects with mild visual impairments had 2.4 times higher odds of having cognitive impairment than those without visual impairment (odds ratio 2.4, 95% confidence interval, 1.5-3.8, p < 0.001) after adjusting for age, sex, and length of education. We conclude that it may be important to maintain good visual acuity to reduce the risk of having cognitive impairment.

  1. Visual Function after Primary Posterior Chamber Intraocular Lens Implantation in Pediatric Unilateral Cataract: Stereopsis and Visual Acuity

    PubMed Central

    Park, Jung Hyun; Kim, Jeong Hun; Kim, Seong Joon; Choung, Ho Kyung

    2007-01-01

    Purpose To investigate the association between binocular function and vision after cataract removal and primary posterior chamber intraocular lens (PC-IOL) implantation in children with unilateral cataract and to identify visual function differences according cataract type. Methods Clinical records of 2- to 6-year-old patients with unilateral cataract removal and primary PC-IOL implantation were reviewed retrospectively. Visual acuity and ocular alignment were measured. Sensory fusion was assessed with the Worth 4-dot test, and stereoacuity with the Titmus stereo test. Cataracts were classified according to cause, lens opacity location, age at onset, and presence of strabismus. Clinical characteristics of patients who obtained good visual function were identified. Results Forty-seven patients were included. Among 22 (46.8%) with good vision (20/40 or better), only 6 (27.3%) achieved good binocular function (the presence of fusion and 100 seconds of arc or better of stereoacuity). Visual acuity was better in eyes with good binocular function (p=0.002). No other variables were significant for achieving good binocular function. Conclusions The removal of unilateral cataract in a visually immature child can result in a combination of good visual acuity and binocular function. Good binocular function is closely related to good visual acuity. PMID:18063882

  2. Foveal photoreceptor explanation of short-term visual acuity recovery associated with laser-induced foveal damage

    NASA Astrophysics Data System (ADS)

    Langus, Amir; Zwick, Harry; Stuck, Bruce E.; Belkin, Michael

    2003-06-01

    Both human laser accident cases and non-human primate behavioral studies demonstrate the possibility of full visual acuity recovery following foveal laser injury. Current explanations of such recovery require suppositions of complex retinal reorganization dynamics or neural reorganization at higher order visual brain systems. However, recent investigation based on data of retinal photoreceptor and ganglion cell topography and connectivity, suggest that the amount of static inherent plasticity, already exists at the retinal level, may also explain visual acuity recovery in the presence of laser-induced foveal damage. Modeling the off-axis visual acuity while utilizing this data, produces a more gradual fall-off in visual acuity, and supports the notion that visual acuity recovery may reside in the topographical organization of the cones. Moreover, considering the filling-in phenomena, which can conceal the presence of retinal damage from being recognized, together with eye movements, could nullify scotoma, as long as the retinal damage is not too extensive.

  3. A Close Eye on the Eagle-Eyed Visual Acuity Hypothesis of Autism

    ERIC Educational Resources Information Center

    Bolte, Sven; Schlitt, Sabine; Gapp, Volker; Hainz, Daniela; Schirman, Shella; Poustka, Fritz; Weber, Bernhard; Freitag, Christine; Ciaramidaro, Angela; Walter, Henrik

    2012-01-01

    Autism spectrum disorders (ASD) have been associated with sensory hypersensitivity. A recent study reported visual acuity (VA) in ASD in the region reported for birds of prey. The validity of the results was subsequently doubted. This study examined VA in 34 individuals with ASD, 16 with schizophrenia (SCH), and 26 typically developing (TYP).…

  4. Short-term visual deprivation, tactile acuity, and haptic solid shape discrimination.

    PubMed

    Crabtree, Charles E; Norman, J Farley

    2014-01-01

    Previous psychophysical studies have reported conflicting results concerning the effects of short-term visual deprivation upon tactile acuity. Some studies have found that 45 to 90 minutes of total light deprivation produce significant improvements in participants' tactile acuity as measured with a grating orientation discrimination task. In contrast, a single 2011 study found no such improvement while attempting to replicate these earlier findings. A primary goal of the current experiment was to resolve this discrepancy in the literature by evaluating the effects of a 90-minute period of total light deprivation upon tactile grating orientation discrimination. We also evaluated the potential effect of short-term deprivation upon haptic 3-D shape discrimination using a set of naturally-shaped solid objects. According to previous research, short-term deprivation enhances performance in a tactile 2-D shape discrimination task - perhaps a similar improvement also occurs for haptic 3-D shape discrimination. The results of the current investigation demonstrate that not only does short-term visual deprivation not enhance tactile acuity, it additionally has no effect upon haptic 3-D shape discrimination. While visual deprivation had no effect in our study, there was a significant effect of experience and learning for the grating orientation task - the participants' tactile acuity improved over time, independent of whether they had, or had not, experienced visual deprivation.

  5. The Effects of Drift and Displacement Motion on Dynamic Visual Acuity

    ERIC Educational Resources Information Center

    Aznar-Casanova, J. Antonio; Quevedo, Lluisa; Sinnett, Scott

    2005-01-01

    Dynamic Visual Acuity (DVA) can be measured from two types of equivalently considered movement referred to as drifting-motion and displacement-motion. Displacement motion can be best described as the horizontal displacement of a stimulus, thus implying pursuit eye movements, and involves moving the stimulus from the fixation point of gaze towards…

  6. Binocular Visual Acuity of Children: Demographic and Socioeconomic Characteristics - United States.

    ERIC Educational Resources Information Center

    National Center for Health Statistics (DHEW/PHS), Hyattsville, MD.

    Reported were estimates of the uncorrected binocular visual acuity levels of distance and near for children aged 6 to 11 years in the noninstitutional population of the United States in relation to their demographic and socioeconomic background. A sample of 7,119 children participated in the Health Examination Survey program of 1963-65. Findings…

  7. A comparison of visual acuity, predictability, and visual function outcomes after intracorneal ring segments and laser in situ keratomileusis.

    PubMed Central

    Suiter, B G; Twa, M D; Ruckhofer, J; Schanzlin, D J

    2000-01-01

    PURPOSE: To compare correction of low myopia by intrastromal corneal ring segments (ICRS) and by laser in situ keratomileusis (LASIK) with respect to early visual recovery and refractive outcomes. METHODS: Eighty-two eyes implanted with ICRS in a phase III study for US Food and Drug Administration review were matched with 133 eyes treated with LASIK by criteria of age (> 18 years, < 65 years), preoperative myopia (-1.00 to -3.50 diopters [D]), astigmatism (< or = 1.00 D), single treatment, and attempted full correction. Examinations were performed preoperatively and postoperatively at days 1 and 7 and months 1 and 3. Visual acuity and manifest refraction data were collected retrospectively. Visual function scores were assigned, and summarized results were compared. RESULTS: Uncorrected visual acuity was 20/20 or better at day 1 in 24% of eyes (20/82) after ICRS and in 55% of eyes (73/133) after LASIK, and at month 3 in 75% of eyes (58/77) after ICRS and in 67% of eyes (84/126) after LASIK. Spherical equivalent refraction at month 3 was within +/- 1.00 D of intended correction in 99% of eyes (76/77) after ICRS and in 96% of eyes (121/126) after LASIK. Excellent visual function scores were noted at month 3 in 90% of eyes (69/77) after ICRS and in 78% of eyes (98/126) after LASIK. CONCLUSION: Patients treated with LASIK showed better uncorrected visual acuity immediately following surgery; however, beyond 1 month, patients treated with ICRS achieved better uncorrected visual acuity that continued to improve with time. Visual function scores indicate that ICRS eyes see at higher levels of uncorrected visual acuity than LASIK eyes do with the same refractive error. The ICRS and LASIK were comparable in the correction of mild myopia. PMID:11190040

  8. PERSPECTIVE: Is acuity enough? Other considerations in clinical investigations of visual prostheses

    NASA Astrophysics Data System (ADS)

    Lepri, Bernard P.

    2009-06-01

    Visual impairing eye diseases are the major frontier facing ophthalmic research today in light of our rapidly aging population. The visual skills necessary for improving the quality of daily function and life are inextricably linked to these impairing diseases. Both research and reimbursement programs are emphasizing outcome-based results. Is improvement in visual acuity alone enough to improve the function and quality of life of visually impaired persons? This perspective summarizes the types of effectiveness endpoints for clinical investigations of visual prostheses that go beyond visual acuity. The clinical investigation of visual prostheses should include visual function, functional vision and quality of life measures. Specifically, they encompass contrast sensitivity, orientation and mobility, activities of daily living and quality of life assessments. The perspective focuses on the design of clinical trials for visual prostheses and the methods of determining effectiveness above and beyond visual acuity that will yield outcomes that are measured by improved function in the visual world and quality of life. The visually impaired population is the primary consideration in this presentation with particular emphases on retinitis pigmentosa and age-related macular degeneration. Clinical trials for visual prostheses cannot be isolated from the need for medical rehabilitation in order to obtain measurements of effectiveness that produce outcomes/evidence-based success. This approach will facilitate improvement in daily function and quality of life of patients with diseases that cause chronic vision impairment. The views and opinions are those of the author and do not necessarily reflect those of the US Food and Drug Administration, the US Department of Health and Human Services or the Public Health Service.

  9. Visual Acuity and Reaction Time in Navy Fighter Pilots,

    DTIC Science & Technology

    1986-12-01

    10. SOUR CW 0FUHND"N NUmIRs Naval Medical Research & Development Command PRGKOM POX ~JCT TASK WORK UNITI IIAMET NO Ný CESSION NO.NMC, National Capital...8. Stimulus sizes were specified in minutes of visual angle ( mva ), and target exposure time was 3 seconds. 2 kdditiotwl details concerning these...This test required the subject to press the joystick iWmmeiately at the appearance of a swrathreshold spot target (2 mva 4iame-. ter). Target

  10. Modulation transfer function as a predictor of visual acuity using a night vision device

    NASA Astrophysics Data System (ADS)

    Fullenkamp, S. C.; Trissell, T. L.; Aleva, D. L.; Dixon, S.; Task, H. L.

    2005-05-01

    Night Vision Goggles (NVGs) are being used increasingly by the military and law enforcement agencies for night operations. One critical issue in assessing the utility of an NVG is its resolving power or capability to make fine detail distinguishable. The resolution of Night Vision Goggles is typically assessed by measuring the visual acuity of an operator looking through the goggles. These methods can be time consuming. Further, inconsistencies associated with visual observations and judgement add to the variance associated with these measurements. NVG Modulation Transfer Function (MTF) was explored as a possible means of characterizing NVG image quality independent of a human observer. MTF maps the potential contrast output of the NVGs as a function of spatial frequency. The results of this MTF measurement were compared with a commonly used method of visual acuity assessment.

  11. Reduction in Dynamic Visual Acuity Reveals Gaze Control Changes Following Spaceflight

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; Brady, Rachel A.; Miller, Chris; Lawrence, Emily L.; Mulavara Ajitkumar P.; Bloomberg, Jacob J.

    2010-01-01

    INTRODUCTION: Exposure to microgravity causes adaptive changes in eye-head coordination that can lead to altered gaze control. This could affect postflight visual acuity during head and body motion. The goal of this study was to characterize changes in dynamic visual acuity after long-duration spaceflight. METHODS: Dynamic Visual Acuity (DVA) data from 14 astro/cosmonauts were collected after long-duration (6 months) spaceflight. The difference in acuity between seated and walking conditions provided a metric of change in the subjects ability to maintain gaze fixation during self-motion. In each condition, a psychophysical threshold detection algorithm was used to display Landolt ring optotypes at a size that was near each subject s acuity threshold. Verbal responses regarding the orientation of the gap were recorded as the optotypes appeared sequentially on a computer display 4 meters away. During the walking trials, subjects walked at 6.4 km/h on a motorized treadmill. RESULTS: A decrement in mean postflight DVA was found, with mean values returning to baseline within 1 week. The population mean showed a consistent improvement in DVA performance, but it was accompanied by high variability. A closer examination of the individual subject s recovery curves revealed that many did not follow a pattern of continuous improvement with each passing day. When adjusted on the basis of previous long-duration flight experience, the population mean shows a "bounce" in the re-adaptation curve. CONCLUSION: Gaze control during self-motion is altered following long-duration spaceflight and changes in postflight DVA performance indicate that vestibular re-adaptation may be more complex than a gradual return to normal.

  12. [Correctly evaluate the role of visual acuity in age-related macular degeneration treatment].

    PubMed

    Zhang, Feng

    2012-02-01

    Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in aged population. As the aging of population, the prevalence of AMD increases gradually. Anti-VEGF medication intravitreal injection, which can obtain good therapeutic efficiency and is relatively safe, becomes the main therapy for neovascular AMD. However, high-frequency repeated treatment increases the intravitreal injections risk, as well as the costs. In clinical practice, to pursue the best-corrected visual acuity, high-frequency repeated injections are implemented and inflict psychological pressure and economic burden on patients. The author believes that to pursue the best corrected visual acuity is the ultimate aim but not the only one for every ophthalmologist and patient. The activity of lesions should be overall evaluated with fundus imaging technologies. Being people-oriented is the principle in clinical medicine. A treatment plan is made according to the patients' sickness and economy and to coordinate the relation between the best corrected visual acuity and the numbers of treatment. Based on the stabilized lesion, patient should be benefited at the lowest risk and cost with the best effect.

  13. Focus adjustment effects on visual acuity and oculomotor balance with aviator night vision displays.

    PubMed

    Kotulak, J C; Morse, S E

    1994-04-01

    Sixteen U.S. Army aviators, who were given training on focus adjustment technique with aviator night vision goggles (NVG), showed an improvement in visual acuity with focus adjustment compared to a fixed infinity focus control. The long-term effect of focus adjustment on vision was not measured; however, adjustment accuracy was found to be generally within acceptable limits based on computer modeling and available physiologic data. Fixed focus eyepieces that are set to a low minus power may partially compensate for instrument myopia, but they may not optimize visual acuity to the extent that adjustable focus eyepieces do. Eyepiece adjustment proficiency with present night vision devices can be improved through training that emphasizes focusing to the least possible minus dioptric power. Future night vision displays can minimize focus misadjustment by providing a tactile zero marking, a limited dioptric adjustment range, and a focusing knob capable of finer adjustment than is available with current NVG's.

  14. Gains following perceptual learning are closely linked to the initial visual acuity.

    PubMed

    Yehezkel, Oren; Sterkin, Anna; Lev, Maria; Levi, Dennis M; Polat, Uri

    2016-04-28

    The goal of the present study was to evaluate the dependence of perceptual learning gains on initial visual acuity (VA), in a large sample of subjects with a wide range of VAs. A large sample of normally sighted and presbyopic subjects (N = 119; aged 40 to 63) with a wide range of uncorrected near visual acuities (VA, -0.12 to 0.8 LogMAR), underwent perceptual learning. Training consisted of detecting briefly presented Gabor stimuli under spatial and temporal masking conditions. Consistent with previous findings, perceptual learning induced a significant improvement in near VA and reading speed under conditions of limited exposure duration. Our results show that the improvements in VA and reading speed observed following perceptual learning are closely linked to the initial VA, with only a minor fraction of the observed improvement that may be attributed to the additional sessions performed by those with the worse VA.

  15. Gains following perceptual learning are closely linked to the initial visual acuity

    PubMed Central

    Yehezkel, Oren; Sterkin, Anna; Lev, Maria; Levi, Dennis M.; Polat, Uri

    2016-01-01

    The goal of the present study was to evaluate the dependence of perceptual learning gains on initial visual acuity (VA), in a large sample of subjects with a wide range of VAs. A large sample of normally sighted and presbyopic subjects (N = 119; aged 40 to 63) with a wide range of uncorrected near visual acuities (VA, −0.12 to 0.8 LogMAR), underwent perceptual learning. Training consisted of detecting briefly presented Gabor stimuli under spatial and temporal masking conditions. Consistent with previous findings, perceptual learning induced a significant improvement in near VA and reading speed under conditions of limited exposure duration. Our results show that the improvements in VA and reading speed observed following perceptual learning are closely linked to the initial VA, with only a minor fraction of the observed improvement that may be attributed to the additional sessions performed by those with the worse VA. PMID:27122254

  16. Measurement of night vision goggle (NVG) visual acuity with the NVG resolution chart.

    PubMed

    DeVilbiss, C A; Antonio, J C

    1994-09-01

    Night vision goggles (NVG) operations are characterized as stressful with high task loading. Any reduction in goggle or visual performance which goes undetected can have a serious effect on flight safety and operational capability. The NVG Test Lane, with its resolution chart, provides an effective cost-efficient method for aircrew members to quickly evaluate the correct positioning and focusing of their NVG's prior to each mission. This evaluation validated the ability of the NVG resolution chart to produce the same performance results as a more detailed psychophysical procedure. NVG visual acuity was measured for five subjects (four pilots and one non-pilot) with two different night vision goggles. The results supported that there is no statistical difference between the results obtained with the individual target format and the 3 x 3 format. Additionally, the pilots with current NVG experience were able to obtain a significantly better acuity level than were those without current NVG experience.

  17. Vision-guided ocular growth in a mutant chicken model with diminished visual acuity

    PubMed Central

    Ritchey, Eric R.; Zelinka, Christopher; Tang, Junhua; Liu, Jun; Code, Kimberly A.; Petersen-Jones, Simon; Fischer, Andy J.

    2012-01-01

    Visual experience is known to guide ocular growth. We tested the hypothesis that vision-guided ocular growth is disrupted in a model system with diminished visual acuity. We examine whether ocular elongation is influenced by form-deprivation (FD) and lens-imposed defocus in the Retinopathy, Globe Enlarged (RGE) chicken. Young RGE chicks have poor visual acuity, without significant retinal pathology, resulting from a mutation in guanine nucleotide-binding protein β3 (GNB3), also known as transducin β3 or Gβ3. The mutation in GNB3 destabilizes the protein and causes a loss of Gβ3 from photoreceptors and ON-bipolar cells. (Ritchey et al. 2010)FD increased ocular elongation in RGE eyes in a manner similar to that seen in wild-type (WT) eyes. By comparison, the excessive ocular elongation that results from hyperopic defocus was increased, whereas myopic defocus failed to significantly decrease ocular elongation in RGE eyes. Brief daily periods of unrestricted vision interrupting FD prevented ocular elongation in RGE chicks in a manner similar to that seen in WT chicks. Glucagonergic amacrine cells differentially expressed the immediate early gene Egr1 in response to growth-guiding stimuli in RGE retinas, but the defocus-dependent up-regulation of Egr1 was lesser in RGE retinas compared to that of WT retinas. We conclude that high visual acuity, and the retinal signaling mediated by Gβ3, is not required for emmetropization and the excessive ocular elongation caused by FD and hyperopic defocus. However, the loss of acuity and Gβ3 from RGE retinas causes enhanced responses to hyperopic defocus and diminished responses to myopic defocus. PMID:22824538

  18. Final Visual Acuity Results in the Early Treatment for Retinopathy of Prematurity Study

    PubMed Central

    2014-01-01

    Objective To compare visual acuity at 6 years of age in eyes that received early treatment for high-risk prethreshold retinopathy of prematurity (ROP) with conventionally-managed eyes. Methods Infants with symmetrical, high-risk prethreshold ROP (N=317) had one eye randomized to earlier treatment at high-risk prethreshold disease and the other eye managed conventionally, treated if ROP progressed to threshold severity. For asymmetric cases (N=84), the high-risk prethreshold eye was randomized to either early treatment or conventional management. Main Outcome Measures ETDRS visual acuity measured at 6 years of age by masked testers. Retinal structure was assessed as a secondary outcome. Results Analysis of all subjects with high-risk prethreshold ROP showed no statistically significant benefit for early treatment (24.6% v. 29.0% unfavorable outcome, P=0.15). Analysis of 6-year visual acuity results according to the Type 1 and 2 clinical algorithm showed a benefit for Type 1 eyes (25.1% v. 32.8%, P=0.02) treated early, but not Type 2 eyes (23.6% v. 19.4%, P=0.37). Early treated eyes showed a significantly better structural outcome compared with conventionally managed eyes (8.9% v. 15.2% unfavorable outcome, P<0.001), with no greater risk of ocular complications. Conclusion Early treatment for Type 1 high-risk prethreshold eyes improved visual acuity outcomes at 6 years of age. Early treatment for Type 2 high-risk prethreshold eyes did not. Application to Clinical Practice Type 1 eyes, not Type 2 eyes should be treated early. These results are particularly important considering that 52 % of Type 2 high-risk prethreshold eyes underwent regression of ROP without requiring treatment. PMID:20385926

  19. Vision-guided ocular growth in a mutant chicken model with diminished visual acuity.

    PubMed

    Ritchey, Eric R; Zelinka, Christopher; Tang, Junhua; Liu, Jun; Code, Kimberly A; Petersen-Jones, Simon; Fischer, Andy J

    2012-09-01

    Visual experience is known to guide ocular growth. We tested the hypothesis that vision-guided ocular growth is disrupted in a model system with diminished visual acuity. We examine whether ocular elongation is influenced by form-deprivation (FD) and lens-imposed defocus in the Retinopathy, Globe Enlarged (RGE) chicken. Young RGE chicks have poor visual acuity, without significant retinal pathology, resulting from a mutation in guanine nucleotide-binding protein β3 (GNB3), also known as transducin β3 or Gβ3. The mutation in GNB3 destabilizes the protein and causes a loss of Gβ3 from photoreceptors and ON-bipolar cells (Ritchey et al., 2010). FD increased ocular elongation in RGE eyes in a manner similar to that seen in wild-type (WT) eyes. By comparison, the excessive ocular elongation that results from hyperopic defocus was increased, whereas myopic defocus failed to significantly decrease ocular elongation in RGE eyes. Brief daily periods of unrestricted vision interrupting FD prevented ocular elongation in RGE chicks in a manner similar to that seen in WT chicks. Glucagonergic amacrine cells differentially expressed the immediate early gene Egr1 in response to growth-guiding stimuli in RGE retinas, but the defocus-dependent up-regulation of Egr1 was lesser in RGE retinas compared to that of WT retinas. We conclude that high visual acuity, and the retinal signaling mediated by Gβ3, is not required for emmetropization and the excessive ocular elongation caused by FD and hyperopic defocus. However, the loss of acuity and Gβ3 from RGE retinas causes enhanced responses to hyperopic defocus and diminished responses to myopic defocus.

  20. Relationship between Optical Coherence Tomography Retinal Parameters and Visual Acuity in Neovascular Age-Related Macular Degeneration

    PubMed Central

    Keane, Pearse A.; Liakopoulos, Sandra; Chang, Karen T.; Wang, Mingwu; Dustin, Laurie; Walsh, Alexander C.; Sadda, Srinivas R.

    2008-01-01

    Purpose To investigate the relationship between optical coherence tomography (OCT)-derived measurements of retinal morphology and visual acuity in patients with neovascular age-related macular degeneration (AMD). Design Retrospective cross-sectional study. Participants Two hundred sixteen consecutive patients (216 eyes) newly diagnosed with neovascular AMD, who underwent StratusOCT imaging at time of diagnosis. Methods Best-corrected Snellen visual acuity was recorded for each patient. Raw exported StratusOCT images for each patient were analyzed using publicly available custom software entitled “OCTOR”, which allows precise positioning of pre-specified boundaries on individual B-scans. Thickness/volume were calculated for morphologic parameters of interest: neurosensory retina, subretinal fluid (SRF), subretinal tissue (SRT), and pigment epithelial detachment (PED). Main Outcome Measures OCT-derived measurements of retinal morphology and visual acuity. Results An increased total volume of SRT was correlated with decreased visual acuity (r=0.370, P<0.0001). Decreased visual acuity was also modestly correlated with increased thickness of the neurosensory retina at the foveal center point (r=0.245, P=0.0004). No statistically significant association was detected between visual acuity and the total volume of SRF or PED. The association between visual acuity and both the neurosensory retina and the SRT, was stronger for lesions classified as minimally classic or occult on fluorescein angiography. For occult lesions, 20% of the variation in visual acuity could be predicted by a multiple regression model that incorporated age and SRT volume; while, for minimally classic lesions, 62% of the variation in visual acuity could be predicted by a multiple regression model that incorporated age, total neurosensory retinal volume, and total SRT volume. Conclusions The presence of increased SRT thickness/volume on OCT, and to a lesser extent increased neurosensory retinal

  1. Optical coherence tomography angiography in eyes with good visual acuity recovery after treatment for optic neuritis

    PubMed Central

    Higashiyama, Tomoaki; Nishida, Yasuhiro; Ohji, Masahito

    2017-01-01

    Objective To evaluate the retinal perfusion using optical coherence tomography (OCT) angiography in eyes with good visual acuity recovery after treatment for optic neuritis (ON). Methods Seven eyes of seven patients with good visual acuity recovery after treatment for monocular ON and seven eyes of each fellow eye used as controls were studied. Retinal perfusion around the disc and at the macula was evaluated using OCT angiography. The retinal nerve fiber layer thickness was measured around the disc. The ganglion cell layer complex thickness or the ganglion cell layer plus the inner plexiform layer thickness were measured at the macula. Results The retinal perfusions in all eyes with ON decreased around the disc and at the macula compared with those of the fellow eyes, as shown by OCT angiography (disc, P = 0.003; macula, P = 0.001). The retinal thicknesses in all eyes with ON also decreased around the disc and at the macula compared with those of the fellow eyes (disc, P < 0.001; macula, P = 0.003). Conclusions Optic neuritis may cause not only retinal structural damage but also decreased retinal perfusion, even after the visual acuity recovered well after treatment. PMID:28192497

  2. Osteological evidence for the evolution of activity pattern and visual acuity in primates.

    PubMed

    Kay, R F; Kirk, E C

    2000-10-01

    Examination of orbit size and optic foramen size in living primates reveals two adaptive phenomena. First, as noted by many authors, orbit size is strongly correlated with activity pattern. Comparisons of large samples of extant primates consistently reveal that nocturnal species exhibit proportionately larger orbits than diurnal species. Furthermore, nocturnal haplorhines (Tarsius and Aotus) have considerably larger orbits than similar-sized nocturnal strepsirrhines. Orbital hypertrophy in Tarsius and Aotus accommodates the enormously enlarged eyes of these taxa. This extreme ocular hypertrophy seen in extant nocturnal haplorhines is an adaptation for both enhanced visual acuity and sensitivity in conditions of low light intensity. Second, the relative size of the optic foramen is highly correlated with the degree of retinal summation and inferred visual acuity. Diurnal haplorhines exhibit proportionately larger optic foramina, less central retinal summation, and much higher visual acuity than do all other primates. Diurnal strepsirrhines exhibit a more subtle but significant parallel enlargement of the optic foramen and a decrease in retinal summation relative to the condition seen in nocturnal primates. These twin osteological variables of orbit size and optic foramen size may be used to draw inferences regarding the activity pattern, retinal anatomy, and visual acuity of fossil primates. Our measurements demonstrate that the omomyiforms Microchoerus, Necrolemur, Shoshonius, and Tetonius, adapiform Pronycticebus, and the possible lorisiform Plesiopithecus were likely nocturnal on the basis of orbit diameter. The adapiforms Leptadapis, Adapis, and Notharctus, the phylogenetically enigmatic Rooneyia, the early anthropoids Proteopithecus, Catopithecus, and Aegyptopithecus, and early platyrrhine Dolichocebus were likely diurnal. The activity pattern of the platyrrhine Tremacebus is obscure. Plesiopithecus, Pronycticebus, Microchoerus, and Necrolemur probably had

  3. A double dissociation of the acuity and crowding limits to letter identification, and the promise of improved visual screening.

    PubMed

    Song, Shuang; Levi, Dennis M; Pelli, Denis G

    2014-05-05

    Here, we systematically explore the size and spacing requirements for identifying a letter among other letters. We measure acuity for flanked and unflanked letters, centrally and peripherally, in normals and amblyopes. We find that acuity, overlap masking, and crowding each demand a minimum size or spacing for readable text. Just measuring flanked and unflanked acuity is enough for our proposed model to predict the observer's threshold size and spacing for letters at any eccentricity. We also find that amblyopia in adults retains the character of the childhood condition that caused it. Amblyopia is a developmental neural deficit that can occur as a result of either strabismus or anisometropia in childhood. Peripheral viewing during childhood due to strabismus results in amblyopia that is crowding limited, like peripheral vision. Optical blur of one eye during childhood due to anisometropia without strabismus results in amblyopia that is acuity limited, like blurred vision. Furthermore, we find that the spacing:acuity ratio of flanked and unflanked acuity can distinguish strabismic amblyopia from purely anisometropic amblyopia in nearly perfect agreement with lack of stereopsis. A scatter diagram of threshold spacing versus acuity, one point per patient, for several diagnostic groups, reveals the diagnostic power of flanked acuity testing. These results and two demonstrations indicate that the sensitivity of visual screening tests can be improved by using flankers that are more tightly spaced and letter like. Finally, in concert with Strappini, Pelli, Di Pace, and Martelli (submitted), we jointly report a double dissociation between acuity and crowding. Two clinical conditions-anisometropic amblyopia and apperceptive agnosia-each selectively impair either acuity A or the spacing:acuity ratio S/A, not both. Furthermore, when we specifically estimate crowding, we find a double dissociation between acuity and crowding. Models of human object recognition will need to

  4. A double dissociation of the acuity and crowding limits to letter identification, and the promise of improved visual screening

    PubMed Central

    Song, Shuang; Levi, Dennis M.; Pelli, Denis G.

    2014-01-01

    Here, we systematically explore the size and spacing requirements for identifying a letter among other letters. We measure acuity for flanked and unflanked letters, centrally and peripherally, in normals and amblyopes. We find that acuity, overlap masking, and crowding each demand a minimum size or spacing for readable text. Just measuring flanked and unflanked acuity is enough for our proposed model to predict the observer's threshold size and spacing for letters at any eccentricity. We also find that amblyopia in adults retains the character of the childhood condition that caused it. Amblyopia is a developmental neural deficit that can occur as a result of either strabismus or anisometropia in childhood. Peripheral viewing during childhood due to strabismus results in amblyopia that is crowding limited, like peripheral vision. Optical blur of one eye during childhood due to anisometropia without strabismus results in amblyopia that is acuity limited, like blurred vision. Furthermore, we find that the spacing:acuity ratio of flanked and unflanked acuity can distinguish strabismic amblyopia from purely anisometropic amblyopia in nearly perfect agreement with lack of stereopsis. A scatter diagram of threshold spacing versus acuity, one point per patient, for several diagnostic groups, reveals the diagnostic power of flanked acuity testing. These results and two demonstrations indicate that the sensitivity of visual screening tests can be improved by using flankers that are more tightly spaced and letter like. Finally, in concert with Strappini, Pelli, Di Pace, and Martelli (submitted), we jointly report a double dissociation between acuity and crowding. Two clinical conditions—anisometropic amblyopia and apperceptive agnosia—each selectively impair either acuity A or the spacing:acuity ratio S/A, not both. Furthermore, when we specifically estimate crowding, we find a double dissociation between acuity and crowding. Models of human object recognition will need

  5. Evaluation of a Public Child Eye Health Tertiary Facility for Pediatric Cataract in Southern Nigeria I: Visual Acuity Outcome

    PubMed Central

    Duke, Roseline E.; Adio, Adedayo; Oparah, Sidney K.; Odey, Friday; Eyo, Okon A.

    2016-01-01

    Purpose: A retrospective study of the outcome of congenital and developmental cataract surgery was conducted in a public child eye health tertiary facility in children <16 years of age in Southern Nigeria, as part of an evaluation. Materials and Method: Manual Small Incision Cataract Surgery with or without anterior vitrectomy was performed. The outcome measures were visual acuity (VA) and change (gain) in visual acuity. The age of the child at onset, duration of delay in presentation, ocular co-morbidity, non ocular co-morbidity, gender, and pre operative visual acuity were matched with postoperative visual acuity. A total of 66 children were studied for a period of six weeks following surgery. Results: Forty eight (72.7%) children had bilateral congenital cataracts and 18 (27.3%) children had bilateral developmental cataracts. There were 38(57.6%) males and 28 (42.4%) females in the study. Thirty Five (53%) children had good visual outcome (normal vision range 6/6/ -6/18) post-operatively. The number of children with blindness (vision <3/60) decreased from 61 (92.4%) pre-operatively to 4 (6.1%) post-operatively. Post operative complication occurred in 6.8% of cases six week after surgery. Delayed presentation had an inverse relationship with change (gain) in visual acuity (r = - 0.342; p-value = 0.005). Pre-operative visual acuity had a positive relationship with post operative change (gain) in visual acuity (r = 0.618; p-value = 0.000). Conclusion: Predictors of change in visual acuity in our study were; delayed presentation and pre-operative VA. Cataract surgery in children showed clinical benefit. PMID:27347247

  6. Contrast-sensitivity loss in a group of former microelectronics workers with normal visual acuity.

    PubMed

    Frenette, B; Mergler, D; Bowler, R

    1991-07-01

    The measurement of contrast sensitivity at varying grating frequencies is used increasingly to study visual and neural disorders. It provides more information than conventional acuity measures. Refractive errors initially affect high spatial frequencies, whereas lower spatial frequencies are affected only when these errors are pronounced. Neurophysiological alterations are reflected by depressed sensitivity to coarse gratings. Visual dysfunction has been associated with workplace exposures to a wide range of organic solvents. In microelectronics assembly where large quantities of organic solvents are used in many aspects of the work processes, visual deficits have been observed. The objective of the present study was to compare contrast sensitivity among former microelectronics assembly workers, with normal far and near visual acuity, and a reference group from the same region, with similar acuity. No significant differences were observed between scores at the two ends of the contrast sensitivity curves; however, at the intermediate spatial frequencies, the former microelectronics workers' scores were significantly lower (Student's t-test; p less than 0.05). For the microelectronics workers, no relation was observed between age and contrast sensitivity at any spatial frequency, whereas for the reference group, contrast sensitivity scores were progressively lower with age at spatial frequencies greater than or equal to 6.0 cpd (r2 = 0.15 at 6 cpd to r2 = 0.45 at 18.0 cpd), suggesting that for the former there is some form of interference with the expected contrast sensitivity loss with age. Lower contrast sensitivity scores in intermediate spatial frequencies, observed among the former microelectronics workers, possibly reflect neural alterations, which may have resulted from exposure to neurotoxic substances. These findings suggest the need for further studies on visual functions in microelectronics workers.

  7. Antihistamines and visual function: studies on dynamic acuity and the pupillary response to light.

    PubMed Central

    Nicholson, A N; Smith, P A; Spencer, M B

    1982-01-01

    1 Effects of three antihistamines, triprolidine (10 mg) in a sustained release form, astemizole (10 mg) and terfenadine (60 mg), have been studied on dynamic visual acuity and on the response of the pupil to light, together with critical flicker fusion, digit symbol substitution and cancellation, and subjective assessment of mood. The study was double-blind and effects were observed from 0.5-4.0 h after ingestion. 2 Triprolidine impaired dynamic acuity and reduced the threshold for subjective fusion of a flickering light, but there were no changes with astemizole or terfenadine. The diameter of the pupil and its response to light were not changed by the drugs. 3 Performance on digit symbol substitution and cancellation was not altered by the drugs. 4 Astemizole and terfenadine are promising antihistamines for those involved in skilled activity. PMID:6128019

  8. A New Visual Stimulation Program for Improving Visual Acuity in Children with Visual Impairment: A Pilot Study

    PubMed Central

    Tsai, Li-Ting; Hsu, Jung-Lung; Wu, Chien-Te; Chen, Chia-Ching; Su, Yu-Chin

    2016-01-01

    The purpose of this study was to investigate the effectiveness of visual rehabilitation of a computer-based visual stimulation (VS) program combining checkerboard pattern reversal (passive stimulation) with oddball stimuli (attentional modulation) for improving the visual acuity (VA) of visually impaired (VI) children and children with amblyopia and additional developmental problems. Six children (three females, three males; mean age = 3.9 ± 2.3 years) with impaired VA caused by deficits along the anterior and/or posterior visual pathways were recruited. Participants received eight rounds of VS training (two rounds per week) of at least eight sessions per round. Each session consisted of stimulation with 200 or 300 pattern reversals. Assessments of VA (assessed with the Lea symbol VA test or Teller VA cards), visual evoked potential (VEP), and functional vision (assessed with the Chinese-version Functional Vision Questionnaire, FVQ) were carried out before and after the VS program. Significant gains in VA were found after the VS training [VA = 1.05 logMAR ± 0.80 to 0.61 logMAR ± 0.53, Z = –2.20, asymptotic significance (2-tailed) = 0.028]. No significant changes were observed in the FVQ assessment [92.8 ± 12.6 to 100.8 ±SD = 15.4, Z = –1.46, asymptotic significance (2-tailed) = 0.144]. VEP measurement showed improvement in P100 latency and amplitude or integration of the waveform in two participants. Our results indicate that a computer-based VS program with passive checkerboard stimulation, oddball stimulus design, and interesting auditory feedback could be considered as a potential intervention option to improve the VA of a wide age range of VI children and children with impaired VA combined with other neurological disorders. PMID:27148014

  9. Visual Acuity, Contrast Sensitivity and Color Vision Three Years After Iodine-125 Brachytherapy for Choroidal and Ciliary Body Melanoma

    PubMed Central

    Tsui, Irena; Beardsley, Robert M; McCannel, Tara A; Oliver, Scott C; Chun, Melissa W; Lee, Steve P; Chow, Phillip E; Agazaryan, Nzhde; Yu, Fei; Straatsma, Bradley R

    2015-01-01

    Purpose : To report visual acuity, contrast sensitivity and color vision prior to, 1 year after, 2 years after and 3 years after iodine-125 brachytherapy for choroidal and ciliary body melanoma (CCM). Design : Prospective interventional case series. Participants : Thirty-seven patients (37 eyes) with CCM. Methods : Patients had best-corrected Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, Pelli-Robson contrast sensitivity and Hardy-Rand-Rittler color vision measurement; comprehensive ophthalmology examination; optical coherence tomography; and ultrasonography at baseline prior to, 1 year after, 2 years after and 3 years after I-125 brachytherapy. Main Outcome Measures : Visual acuity, contrast sensitivity and color vision prior to, 1 year after, 2 years after and 3 years after brachytherapy. Results : Nineteen (19) men and 18 women with mean age of 58 years (SD 13, range 30-78) prior to, 1 year after, 2 years after and 3 years after brachytherapy had mean best-corrected visual acuity of 77 letters (20/32), 65 letters (20/50), 56 letters (20/80) and 47 letters (20/125); contrast sensitivity of 30, 26, 22 and 19 letters; color vision of 26, 20, 17 and 14 test figures, respectively. Decrease in visual acuity, contrast sensitivity and color vision was statistically significant from baseline at 1 year, 2 years, and 3 years after brachytherapy. Decreased acuity at 3 years was associated with mid-choroid and macula melanoma location, ≥ 4.1 mm melanoma height, radiation maculopathy and radiation optic neuropathy. Conclusion : 1, 2 and 3 years after brachytherapy, eyes with CCM had significantly decreased visual acuity, contrast sensitivity and color vision. PMID:26312123

  10. Microperimetric Biofeedback Training Improved Visual Acuity after Successful Macular Hole Surgery

    PubMed Central

    Ueda-Consolvo, Tomoko; Otsuka, Mitsuya; Hayashi, Yumiko; Ishida, Masaaki; Hayashi, Atsushi

    2015-01-01

    Purpose. To evaluate the efficacy of setting a preferred retinal locus relocation target (PRT) and performing Macular Integrity Assessment (MAIA) biofeedback training in patients showing insufficient recovery of best corrected visual acuity (BCVA) despite successful closure of an idiopathic macular hole (MH). Methods. Retrospective interventional case series. Nine eyes of 9 consecutive patients with the decimal BCVA of less than 0.6 at more than 3 months after successful MH surgery were included. A PRT was chosen based on MAIA microperimetry and the patients underwent MAIA biofeedback training. BCVA, reading speed, fixation stability, and 63% bivariate contour ellipse area (BCEA) were evaluated before and after the training. Statistical analysis was carried out using paired Student's t-test. Results. PRT was chosen on the nasal side of the closed MH fovea in 8 patients. After the MAIA training, BCVA improved in all patients. The mean logMAR value of BCVA significantly improved from 0.33 to 0.12 (p = 0.007). Reading speed improved in all patients (p = 0.29), fixation stability improved in 5 patients (p = 0.70), and 63% BCEA improved in 7 patients (p = 0.21), although these improvements were not statistically significant. Conclusion. MAIA biofeedback training improved visual acuity in patients with insufficient recovery of BCVA after successful MH surgery. PMID:26783452

  11. Night vision goggle (NVG) visual acuity under ideal conditions with various adjustment procedures.

    PubMed

    DeVilbiss, C A; Antonio, J C; Fiedler, G M

    1994-08-01

    Night operations involve diverse mission areas and require an increased reliance on the use of night vision devices, such as night vision goggles (NVG's). Any reduction in goggle or visual performance which goes undetected can have a serious effect on flight safety and operational capability. Under controlled lighting conditions, a crewmember should be able to obtain the best possible goggle performance, and to determine if the goggle is functioning properly. These data represent a sample of 218 current USAF aircrew members representing all crew positions in both rotary and fixed-wing aircraft. Three measurements of goggle performance, expressed as NVG visual acuity, were obtained. The first measure, obtained after crewmembers adjusted the goggles with their usual adjustment methods, showed that they routinely obtain less than optimal acuity levels; i.e., averaging between 20/50 and 20/55. The second measure, taken when the NVG Resolution Chart was provided to augment their "usual" method of adjustment, showed improved performance; i.e., averaging 20/45. The third measure, taken following participation in an NVG Adjustment Procedures class, showed the greatest improvement, averaging between 20/35 and 20/40. In summary, it is reasonable to conclude that aircrew members who are able to obtain the best possible performance for their NVG's under controlled preflight conditions will obtain the best possible goggle performance under the widely varying flight conditions.

  12. Dynamic Visual Acuity While Walking in Normals and Labyrinthine-Deficient Patients

    NASA Technical Reports Server (NTRS)

    Hillman, Edward J.; Bloomberg, Jacob J.; McDonald, P. Vernon; Cohen, Helen S.

    1996-01-01

    We describe a new, objective, easily administered test of dynamic visual acuity (DVA) while walking. Ten normal subjects and five patients with histories of severe bilateral vestibular dysfunctions participated in this study. Subjects viewed a visual display of numerals of different font sizes presented on a laptop computer while they stood still and while they walked on a motorized treadmill. Treadmill speed was adapted for 4 of 5 patients. Subjects were asked to identify the numerals as they appeared on the computer screen. Test results were reasonably repeatable in normals. The percent correct responses at each font size dropped slightly while walking in normals and dropped significantly more in patients. Patients performed significantly worse than normals while standing still and while walking. This task may be useful for evaluating post-flight astronauts and vestibularly impaired patients.

  13. The Use of Dynamic Visual Acuity as a Functional Test of Gaze Stabilization Following Space Flight

    NASA Technical Reports Server (NTRS)

    Peters, B. T.; Mulavara, A. P.; Brady, R.; Miller, C. A.; Richards, J. T.; Warren, L. E.; Cohen, H. S.; Bloomberg, J. J.

    2006-01-01

    After prolonged exposure to a given gravitational environment the transition to another is accompanied by adaptations in the sensorimotor subsystems, including the vestibular system. Variation in the adaptation time course of these subsystems, and the functional redundancies that exist between them make it difficult to accurately assess the functional capacity and physical limitations of astro/cosmonauts using tests on individual subsystems. While isolated tests of subsystem performance may be the only means to address where interventions are required, direct measures of performance may be more suitable for assessing the operational consequences of incomplete adaptation to changes in the gravitational environment. A test of dynamic visual acuity (DVA) is currently being used in the JSC Neurosciences Laboratory as part of a series of measures to assess the efficacy of a countermeasure to mitigate postflight locomotor dysfunction. In the current protocol, subjects visual acuity is determined using Landolt ring optotypes presented sequentially on a computer display. Visual acuity assessments are made both while standing and while walking at 1.8 m/s on a motorized treadmill. The use of a psychophysical threshold detection algorithm reduces the required number of optotype presentations and the results can be presented immediately after the test. The difference between the walking and standing acuity measures provides a metric of the change in the subject s ability to maintain gaze fixation on the visual target while walking. This functional consequence is observable regardless of the underlying subsystem most responsible for the change. Data from 15 cosmo/astronauts have been collected following long-duration (approx. 6 months) stays in space using a visual target viewing distance of 4.0 meters. An investigation of the group mean shows a change in DVA soon after the flight that asymptotes back to baseline approximately one week following their return to earth. The

  14. Designing GUIs for low vision by simulating reduced visual acuity: reduced resolution versus shrinking.

    PubMed

    Sandnes, Frode Eika

    2015-01-01

    The visual uniqueness of information carrying icon and text elements has received little attention in the HCI research literature. The information carrying elements of graphical designs must be visually unique in order to be visually recognizable. This is increasingly important with the diversity of form factors and types of information displays. This paper explores two simple strategies for testing visual designs by simulating low visual acuity, namely by reducing the resolution and by shrinking. Two case studies demonstrate that low vision simulation by shrinking is more effective than reducing the resolution. Moreover, the case studies show how the low vision simulation can help identify design aspects that need attention. Design shrinking is not a substitute for user testing on actual user groups, but meant as a tool for early screening of designs and an aid for designers to help understand the effects of their design. The method can also be used as a tool for communicating design problems and justifying design decisions to stakeholders of a project through presentations and reports.

  15. Proximal versus distal cue utilization in spatial navigation: the role of visual acuity?

    PubMed

    Carman, Heidi M; Mactutus, Charles F

    2002-09-01

    Proximal versus distal cue use in the Morris water maze is a widely accepted strategy for the dissociation of various problems affecting spatial navigation in rats such as aging, head trauma, lesions, and pharmacological or hormonal agents. Of the limited number of ontogenetic rat studies conducted, the majority have approached the problem of preweanling spatial navigation through a similar proximal-distal dissociation. An implicit assumption among all of these studies has been that the animal's visual system is sufficient to permit robust spatial navigation. We challenged this assumption and have addressed the role of visual acuity in spatial navigation in the preweanling Fischer 344-N rat by training animals to locate a visible (proximal) or hidden (distal) platform using double or null extramaze cues within the testing environment. All pups demonstrated improved performance across training, but animals presented with a visible platform, regardless of extramaze cues, simultaneously reached asymptotic performance levels; animals presented with a hidden platform, dependent upon location of extramaze cues, differentially reached asymptotic performance levels. Probe trial performance, defined by quadrant time and platform crossings, revealed that distal-double-cue pups demonstrated spatial navigational ability superior to that of the remaining groups. These results suggest that a pup's ability to spatially navigate a hidden platform is dependent on not only its response repertoire and task parameters, but also its visual acuity, as determined by the extramaze cue location within the testing environment. The standard hidden versus visible platform dissociation may not be a satisfactory strategy for the control of potential sensory deficits.

  16. Comparison of distance and near visual acuity in patients with vision loss due to cataract.

    PubMed

    Mercado, Carmel L; Doroslovački, Pavle; Wang, Jiangxia; Siddiqui, Aazim A; Kolker, Andrew F; Kolker, Richard J

    2017-02-01

    The purpose of this study was to assess whether there is a disparity in distance and near best-corrected visual acuity (BCVA) in cataract eyes. 102 patients with cataract (N = 121 eyes) were seen in clinic between January and November 2013 at the Wilmer Eye Institute Comprehensive Eye Service. An age-related macular degeneration (ARMD) group (N = 27 eyes) was also identified for comparison. Distance and near BCVA were measured as part of the standard ophthalmic evaluation. Snellen measurements were converted to their LogMAR equivalents for statistical analysis. Near was better than distance BCVA with mean difference of 1.38 lines (P < 0.001) in the cataract eyes. This disparity was not seen in the ARMD eyes. Near-distance BCVA disparity is a statistically significant finding seen with cataracts. This may have further implications in patients with both cataract and ARMD as the presence of disparity may suggest a cataract etiology playing a greater role in vision loss. This comparison may be useful for surgical prognostication and as a quick triage tool in conjunction with, or in place of, a potential acuity meter and dilated near-pinhole test.

  17. Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences

    PubMed Central

    Bartholomew, Alex J.; Lad, Eleonora M.; Cao, Dingcai; Bach, Michael; Cirulli, Elizabeth T.

    2016-01-01

    Despite the large amount of variation found in the night (scotopic) vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA) and contrast sensitivity (CS) to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain <30% of the variation in scotopic vision. The wide variation seen in young healthy volunteers with excellent photopic vision, the high test-retest agreement, and the vast majority of the variation in scotopic vision remaining unexplained by obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS) of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision. PMID:26886100

  18. The Effect of 3D Visual Simulator on Children’s Visual Acuity - A Pilot Study Comparing Two Different Modalities

    PubMed Central

    Ide, Takeshi; Ishikawa, Mariko; Tsubota, Kazuo; Miyao, Masaru

    2013-01-01

    Purpose : To evaluate the efficacy of two non-surgical interventions of vision improvement in children. Methods : A prospective, randomized, pilot study to compare fogging method and the use of head mounted 3D display. Subjects were children, between 5 to 15 years old, with normal best corrected visual acuity (BCVA) and up to -3D myopia. Subjects played a video game as near point work, and received one of the two methods of treatments. Measurements of uncorrected far visual acuity (UCVA), refraction with autorefractometer, and subjective accommodative amplitude were taken 3 times, at the baseline, after the near work, and after the treatment. Results : Both methods applied after near work, improved UCVA. Head mounted 3D display group showed significant improvement in UCVA and resulted in better UCVA than baseline. Fogging group showed improvement in subjective accommodative amplitude. While 3D display group did not show change in the refraction, fogging group’s myopic refraction showed significant increase indicating the eyes showed myopic change of eyes after near work and treatment. Discussion : Despite our lack of clear knowledge in the mechanisms, both methods improved UCVA after the treatments. The improvement in UCVA was not correlated to measured refraction values. Conclusion : UCVA after near work can be improved by repeating near and distant accommodation by fogging and 3D image viewing, although at the different degrees. Further investigation on mechanisms of improvements and their clinical significance are warranted. PMID:24222810

  19. [Laser pointers are not toys; eye injury with permanent loss of visual acuity].

    PubMed

    Keunen, Jan E E; Delbecq, Ann-Laure M H; Cruysberg, J R M Hans; van Meurs, Jan C; Gan, Ivan M; Berendschot, Tos T J M

    2014-01-01

    In the nineteen-nineties, there was much hype in the European media about presumed laser pointer maculopathy. However, the recent introduction of more powerful and therefore more dangerous laser pointers and their easy availability on the internet necessitates vigilance on the issue. This is an urgent matter, as here we report three cases of proven maculopathy due to an unsafe laser pointer. Three boys aged 13, 9 and 12 years used an unsafe laser pointer as a toy and looked repeatedly into the pointer, resulting in a permanent reduction in visual acuity due to macular damage. Laser pointers are not designed to be children's toys or instruments to annoy people in a crowd. Health authorities and the ophthalmic community should be aware of the potential danger of improper use of high-output laser pointers and warn the general public before the widespread availability of unsafe laser pointers and consequently laser pointer-induced macular damage becomes a true social problem.

  20. The Correlation of Age and Postoperative Visual Acuity for Age-Related Cataract

    PubMed Central

    Li, Xiaochun; Cao, Xiaoguang; Hou, Xianru; Bao, Yongzhen

    2016-01-01

    Purpose. Clinically, what is the best time for age-related cataract (ARC) patients to receive surgeries and get the most benefits is important. We explored the relationship between age and presenting postoperative visual acuity (POVA) in patients from rural China. Methods. Three Lifeline Express Hospital Eye-Train missions of Peking University People's Hospital were chosen. At the first day after surgery, 3452 ARC eyes with the presenting POVA ≥ 6/60 were enrolled. The relationship between age and POVA was analyzed statistically. Results. In these three missions, there were more female patients than males; the ratio of females to males was 1.71. The average age of females was older than males. Overall, the percentages of patients with good visual outcomes (≥6/18) were significantly decreased with aging. Different regions had variations, but the trends were the same. There was weak linear correlation between age and POVA. The correlations of females were stronger than males in Yuncheng and Sanmenxia and weaker than males in Zhoukou. Conclusion. The good visual outcomes of presenting POVA were significantly decreased with aging and there were weak linear correlations between age and POVA in rural China. The linear correlation might be influenced by the difference of gender and region. PMID:26881225

  1. Visual Acuity of Youths 12-17 Years, United States. Vital and Health Statistics, Series 11, No. 127.

    ERIC Educational Resources Information Center

    Roberts, Jean; Slaby, David

    Presented are the findings of a national health examination survey of uncorrected and corrected monocular and binocular visual acuity of 7,514 noninstitutionalized youth 12 to 17 years of age analyzed with respect to age, sex, race, geographic region, size of place of residence, and annual family income. Among findings reported are that 70 0/0 of…

  2. Brief Report: The Relationship between Visual Acuity, the Embedded Figures Test and Systemizing in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Brosnan, Mark J.; Gwilliam, Lucy R.; Walker, Ian

    2012-01-01

    Enhanced performance upon the Embedded Figures Test (EFT) in individuals with autism spectrum disorder (ASD) has informed psychological theories of the non-social aspects that characterise ASD. The Extreme Male Brain theory of autism proposes that enhanced visual acuity underpins greater attention to detail (assessed by the EFT) which is a…

  3. The level of improvement of visual acuity in high corneal astigmatism with rigid gas permeable contact lenses.

    PubMed

    Opačić, Dalibor; Miljak, Snježana; Ćuruvija-Opačić, Ksenija

    2015-03-01

    The aim of this study was to calculate the level of improvement of visual acuity comparing the best corrected visual acuity (VA) achieved with spectacles with the best corrected VA achieved with rigid gas permeable (RGP) contact lenses in patients with high, simple or compound corneal astigmatism (myopic, hypermetropic and mixed). The investigation of patients included auto-kerato-refractometry, manual keratometry, corneal topography and visual acuity with Snellen chart. The best corrected VA obtained with spectacles was compared with the best corrected VA obtained with RGP contact lenses in 72 patients (116 eyes). All patients showed a significant improvement in visual acuity with RGP lenses from one to seven lines compared to spectacles (p = 0.0001). Level of improvement in VA represented as the number of lines obtained was as follows: 74 percent of patients got two to four lines more in VA with RGP lenses compared to spectacles, and almost 10 percent of patients got five to seven lines. RGP contact lenses provide a significant improvement in VA compared to VA reached with spectacles in patients with high corneal astigmatism. The benefit in VA with RGP lenses is higher as the astigmatism is higher.

  4. Changes in Near Visual Acuity of Over Time in the Astronaut Corps

    NASA Technical Reports Server (NTRS)

    Taiym, Wafa; Wear, Mary L.; Locke, James; Mason, Sara; VanBaalen, Mary

    2014-01-01

    We hypothesized that visual impairment due to intracranial pressure (VIIP) would increase the rate of which presbyopia would occur in the astronaut population, with long durations flyers at an especially high risk. Presbyopia is characterized as the gradual loss of near visual acuity overtime due to a loss in ability to accommodate. It generally develops in the mid-40s and progresses until about age 65. This analysis considered annual vision exams conducted on active NASA astronauts with spaceflight experience currently between the ages of 40 to 60 years of age. Onset of presbyopia was characterized as a shift of at least 20 units on the standard Snellen test from one annual exam to the next. There were 236 short duration and 48 long duration flyers, the majority of whom did experience onset of presbyopia between age 40 and 60. This shift however, did not necessarily come after spaceflight. In comparing the short and long duration flyers the mean age of onset was 47 years old (SD+/-3.7). The mean of onset within the general population is 45 to 47 years old [1, 2]. The mean age of the onset of presbyopia as compared to the general population indicates that space flight does not induce early development of presbyopia.

  5. Spatial and temporal acuity of visual perception can be enhanced selectively by attentional set.

    PubMed

    Correa, Angel; Nobre, Anna C

    2008-08-01

    The aim of this research was to study the relationship between perceptual judgments about space and time. If spatial and temporal judgments were dissociable, they should be modulated selectively by attention. We compared the effect of the attentional set upon fine-grained spatial versus temporal discrimination of visual perception in two experiments. Using identical sensory stimulation, we measured perceptual judgments on either the size of a small spatial gap or the duration of a brief temporal gap. The attentional set was manipulated by cuing the task that was most likely to be performed. In one experiment, a neutral cue was also used, to measure relative benefits and costs of spatial and temporal task sets. If the attentional set could be directed selectively to spatial and temporal task-relevant dimensions, performance on both spatial and temporal acuity tasks should be specifically modulated by task cuing. The results showed that the attentional set enhanced the speed and accuracy of perceptual judgments similarly on both spatial and temporal tasks. Moreover, accuracy in one task was selectively enhanced by attending to that task while remaining unaffected by attending to the alternative task. This finding suggests multiple mechanisms, by which visual processing of spatial and temporal features can be selectively prepared without interfering with one another.

  6. A randomised comparison between an inexpensive, general-purpose headlight and a purpose-built surgical headlight on users' visual acuity and colour vision.

    PubMed

    Street, I; Sayles, M; Nistor, M; McRae, A R

    2014-02-01

    To determine if there are any differences in near visual acuity and colour vision between an inexpensive general-purpose light emitting diode (LED) headlight and a purpose-built surgical LED headlight. A prospective study was conducted sequentially comparing near visual acuity and colour vision, the headlights being tested in random order, in a testing room with a constant minimal amount of background light. The participants were NHS employee volunteers, with self-declared normal (or corrected) vision, working in occupations requiring full literacy. For visual acuity, outcome was measured by recording the smallest font legible when using each headlight when the subject read a near visual acuity test card. For colour vision, the outcome was passing or failing the Ishihara test. There was no statistically significant difference between the general-purpose and the purpose-built headlights in users' near visual acuity or colour vision.

  7. Visual Acuity, Retinal Sensitivity, and Macular Thickness Changes in Diabetic Patients without Diabetic Retinopathy after Cataract Surgery.

    PubMed

    Stunf Pukl, Spela; Vidović Valentinčič, Nataša; Urbančič, Mojca; Irman Grčar, Irena; Grčar, Rok; Pfeifer, Vladimir; Globočnik Petrovič, Mojca

    2017-01-01

    Aim. Functional and morphological macular study after cataract surgery in a group of diabetics without diabetic retinopathy compared to nondiabetics to evaluate the effect of surgical oxidative stress on diabetic retina. Methods. Prospective, comparative study. Preoperative eye exam, best corrected visual acuity (BCVA) measured by ETDRS letters, and optical coherence tomography (OCT) were followed by standard cataract surgery. The follow-up visits at 1, 3, and 6 months postoperatively included BCVA, OCT, and microperimetry, to analyze changes within and between the groups. Results. The BCVA improved significantly in diabetics and controls: 64.2 to 81.0 and 61.9 to 82.1 ETDRS at 6 months, respectively. The central macula at OCT significantly thickened in both groups, while the central 5 fields, corresponding to the microperimetry area, subclinically thickened from 284.20 to 291.18 μm at 6 months only in diabetics (p = 0.026). A matching slight decrease in the microperimetry sensitivity from 1 to 6 months was found also only in diabetics, with mean average difference -0.75 dB (p = 0.04). Conclusion. Underlying diabetes does not influence the surgical outcome in diabetics without diabetic retinopathy. However, slight thickening of wider macula and corresponding decrease in retinal sensitivity observed in diabetics 6 months postoperatively might influence visual function on long term.

  8. Visual Acuity, Retinal Sensitivity, and Macular Thickness Changes in Diabetic Patients without Diabetic Retinopathy after Cataract Surgery

    PubMed Central

    Irman Grčar, Irena; Grčar, Rok; Pfeifer, Vladimir

    2017-01-01

    Aim. Functional and morphological macular study after cataract surgery in a group of diabetics without diabetic retinopathy compared to nondiabetics to evaluate the effect of surgical oxidative stress on diabetic retina. Methods. Prospective, comparative study. Preoperative eye exam, best corrected visual acuity (BCVA) measured by ETDRS letters, and optical coherence tomography (OCT) were followed by standard cataract surgery. The follow-up visits at 1, 3, and 6 months postoperatively included BCVA, OCT, and microperimetry, to analyze changes within and between the groups. Results. The BCVA improved significantly in diabetics and controls: 64.2 to 81.0 and 61.9 to 82.1 ETDRS at 6 months, respectively. The central macula at OCT significantly thickened in both groups, while the central 5 fields, corresponding to the microperimetry area, subclinically thickened from 284.20 to 291.18 μm at 6 months only in diabetics (p = 0.026). A matching slight decrease in the microperimetry sensitivity from 1 to 6 months was found also only in diabetics, with mean average difference −0.75 dB (p = 0.04). Conclusion. Underlying diabetes does not influence the surgical outcome in diabetics without diabetic retinopathy. However, slight thickening of wider macula and corresponding decrease in retinal sensitivity observed in diabetics 6 months postoperatively might influence visual function on long term. PMID:28243608

  9. Visual acuity performance of several observers using the triangle orientation discrimination methodology

    NASA Astrophysics Data System (ADS)

    Mündel, Julia; Geisel, Bärbel; Braesicke, Katrin; Bürsing, Helge

    2016-10-01

    The Triangle Orientation Discrimination (TOD) is one of several methods to characterize electro-optical system performance. It is conducted by presenting an equilateral triangle pointing either up, down, right or left, to an observer who is forced to judge the direction. Based from the probability on the correctness of the answers in dependence of the size of the triangle, the quality of the system can be assessed. In order to gain experience with this method it was applied here to test Fraunhofer IOSBs new equipment for perception experiments. An experiment with four observers, ten contrast levels and six triangle sizes was conducted. Its results were analysed for observer performance versus time, illumination conditions and variations in the TOD-curve. Furthermore, different approaches on analysing the data were compared. The outcome showed the observers performance variation on different days to be statistically insignificant. In addition, the illumination conditions had no statistically significant influence on the result. Interestingly a larger difference was found between the observers. Although they had normal or corrected to normal eyesight, different visual acuity is the only explanation for the differences. This leads to the necessity to check observers of perception experiments more closely. The different approaches to curve fitting also gave variations, which would result in different ranges when applied in camera assessment. Here a standardization seems necessary when the method is applied in analytical models for imaging systems.

  10. Improvement of visual acuity in diabetic and nondiabetic patients after Nd:YAG laser capsulotomy

    PubMed Central

    Awan, Muhammed Tayyab; Khan, Muhammed Anwar; Al-Khairy, Saba; Malik, Samina

    2013-01-01

    Purpose The aim of the study reported here was to compare the improvement of visual acuity (VA) of diabetic and nondiabetic patients after neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser capsulotomy. Methods In this prospective cohort study, 50 age- and sex-matched patients, comprising 25 nondiabetics and 25 diabetics (referred to as Group A and B, respectively), with posterior chamber poly(methyl methacrylate) non-foldable intraocular lens implants attending our clinic at Karachi for capsulotomy had pre- and postoperative measures of VA, posterior pole visibility, and grading of posterior capsular opacity as seen on slit-lamp examination. VA was recorded before and after performing standard capsulotomy. Results The postoperative (mean) VA in nondiabetics was 0.25, 0.23, and 0.21 logMAR as compared with 0.25, 0.25, and 0.24 logMAR in diabetics at 1 week, 1 month, and 6 months, respectively. P-values of 0.47, 0.47, and 0.24, respectively, were determined, which were not significant. Preoperative VA improvement was recorded in 92% of diabetics in Group B and 96% of nondiabetics in Group A. Two (8%) diabetic patients developed glaucoma and did not participate in the study further. Conclusion Remarkable improvement in VA was achieved in both Group A and B, but the Group A nondiabetics showed more improvement in best-corrected VA after Nd:YAG laser capsulotomy. PMID:24143068

  11. Origins of superior dynamic visual acuity in baseball players: superior eye movements or superior image processing.

    PubMed

    Uchida, Yusuke; Kudoh, Daisuke; Murakami, Akira; Honda, Masaaki; Kitazawa, Shigeru

    2012-01-01

    Dynamic visual acuity (DVA) is defined as the ability to discriminate the fine parts of a moving object. DVA is generally better in athletes than in non-athletes, and the better DVA of athletes has been attributed to a better ability to track moving objects. In the present study, we hypothesized that the better DVA of athletes is partly derived from better perception of moving images on the retina through some kind of perceptual learning. To test this hypothesis, we quantitatively measured DVA in baseball players and non-athletes using moving Landolt rings in two conditions. In the first experiment, the participants were allowed to move their eyes (free-eye-movement conditions), whereas in the second they were required to fixate on a fixation target (fixation conditions). The athletes displayed significantly better DVA than the non-athletes in the free-eye-movement conditions. However, there was no significant difference between the groups in the fixation conditions. These results suggest that the better DVA of athletes is primarily due to an improved ability to track moving targets with their eyes, rather than to improved perception of moving images on the retina.

  12. Aircrew visual acuity viewing with different night vision goggle eyepiece diopter settings

    NASA Astrophysics Data System (ADS)

    Angel, Share-Dawn P.; Baldwin, J. Bruce

    2004-09-01

    The AN/AVS-9 night vision goggle (NVG) has an eyepiece lens that can be adjusted from +2 to -6 diopters (D). We have shown previously1,2,3 that on average NVG users tend to select about -1D, with a range of +0.5D to -4D3. This study was designed to evaluate NVG visual acuity (NVG VA) and subjective ratings for a range of diopter settings including user-selected and three fixed settings of -0.25D, -1D and -2D. Twenty-one experienced USAF Special Operations aircrew members, including 15 pilots, served as subjects. The median user-selected setting was -1.25D and ranged from +0.5D to -3.5D. Only 2 of the 21 subjects had user-selected NVG VA significantly better than a fixed setting of -1D. Of those two, one was not wearing prescribed glasses and the other was 49 years old, presbyopic, and could not focus through the -1D lenses. Subjective ratings and NVG VA indicated that most people could fly with a fixed setting of -1D for each eye, although two individuals needed different diopter settings for the right and left eyes. The new Panoramic NVG (PNVG) has a fixed eyepiece focus of -1D. Results suggest the PNVG should have a limited set of accessory lenses available.

  13. How well do you see what you hear? The acuity of visual-to-auditory sensory substitution

    PubMed Central

    Haigh, Alastair; Brown, David J.; Meijer, Peter; Proulx, Michael J.

    2013-01-01

    Sensory substitution devices (SSDs) aim to compensate for the loss of a sensory modality, typically vision, by converting information from the lost modality into stimuli in a remaining modality. “The vOICe” is a visual-to-auditory SSD which encodes images taken by a camera worn by the user into “soundscapes” such that experienced users can extract information about their surroundings. Here we investigated how much detail was resolvable during the early induction stages by testing the acuity of blindfolded sighted, naïve vOICe users. Initial performance was well above chance. Participants who took the test twice as a form of minimal training showed a marked improvement on the second test. Acuity was slightly but not significantly impaired when participants wore a camera and judged letter orientations “live”. A positive correlation was found between participants' musical training and their acuity. The relationship between auditory expertise via musical training and the lack of a relationship with visual imagery, suggests that early use of a SSD draws primarily on the mechanisms of the sensory modality being used rather than the one being substituted. If vision is lost, audition represents the sensory channel of highest bandwidth of those remaining. The level of acuity found here, and the fact it was achieved with very little experience in sensory substitution by naïve users is promising. PMID:23785345

  14. Metformin Impairs Spatial Memory and Visual Acuity in Old Male Mice

    PubMed Central

    Thangthaeng, Nopporn; Rutledge, Margaret; Wong, Jessica M.; Vann, Philip H.; Forster, Michael J.; Sumien, Nathalie

    2017-01-01

    Metformin is an oral anti-diabetic used as first-line therapy for type 2 diabetes. Because benefits of metformin extend beyond diabetes to other age-related pathology, and because its effect on gene expression profiles resembles that of caloric restriction, metformin has a potential as an anti-aging intervention and may soon be assessed as an intervention to extend healthspan. However, beneficial actions of metformin in the central nervous system have not been clearly established. The current study examined the effect of chronic oral metformin treatment on motor and cognitive function when initiated in young, middle-aged, or old male mice. C57BL/6 mice aged 4, 11, or 22 months were randomly assigned to either a metformin group (2 mg/ml in drinking water) or a control group. The mice were monitored weekly for body weight, as well as food and water intake and a battery of behavioral tests for motor, cognitive and visual function was initiated after the first month of treatment. Liver, hippocampus and cortex were collected at the end of the study to assess redox homeostasis. Overall, metformin supplementation in male mice failed to affect blood glucose, body weights and redox homeostasis at any age. It also had no beneficial effect on age-related declines in psychomotor, cognitive or sensory functions. However, metformin treatment had a deleterious effect on spatial memory and visual acuity, and reduced SOD activity in brain regions. These data confirm that metformin treatment may be associated with deleterious effect resulting from the action of metformin on the central nervous system. PMID:28203479

  15. A novel computer software for the evaluation of dynamic visual acuity

    PubMed Central

    Quevedo, Lluïsa; Aznar-Casanova, José Antonio; Merindano-Encina, Dolores; Cardona, Genís; Solé-Fortó, Joan

    2012-01-01

    Purpose Dynamic visual acuity (DVA) is defined as the ability to discriminate fine details in a moving target. Albeit a growing interest in DVA, there is a lack of standardized, validated instrumentation and procedures for the assessment of this visual function parameter. The aim of the present study was to analyze qualitative construct validity and test–retest reliability of a novel, computer-assisted instrument (DinVA 3.0) for the measurement of DVA. Methods Two different experiments are presented, involving the participation of 33 subjects. The first experiment aimed at testing qualitative construct validity of the DinVA 3.0 by comparing the outcome of a series of trials consisting in different speeds, contrasts and trajectories of the target stimuli with those reported in the literature. The second experiment assessed test–retest reliability by repeating a series of trials at three different time intervals, at maximum target stimuli contrast and either high or low speed configurations. Results The results of the first experiment gave support to the qualitative construct validity of DinVA 3.0, as the DVA scores were found to be modulated by the speed of the moving target (high speeds yielded lower DVA), contrast (high contrast resulted in better DVA) and trajectory (DVA was better at horizontal rather than oblique trajectories). Test–retest reliability was found to be good, with a small insignificant trend towards improvement with learning. Conclusion The DinVA 3.0 proved to be a valid and reliable instrument for the assessment of DVA and may be considered a promising tool for both clinicians and researchers.

  16. Associations among Visual Acuity and Vision- and Health-Related Quality of Life among Patients in the Multicenter Uveitis Steroid Treatment Trial

    PubMed Central

    Drye, Lea T.; Kempen, John H.; Dunn, James P.; Holland, Gary N.; Latkany, Paul; Rao, Narsing A.; Sen, H. Nida; Sugar, Elizabeth A.; Thorne, Jennifer E.; Wang, Robert C.; Holbrook, Janet T.

    2012-01-01

    Purpose. To evaluate the associations between visual acuity and self-reported visual function; visual acuity and health-related quality of life (QoL) metrics; a summary measure of self-reported visual function and health-related QoL; and individual domains of self-reported visual function and health-related QoL in patients with uveitis. Methods. Best-corrected visual acuity, vision-related functioning as assessed by the NEI VFQ-25, and health-related QoL as assessed by the SF-36 and EuroQoL EQ-5D questionnaires were obtained at enrollment in a clinical trial of uveitis treatments. Multivariate regression and Spearman correlations were used to evaluate associations between visual acuity, vision-related function, and health-related QoL. Results. Among the 255 patients, median visual acuity in the better-seeing eyes was 20/25, the vision-related function score indicated impairment (median, 60), and health-related QoL scores were within the normal population range. Better visual acuity was predictive of higher visual function scores (P ≤ 0.001), a higher SF-36 physical component score, and a higher EQ-5D health utility score (P < 0.001). The vision-specific function score was predictive of all general health-related QoL (P < 0.001). The correlations between visual function score and general quality of life measures were moderate (ρ = 0.29–0.52). Conclusions. The vision-related function score correlated positively with visual acuity and moderately positively with general QoL measures. Cost–utility analyses relying on changes in generic healthy utility measures will be more likely to detect changes when there are clinically meaningful changes in vision-related function, rather than when there are only changes in visual acuity. (ClinicalTrials.gov number, NCT00132691.) PMID:22247489

  17. Quantitative Analysis of the Effects of a Bangerter Filter on Gross Stereopsis in Experimental Models of Reduced Visual Acuity.

    PubMed

    Miyata, Manabu; Nakahara, Ryuichi; Hamasaki, Ichiro; Hasebe, Satoshi; Furuse, Takashi; Ohtsuki, Hiroshi

    2016-10-01

    Although a 0.3 Bangerter filter, which reduces visual acuity, is frequently used for treating moderate amblyopia, the effects on gross stereopsis are not well known. This study quantitatively evaluated whether gross stereopsis is degraded by a Bangerter filter. Seven healthy subjects (median age: 29 years) participated in this psychophysical study. Targets with crossed disparities of 1°, 2°, 3°, 4°, and 5° were randomly presented on a three-dimensional television display. The subjects indicated the point at which the targets popped out from the television screen (matching method). The distance from the screen to the point was defined as the degree of stereopsis. This experiment was performed with and without a 0.3 Bangerter filter. The corrected monocular visual acuities were decreased to about 20/63 by the filter in all subjects. No significant difference was observed for any of the disparities (1°-5°), between the degree of stereopsis visualized with and without filters for either the dominant or the non-dominant eye. The degree of stereopsis was not degraded by the reduced visual acuity induced by the use of 0.3 Bangerter filters. In this regard, the use of 0.3 Bangerter filters may be considered safer than occlusion eye patches for the patients with normal binocular vision.

  18. Comparison of Visual Acuity in Reduced Lumination and Facility of Ocular Accommodation in Table Tennis Champions and Non- Players

    PubMed Central

    Jafarzadehpur, Ebrahim; Yarigholi, Mohammad R.

    2004-01-01

    A table tennis player should fixate at different distances; track the objects with different speed, and in different visual environment. Their visual skills must be well developed for these capabilities. Therefore, visual acuity in reduced lumination and facility of ocular accommodation those are two criteria for visual skills have been compared in table tennis players and normal non-players. Twenty-nine young table tennis champions and 29 normal matched non-players (did not take part in any racket sports game) were evaluated. Basic visual and eye examinations were done for both of them. Normal results in basic examination were fundamental requirement for all the subjects. +/-2.00 sphere lenses for accommodation facility are used. An electrical current regulator changed the output light intensity of a conventional chart projector (Topcon). Light intensity decreased to 10 cd·m-2 and visual acuity tested. In comparison of visual acuity in reduced lumination and facility of ocular accommodation in table tennis champions and non-players there are significant differences (p < 0.001). In the preliminary visual tests there was not any significant different in the two groups but the results in the top level table tennis player was very uniform and in every test and the standard deviation was lesser in tennis player group than non-players. These results show that motor and sensorial functions of expert players are well developed. That is consistent with other researchers. This result was interpreted as reflecting a better perceptual system of experts to the constraints encountered during table tennis and its use in practical settings for evaluating athletes or detecting sport talents. However some visual and perceptual training that usually used in orthoptics can be used for novice table tennis player to improve their abilities. Key Points That the ability of a champion depends on many sensory, motor and perceptual factors. Visual factors such as facility of accommodation

  19. Change in visual acuity is highly correlated with change in six image quality metrics independent of wavefront error and/or pupil diameter

    PubMed Central

    Ravikumar, Ayeswarya; Sarver, Edwin J.; Applegate, Raymond A.

    2012-01-01

    It is well known that the wavefront error (WFE) of the eye varies from individual to individual with pupil diameter (PD) and age. Numerous studies have been proposed evaluating the relationship between visual acuity and WFE, but all these studies were performed with either a fixed or natural PD. It is still not clear if metrics of image quality correlate well with visual acuity independent of PD. Here we investigate the correlation between the change in visual acuity and the change in 30 image quality metrics for a range of optical quality typically established in normal eyes that varies both with age and PD. Visual acuity was recorded for 4 normal subjects using simulated blurred logMAR acuity charts generated from the point spread functions of different scaled WFEs for 6 different PDs (2–7 mm in 1 mm steps). Six image quality metrics (log neural sharpness, log visual Strehl [spatial domain], log visual Strehl [MTF method], log pupil fraction [tessellated], log pupil fraction [concentric area], and log root mean square of WFE slope) accounted for over 80% of variance in change in acuity across all WFEs and all PDs. Multiple regression analysis did not significantly increase the R2. Simple metrics derived from WFE could potentially act as an objective surrogate to visual acuity without the need for complex models. PMID:22984224

  20. Outcomes of visual acuity in carbon ion radiotherapy: Analysis of dose-volume histograms and prognostic factors

    SciTech Connect

    Hasegawa, Azusa . E-mail: azusa@nirs.go.jp; Mizoe, Jun-etsu; Mizota, Atsushi; Tsujii, Hirohiko

    2006-02-01

    Purpose: To analyze the tolerance dose for retention of visual acuity in patients with head-and-neck tumors treated with carbon ion radiotherapy. Methods and Materials: From June 1994 to March 2000, 163 patients with tumors in the head and neck or skull base region were treated with carbon ion radiotherapy. Analysis was performed on 54 optic nerves (ONs) corresponding to 30 patients whose ONs had been included in the irradiated volume. These patients showed no evidence of visual impairment due to other factors and had a follow-up period of >4 years. All patients had been informed of the possibility of visual impairment before treatment. We evaluated the dose-complication probability and the prognostic factors for the retention of visual acuity in carbon ion radiotherapy, using dose-volume histograms and multivariate analysis. Results: The median age of 30 patients (14 men, 16 women) was 57.2 years. Median prescribed total dose was 56.0 gray equivalents (GyE) at 3.0-4.0 GyE per fraction per day (range, 48-64 GyE; 16-18 fractions; 4-6 weeks). Of 54 ONs that were analyzed, 35 had been irradiated with <57 GyE (maximum dose [D{sub max}]) resulting in no visual loss. Conversely, 11 of the 19 ONs (58%) irradiated with >57 GyE (D{sub max}) suffered a decrease of visual acuity. In all of these cases, the ONs had been involved in the tumor before carbon ion radiotherapy. In the multivariate analysis, a dose of 20% of the volume of the ON (D{sub 2}) was significantly associated with visual loss. Conclusions: The occurrence of visual loss seems to be correlated with a delivery of >60 GyE to 20% of the volume of the ON.

  1. Is 20/20 vision good enough? Visual acuity differences within the normal range predict contour element detection and integration.

    PubMed

    Keane, Brian P; Kastner, Sabine; Paterno, Danielle; Silverstein, Steven M

    2015-02-01

    Contour integration (CI) combines appropriately aligned and oriented elements into continuous boundaries. Collinear facilitation (CF) occurs when a low-contrast oriented element becomes more visible when flanked by collinear high-contrast elements. Both processes rely at least partly on long-range horizontal connections in early visual cortex, and thus both have been extensively studied to understand visual cortical functioning in aging, development, and clinical disorders. Here, we ask: Can acuity differences within the normal range predict CI or CF? To consider this question, we measured binocular visual acuity and compared subjects with 20/20 vision to those with better-than-20/20 vision (SharpPerceivers) on two tasks. In the CI task, subjects located an integrated shape embedded in varying amounts of noise; in the CF task, subjects detected a low-contrast element flanked by collinear or orthogonal high-contrast elements. In each case, displays were scaled in size to modulate element visibility and spatial frequency (4-12 cycles/deg). SharpPerceivers could integrate contours under noisier conditions than the 20/20 group (p = .0002), especially for high spatial frequency displays. Moreover, although the two groups exhibited similar collinear facilitation, SharpPerceivers could detect the central target with lower contrast at high spatial frequencies (p <. 05). These results suggest that small acuity differences within the normal range--corresponding to about a one line difference on a vision chart--strongly predict element detection and integration. Furthermore, simply ensuring that subjects have normal or corrected-to-normal vision is not sufficient when comparing groups on contour tasks; visual acuity confounds also need to be ruled out.

  2. Stroboscopic Goggles as a Countermeasure for Dynamic Visual Acuity and Landing Sickness in Crewmembers Returning from Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Rosenberg, M. J. F.; Kreutzberg, G. A.; Peters, B. T.; Reschke, M. F.

    2017-01-01

    Long-term exposure to microgravity causes sensorimotor adaptations that result in functional deficits upon returning to a gravitational environment. At landing, the vestibular system and the central nervous system, responsible for coordinating head and eye movements via the vestibulo-occular reflex (VOR), are adapted to microgravity and must re-adapt to the Earth's gravitational environment. This re-adaptation causes decrements in gaze control and dynamic visual acuity, with astronauts reporting oscillopsia and blurred vision. These effects are caused by retinal slip, or the inability to keep an image focused on their retina, which is thought to drive motion sickness symptoms experienced upon landing. Retinal slip can be estimated by dynamic visual acuity (DVA); visual acuity while in motion. Peters et al. (2011) find that DVA is worsened in astronauts by an average of 0.75 eye-chart lines one day after landing. Previously, the use of stroboscopic goggles has shown to be effective in minimizing motion sickness symptoms due to retinal slip (Reschke et al. 2007). In this study, we simulated the decrement in DVA caused by sensorimotor re-adaptation by using minifying lenses and then testing the efficacy of stroboscopic goggles in preventing retinal slip and improving DVA. Dynamic visual acuity is assessed using an oscillating chair developed in the Neuroscience Laboratory at JSC. This chair is motor-driven and oscillates vertically at 2 Hz with a vertical displacement of +/- 2 cm to simulate the vertical translations that occur while walking. As the subject is being oscillated, they are asked to discern the direction of Landolt-C optotypes of varying sizes and record their direction using a gamepad. The visual acuity thresholds are determined using an algorithm that alters the size of the optotype based on the previous responses of the subject using a forced-choice best parameter estimation that is able to rapidly converge on the threshold value. Visual acuity

  3. Testing vision testing: quantifying the effect of movement on visual acuity measurement

    PubMed Central

    Tidbury, L P; O'Connor, A R

    2015-01-01

    Purpose Assessment of visual acuity (VA) has been shown to vary between tests, which may be attributable in part to test inaccuracies, such as a change in the distance between the chart and subject. Therefore, the study aim was to quantify changes in chart/patient separation during near and distance VA testing, and to analyse the relationship between VA and movement observed. Methods Volunteer orthoptists and subjects were filmed during near and distance VA testing, with the amount of movement determined from the recording. Controlling for movement using chin rests and chart stands, VA was retested. Actual changes in VA due to a change in subject or chart movement were compared with theoretical predictions. Results Fifty-one subjects (18–73 years) were assessed. Median (interquartile) movements of 0.06 m (0.07) towards and 0.11 m (0.08) away from the chart were measured (maximum 0.17 m towards and 0.24 m away). Significant differences in VA score were measured when movement was restricted, at near and distance (P<0.05). VA score change agreed with predicted values in 67% of the cases, however, reduced test distance during near vision testing resulted in a degradation of VA, opposite to the improvement expected. Conclusion There were significant variations in subject/chart separation during testing, which could have affected VA values. While this movement is associated with a change in VA, additional factors to movement appear to influence the score achieved during near testing. Procedures to minimise variation, by eliminating movement of test chart or subject, will improve VA test accuracy. PMID:25341437

  4. A phytochemical-rich diet may explain the absence of age-related decline in visual acuity of Amazonian hunter-gatherers in Ecuador.

    PubMed

    London, Douglas S; Beezhold, Bonnie

    2015-02-01

    Myopia is absent in undisturbed hunter-gatherers but ubiquitous in modern populations. The link between dietary phytochemicals and eye health is well established, although transition away from a wild diet has reduced phytochemical variety. We hypothesized that when larger quantities and greater variety of wild, seasonal phytochemicals are consumed in a food system, there will be a reduced prevalence of degenerative-based eye disease as measured by visual acuity. We compared food systems and visual acuity across isolated Amazonian Kawymeno Waorani hunter-gatherers and neighboring Kichwa subsistence agrarians, using dietary surveys, dietary pattern observation, and Snellen Illiterate E visual acuity examinations. Hunter-gatherers consumed more food species (130 vs. 63) and more wild plants (80 vs. 4) including 76 wild fruits, thereby obtaining larger variety and quantity of phytochemicals than agrarians. Visual acuity was inversely related to age only in agrarians (r = -.846, P < .001). As hypothesized, when stratified by age (<40 and ≥ 40 years), Mann-Whitney U tests revealed that hunter-gatherers maintained high visual acuity throughout life, whereas agrarian visual acuity declined (P values < .001); visual acuity of younger participants was high across the board, however, did not differ between groups (P > .05). This unusual absence of juvenile-onset vision problems may be related to local, organic, whole food diets of subsistence food systems isolated from modern food production. Our results suggest that intake of a wider variety of plant foods supplying necessary phytochemicals for eye health may help maintain visual acuity and prevent degenerative eye conditions as humans age.

  5. Low contrast visual acuity testing is associated with cognitive performance in multiple sclerosis: a cross-sectional pilot study

    PubMed Central

    2013-01-01

    Background Cognitive impairment and visual deterioration are two key clinical symptoms in MS and affect 50 to 80% of patients. Little is known about the influence of cognitive impairment on visual tests recommended for MS such as low contrast sensitivity testing. Our objective was to investigate whether low contrast sensitivity testing is influenced by cognitive impairment in multiple sclerosis (MS) patients. Methods Cross-sectional study including 89 patients with relapsing-remitting MS. All patients received cognitive evaluation using Rao’s Brief Repeatable Battery of Neuropsychological Testing (BRB-N). Visual assessments included low contrast sensitivity (CS) by functional acuity contrast testing and high contrast visual acuity (VA) using ETDRS charts. Retinal morphology as visual impairment correlate was measured using retinal nerve fiber layer (RNFL) thickness by optical coherence tomography. Results In combined analyses using generalized estimating equation models, Paced Auditory Serial Addition Test (PASAT) and RNFL as well as and the Symbol Digit Modalities Test (SDMT) and RNFL predicted CS. To further control for a potential influence of the anterior visual system we performed partial correlation analyses between visual function and cognitive function test results but controlling for RNFL. Even when controlling for RNFL, CS was associated with PASAT performance and SDMT performance. Conclusion Our data show that: a) cognitive impairment and performance in visual function tests such as low contrast sensitivity testing are associated; b) the main cognitive domains correlating with visual test performance are information processing speed and, to a lesser degree, memory; This preliminary data needs to be substantiated in further studies investigating patients with a higher cognitive burden, healthy controls and in longitudinal settings. PMID:24206900

  6. Sporadic Visual Acuity Loss in the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT)

    PubMed Central

    Kim, Benjamin J.; Ying, Gui-Shuang; Huang, Jiayan; Levy, Nicole E.; Maguire, Maureen G.

    2014-01-01

    Purpose To evaluate transient, large visual acuity (VA) decreases, termed sporadic vision loss, during anti-vascular endothelial growth factor treatment for neovascular age-related macular degeneration (AMD). Design Cohort within a randomized clinical trial. Methods Setting Comparison of AMD Treatments Trials (CATT). Study Population 1185 CATT patients. Main Outcome Measures incidence of sporadic vision loss and odds ratio (OR) for association with patient and ocular factors. Sporadic vision loss was a decline of ≥ 15 letters from the previous visit, followed by a return at the next visit to no more than 5 letters worse than the visit before the VA loss. Results There were 143 sporadic vision loss events in 122/1185 (10.3%) patients. Mean VA at two years for those with and without sporadic vision loss was 58.5 (~20/63) and 68.4 (~20/40) letters, respectively (P < 0.001). Among patients treated pro re nata, no injection was given for 27.6% (27/98) of sporadic vision loss events. Multivariate analysis demonstrated that baseline predictors for sporadic vision loss included worse baseline VA (OR 2.92, 95%CI:1.65–5.17 for ≤ 20/200 compared with ≥ 20/40), scar (OR 2.21, 95%CI:1.22–4.01), intraretinal foveal fluid on optical coherence tomography (OR 1.80, 95%CI:1.11–2.91), and medical history of anxiety (OR 1.90, 95%CI:1.12–3.24) and syncope (OR 2.75, 95%CI:1.45–5.22). Refraction decreased the likelihood of sporadic vision loss (OR 0.62, 95%CI:0.42–0.91). Conclusions Approximately 10% of CATT patients had sporadic vision loss. Baseline predictors included AMD-related factors and factors independent of AMD. These data are relevant for clinicians in practice and those involved in clinical trials. PMID:24727261

  7. Impact of visual acuity on developing literacy at age 4–5 years: a cohort-nested cross-sectional study

    PubMed Central

    Bruce, Alison; Fairley, Lesley; Chambers, Bette; Wright, John; Sheldon, Trevor A

    2016-01-01

    Objectives To estimate the prevalence of poor vision in children aged 4–5 years and determine the impact of visual acuity on literacy. Design Cross-sectional study linking clinical, epidemiological and education data. Setting Schools located in the city of Bradford, UK. Participants Prevalence was determined for 11 186 children participating in the Bradford school vision screening programme. Data linkage was undertaken for 5836 Born in Bradford (BiB) birth cohort study children participating both in the Bradford vision screening programme and the BiB Starting Schools Programme. 2025 children had complete data and were included in the multivariable analyses. Main outcome measures Visual acuity was measured using a logMAR Crowded Test (higher scores=poorer visual acuity). Literacy measured by Woodcock Reading Mastery Tests-Revised (WRMT-R) subtest: letter identification (standardised). Results The mean (SD) presenting visual acuity was 0.14 (0.09) logMAR (range 0.0–1.0). 9% of children had a presenting visual acuity worse than 0.2logMAR (failed vision screening), 4% worse than 0.3logMAR (poor visual acuity) and 2% worse than 0.4logMAR (visually impaired). Unadjusted analysis showed that the literacy score was associated with presenting visual acuity, reducing by 2.4 points for every 1 line (0.10logMAR) reduction in vision (95% CI −3.0 to −1.9). The association of presenting visual acuity with the literacy score remained significant after adjustment for demographic and socioeconomic factors reducing by 1.7 points (95% CI −2.2 to −1.1) for every 1 line reduction in vision. Conclusions Prevalence of decreased visual acuity was high compared with other population-based studies. Decreased visual acuity at school entry is associated with reduced literacy. This may have important implications for the children's future educational, health and social outcomes. PMID:26883240

  8. Stroboscopic Goggles as a Countermeasure for Dynamic Visual Acuity and Landing Sickness After Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Rosenberg, M. J. F.; Kreutzberg, G. A.; Peters, B. T.; Reschke, M. F.

    2017-01-01

    Gravity transitions cause changes in the vestibulo-occular reflex (VOR), which manifests as poor gaze control, a decrement in dynamic visual acuity (the ability to maintain gaze while in motion), both of which are caused by retinal slip. Retinal slip, the inability to keep an image focused on the retina, can drive or worsen sensory conflict, resulting in motion sickness (MS). Currently 100% of returning crewmembers report MS symptoms, which might affect their ability to perform mission critical tasks immediately after landing. Reschke et al. (2007) demonstrate that stroboscopic vision goggles improve motion sickness onset and symptom severity in motion sickness driven by retinal slip.

  9. "Far" and "Near" Visual Acuity While Walking and the Collective Contributions of Non-Ocular Mechanisms to Gaze Stabilization

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; vanEmmerik, Richard E. A.; Bloomberg, Jacob J.

    2006-01-01

    Gaze stabilization was quantified in subjects (n=11) as they walked on a motorized treadmill (1.8 m/s) and viewed visual targets at two viewing distances. A "far" target was positioned at 4 m (FAR) in front of the subject and the "near" target was placed at a distance of 0.5 m (NEAR). A direct measure of visual acuity was used to assess the overall effectiveness of the gaze stabilization system. The contributions of nonocular mechanisms to the gaze goal were also quantified using a measure of the distance between the subject and point in space where fixation of the visual target would require the least eye movement amplitude (i.e. the head fixation distance (HFD)). Kinematic variables mirrored those of previous investigations with the vertical trunk translation and head pitch signals, and the lateral translation and head yaw signals maintaining what appear as antiphase relationships. However, an investigation of the temporal relationships between the maxima and minima of the vertical translation and head pitch signals show that while the maximum in vertical translation occurs at the point of the minimum head pitch signal, the inverse is not true. The maximum in the head pitch signal lags the vertical translation minimum by an average of greater than 12 percent of the step cycle time. Three HFD measures, one each for data in the sagittal and transverse planes, and one that combined the movements from both planes, all revealed changes between the FAR and NEAR target viewing conditions. This reorganization of the nonocular degrees of freedom while walking was consistent with a strategy to reduce the magnitude of the eye movements required when viewing the NEAR target. Despite this reorganization, acuity measures show that image stabilization is not occurring while walking and viewing the NEAR target. Group means indicate that visual acuity is not affected while walking in the FAR condition, but a decrement of 0.15 logMAR (i.e. 1.5 eye chart lines) exists between the

  10. Reproducibility of Nigh Vision Goggle Visual Acuity Measurements Using Landolt C’s

    DTIC Science & Technology

    1999-12-08

    Task, 1979), Snellen Acuity (Bailey & Lovie, 1979; Wiley, 1989; Miller, Provines, Block & Tredici, 1984), square-wave targets (Task & Genco , 1986...the observer focused the corresponding objective lens by viewing the 3 x 3A, NVG high- contrast square-wave resolution chart (Task & Genco , 1986...for television displays. Technical Report No. AMRL-TR-79-7. NTIS: Alexandria VA. Task, H. L. and Genco , L. V. (1986). Contrast sensitivity function

  11. Higher Cognitive Function in Elderly Individuals with Previous Cataract Surgery: Cross-Sectional Association Independent of Visual Acuity in the HEIJO-KYO Cohort.

    PubMed

    Miyata, Kimie; Obayashi, Kenji; Saeki, Keigo; Tone, Nobuhiro; Tanaka, Kunihiko; Nishi, Tomo; Morikawa, Masayuki; Kurumatani, Norio; Ogata, Nahoko

    2016-06-01

    Cataract surgery improves visual acuity and drastically increases the capacity for light reception to the retina. Although previous studies suggested that both light exposure and visual acuity were associated with cognitive function, the relationships between cataract surgery, visual acuity, and cognitive function have not been evaluated in large populations. In this cross-sectional study, we measured cognitive function using the Mini-Mental State Examination and best-corrected visual acuity in pseudophakic (previous cataract surgery) and phakic (no previous cataract surgery) elderly individuals. Of 945 participants (mean age 71.7 years), 166 (17.6%) had pseudophakia and 317 (33.5%) had impaired cognitive function (score ≤26). The pseudophakic group showed significantly better visual acuity than the phakic group (p = 0.003) and lower age-adjusted odds ratio (ORs) for cognitive impairment (OR 0.66; p = 0.038). Consistently, in multivariate logistic regression models, after adjusting for confounding factors, including visual acuity and socioeconomic status, ORs for cognitive impairment were significantly lower in the pseudophakic group than in the phakic group (OR 0.64; 95% confidence interval 0.43-0.96; p = 0.031). This association remained significant in sensitivity analysis, excluding participants with low cognitive score ≤23 (n = 36). In conclusion, in a general elderly population, prevalence of cognitive impairment was significantly lower in pseudophakic individuals independently of visual acuity. The association was also independent of several major causes of cognitive impairment such as aging, gender, obesity, socioeconomic status, hypertension, diabetes, sleep disturbances, depressive symptoms, and physical inactivity.

  12. Higher-order aberrations and best-corrected visual acuity in Native American children with a high prevalence of astigmatism

    PubMed Central

    Miller, Joseph M.; Harvey, Erin M.; Schwiegerling, Jim

    2016-01-01

    Purpose To determine whether higher-order aberrations (HOAs) in children from a highly astigmatic population differ from population norms and whether HOAs are associated with astigmatism and reduced best-corrected visual acuity. Methods Subjects were 218 Tohono O’odham Native American children 5–9 years of age. Noncycloplegic HOA measurements were obtained with a handheld Shack-Hartmann sensor (SHS). Signed (z06s to z14s) and unsigned (z06u to z14u) wavefront aberration Zernike coefficients Z(3,−3) to Z(4,4) were rescaled for a 4 mm diameter pupil and compared to adult population norms. Cycloplegic refraction and best-corrected logMAR letter visual acuity (BCVA) were also measured. Regression analyses assessed the contribution of astigmatism (J0) and HOAs to BCVA. Results The mean root-mean-square (RMS) HOA of 0.191 ± 0.072 μm was significantly greater than population norms (0.100 ± 0.044 μm. All unsigned HOA coefficients (z06u to z14u) and all signed coefficients except z09s, z10s, and z11s were significantly larger than population norms. Decreased BCVA was associated with astigmatism (J0) and spherical aberration (z12u) but not RMS coma, with the effect of J0 about 4 times as great as z12u. Conclusions Tohono O’odham children show elevated HOAs compared to population norms. Astigmatism and unsigned spherical aberration are associated with decreased acuity, but the effects of spherical aberration are minimal and not clinically significant. PMID:26239206

  13. Visual acuity and patient satisfaction at varied distances and lighting conditions after implantation of an aspheric diffractive multifocal one-piece intraocular lens

    PubMed Central

    Chang, Daniel H

    2016-01-01

    Purpose The aim of the study is to evaluate the visual acuity and patient satisfaction at varied distances under photopic and mesopic lighting conditions in patients bilaterally implanted with aspheric diffractive multifocal one-piece intraocular lenses. Methods In this retrospective–prospective study, 16 patients with a mean age of 66.2±9.2 years (range: 50–81 years) who had undergone bilateral phacoemulsification surgery with implantation of a Tecnis multifocal one-piece intraocular lens (ZMB00) were evaluated. Monocular and binocular uncorrected and distance-corrected visual acuities were measured at distance (20 ft), intermediate (70–80 cm), and near (35–40 cm) under photopic (85 cd/m2) and mesopic (3 cd/m2) lighting conditions and were compared using the paired t-test. All patients also completed a subjective questionnaire. Results At a mean follow-up of 9.5±3.9 months, distance, near, and intermediate visual acuity improved significantly from preoperative acuity. Under photopic and mesopic conditions, 93.8% and 62.5% of patients, respectively, had binocular uncorrected intermediate visual acuity of 20/40 or better, and 62.5% and 31.3% of patients had binocular uncorrected near visual acuity of 20/20 or better. All patients were satisfied with their overall vision without using glasses and/or contact lenses when compared with before surgery. A total of 87.5% of patients reported no glare and 68.8% of patients reported no halos around lights at night. Conclusion Tecnis multifocal one-piece intraocular lenses provide good distance, intermediate, and near visual acuity under photopic as well as mesopic lighting conditions. High levels of spectacle independence with low levels of photic phenomenon were achieved, resulting in excellent patient satisfaction. PMID:27536061

  14. Intraocular pressure, retinal vascular, and visual acuity changes during 48 hours of 10-deg head-down tilt

    NASA Technical Reports Server (NTRS)

    Mader, Thomas H.; Taylor, Gerald R.; Hunter, Norwood; Caputo, Michael; Meehan, Richard T.

    1990-01-01

    Intraocular pressures, retinal vascular diameters, and visual acuities of nine men, were repeatedly measured while the subjects were tilted 10 deg head-down for 48 h and while they were seated before (baseline), and after the tilt. An immediate increase in intraocular pressure, measured by pneumatonometer was recorded when subjects assumed the head-down position, and diurnal variations in intraocular pressures were observed for the 48 h. The initial and final head-down intraocular pressures were not significantly different. However, when subjects resumed the sitting position, intraocular pressures fell below the initial sitting values. Computer image analysis of the retinal vasculature detected a 6 percent and 2 percent reduction in the caliber of arteries and veins, respectively, as compared with sitting baseline values. No changes in visual acuity were documented during the 48 h of head-down tilt. The data suggest that the choroidal blood reservoir increases in volume over 48 h at continuous head-down position with a compensatory decrease in aqueous volume. These findings may explain intraocular pressure changes noted in astronauts during previous space missions and in studies associated with change in body position.

  15. Comparison of energy expenditure during the Y-balance test in older adults with different visual acuities

    PubMed Central

    Shin, Sun-Shil; An, Duk-Hyun

    2015-01-01

    [Purpose] This study compared the energy expenditure during the Y-balance test (YBT) between elderly women with good binocular visual acuity (BVA) and those with poor BVA. [Subjects] Twenty-one elderly women who could walk independently were recruited from a community dwelling. Eleven participants had a BVA equal to or less than 0.4 logarithm of the minimum angle of resolution (logMAR), and the other 10 participants had a BVA equal to or better than 0.3 logMAR. [Methods] The participants had an accelerometer attached over the L3 spinous process for measurement of energy expenditure and performed the YBT in the anterior, posteromedial, and posterolateral directions. [Results] The normalized reach distance in the good BVA group during the YBT in three directions and composite reach distance were significantly longer compared with the values in the poor BVA group. The energy expenditure in the good BVA group during the YBT in the three directions was significantly reduced compared with the values in the poor BVA group. [Conclusion] We suggest that visual acuity in the elderly influences dynamic balance and energy expenditure. Elderly subjects with poor BVA showed poor dynamic balance control and an inefficient biomechanical cost strategy compared to subjects with good BVA. PMID:25931711

  16. Quantification of the outer retinal layers: correlation to visual acuity in healthy subjects and patients with central serous chorioretinopathy

    NASA Astrophysics Data System (ADS)

    Sander, Birgit; Christensen, Ulrik; Larsen, Michael; Jørgensen, Thomas M.

    2007-07-01

    Purpose: Quantification of outer retinal layers in humans. Method: 11 eyes in healthy subjects and 3 eyes in patients after resolution of central serous chorioretinopathy (CSCR). Multiple line scans were obtained using OCT Stratus and scans were registered and averaged to enhance contrast. The distance from the inner-outer segment junction to the posterior part of the retinal pigment epithelium (RPE-OS complex) was calculated. In addition, the reflectance of the outer photoreceptor layer in the foveal center was compared to that peripheral to the fovea. Results: Mean thickness of the RPE-OS complex in healthy subjects was 77.3 μm, in CSCR 52.9 μm. The thickness of the RPE-OS complex was significantly correlated to visual acuity (r=0.95, p<0.01). The ratio of reflectance (fovea/parafovea) was 1.06 in healthy subjects, 1.18 in CSCR eyes. Conclusion: The RPE-OS complex thickness was markedly reduced in eyes after resolution of CSCR and highly correlated to the visual acuity, the correlation to total foveal thickness was less. An increased backscatter was seen in CSCR, probably due to photoreceptor disorganization and atrophy.

  17. Interocular Shift of Visual Attention Enhances Stereopsis and Visual Acuities of Anisometropic Amblyopes beyond the Critical Period of Visual Development: A Novel Approach

    PubMed Central

    Huang, Liwen; Sun, Xinghuai; Liu, Shuai; Liu, Rui; Mansouri, Behzad; Wong, Vicky wing lai; Wen, Wen; Liu, Hong; Wang, Ai-Hou

    2014-01-01

    Aims. Increasing evidence shows that imbalanced suppressive drive prior to binocular combination may be the key factor in amblyopia. We described a novel binocular approach, interocular shift of visual attention (ISVA), for treatment of amblyopia in adult patients. Methods. Visual stimuli were presented anaglyphically on a computer screen. A square target resembling Landolt C had 2 openings, one in red and one in cyan color. Through blue-red goggles, each eye could only see one of the two openings. The patient was required to report the location of the opening presented to the amblyopic eye. It started at an opening size of 800 sec of arc, went up and down in 160 sec of arc step, and stopped when reaching the 5th reversals. Ten patients with anisometropic amblyopia older than age 14 (average age: 26.7) were recruited and received ISVA treatment for 6 weeks, with 2 training sessions per day. Results. Both Titmus stereopsis (z = −2.809, P = 0.005) and Random-dot stereopsis (z = −2.317, P = 0.018) were significantly improved. Average improvement in best corrected visual acuity (BCVA) was 0.74 line (t = 5.842, P < 0.001). Conclusions. The ISVA treatment may be effective in treating amblyopia and restoring stereoscopic function. PMID:25580280

  18. Loss of Visual Acuity after Successful Surgery for Macula-On Rhegmatogenous Retinal Detachment in a Prospective Multicentre Study

    PubMed Central

    Di Lauro, Salvatore; Castrejón, Melissa; Fernández, Itziar; Rojas, Jimena; Coco, Rosa M.; Sanabria, María R.; Rodríguez de la Rua, Enrique; Pastor, J. Carlos

    2015-01-01

    Purpose. To quantify the frequency of visual loss after successful retinal detachment (RD) surgery in macula-on patients in a multicentric, prospective series of RD. Methods. Clinical variables from consecutive macula-on RD patients were collected in a prospective multicentric study. Visual loss was defined as at least a reduction in one line in best corrected visual acuity (VA) with Snellen chart. The series were divided into 4 subgroups: (1) all macula-on eyes (n = 357); (2) macula-on patients with visual loss at the third month of follow-up (n = 53) which were further subdivided in (3) phakic eyes (n = 39); and (4) pseudophakic eyes (n = 14). Results. Fifty-three eyes (14.9%) had visual loss three months after surgery (n = 39 phakic eyes; n = 14 pseudophakic eyes). There were no statistically significant differences between them regarding their clinical characteristics. Pars plana vitrectomy (PPV) was used in 67.2% of cases, scleral buckle in 57.7%, and scleral explant in 11.9% (36.1% were combined procedures). Conclusions. Around 15% of macula-on RD eyes lose VA after successful surgery. Development of cataracts may be one cause in phakic eyes, but vision loss in pseudophakic eyes could have other explanations such as the effect of released factors produced by retinal ischemia on the macula area. Further investigations are necessary to elucidate this hypothesis. PMID:26640704

  19. Influence of adaptive-optics ocular aberration correction on visual acuity at different luminances and contrast polarities.

    PubMed

    Marcos, Susana; Sawides, Lucie; Gambra, Enrique; Dorronsoro, Carlos

    2008-10-06

    We evaluated the visual benefit of correcting astigmatism and high-order aberrations with adaptive optics (AO) on visual acuity (VA) measured at 7 different luminances (ranging from 0.8 to 50 cd/m(2)) and two contrast polarities (black letters on white background, BoW, and white letters on black background, WoB) on 7 subjects. For the BoW condition, VA increased with background luminance in both natural and AO-corrected conditions, and there was a benefit of AO correction at all luminances (by a factor of 1.29 on average across luminances). For WoB VA increased with foreground luminance but decreased for the highest luminances. In this reversed polarity condition AO correction increased VA by a factor of 1.13 on average and did not produce a visual benefit at high luminances. The improvement of VA (averaged across conditions) was significantly correlated (p = 0.04) with the amount of corrected aberrations (in terms of Strehl ratio). The improved performance with WoB targets with respect to BoW targets is decreased when correcting aberrations, suggesting a role of ocular aberrations in the differences in visual performance between contrast polarities.

  20. Factors Affecting Crowded Acuity: Eccentricity and Contrast

    PubMed Central

    Coates, Daniel R.; Chin, Jeremy M.; Chung, Susana T. L.

    2013-01-01

    Purpose Acuity measurement is a fundamental method to assess visual performance in the clinic. Little is known about how acuity measured in the presence of neighboring letters, as in the case of letter charts, changes with contrast and with non-foveal viewing. This information is crucial for acuity measurement using low-contrast charts and when patients cannot use their fovea. In this study, we evaluated how optotype acuity, with and without flankers, is affected by contrast and eccentricity. Methods Five young adults with normal vision identified the orientation of a Tumbling-E alone or in the presence of four flanking Tumbling-Es. Edge-to-edge letter spacing ranged from 1 to 20 bar widths. Stimuli were presented on a white background for 150 ms with Weber contrast ranging from −2.5% to −99%. Flankers had the same size and contrast as the target. Testings were performed at the fovea, 3, 5 and 10 degrees in the inferior visual field. Results When plotted as a function of letter spacing, acuity remains unaffected by the presence of flankers until the flankers are within the critical spacing, which averages an edge-to-edge spacing of 4.4 bar widths at the fovea, and approximately 16 bar widths at all three eccentricities. Critical spacing decreases with a reduction in contrast. When plotted as a function of contrast, acuity only worsens when the contrast falls below approximately 24% at the fovea and 17% in the periphery, for flanked and unflanked conditions alike. Conclusions The letter spacing on conventional letter charts exceeds the critical spacing for acuity measurement at the fovea, at all contrast levels. Thus these charts are appropriate for assessing foveal acuity. In the periphery, the critical spacing is larger than the letter spacing on conventional charts. Consequently, these charts may underestimate the acuity measured in the periphery due to the effects of crowding. PMID:23770657

  1. Global motion perception is independent from contrast sensitivity for coherent motion direction discrimination and visual acuity in 4.5-year-old children

    PubMed Central

    Chakraborty, Arijit; Anstice, Nicola S.; Jacobs, Robert J.; Paudel, Nabin; LaGasse, Linda L.; Lester, Barry M.; Wouldes, Trecia A.; Harding, Jane E.; Thompson, Benjamin

    2015-01-01

    Global motion processing depends on a network of brain regions that includes extrastriate area V5 in the dorsal visual stream. For this reason, psychophysical measures of global motion perception have been used to provide a behavioural measure of dorsal stream function. This approach assumes that global motion is relatively independent of visual functions that arise earlier in the visual processing hierarchy such as contrast sensitivity and visual acuity. We tested this assumption by assessing the relationships between global motion perception, contrast sensitivity for coherent motion direction discrimination (henceforth referred to as contrast sensitivity) and habitual visual acuity in a large group of 4.5-year-old children (n = 117). The children were born at risk of abnormal neurodevelopment because of prenatal drug exposure or risk factors for neonatal hypoglycaemia. Motion coherence thresholds, a measure of global motion perception, were assessed using random dot kinematograms. The contrast of the stimuli was fixed at 100% and coherence was varied. Contrast sensitivity was measured using the same stimuli by fixing motion coherence at 100% and varying dot contrast. Stereoacuity was also measured. Motion coherence thresholds were not correlated with contrast sensitivity or visual acuity. However, lower (better) motion coherence thresholds were correlated with finer stereoacuity (rho=0.38, p=0.004). Contrast sensitivity and visual acuity were also correlated (rho= −0.26, p=0.004) with each other. These results indicate that global motion perception for high contrast stimuli is independent of contrast sensitivity and visual acuity and can be used to assess motion integration mechanisms in children. PMID:26318529

  2. Preserved functional and structural integrity of the papillomacular area correlates with better visual acuity in retinitis pigmentosa.

    PubMed

    Konieczka, K; Bojinova, R I; Valmaggia, C; Schorderet, D F; Todorova, M G

    2016-10-01

    PurposeLinking multifocal electroretinography (mfERG) and optical coherence tomography (OCT) findings with visual acuity in retinitis pigmentosa (RP) patients.DesignProspective, cross-sectional, nonintervention study.SubjectsPatients with typical RP and age-matched controls, who underwent SD-OCT (spectral domain OCT) and mfERG, were included.MethodsMfERG responses were averaged in three zones (zone 1 (0°-3°), zone 2 (3°-8°), and zone 3 (8°-15°)). Baseline-to-trough- (N1) and trough-to-peak amplitudes (N1P1) of the mfERG were compared with corresponding areas of the OCT. The papillomacular area (PMA) was analyzed separately. Correlations between best-corrected visual acuity (BCVA, logMAR) and each parameter were determined.Main outcome measuresComparing structural (OCT) and functional (mfERG) measures with the BCVA.ResultsIn RP patients, the N1 and N1P1 responses showed positive association with the central retinal thickness outside zone 1 (P≤0.002), while the central N1 and the N1P1 responses in zones 1, 2, and 3-with the BCVA (P≤0.007). The integrity of the IS/OS line on OCT showed also a positive association with the BCVA (P<0.001). Isolated analysis of the PMA strengthened further the structure-function association with the BCVA (P≤0.037). Interactions between the BCVA and the OCT, respectively, the mfERG parameters were more pronounced in the RP subgroup without macular edema (P≤0.020).ConclusionIn RP patients, preserved structure-function of PMA, measured by mfERG amplitude and OCT retinal thickness, correlated well with the remaining BCVA. The subgroup analyses revealed stronger links between the examined parameters, in the RP subgroup without appearance of macular edema.

  3. Presbyopia: a pilot investigation of the barriers and benefits of near visual acuity correction among a rural Filipino population

    PubMed Central

    2014-01-01

    Background Presbyopia is the age-related decline in accommodation that diminishes the ability of the eye to focus on near objects. Presbyopia is common and easy to correct; however, many communities lack access to basic eye care. The purpose of this project was to assess the burden of uncorrected presbyopia in a rural Filipino population and to pilot an intervention aimed at increasing access to reading glasses in the community. Methods Individuals above the age of 40 who presented to a health outreach in the Philippines were invited to undergo a near vision exam to detect the presence of functional presbyopia and be fitted with ready-made, single-vision glasses. The change in stereoacuity was used as a surrogate measure of functional improvement after near vision correction. A questionnaire was administered to assess this population’s perceived barriers and benefits to correcting near vision. Results The average age of the participants was 57 ± 11 years, with 87.6% of participants having an uncorrected near visual acuity of <20/50. Reading glasses improved near vision to 20/40 or better in 77.7% of participants having near-vision impairment (uncorrected near visual acuity of <20/40). Over 75% of participants also showed improvement in stereoacuity. Cost, rather than availability, was perceived to be the greater barrier to the procurement of glasses, and 84% of participants reported that the glasses dispensed would greatly improve their ability to earn a living. Conclusions Dispensing ready-made, single-vision glasses is a simple and cost-effective intervention to improve near vision and enhance depth perception. A greater understanding of the barriers and benefits to correcting near vision will inform the design and execution of a sustainable program to correct presbyopia in developing countries. PMID:24467667

  4. Sociodemographic correlates of visual acuity impairment in Hispanic children and adolescents.

    PubMed

    Lee, D J; Gomez-Marin, O; Lam, B L; Ma, F

    1999-10-01

    Sociodemographic correlates of visual impairment were examined in 6- to 19-year-old Hispanic children and adolescents using data from the Hispanic Health and Nutrition Examination Survey. Mexican American and Puerto Rican children whose parents had 0 to 6 years of education were more likely to remain visually impaired even when tested with their glasses or contact lenses, if any (i.e., with usual correction) than children whose parents reported 12 to 17 years of education. Mexican Americans residing below versus at or above the poverty line were more likely to remain visually impaired even with the usual correction. Mexican Americans enrolled in the Medicaid program or who were without health insurance were more likely to remain visually impaired than Mexican Americans with private health insurance. When tested without glasses or contact lenses, Cuban Americans and Mexican Americans born outside of the mainland United States had lower rates of visual impairment compared to those born in the United States; however, children in this latter group were more likely to remain visually impaired with usual correction than U.S.-born Mexican Americans. These findings suggest that Hispanic children from economically disadvantaged households and those born outside the United States may not be receiving optimal eye care that could improve visual function.

  5. Prospective Evaluation of Mesopic Night Vision and Night Vision Goggle Visual Acuity After Photorefractive Keratectomy (PRK)

    DTIC Science & Technology

    2005-03-01

    DTIC) should direct requests for copies to: Defense Technical Information Center, 8725 John J. Kingman Rd., STE 0944, Ft. Belvior, VA 22060-6218. Non...770-6. 9. Verdon W, Bullimore M, Maloney RK. Visual Performance after Photorefractive Keratectomy. A Prospective Study. Arch Ophthalmol. December

  6. Ockham's razor revisited: decreased visual acuity secondary to keratoconus in a patient with intracranial hypertension

    PubMed Central

    Fung, Adrian T; Azar, Domit; Fraser-Bell, Samantha; McCluskey, Peter; Grigg, John

    2011-01-01

    Both intracranial hypertension and keratoconus may be associated with visual impairment. The authors present a case of a young female with poor right vision that did not improve despite treatment of her intracranial hypertension. Ophthalmic consultation diagnosed keratoconus as the cause. PMID:22707492

  7. The Potential Importance of Detection of Neovascular Age-Related Macular Degeneration When Visual Acuity Is Relatively Good.

    PubMed

    Ho, Allen C; Albini, Thomas A; Brown, David M; Boyer, David S; Regillo, Carl D; Heier, Jeffrey S

    2017-03-01

    The advent of anti-vascular endothelial growth factor treatment has changed the prognosis for patients with neovascular age-related macular degeneration (nvAMD). The ability to stabilize or improve vision with these treatments is a major step in enabling patients to continue to function at the highest possible level. Many studies have demonstrated that the better the visual acuity (VA) is at the time of treatment initiation, the higher the likelihood that VA will be better during at least the following 2 years; as such, detection of nvAMD when VA is relatively good is important. Data on the VA of patients with intermediate AMD and VA at the time of nvAMD diagnosis suggest that patients are typically losing an average of 3 to 5 lines of vision and possibly more between the time that intermediate AMD progresses to nvAMD and the diagnosis of nvAMD is made. The average patient may have nvAMD for 6 to 12 months before diagnosis and treatment initiation. Current efforts in management of nvAMD are primarily aimed at optimizing anti-vascular endothelial growth factor treatments that have the potential to improve VA outcomes by a magnitude of letters. Additional tools or other efforts to identify patients with nvAMD before substantial vision loss has occurred may reduce the amount of visual loss sustained with anti-vascular endothelial growth factor therapy, and have the potential to improve VA outcomes substantially.

  8. Successful Restoration of Visual Acuity with an Extended Range of Vision Intraocular Lens after Multifocal Laser Ablation.

    PubMed

    Black, Sondra

    2016-01-01

    As our baby boomer population is aging and developing cataracts, so are our post-LASIK patients. These patients underwent LASIK surgery as they wished to be spectacle-free and are hoping to remain so after intraocular lens (IOL) surgery. Unfortunately, very little information is available regarding the suitability of presbyopia correcting IOLs for post-LASIK patients. This case represents successful implantation of an extended range of vision IOL in a 59-year-old patient who underwent multifocal ablation excimer laser surgery 12 years before. Emmetropia was targeted for the dominant eye and -0.5 D for the fellow eye. The 13 month follow-up after bilateral implantation of the TECNIS Symfony IOL revealed an uncorrected visual acuity of 20/25 for distance, 20/20 for intermediate and 20/16 for near. The patient is very happy and did not report any visual symptoms when asked. This successful case should encourage surgeons to consider implanting an extended range of vision IOLs in post-LASIK patients.

  9. Successful Restoration of Visual Acuity with an Extended Range of Vision Intraocular Lens after Multifocal Laser Ablation

    PubMed Central

    Black, Sondra

    2016-01-01

    As our baby boomer population is aging and developing cataracts, so are our post-LASIK patients. These patients underwent LASIK surgery as they wished to be spectacle-free and are hoping to remain so after intraocular lens (IOL) surgery. Unfortunately, very little information is available regarding the suitability of presbyopia correcting IOLs for post-LASIK patients. This case represents successful implantation of an extended range of vision IOL in a 59-year-old patient who underwent multifocal ablation excimer laser surgery 12 years before. Emmetropia was targeted for the dominant eye and −0.5 D for the fellow eye. The 13 month follow-up after bilateral implantation of the TECNIS Symfony IOL revealed an uncorrected visual acuity of 20/25 for distance, 20/20 for intermediate and 20/16 for near. The patient is very happy and did not report any visual symptoms when asked. This successful case should encourage surgeons to consider implanting an extended range of vision IOLs in post-LASIK patients. PMID:28101037

  10. Determinants of visual acuity outcomes in eyes with neovascular AMD treated with anti-VEGF agents: an instrumental variable analysis of the AURA study.

    PubMed

    Holz, F G; Tadayoni, R; Beatty, S; Berger, A R; Cereda, M G; Hykin, P; Staurenghi, G; Wittrup-Jensen, K; Nilsson, J; Kim, K; Sivaprasad, S

    2016-08-01

    PurposeTo identify the strongest variable(s) linked with the number of ranibizumab injections and outcomes in AURA, and to identify ways to improve outcomes using this association.MethodsAURA was a large observational study that monitored visual acuity over a 2-year period in patients with neovascular age-related macular degeneration (AMD) who received ranibizumab injections. Baseline characteristics, resource use, and outcomes were analyzed using an instrumental variable approach and regression analysis.ResultsData were analyzed from 2227 patients enrolled in AURA. Optical coherence tomography (OCT) and ophthalmoscopy were the most common diagnostic tests used, and this combination was the strongest instrumental variable. Use of OCT and ophthalmoscopy affected the number of injections given and resulted in an increase in visual acuity gains from baseline of 17.6 letters in year 1 and 2.5 letters in year 2. Regression models using the instrumental variable (OCT and ophthalmoscopy combined) showed that ≥5.1 (95% CI: 3.3-11.4) ranibizumab injections were needed to maintain visual acuity from baseline to year 1 and ≥8.3 (95% CI: 5.3-18.8) injections were needed to maintain visual acuity from year 1 to year 2. To gain ≥15 letters, ≥7.9 (95% CI: 5.1-17.5) ranibizumab injections would be needed in year 1 and ≥16.1 (95% CI: 10.3-36.4) injections would be needed over 2 years.ConclusionsThese findings highlight the role that regular monitoring plays in guiding neovascular AMD therapy and they showed that the number of ranibizumab injections needed to maintain visual acuity is higher than that administered in AURA.

  11. Macular edema in Asian Indian premature infants with retinopathy of prematurity: Impact on visual acuity and refractive status after 1-year

    PubMed Central

    Vinekar, Anand; Mangalesh, Shwetha; Jayadev, Chaitra; Bauer, Noel; Munusamy, Sivakumar; Kemmanu, Vasudha; Kurian, Mathew; Mahendradas, Padmamalini; Avadhani, Kavitha; Shetty, Bhujang

    2015-01-01

    Purpose: To report the impact of transient, self-resolving, untreated “macular edema” detected on spectral domain optical coherence tomography in Asian Indian premature infants with retinopathy of prematurity (ROP) on visual acuity (VA) and refraction at 1-year of corrected age. Materials and Methods: Visual acuity and refraction of 11 infants with bilateral macular edema (Group A) was compared with gestational age-matched 16 infants with ROP without edema (Group B) and 17 preterms infants without ROP and without edema (Group C) at 3, 6, 9 and 12 months of corrected age using Teller Acuity Cards and cycloplegic retinoscopy. Sub-group analysis of the previously described pattern A and B macular edema was performed. Results: Visual acuity was lower in infants with macular edema compared with the other two control groups throughout the study period, but statistically significant only at 3 months. Visual improvement in these infants was highest between the 3rd and 6th month and plateaued by the end of the 1st year with acuity comparable to the other two groups. The edema cohort was more hyperopic compared to the other two groups between 3 and 12 months of age. Pattern A edema had worse VA compared to pattern B, although not statistically significant. Conclusion: Macular edema, although transient, caused reduced VA as early as 3 months of corrected age in Asian Indian premature infants weighing <2000 g at birth. The higher hyperopia in these infants is possibly due to visual disturbances caused at a critical time of fovealization. We hypothesize a recovery and feedback mechanism based on the principles of active emmetropization to explain our findings. PMID:26139806

  12. Visual Acuity after Cataract Surgery in Patients with Age-Related Macular Degeneration. Age-Related Eye Disease Study 2 Report No. 5

    PubMed Central

    Huynh, Nancy; Nicholson, Benjamin P.; Agrón, Elvira; Clemons, Traci E.; Bressler, Susan B.; Rosenfeld, Philip J.; Chew, Emily Y.

    2014-01-01

    Objective To evaluate visual acuity outcomes after cataract surgery in persons with varying severity of age-related macular degeneration (AMD). Design Cohort study. Participants A total of 1232 eyes of 793 participants who underwent cataract surgery during the Age-Related Eye Disease Study 2 (AREDS2), a prospective, multicenter, randomized controlled trial of nutritional supplements for treatment of AMD. Methods Preoperative and postoperative characteristics of participants who underwent cataract extraction during the 5 year trial were analyzed. Both clinical data and standardized red-reflex lens and fundus photographs were obtained at baseline and annually. Photographs were graded by a centralized reading center for cortical and posterior subcapsular lens opacities and for AMD severity. Cataract surgery was documented at annual study visits or by history during the 6 month telephone calls. Analyses were conducted using multivariate repeated-measures regression. Main Outcome Measures Change in best-corrected visual acuity (BCVA) after cataract surgery compared with preoperative BCVA. Results Adjusting for age at time of surgery, gender, interval between preoperative and postoperative visits, and type and severity of cataract, the mean changes in visual acuity were as follows: eyes with mild AMD (n=30) gained 11.2 letters (95% confidence interval (CI), 6.9-15.5), eyes with moderate AMD (n=346) gained 11.1 letters (95% CI, 9.1-13.2), eyes with severe AMD (n=462) gained 8.7 letters (95% CI, 6.7-10.7), eyes with non-central geographic atrophy (n=70) gained 8.9 letters (95% CI, 5.8-12.1), and eyes with advanced AMD (central geographic atrophy and/or neovascular) AMD (n=324) gained 6.8 letters (95% CI, 4.9-8.8). The visual acuity gain across all AMD severity groups was statistically significant from pre-operative state (P<0.0001). Conclusions Mean visual acuities improved significantly after cataract surgery across varying degrees of AMD severity. PMID:24613825

  13. Visual field asymmetries in visual evoked responses

    PubMed Central

    Hagler, Donald J.

    2014-01-01

    Behavioral responses to visual stimuli exhibit visual field asymmetries, but cortical folding and the close proximity of visual cortical areas make electrophysiological comparisons between different stimulus locations problematic. Retinotopy-constrained source estimation (RCSE) uses distributed dipole models simultaneously constrained by multiple stimulus locations to provide separation between individual visual areas that is not possible with conventional source estimation methods. Magnetoencephalography and RCSE were used to estimate time courses of activity in V1, V2, V3, and V3A. Responses to left and right hemifield stimuli were not significantly different. Peak latencies for peripheral stimuli were significantly shorter than those for perifoveal stimuli in V1, V2, and V3A, likely related to the greater proportion of magnocellular input to V1 in the periphery. Consistent with previous results, sensor magnitudes for lower field stimuli were about twice as large as for upper field, which is only partially explained by the proximity to sensors for lower field cortical sources in V1, V2, and V3. V3A exhibited both latency and amplitude differences for upper and lower field responses. There were no differences for V3, consistent with previous suggestions that dorsal and ventral V3 are two halves of a single visual area, rather than distinct areas V3 and VP. PMID:25527151

  14. Change in visual acuity is well correlated with change in image-quality metrics for both normal and keratoconic wavefront errors.

    PubMed

    Ravikumar, Ayeswarya; Marsack, Jason D; Bedell, Harold E; Shi, Yue; Applegate, Raymond A

    2013-11-26

    We determined the degree to which change in visual acuity (VA) correlates with change in optical quality using image-quality (IQ) metrics for both normal and keratoconic wavefront errors (WFEs). VA was recorded for five normal subjects reading simulated, logMAR acuity charts generated from the scaled WFEs of 15 normal and seven keratoconic eyes. We examined the correlations over a large range of acuity loss (up to 11 lines) and a smaller, more clinically relevant range (up to four lines). Nine IQ metrics were well correlated for both ranges. Over the smaller range of primary interest, eight were also accurate and precise in estimating the variations in logMAR acuity in both normal and keratoconic WFEs. The accuracy for these eight best metrics in estimating the mean change in logMAR acuity ranged between ±0.0065 to ±0.017 logMAR (all less than one letter), and the precision ranged between ±0.10 to ±0.14 logMAR (all less than seven letters).

  15. Adherence to Occlusion Therapy in the First Six Months of Follow-Up and Visual Acuity among Participants in the Infant Aphakia Treatment Study (IATS)

    PubMed Central

    Drews-Botsch, Carolyn D.; Celano, Marianne; Kruger, Stacey; Hartmann, E. Eugenie

    2012-01-01

    Purpose. Achieving good vision in infants born with a unilateral cataract is believed to require early surgery and consistent occlusion of the fellow eye. This article examines the relationship between adherence to patching and grating acuity. Methods. Data came from the Infant Aphakia Treatment Study, a randomized clinical trial of treatment for unilateral congenital cataract. Infants were either left aphakic (n = 53) or had an intraocular lens implanted (n = 55). Patching was prescribed 1 hour per day per month of age until 8 months of age and 50% of waking hours thereafter. Adherence was measured as the mean percentage of prescribed patching reported in a 7-day diary completed 2 months after surgery, and 48-hour recall interviews conducted 3 and 6 months after surgery. Grating visual acuity was measured within 1 month of the infant's first birthday (n = 108) using Teller Acuity Cards by a tester masked to treatment. Nonparametric correlations were used to examine the relationship with grating acuity. Results. On average, caregivers reported patching 84.3% (SD = 31.2%) of prescribed time and adherence did not differ by treatment (t = −1.40, df = 106, p = 0.16). Adherence was associated with grating acuity (rSpearman = −0.27, p < 0.01), but more so among pseudophakic (rSpearman = −0.41, p < 0.01) than aphakic infants (rSpearman = −0.10, p = 0.49). Conclusions. This study empirically has shown that adherence to patching during the first 6 months after surgery is associated with better grating visual acuity at 12 months of age after treatment for unilateral cataract and that implanting an intraocular lens is not associated with adherence. (ClinicalTrials.gov number, NCT00212134.) PMID:22491410

  16. FAR and NEAR Target Dynamic Visual Acuity: A Functional Assessment of Canal and Otolith Performance

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; Brady, Rachel A.; Landsness, Eric C.; Black, F. Owen; Bloomberg, Jacob J.

    2004-01-01

    Upon their return to earth, astronauts experience the effects of vestibular adaptation to microgravity. The postflight changes in vestibular information processing can affect postural and locomotor stability and may lead to oscillopsia during activities of daily living. However, it is likely that time spent in microgravity affects canal and otolith function differently. As a result, the isolated rotational stimuli used in traditional tests of canal function may fail to identify vestibular deficits after spaceflight. Also, the functional consequences of deficits that are identified often remain unknown. In a gaze control task, the relative contributions of the canal and otolith organs are modulated with viewing distance. The ability to stabilize gaze during a perturbation, on visual targets placed at different distances from the head may therefore provide independent insight into the function of this systems. Our goal was to develop a functional measure of gaze control that can also offer independent information about the function of the canal and otolith organs.

  17. Visual Learning in Field Biology.

    ERIC Educational Resources Information Center

    Stanley, Ethel D.

    Visual learning has long been recognized as an integral process in educating biology undergraduates, who must develop specific visual skills and knowledge in order to communicate and work in the extensive visual culture shared by practicing biologists. Student experiences with field observations and the development and application of verbal/visual…

  18. Visual field defects in onchocerciasis.

    PubMed Central

    Thylefors, B; Tønjum, A M

    1978-01-01

    Lesions in the posterior segment of the eye in onchocerciasis may give visual field defects, but so far no detailed investigation has been done to determine the functional visual loss. Examination of the visual fields in 18 selected cases of onchocerciasis by means of a tangent screen test revealed important visual field defects associated with lesions in the posterior segment of the eye. Involvement of the optic nerve seemed to be important, giving rise to severely constricted visual fields. Cases of postneuritic optic atrophy showed a very uniform pattern of almost completely constricted visual fields, with only 5 to 10 degree central rest spared. Papillitis gave a similar severe constriction of the visual fields. The pattern of visual fields associated with optic neuropathy in onchocerciasis indicates that a progressive lesion of the optic nerve from the periphery may be responsible for the loss of vision. The visual field defects in onchocerciasis constitute a serious handicap, which must be taken into consideration when estimating the socioeconomic importance of the disease. Images PMID:678499

  19. Decreased visual acuity resulting from glistening and sub-surface nano-glistening formation in intraocular lenses: A retrospective analysis of 5 cases

    PubMed Central

    Matsushima, Hiroyuki; Nagata, Mayumi; Katsuki, Yoko; Ota, Ichiro; Miyake, Kensaku; Beiko, George H.H.; Grzybowski, Andrzej

    2015-01-01

    Background To report on five patients with decreased visual acuity due to glistening and severe sub-surface nano-glistening (SSNG) formation within their intraocular lenses (IOLs). Design Case reports and analysis of extracted IOLs. Participants and samples We report improved visual acuity when IOLs with severe glistening and SSNG were exchanged for clear IOLs in five patients. Methods Case reports. Main outcome measures The main outcome measure was visual acuity. The secondary outcome measure was light transmission. Explanted IOLs were subjected to investigation. Pre- and postoperative slit lamp images of the anterior eye and microscopic images of the extracted IOLs were taken and compared. Light transmission of the IOL was measured using a double beam type spectrophotometer. An integrated value of the percentage light transmittance in the visible light spectrum was calculated. Results We report on five patients whose visual acuity improved when IOLs were exchanged because of severe glistening and SSNG. All of the affected IOLs were MA60BM (Alcon, Forth Wroth Texas, USA) and the original implantation had occurred over a range of 6–15 years prior to the IOL exchange. Light transmission was decreased in all affected lenses compared to a similar control IOL. Conclusions Although only a few reports of cases in which glistening and SSNG have progressed to the level of decreased visual function have been published, the likelihood is that this phenomena will increase as the severity and incidence of these inclusions have been shown to increase with time. Appropriate evaluations of visual function in such patients are needed and consideration should be given to IOL exchange in symptomatic patients. PMID:26586975

  20. Longitudinal comparison of visual acuity as measured by the ETDRS chart and by the potential acuity meter in eyes with macular edema, and its relationship with retinal thickness and sensitivity

    PubMed Central

    Hatef, E; Hanout, M; Moradi, A; Colantuoni, E; Bittencourt, M; Liu, H; Sepah, Y J; Ibrahim, M; Do, D V; Guyton, D L; Nguyen, Q D

    2014-01-01

    Purpose To evaluate the relationship between visual acuity as measured by the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and by the potential acuity meter (PAM) with retinal thickness and sensitivity measured by a combined microperimetry/optical coherence tomography system (OCT). Methods Forty-four patients with macular edema (ME) were included in a prospective observational study. Visual acuity (VA) was assessed using the ETDRS chart (with best correction) as well as by the PAM. Retinal thickness and sensitivity was measured by an automatic fundus perimetry/tomography system. Results Best-corrected VA using the ETDRS chart ranged from 20/20 to 20/400 (median: 20/50). VA measured by the PAM without correction ranged from 20/20 to 20/400 (median: 20/40). The mean retinal thickness was 369.57 μm (s.d.: 140.28 μm) on spectral domain-OCT and the mean retinal sensitivity was 8.12 decibels (dB) (s.d.: 5.78 dB). The mean LogMAR value using the ETDRS chart was 0.43, whereas it was 0.38 using the PAM (P-value: 0.009). Conclusions VA values measured by the PAM were statistically significantly better than those measured by the ETDRS chart in eyes with ME secondary to various retinal vascular and uveitic diseases. VA measured by the PAM may be a more sensitive predictor of macular function than that obtained by ETDRS testing in eyes with ME. PMID:25104744

  1. Sports can protect dynamic visual acuity from aging: A study with young and older judo and karate martial arts athletes.

    PubMed

    Muiños, Mónica; Ballesteros, Soledad

    2015-08-01

    A major topic of current research in aging has been to investigate ways to promote healthy aging and neuroplasticity in order to counteract perceptual and cognitive declines. The aim of the present study was to investigate the benefits of intensive, sustained judo and karate martial arts training in young and older athletes and nonathletes of the same age for attenuating age-related dynamic visual acuity (DVA) decline. As a target, we used a moving stimulus similar to a Landolt ring that moved horizontally, vertically, or obliquely across the screen at three possible contrasts and three different speeds. The results indicated that (1) athletes had better DVA than nonathletes; (2) the older adult groups showed a larger oblique effect than the younger groups, regardless of whether or not they practiced a martial art; and (3) age modulated the results of sport under the high-speed condition: The DVA of young karate athletes was superior to that of nonathletes, while both judo and karate older athletes showed better DVA than did sedentary older adults. These findings suggest that in older adults, the practice of a martial art in general, rather than the practice of a particular type of martial art, is the crucial thing. We concluded that the sustained practice of a martial art such as judo or karate attenuates the decline of DVA, suggesting neuroplasticity in the aging human brain.

  2. Visual acuity outcomes following surgery for idiopathic epiretinal membrane: an analysis of data from 2001 to 2011

    PubMed Central

    Dawson, S R; Shunmugam, M; Williamson, T H

    2014-01-01

    Purpose Pars plana vitrectomy (PPV) is commonly used to remove the epiretinal membrane (ERM), but the timing of surgical intervention guided by visual acuity (VA) performance at presentation is uncertain. Patients and methods Prospectively entered clinical data of 237 patients on an electronic patient record from 2001 to 2011 were analysed to determine visual outcomes, in particular in relation to pre-operative VA. Results The mean age of the patients was 68.8 years and 54.4% were female. Median follow-up was 0.55 years. The median pre-operative logMAR VA was 0.60 (SD 0.48–0.78, Snellen equivalent 6/36) and post-operative VA was 0.30 (SD 0.18–0.60, 6/12, P<0.005). Pre-operative VA correlated with post-operative VA (linear R2=0.22, P<0.0001). In all, 69.6% of patients showed an improvement in VA, 15.2% showed no change, and the condition of 15.2% worsened. The number of patients with an improvement in logMAR VA of more than 0.3 was greatest in those who had a pre-operative VA of 1.0 (6/60) or worse, followed by those in the range of 0.6–0.9 and then those with pre-operative VA of 0.5 or better (P<0.001). The proportion of patients with visual improvement of logMAR VA of more than 0.3 increased statistically with progressing years (P=0.019). Conclusion In conclusion, this study shows improvement in VA after PPV and ERM removal. Patients with better initial VA achieve higher levels of visual outcome but those with poorer pre-operative VA show a greater change in VA following ERM surgery. Results of surgery improved over the time period of the study. PMID:24310238

  3. An Assessment of the Contrast Sensitivity in Patients with Ametropic and Anisometropic Amblyopia in Achieving the Corrected Visual Acuity of 1.0.

    PubMed

    Wang, Guipan; Zhao, Congling; Ding, Qiang; Wang, Ping

    2017-02-07

    Both visual acuity (VA) and contrast sensitivity (CS) are important parameters for measuring visual function. In this research, we investigated the CS of patients with ametropic or anisometropic amblyopia, whose corrected visual acuity (CVA) recovered to 1.0. Fifty-five cases with amblyopia and 22 control cases with a normal visual acuity of 1.0 were enrolled. The CS of the patients whose ametropic amblyopia had recovered to a CVA of 1.0 at 18 cpd spatial frequency was still lower than that of the normal control group under both photopic and scotopic conditions (P = 0.001, 0.025), but there were no significant differences at low- and middle-spatial frequencies. The CS of amblyopic eyes of the patients with anisometropic amblyopia was lower than that of the normal control group at the 18 cpd spatial frequency under photopic conditions (P = 0.005), and at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.008, <0.001, 0.004, respectively). The CS between the amblyopic eyes and the sound eyes of patients with anisometropic amblyopia presented significant differences at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.025, 0.045, 0.019, respectively). We suggest that amblyopia treatment should involve not only the correction of VA but also the improvement of CS.

  4. An Assessment of the Contrast Sensitivity in Patients with Ametropic and Anisometropic Amblyopia in Achieving the Corrected Visual Acuity of 1.0

    PubMed Central

    Wang, Guipan; Zhao, Congling; Ding, Qiang; Wang, Ping

    2017-01-01

    Both visual acuity (VA) and contrast sensitivity (CS) are important parameters for measuring visual function. In this research, we investigated the CS of patients with ametropic or anisometropic amblyopia, whose corrected visual acuity (CVA) recovered to 1.0. Fifty-five cases with amblyopia and 22 control cases with a normal visual acuity of 1.0 were enrolled. The CS of the patients whose ametropic amblyopia had recovered to a CVA of 1.0 at 18 cpd spatial frequency was still lower than that of the normal control group under both photopic and scotopic conditions (P = 0.001, 0.025), but there were no significant differences at low- and middle-spatial frequencies. The CS of amblyopic eyes of the patients with anisometropic amblyopia was lower than that of the normal control group at the 18 cpd spatial frequency under photopic conditions (P = 0.005), and at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.008, <0.001, 0.004, respectively). The CS between the amblyopic eyes and the sound eyes of patients with anisometropic amblyopia presented significant differences at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.025, 0.045, 0.019, respectively). We suggest that amblyopia treatment should involve not only the correction of VA but also the improvement of CS. PMID:28169333

  5. Validity and Reliability of Dynamic Visual Acuity (DVA) Measurement During Walking

    NASA Technical Reports Server (NTRS)

    Deshpande, Nandini; Peters, Brian T.; Bloomberg, Jacob J.

    2014-01-01

    DVA is primarily subserved by the vestibulo-ocular reflex mechanism. Individuals with vestibular hypofunction commonly experience highly debilitating illusory movement or blurring of visual images during daily activities possibly, due to impaired DVA. Even without pathologies, gradual age-related morphological deterioration is evident in all components of the vestibular system. We examined the construct validity to detect age-related differences and test-retest reliability of DVA measurements performed during walking. METHODS: Healthy adults were recruited into 3 groups: 1. young (20-39years, n=18), 2. middle-aged (40-59years, n=14), and 3. older adults (60-80years, n=15). Randomly selected seven participants from each group (n=21) participated in retesting. Participants were excluded if they had a history of vestibular or neuromuscular pathologies, dizziness/vertigo or >1 falls in the past year. Older persons with MMSE scores <29/30 were excluded to minimize cognitive errors. Participants' age, height, weight and normal walking speed were recorded. The binocular DVA was measured while walking on a treadmill at 0.8 m/s, 1.0 m/s and 1.2 m/s speeds. The walking speeds chosen represent a range of slow to moderate walking speeds for adult life span in participants who have no current mobility problems. The monitor that displayed Landolt 'C' optotypes was placed at 50 cm from the eyes for nearDVA (primary compensation by otolith organs) and at 3.0 m for farDVA (primary compensation by semicircular canals). A mixed factor ANOVA (age group x speed) was performed separately for the Near and FarDVA for detecting group differences. Intraclass correlation coefficients (ICCs) were calculated for each condition to determine test-retest reliability. RESULTS: The three age groups were not different in their height, weight and normal walking speed (p>0.05). The post hoc analyses for DVA measurements demonstrated that each group was significantly different from the other two groups

  6. Evaluation of Visual Acuity Measurements after Autorefraction versus Manual Refraction in Eyes with and without Diabetic Macular Edema

    PubMed Central

    Sun, Jennifer K.; Qin, Haijing; Aiello, Lloyd Paul; Melia, Michele; Beck, Roy W.; Andreoli, Christopher M.; Edwards, Paul A.; Glassman, Adam R.; Pavlica, Michael R.

    2012-01-01

    Objective To compare visual acuity (VA) scores after autorefraction versus research protocol manual refraction in eyes of patients with diabetes and a wide range of VA. Methods Electronic Early Treatment Diabetic Retinopathy Study (E-ETDRS) VA Test© letter score (EVA) was measured after autorefraction (AR-EVA) and after Diabetic Retinopathy Clinical Research Network (DRCR.net) protocol manual refraction (MR-EVA). Testing order was randomized, study participants and VA examiners were masked to refraction source, and a second EVA utilizing an identical manual refraction (MR-EVAsupl) was performed to determine test-retest variability. Results In 878 eyes of 456 study participants, median MR-EVA was 74 (Snellen equivalent approximately 20/32). Spherical equivalent was often similar for manual and autorefraction (median difference: 0.00, 5th and 95th percentiles −1.75 to +1.13 Diopters). However, on average, MR-EVA results were slightly better than AR-EVA results across the entire VA range. Furthermore, variability between AR-EVA and MR-EVA was substantially greater than the test-retest variability of MR-EVA (P<0.001). Variability of differences was highly dependent on autorefractor model. Conclusions Across a wide range of VA at multiple sites using a variety of autorefractors, VA measurements tend to be worse with autorefraction than manual refraction. Differences between individual autorefractor models were identified. However, even among autorefractor models comparing most favorably to manual refraction, VA variability between autorefraction and manual refraction is higher than the test-retest variability of manual refraction. The results suggest that with current instruments, autorefraction is not an acceptable substitute for manual refraction for most clinical trials with primary outcomes dependent on best-corrected VA. PMID:22159173

  7. Visual Impairment as a Function of Visual Acuity in Both Eyes and Its Impact on Patient Reported Preferences

    PubMed Central

    Finger, Robert P.; Fenwick, Eva; Hirneiss, Christoph W.; Hsueh, Arthur; Guymer, Robyn H.; Lamoureux, Ecosse L.; Keeffe, Jill E.

    2013-01-01

    Purpose To assess the impact of VA loss on patient reported utilities taking both eyes into account compared to taking only the better or the worse eye into account. Methods In this cross-sectional study 1085 patients and 254 controls rated preferences with the generic health-related (EQ-5D; n = 868) and vision-specific (Vision and Quality of Life Index (VisQoL); n = 837) multi-attribute utility instruments (MAUIs). Utilities were calculated for three levels of VA in the better and worse eyes, as well as for 6 different vision states based on combinations of the better and worse eye VA. Results Using the VisQoL, utility scores decreased significantly with deteriorating vision in both the better and worse eyes when analysed separately. When stratified by the 6 vision states, VisQoL utilities decreased as VA declined in the worse eye despite stable VA in the better eye. Differences in VisQoL scores were statistically significant for cases where the better eye had no vision impairment and the worse seeing fellow eye had mild, moderate or severe vision impairment. In contrast, the EQ-5D failed to capture changes in better or worse eye VA, or any of the six vision states. Conclusions Calculating utilities based only on better eye VA or using a generic MAUI is likely to underestimate the impact of vision impairment, particularly when the better eye has no or little VA loss and the worse eye is moderately to severely visually impaired. These findings have considerable implications for the assessment of overall visual impairment as well as economic evaluations within eye health. PMID:24339893

  8. Key drivers of visual acuity gains in neovascular age-related macular degeneration in real life: findings from the AURA study

    PubMed Central

    Holz, Frank G; Tadayoni, Ramin; Beatty, Stephen; Berger, Alan; Cereda, Matteo Giuseppe; Hykin, Philip; Staurenghi, Giovanni; Wittrup-Jensen, Kim; Altemark, Andreas; Nilsson, Jonas; Kim, Kun; Sivaprasad, Sobha

    2016-01-01

    Background/aims To identify predictive markers for the outcomes of anti-vascular endothelial growth factor therapy for neovascular age-related macular degeneration (nAMD). Methods AURA was a retrospective, observational, multicentre study that monitored the 2-year outcomes following intravitreal ranibizumab treatment in patients with nAMD. Using stepwise regression analysis, we evaluated the association between visual acuity outcomes, baseline characteristics and resource utilisation in order to determine which variables are significantly linked to outcomes in AURA. We also examined the relationship between visual acuity outcomes and number of injections received. Results Analyses were performed using data from year 1 (n=1695) and year 2 completers (n=1184). Logistic analysis showed that baseline visual acuity score, age at start of therapy, number of ophthalmoscopies and optical coherence tomography (OCT) (combined) and number of injections (ranibizumab) were significant (p<0.05) prognostic factors for vision maintenance (loss <15 letters) or vision gain (≥15 letters). Patients who received >7 injections (in 1 year) or >14 injections (over 2 years) gained more letters and demonstrated greater vision maintenance (loss of <15 letters) than patients who received fewer injections. There was a significant (p<0.05) association between number of injections and national reimbursement schemes and OCT. Conclusions A number of factors that are predictive of treatment outcomes in a real-life setting were identified. Notably, the decline of treatment benefits may be linked to number of injections and a failure to visit clinicians and receive OCT as required. These findings may be helpful in guiding ophthalmologist treatment decisions under limited time and financial constraints. Trial registration number NCT01447043. PMID:27030279

  9. The Royal College of Ophthalmologists' National Ophthalmology Database Study of cataract surgery: report 2, relationships of axial length with ocular copathology, preoperative visual acuity, and posterior capsule rupture

    PubMed Central

    Day, A C; Donachie, P H J; Sparrow, J M; Johnston, R L

    2015-01-01

    Purpose To describe the relationships of axial length with ocular copathology, preoperative visual acuity, and posterior capsule rupture rates in patients undergoing cataract surgery. Design The Royal College of Ophthalmologists' National Ophthalmology Database (NOD) study. Methods Anonymised data on 180 114 eyes from 127 685 patients undergoing cataract surgery between August 2006 and November 2010 were collected prospectively from 28 sites. Data parameters included: demographics, biometry, ocular copathology, visual acuity measurements, and surgical complications including posterior capsule rupture, or vitreous loss or both (PCR). Results Consultant surgeons performed a higher proportion of operations on eyes whose axial length were at the extremes. Glaucoma and age related macular degeneration were more common in eyes with shorter axial lengths, whilst previous vitrectomy was associated with longer axial lengths. Eyes with brunescent or white cataracts or amblyopia were more common at both axial length extremes. Preoperative visual acuities were similar for eyes with axial length measurements up to approximately 28 mm and worse for eyes with longer axial length measurements. PCR rates showed little change with axial length (overall mean 1.95%, 95% CI: 1.89 to 2.01%), except for a borderline increase in eyes with axial length <20.0 mm where rates were 3.6% (95% CI: 2.0 to 6.3%). The likelihood of PCR in eyes with axial length <20.0 mm was 1.88 times higher than those of ≥20.0 mm (P=0.0373). Conclusion Rates of ocular comorbidities vary by axial length. PCR rates in eyes with very short or long axial lengths were lower than expected. PMID:26493034

  10. Mismatch Receptive Fields in Mouse Visual Cortex.

    PubMed

    Zmarz, Pawel; Keller, Georg B

    2016-11-23

    In primary visual cortex, a subset of neurons responds when a particular stimulus is encountered in a certain location in visual space. This activity can be modeled using a visual receptive field. In addition to visually driven activity, there are neurons in visual cortex that integrate visual and motor-related input to signal a mismatch between actual and predicted visual flow. Here we show that these mismatch neurons have receptive fields and signal a local mismatch between actual and predicted visual flow in restricted regions of visual space. These mismatch receptive fields are aligned to the retinotopic map of visual cortex and are similar in size to visual receptive fields. Thus, neurons with mismatch receptive fields signal local deviations of actual visual flow from visual flow predicted based on self-motion and could therefore underlie the detection of objects moving relative to the visual flow caused by self-motion. VIDEO ABSTRACT.

  11. [Usefulness of extradural optic canal unroofing and decompression of the optic nerve for improvement of visual acuity in traumatic optic neuropathy].

    PubMed

    Nishida, Sho; Otani, Naoki; Inaka, Yasufumi; Morinaga, Yusuke; Kimura, Shohei; Tomura, Satoshi; Osada, Hideo; Harimoto, Kohzou; Takeuchi, Masaru; Wada, Kojiro; Mori, Kentaro

    2014-11-01

    An 81-year-old man presented with poor visual acuity of the left eye, swelling of the left eyelid, and elevation of the left intraocular pressure after contusion of the left palpebral portion. CT revealed left ocular proptosis and left intraorbital hematoma. Traumatic optic neuropathy was suspected, and emergent optic nerve decompression was performed through extradural anterior clinoidectomy followed by optic canal release. Postoperatively, his left visual acuity was markedly improved and the elevated intraocular pressure decreased. Postoperative CT demonstrated improvement of the left ocular proptosis and decompression of the optic nerve. Emergent optic canal release has been recommended in patients who have suffered visual dysfunction caused by optic canal fracture or intraorbital hematoma. The advantages of extradural anterior clinoidectomy followed by optic canal release include a shorter surgical route and easy identification of the optic nerve, resulting in fewer surgical complications. In addition, this procedure can achieve intraorbital decompression. We recommend extradural anterior clinoidectomy followed by optic canal release as a safe and reliable procedure for optic nerve decompression in patients with traumatic optic neuropathy.

  12. Introduction to Vector Field Visualization

    NASA Technical Reports Server (NTRS)

    Kao, David; Shen, Han-Wei

    2010-01-01

    Vector field visualization techniques are essential to help us understand the complex dynamics of flow fields. These can be found in a wide range of applications such as study of flows around an aircraft, the blood flow in our heart chambers, ocean circulation models, and severe weather predictions. The vector fields from these various applications can be visually depicted using a number of techniques such as particle traces and advecting textures. In this tutorial, we present several fundamental algorithms in flow visualization including particle integration, particle tracking in time-dependent flows, and seeding strategies. For flows near surfaces, a wide variety of synthetic texture-based algorithms have been developed to depict near-body flow features. The most common approach is based on the Line Integral Convolution (LIC) algorithm. There also exist extensions of LIC to support more flexible texture generations for 3D flow data. This tutorial reviews these algorithms. Tensor fields are found in several real-world applications and also require the aid of visualization to help users understand their data sets. Examples where one can find tensor fields include mechanics to see how material respond to external forces, civil engineering and geomechanics of roads and bridges, and the study of neural pathway via diffusion tensor imaging. This tutorial will provide an overview of the different tensor field visualization techniques, discuss basic tensor decompositions, and go into detail on glyph based methods, deformation based methods, and streamline based methods. Practical examples will be used when presenting the methods; and applications from some case studies will be used as part of the motivation.

  13. Reducing Short-Wavelength Blue Light in Dry Eye Patients with Unstable Tear Film Improves Performance on Tests of Visual Acuity

    PubMed Central

    Kaido, Minako

    2016-01-01

    Purpose To investigate whether suppression of blue light can improve visual function in patients with short tear break up time (BUT) dry eye (DE). Methods Twenty-two patients with short BUT DE (10 men, 12 women; mean age, 32.4 ± 6.4 years; age range, 23–43 years) and 18 healthy controls (10 men, 8 women; mean age, 30.1 ± 7.4 years; age range, 20–49 years) underwent functional visual acuity (VA) examinations with and without wearing eyeglasses with 50% blue light blocked lenses. The functional VA parameters were starting VA, functional VA, and visual maintenance ratio. Results The baseline mean values (logarithm of the minimum angle of resolution, logMAR) of functional VA and the visual maintenance ratio were significantly worse in the DE patients than in the controls (P < 0.05), while no significant difference was observed in the baseline starting VA (P > 0.05). The DE patients had significant improvement in mean functional VA and visual maintenance ratio while wearing the glasses (P < 0.05), while there were no significant changes with and without the glasses in the control group (P > 0.05), Conclusions Protecting the eyes from short-wavelength blue light may help to ameliorate visual impairment associated with tear instability in patients with DE. This finding represents a new concept, which is that the blue light exposure might be harmful to visual function in patients with short BUT DE. PMID:27045760

  14. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Visual fields. 4.77... DISABILITIES Disability Ratings The Organs of Special Sense § 4.77 Visual fields. (a) Examination of visual... who are well adapted to intraocular lens implant or contact lens correction, visual field...

  15. Correlation Between the Findings of Optical Coherent Retinal Tomography (OCT), Stereo Biomicroscopic Images from Fundus of an Eye and Values from Visual Acuity of Diabetic Macular Edema

    PubMed Central

    Nisic, Faruk; Turkovic, Samir; Mavija, Milka; Jovanovic, Nina; Alimanovic, Emina Halilovic-

    2014-01-01

    Introduction: Diabetic maculopathy is the major cause of reduced visual acuity in patients with non-proliferative diabetic retinopathy and occurs on average in 29% of patients who have diabetes for 20 or more years. Aim: The aim of this study is to re examine the correlation between the findings of optical coherence retinal tomography, stereo bio-microscopic images from fundus of an eye and values from visual acuity of diabetic macular edema. In addition, the aim is to show the importance of various ophthalmic tests for establishing diagnosis in time. Material and methods: The research sample consisted of 90 subjects-patients from Cabinet for photographic documentation, fluorescein angiography and laser photocoagulation in Department of Ophthalmology at the University Clinical Centre in Sarajevo. The study was a one-year long, prospective, clinical study. Results: Research has shown a positive correlation between the various tests that are applied for the diagnosis of diabetic macular edema. Accurate and early diagnosis is of great importance for the treatment in time of this disease by applying laser photocoagulation, intravitreal injections of Anti-VEGF drugs or surgical treatment by Pars Plana Vitrectomy. PMID:25395723

  16. Myopia prevention, near work, and visual acuity of college students: integrating the theory of planned behavior and self-determination theory.

    PubMed

    Chan, Derwin King-Chung; Fung, Ying-Ki; Xing, Suxuan; Hagger, Martin S

    2014-06-01

    There has been little research examining the psychological antecedents of safety-oriented behavior aimed at reducing myopia risk. This study utilizes self-determination theory (SDT) and the theory of planned behavior (TPB) to understand the role of motivational and social-cognitive factors on individuals' near-work behavior. Adopting a prospective design, undergraduate students (n = 107) completed an initial questionnaire based on SDT in week 1, a second questionnaire containing measures of TPB variables in week 2, and objective measures of reading distance and visual acuity in week 6. The data were analyzed by variance-based structural equation modeling. The results showed that perceived autonomy support and autonomous motivation from SDT significantly predicted attitude, subjective norm, and perceived behavioral control from the TPB. These social-cognitive factors were significantly associated with intention and intention significantly predicted reading distance. The relationships in the model held when controlling for visual acuity. In conclusion, the integrated model of SDT and the TPB may help explain myopia-preventive behaviors.

  17. Impaired visual competition in patients with homonymous visual field defects.

    PubMed

    Geuzebroek, A C; van den Berg, A V

    2017-03-01

    Intense visual training can lead to partial recovery of visual field defects caused by lesions of the primary visual cortex. However, the standard visual detection and discrimination tasks, used to assess this recovery process tend to ignore the complexity of the natural visual environment, where multiple stimuli continuously interact. Visual competition is an essential component for natural search tasks and detecting unexpected events. Our study focused on visual decision-making and to what extent the recovered visual field can compete for attention with the 'intact' visual field. Nine patients with visual field defects who had previously received visual discrimination training, were compared to healthy age-matched controls using a saccade target-selection paradigm, in which participants actively make a saccade towards the brighter of two flashed targets. To further investigate the nature of competition (feed-forward or feedback inhibition), we presented two flashes that reversed their intensity difference during the flash. Both competition between recovered visual field and intact visual field, as well as competition within the intact visual field, were assessed. Healthy controls showed the expected primacy effect; they preferred the initially brighter target. Surprisingly, choice behaviour, even in the patients' supposedly 'intact' visual field, was significantly different from the control group for all but one. In the latter patient, competition was comparable to the controls. All other patients showed a significantly reduced preference to the brighter target, but still showed a small hint of primacy in the reversal conditions. The present results indicate that patients and controls have similar decision-making mechanisms but patients' choices are affected by a strong tendency to guess, even in the intact visual field. This tendency likely reveals slower integration of information, paired with a lower threshold. Current rehabilitation should therefore also

  18. Effects of Mild Hypercapnia During Head-Down Bed Rest on Ocular Structures, Cerebral Blood Flow, aud Visual Acuity in Healthy Human Subjects

    NASA Technical Reports Server (NTRS)

    Laurie, S. S.; Taibbi, G.; Lee, S. M. C.; Martin, D. S.; Zanello, S.; Ploutz-Snyder, R.; Hu, X.; Stenger, M. B.; Vizzeri, G.

    2014-01-01

    The cephalad fluid shift induced by microgravity has been hypothesized to cause an elevation in intracranial pressure (ICP) and contribute to the development of the Visual Impairment/Intracranial Pressure (VIIP) syndrome, as experienced by some astronauts during long-duration space flight. Elevated ambient partial pressure of carbon dioxide (PCO2) on ISS may also raise ICP and contribute to VIIP development. We seek to determine if the combination of mild CO2 exposure, similar to that occurring on the International Space Station, with the cephalad fluid shift induced by head-down tilt, will induce ophthalmic and cerebral blood flow changes similar to those described in the VIIP syndrome. We hypothesize that mild hypercapnia in the head-down tilt position will increase choroidal blood volume and cerebral blood flow, raise intraocular pressure (IOP), and transiently reduce visual acuity as compared to the seated or the head-down tilt position without elevated CO2, respectively.

  19. Highly selective receptive fields in mouse visual cortex.

    PubMed

    Niell, Cristopher M; Stryker, Michael P

    2008-07-23

    Genetic methods available in mice are likely to be powerful tools in dissecting cortical circuits. However, the visual cortex, in which sensory coding has been most thoroughly studied in other species, has essentially been neglected in mice perhaps because of their poor spatial acuity and the lack of columnar organization such as orientation maps. We have now applied quantitative methods to characterize visual receptive fields in mouse primary visual cortex V1 by making extracellular recordings with silicon electrode arrays in anesthetized mice. We used current source density analysis to determine laminar location and spike waveforms to discriminate putative excitatory and inhibitory units. We find that, although the spatial scale of mouse receptive fields is up to one or two orders of magnitude larger, neurons show selectivity for stimulus parameters such as orientation and spatial frequency that is near to that found in other species. Furthermore, typical response properties such as linear versus nonlinear spatial summation (i.e., simple and complex cells) and contrast-invariant tuning are also present in mouse V1 and correlate with laminar position and cell type. Interestingly, we find that putative inhibitory neurons generally have less selective, and nonlinear, responses. This quantitative description of receptive field properties should facilitate the use of mouse visual cortex as a system to address longstanding questions of visual neuroscience and cortical processing.

  20. Local Tumor Control, Visual Acuity, and Survival After Hypofractionated Stereotactic Photon Radiotherapy of Choroidal Melanoma in 212 Patients Treated Between 1997 and 2007

    SciTech Connect

    Dunavoelgyi, Roman; Dieckmann, Karin; Gleiss, Andreas; Sacu, Stefan; Kircher, Karl; Georgopoulos, Michael; Georg, Dietmar; Zehetmayer, Martin; Poetter, Richard

    2011-09-01

    Purpose: To evaluate long-term local tumor control, visual acuity, and survival after hypofractionated linear accelerator-based stereotactic photon radiotherapy in patients with choroidal melanoma. Methods and Materials: Between 1997 and 2007, 212 patients with choroidal melanoma unsuitable for ruthenium-106 brachytherapy or local resection were treated stereotactically at a linear accelerator with 6-MV photon beams at the Medical University of Vienna in five fractions over 7 days. Twenty-four patients received a total dose of 70 Gy (five fractions of 14 Gy), 158 a total dose of 60 Gy (five fractions of 12 Gy) and 30 patients a total dose of 50 Gy (five fractions of 10 Gy) applied on the 80% isodose. Ophthalmologic examinations were performed at baseline and every 3 months in the first 2 years, every 6 months until 5 years, and once a year thereafter until 10 years after radiotherapy. Assessment of visual acuity, routine ophthalmologic examinations, and measurement of tumor base dimension and height using standardized A-scan and B-scan echography were done at each visit. Funduscopy and fluorescein angiography were done when necessary to document tumor response. Results: Median tumor height and volume decreased from 4.8 mm and 270.7 mm{sup 3} at baseline to 2.6 mm and 86.6 mm{sup 3} at the last individual follow-up, respectively (p < 0.001, p < 0.001). Median visual acuity decreased from 0.55 at baseline to hand motion at the last individual follow-up (p < 0.001). Local tumor control was 95.9% after 5 years and 92.6% after 10 years. Thirty-two patients developed metastatic disease, and 22 of these patients died during the follow-up period. Conclusion: Hypofractionated stereotactic photon radiotherapy with 70 to 50 Gy delivered in five fractions in 7 days is sufficient to achieve excellent local tumor control in patients with malignant melanoma of the choroid. Disease outcome and vision are comparable to those achieved with proton beam radiotherapy. Decreasing the

  1. Interpupillary and Vertex Distance Effects on Field-of-View and Acuity With ANVIS

    DTIC Science & Technology

    1992-01-01

    derived from binocular as opposed to monocular viewing ( Arditi , 1986; Boff and Lincoln, 1988). As an ANVIS with its IPD set to other than the optimal value...periphery of the field-of-view and under conditions of low stimulus contrast. 28 References Arditi , A. 1986. Binocular vision, in Boff, K.R., Kaufman

  2. Visualizing the blind brain: brain imaging of visual field defects from early recovery to rehabilitation techniques

    PubMed Central

    Urbanski, Marika; Coubard, Olivier A.; Bourlon, Clémence

    2014-01-01

    Visual field defects (VFDs) are one of the most common consequences observed after brain injury, especially after a stroke in the posterior cerebral artery territory. Less frequently, tumors, traumatic brain injury, brain surgery or demyelination can also determine various visual disabilities, from a decrease in visual acuity to cerebral blindness. Visual field defects is a factor of bad functional prognosis as it compromises many daily life activities (e.g., obstacle avoidance, driving, and reading) and therefore the patient’s quality of life. Spontaneous recovery seems to be limited and restricted to the first 6 months, with the best chance of improvement at 1 month. The possible mechanisms at work could be partly due to cortical reorganization in the visual areas (plasticity) and/or partly to the use of intact alternative visual routes, first identified in animal studies and possibly underlying the phenomenon of blindsight. Despite processes of early recovery, which is rarely complete, and learning of compensatory strategies, the patient’s autonomy may still be compromised at more chronic stages. Therefore, various rehabilitation therapies based on neuroanatomical knowledge have been developed to improve VFDs. These use eye-movement training techniques (e.g., visual search, saccadic eye movements), reading training, visual field restitution (the Vision Restoration Therapy, VRT), or perceptual learning. In this review, we will focus on studies of human adults with acquired VFDs, which have used different imaging techniques (Positron Emission Tomography, PET; Diffusion Tensor Imaging, DTI; functional Magnetic Resonance Imaging, fMRI; Magneto Encephalography, MEG) or neurostimulation techniques (Transcranial Magnetic Stimulation, TMS; transcranial Direct Current Stimulation, tDCS) to show brain activations in the course of spontaneous recovery or after specific rehabilitation techniques. PMID:25324739

  3. Current smoking is associated with a poor visual acuity improvement after intravitreal ranibizumab therapy in patients with exudative age-related macular degeneration.

    PubMed

    Lee, Sangmoon; Song, Su Jeong; Yu, Hyeong Gon

    2013-05-01

    In this study, the risk factors that may influence visual improvement after intravitreal ranibizumab (IVR) treatment for exudative age-related macular degeneration (AMD) were examined. From 2008 to 2012, 420 patients (448 eyes) with exudative AMD were prospectively registered at Seoul National University Hospital. From this group of patients, 125 eyes were included in this study. All patients were treated with 3 consecutive IVR injections. The visual acuity (VA) was evaluated at baseline and 1 month after the third ranibizumab injection. To evaluate the risk factors associated with VA improvement after IVR, patient demographic data and systemic risk factors were analyzed. Patients were divided into a poor VA improvement group and a good VA improvement group, with reference to the median visual improvement in all eyes. Among 125 eyes, 66 eyes (52.8%) were included in the responder group and 59 eyes (47.2%) in the non-responder group. The median VA improvement after 3 monthly ranibizumab injections was -0.05 logMAR. Multivariate analyses revealed that current smoking (adjusted OR, 7.540; 95% CI, 1.732-32.823) was independently associated with poor VA improvement after IVR treatment for exudative AMD. In conclusion, cigarette smoking is an independent risk factor for lower VA gains with IVR treatment for exudative AMD.

  4. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... meridians 221/2 degrees apart for each eye and indicate the Goldmann equivalent used. See Table III for the... visual fields. Determine the average concentric contraction of the visual field of each eye by measuring... defect are present in one or both eyes and are service connected, separately evaluate the visual...

  5. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... meridians 221/2 degrees apart for each eye and indicate the Goldmann equivalent used. See Table III for the... visual fields. Determine the average concentric contraction of the visual field of each eye by measuring... defect are present in one or both eyes and are service connected, separately evaluate the visual...

  6. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... meridians 221/2 degrees apart for each eye and indicate the Goldmann equivalent used. See Table III for the... visual fields. Determine the average concentric contraction of the visual field of each eye by measuring... defect are present in one or both eyes and are service connected, separately evaluate the visual...

  7. Visualizing second order tensor fields with hyperstreamlines

    NASA Technical Reports Server (NTRS)

    Delmarcelle, Thierry; Hesselink, Lambertus

    1993-01-01

    Hyperstreamlines are a generalization to second order tensor fields of the conventional streamlines used in vector field visualization. As opposed to point icons commonly used in visualizing tensor fields, hyperstreamlines form a continuous representation of the complete tensor information along a three-dimensional path. This technique is useful in visulaizing both symmetric and unsymmetric three-dimensional tensor data. Several examples of tensor field visualization in solid materials and fluid flows are provided.

  8. Vernier acuity through night vision goggles.

    PubMed

    Rabin, J

    1993-08-01

    Night vision goggles (NVG's) are being used increasingly in military and civilian environments. Despite the use of these devices, relatively few tests exist to assess visual performance through NVG's. Hyperacuity tasks may provide a sensitive index of performance through night vision devices. In this study, grating vernier acuity was measured through NVG's. As reported previously, a power law relation was observed between vernier acuity and stimulus contrast. Comparison of vernier acuity with and without NVG's indicated that performance is limited by the contrast transfer of the device. Vernier acuity measurements can be used to assess the quality of vision and quantity of contrast transferred through night vision devices.

  9. Do picture-based charts overestimate visual acuity? Comparison of Kay Pictures, Lea Symbols, HOTV and Keeler logMAR charts with Sloan letters in adults and children

    PubMed Central

    Simkin, Samantha K.; Thomson, Melissa

    2017-01-01

    Purpose Children may be tested with a variety of visual acuity (VA) charts during their ophthalmic care and differences between charts can complicate the interpretation of VA measurements. This study compared VA measurements across four pediatric charts with Sloan letters and identified chart design features that contributed to inter-chart differences in VA. Methods VA was determined for right eyes of 25 adults and 17 children (4–9 years of age) using Crowded Kay Pictures, Crowded linear Lea Symbols, Crowded Keeler logMAR, Crowded HOTV and Early Treatment of Diabetic Retinopathy Study (ETDRS) charts in focused and defocused (+1.00 DS optical blur) conditions. In a separate group of 25 adults, we compared the VA from individual Kay Picture optotypes with uncrowded Landolt C VA measurements. Results Crowded Kay Pictures generated significantly better VA measurements than all other charts in both adults and children (p < 0.001; 0.15 to 0.30 logMAR). No significant differences were found between other charts in adult participants; children achieved significantly poorer VA measurements on the ETDRS chart compared with pediatric acuity tests. All Kay Pictures optotypes produced better VA (p < 0.001), varying from -0.38 ± 0.13 logMAR (apple) to -0.57 ± 0.10 logMAR (duck), than the reference Landolt C task (mean VA -0.19 ± 0.08 logMAR). Conclusion Kay Pictures over-estimated VA in all participants. Variability between Kay Pictures optotypes suggests that shape cues aid in optotype determination. Other pediatric charts offer more comparable VA measures and should be used for children likely to progress to letter charts. PMID:28152076

  10. Complex visual hallucinations in the hemianopic field.

    PubMed Central

    Kölmel, H W

    1985-01-01

    From 120 patients with an homonymous hemianopia 16 experienced complex visual hallucinations in the hemianopic field. The brain lesion was located in the occipital lobe, though damage was not limited to this area. Complex hallucinations appeared after a latent period. They were weak in colour and stereotypical in appearance, which allowed differentiation from visual hallucinations of other causes. Different behaviour after saccadic eye movement differentiated between complex visual hallucinations in the hemianopic field and visual auras of an epileptic origin. PMID:3973619

  11. Visual acuity measured with luminance-modulated and contrast-modulated noise letter stimuli in young adults and adults above 50 years old

    PubMed Central

    Woi, Pui Juan; Kaur, Sharanjeet; Waugh, Sarah J.; Hairol, Mohd Izzuddin

    2016-01-01

    The human visual system is sensitive in detecting objects that have different luminance level from their background, known as first-order or luminance-modulated (LM) stimuli. We are also able to detect objects that have the same mean luminance as their background, only differing in contrast (or other attributes). Such objects are known as second-order or contrast-modulated (CM), stimuli. CM stimuli are thought to be processed in higher visual areas compared to LM stimuli, and may be more susceptible to ageing. We compared visual acuities (VA) of five healthy older adults (54.0±1.83 years old) and five healthy younger adults (25.4±1.29 years old) with LM and CM letters under monocular and binocular viewing. For monocular viewing, age had no effect on VA [F(1, 8)= 2.50, p> 0.05]. However, there was a significant main effect of age on VA under binocular viewing [F(1, 8)= 5.67, p< 0.05].  Binocular VA with CM letters in younger adults was approximately two lines better than that in older adults. For LM, binocular summation ratios were similar for older (1.16±0.21) and younger (1.15±0.06) adults. For CM, younger adults had higher binocular summation ratio (1.39±0.08) compared to older adults (1.12±0.09). Binocular viewing improved VA with LM letters for both groups similarly. However, in older adults, binocular viewing did not improve VA with CM letters as much as in younger adults. This could reflect a decline of higher visual areas due to ageing process, most likely higher than V1, which may be missed if measured with luminance-based stimuli alone. PMID:28184281

  12. Visual acuity measured with luminance-modulated and contrast-modulated noise letter stimuli in young adults and adults above 50 years old.

    PubMed

    Woi, Pui Juan; Kaur, Sharanjeet; Waugh, Sarah J; Hairol, Mohd Izzuddin

    2016-01-01

    The human visual system is sensitive in detecting objects that have different luminance level from their background, known as first-order or luminance-modulated (LM) stimuli. We are also able to detect objects that have the same mean luminance as their background, only differing in contrast (or other attributes). Such objects are known as second-order or contrast-modulated (CM), stimuli. CM stimuli are thought to be processed in higher visual areas compared to LM stimuli, and may be more susceptible to ageing. We compared visual acuities (VA) of five healthy older adults (54.0±1.83 years old) and five healthy younger adults (25.4±1.29 years old) with LM and CM letters under monocular and binocular viewing. For monocular viewing, age had no effect on VA [F(1, 8)= 2.50, p> 0.05]. However, there was a significant main effect of age on VA under binocular viewing [F(1, 8)= 5.67, p< 0.05].  Binocular VA with CM letters in younger adults was approximately two lines better than that in older adults. For LM, binocular summation ratios were similar for older (1.16±0.21) and younger (1.15±0.06) adults. For CM, younger adults had higher binocular summation ratio (1.39±0.08) compared to older adults (1.12±0.09). Binocular viewing improved VA with LM letters for both groups similarly. However, in older adults, binocular viewing did not improve VA with CM letters as much as in younger adults. This could reflect a decline of higher visual areas due to ageing process, most likely higher than V1, which may be missed if measured with luminance-based stimuli alone.

  13. Mechanisms compensating for visual field restriction in adolescents with damage to the retro-geniculate visual system

    PubMed Central

    Jacobson, L; Lennartsson, F; Pansell, T; Öqvist Seimyr, G; Martin, L

    2012-01-01

    Background To describe visual field (VF) outcome in three adolescents with damage to the optic radiation and to focus on mechanisms that may compensate the practical functional limitations of VF defects. Design Descriptive, prospective multi-case study in a hospital setting. Participants Three teenagers with cerebral visual dysfunction because of damage to the retro-geniculate visual pathways. Methods Best-corrected visual acuity and eye alignment were assessed. Visual field function was tested with Goldmann perimetry, and with Rarebit, Humphrey Visual Field Analyzer and Esterman computerized techniques. Fixation was registered with video oculography during Rarebit examination. Magnetic resonance imaging of the brain illustrated brain damage and its relation to the posterior visual system. Results One of the three subjects had bilateral asymmetric white matter damage of immaturity, early-onset exotropia, and a relative homonymous VF defect, but normal binocular VF. The second subject also had bilateral asymmetric white matter damage of immaturity and showed an inferior right quadrantanopia, confirmed by the binocular field. Registration of fixation revealed automatic scanning during perimetry. The third subject had an almost total left homonymous hemianopia after resection of a brain tumour in the right temporal lobe. The hemianopia could be compensated for by fast voluntary scanning. Conclusion Congenital and later-acquired homonymous VF defects may, at least in young subjects, be compensated for by scanning. Exotropia may compensate VF defects and, therefore, the VF should be tested before strabismus surgery. PMID:22995940

  14. Early clinical and subclinical visual evoked potential and Humphrey's visual field defects in cryptococcal meningitis.

    PubMed

    Moodley, Anand; Rae, William; Bhigjee, Ahmed; Connolly, Cathy; Devparsad, Natasha; Michowicz, Andrew; Harrison, Thomas; Loyse, Angela

    2012-01-01

    Cryptococcal induced visual loss is a devastating complication in survivors of cryptococcal meningitis (CM). Early detection is paramount in prevention and treatment. Subclinical optic nerve dysfunction in CM has not hitherto been investigated by electrophysiological means. We undertook a prospective study on 90 HIV sero-positive patients with culture confirmed CM. Seventy-four patients underwent visual evoked potential (VEP) testing and 47 patients underwent Humphrey's visual field (HVF) testing. Decreased best corrected visual acuity (BCVA) was detected in 46.5% of patients. VEP was abnormal in 51/74 (68.9%) right eyes and 50/74 (67.6%) left eyes. VEP P100 latency was the main abnormality with mean latency values of 118.9 (±16.5) ms and 119.8 (±15.7) ms for the right and left eyes respectively, mildly prolonged when compared to our laboratory references of 104 (±10) ms (p<0.001). Subclinical VEP abnormality was detected in 56.5% of normal eyes and constituted mostly latency abnormality. VEP amplitude was also significantly reduced in this cohort but minimally so in the visually unimpaired. HVF was abnormal in 36/47 (76.6%) right eyes and 32/45 (71.1%) left eyes. The predominant field defect was peripheral constriction with an enlarged blind spot suggesting the greater impact by raised intracranial pressure over that of optic neuritis. Whether this was due to papilloedema or a compartment syndrome is open to further investigation. Subclinical HVF abnormalities were minimal and therefore a poor screening test for early optic nerve dysfunction. However, early optic nerve dysfunction can be detected by testing of VEP P100 latency, which may precede the onset of visual loss in CM.

  15. Early Clinical and Subclinical Visual Evoked Potential and Humphrey's Visual Field Defects in Cryptococcal Meningitis

    PubMed Central

    Moodley, Anand; Rae, William; Bhigjee, Ahmed; Connolly, Cathy; Devparsad, Natasha; Michowicz, Andrew; Harrison, Thomas; Loyse, Angela

    2012-01-01

    Cryptococcal induced visual loss is a devastating complication in survivors of cryptococcal meningitis (CM). Early detection is paramount in prevention and treatment. Subclinical optic nerve dysfunction in CM has not hitherto been investigated by electrophysiological means. We undertook a prospective study on 90 HIV sero-positive patients with culture confirmed CM. Seventy-four patients underwent visual evoked potential (VEP) testing and 47 patients underwent Humphrey's visual field (HVF) testing. Decreased best corrected visual acuity (BCVA) was detected in 46.5% of patients. VEP was abnormal in 51/74 (68.9%) right eyes and 50/74 (67.6%) left eyes. VEP P100 latency was the main abnormality with mean latency values of 118.9 (±16.5) ms and 119.8 (±15.7) ms for the right and left eyes respectively, mildly prolonged when compared to our laboratory references of 104 (±10) ms (p<0.001). Subclinical VEP abnormality was detected in 56.5% of normal eyes and constituted mostly latency abnormality. VEP amplitude was also significantly reduced in this cohort but minimally so in the visually unimpaired. HVF was abnormal in 36/47 (76.6%) right eyes and 32/45 (71.1%) left eyes. The predominant field defect was peripheral constriction with an enlarged blind spot suggesting the greater impact by raised intracranial pressure over that of optic neuritis. Whether this was due to papilloedema or a compartment syndrome is open to further investigation. Subclinical HVF abnormalities were minimal and therefore a poor screening test for early optic nerve dysfunction. However, early optic nerve dysfunction can be detected by testing of VEP P100 latency, which may precede the onset of visual loss in CM. PMID:23285220

  16. Mapping the Visual Communication Field.

    ERIC Educational Resources Information Center

    Moriarty, Sandra E.

    This paper discusses visual communication theory. After an examination of the literature, this study built a more extensive bibliography of visual communication in general--theory, research, teaching--as well as a taxonomy that was better grounded. A 95-page bibliography was developed for works from a number of scholarly journals dealing with…

  17. Structural analysis of retinal photoreceptor ellipsoid zone and postreceptor retinal layer associated with visual acuity in patients with retinitis pigmentosa by ganglion cell analysis combined with OCT imaging

    PubMed Central

    Liu, Guodong; Li, Hui; Liu, Xiaoqiang; Xu, Ding; Wang, Fang

    2016-01-01

    Abstract The aim of this study was to examine changes in photoreceptor ellipsoid zone (EZ) and postreceptor retinal layer in retinitis pigmentosa (RP) patients by ganglion cell analysis (GCA) combined with optical coherence tomography (OCT) imaging to evaluate the structure–function relationships between retinal layer changes and best corrected visual acuity (BCVA). Sixty-eight eyes of 35 patients with RP and 65 eyes of 35 normal controls were analyzed in the study. The average length of EZ was 911.1 ± 208.8 μm in RP patients, which was shortened with the progression of the disease on the OCT images. The average ganglion cell–inner plexiform layer thickness (GCIPLT) was 54.7 ± 18.9 μm in RP patients, while in normal controls it was 85.6 ± 6.8 μm. The GCIPLT in all quarters became significantly thinner along with outer retinal thinning. There was a significantly positive correlation between BCVA and EZ (r = −0.7622, P < 0.001) and GCIPLT (r = −0.452, P < 0.001). Therefore, we assess the retinal layer changes from a new perspective in RP patients, which suggests that EZ and GCIPLT obtained by GCA combined with OCT imaging are the direct and valid indicators to diagnosis and predict the pathological process of RP. PMID:28033301

  18. Spatial classification of glaucomatous visual field loss.

    PubMed Central

    Henson, D. B.; Spenceley, S. E.; Bull, D. R.

    1996-01-01

    AIMS--To develop and describe an objective classification system for the spatial patterns of visual field loss found in glaucoma. METHODS--The 560 Humphrey visual field analyser (program 24-2) records were used to train an artificial neural network (ANN). The type of network used, a Kohonen self organising feature map (SOM), was configured to organise the visual field defects into 25 classes of superior visual field loss and 25 classes of inferior visual field loss. Each group of 25 classes was arranged in a 5 by 5 map. RESULTS--The SOM successfully classified the defects on the basis of the patterns of loss. The maps show a continuum of change as one moves across them with early loss at one corner and advanced loss at the opposite corner. CONCLUSIONS--ANNs can classify visual field data on the basis of the pattern of loss. Once trained the ANN can be used to classify longitudinal visual field data which may prove valuable in monitoring visual field loss. PMID:8759263

  19. Visual-field function in pseudophakia.

    PubMed

    Klewin, K M; Radius, R L; Schultz, R O

    1988-08-01

    An automated perimeter (Octopus 2000) was used to examine visual-field function in 52 pseudophakic eyes. Threshold sensitivity was reduced throughout the visual field by from 0.4 to 20.0 decibels from that of threshold sensitivity in age-matched normal eyes. This reduction was comparable to that seen in contact-lens-corrected aphakic eyes.

  20. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... who are well adapted to intraocular lens implant or contact lens correction, visual field examinations.... For aphakic individuals not well adapted to contact lens correction or pseudophakic individuals not well adapted to intraocular lens implant, visual field examinations must be conducted using...

  1. Visual Field Asymmetry in Attentional Capture

    ERIC Educational Resources Information Center

    Du, Feng; Abrams, Richard A.

    2010-01-01

    The present study examined the spatial distribution of involuntary attentional capture over the two visual hemi-fields. A new experiment, and an analysis of three previous experiments showed that distractors in the left visual field that matched a sought-for target in color produced a much larger capture effect than identical distractors in the…

  2. Visual Field Map Clusters in Macaque Extrastriate Visual Cortex

    PubMed Central

    Kolster, Hauke; Mandeville, Joseph B.; Arsenault, John T.; Ekstrom, Leeland B.; Wald, Lawrence L.; Vanduffel, Wim

    2009-01-01

    The macaque visual cortex contains more than 30 different functional visual areas, yet surprisingly little is known about the underlying organizational principles that structure its components into a complete ‘visual’ unit. A recent model of visual cortical organization in humans suggests that visual field maps are organized as clusters. Clusters minimize axonal connections between individual field maps that represent common visual percepts, with different clusters thought to carry out different functions. Experimental support for this hypothesis, however, is lacking in macaques, leaving open the question of whether it is unique to humans or a more general model for primate vision. Here we show, using high-resolution BOLD fMRI data in the awake monkey at 7 Tesla, that area MT/V5 and its neighbors are organized as a cluster with a common foveal representation and a circular eccentricity map. This novel view on the functional topography of area MT/V5 and satellites indicates that field map clusters are evolutionarily preserved and may be a fundamental organizational principle of the old world primate visual cortex. PMID:19474330

  3. Five-year visual acuity outcomes and injection patterns in patients with pro-re-nata treatments for AMD, DME, RVO and myopic CNV

    PubMed Central

    Wecker, Thomas; Ehlken, Christoph; Bühler, Anima; Lange, Clemens; Agostini, Hansjürgen; Böhringer, Daniel; Stahl, Andreas

    2017-01-01

    Background Anti vascular endothelial growth factor (VEGF) therapy is an established treatment for various retinal diseases. Long-term data on injection frequencies and visual acuity (VA), however, are still rare. Methods Five-year analysis of real-life VA developments and injection patterns from 2072 patients (2577 eyes; 33 187 injections) with chronically active disease undergoing pro-re-nata treatment for age-related macular degeneration (AMD), diabetic macular oedema (DME), retinal vein occlusion (RVO) and myopic choroidal neovascularisation (CNV). Results Maximum mean VA gain in year 1 was+5.2 letters in AMD, +6.2 in DME, +10 in RVO and+7.2 in myopic CNV. Over 5 years, however, VA in patients with AMD declined. By year 5, 34% of patients with AMD had experienced VA loss of >15 letters, 56% had remained stable and 10% had gained >15 letters. Long-term VA developments in DME and RVO were more favourable with 81% of DME and 79% of patients with RVO gaining or maintaining vision at 5 years. In AMD, median injection frequency was six in year 1 and between four and five in consecutive years. In DME and RVO, median injection frequency was six in year 1 but lower compared with AMD in consecutive years. Injection frequency in DME was weakly associated with patient age (rs=0.1; p=0.03). Conclusions In AMD, the initial VA gain was not maintained long term despite higher injection numbers compared with DME, RVO and myopic CNV. The presented real-world data provide a peer-group-based estimate of VA developments and injection frequencies for counselling patients undergoing long-term anti-VEGF therapy. PMID:27215744

  4. Importance of Central Retinal Sensitivity for Prediction of Visual Acuity after Intravitreal Bevacizumb in Eyes with Macular Edema Associated with Branch Retinal Vein Occlusion

    PubMed Central

    Sugimoto, Masahiko; Ichio, Atsushi; Kondo, Mineo

    2016-01-01

    Objective To determine whether the baseline retinal sensitivity can predict the best-corrected visual acuity (BCVA) at 1 month after intravitreal bevacizumab (IVB) in eyes with macular edema (ME) associated with a branch retinal vein occlusion (BRVO). Subjects and Methods We evaluated 16 eyes of 16 patients who had ME associated with a BRVO. The mean ± standard deviation age was 69.1 ± 8.9 years, and all had a single IVB injection. The BCVA, central macular thickness (CMT), integrity of the ellipsoid zone (EZ) of the photoreceptors, and retinal sensitivity were determined before (baseline) and at 1 day, 1 week, and 1 month following the IVB. The average threshold retinal sensitivity (AT) within the central 10° was determined by Macular Integrity Assessment. The correlations between the BCVA at 1 month and the CMT, integrity of the EZ, and AT at each visit were determined. Results One month after IVB, the BCVA improved significantly from 0.56 ± 0.27 logMAR units to 0.32 ± 0.28 logMAR units, and the CMT from 611.4 ± 209.3 μm to 258.7 ± 64.0 μm (P <0.05). The AT improved significantly from 17.9 ± 5.3 dB to 21.2 ± 5.0 dB (P <0.05). At 1 day after the treatment, both the integrity of the EZ (r = 0.59) and the retinal sensitivity (r = 0.76) were moderately correlated with the BCVA at 1 month. Conclusion These results indicate that both the integrity of the EZ and the AT at 1 day after the IVB can predict the BCVA after treatment for ME associated with BRVO. There is a possibility that these parameters will predict the effectiveness of IVB for each case. PMID:26885822

  5. The UK Neovascular AMD Database Report 3: inter-centre variation in visual acuity outcomes and establishing real-world measures of care.

    PubMed

    Liew, G; Lee, A Y; Zarranz-Ventura, J; Stratton, I; Bunce, C; Chakravarthy, U; Lee, C S; Keane, P A; Sim, D A; Akerele, T; McKibbin, M; Downey, L; Natha, S; Bailey, C; Khan, R; Antcliff, R; Armstrong, S; Varma, A; Kumar, V; Tsaloumas, M; Mandal, K; Egan, C; Johnston, R L; Tufail, A

    2016-11-01

    PurposeInternational variations in visual acuity (VA) outcomes of eyes treated for neovascular age-related macular degeneration (nAMD) are well-documented, but intra-country inter-centre regional variations are not known. These data are important for national quality outcome indicators. We aimed to determine intra-country and inter-centre regional variations in outcomes for treatment of nAMD.Patients and methodsProspective multicentre national database study of 13 UK centres that treated patients according to a set protocol (three loading doses, followed by Pro-Re-Nata retreatment). A total of 5811 treatment naive eyes of 5205 patients received a total of 36 206 ranibizumab injections over 12 months.ResultsMean starting VA between centres varied from 48.9 to 59.9 ETDRS letters. Mean inter-centre VA change from baseline to 12 months varied from +6.9 letters to -0.6 letters (mean of +2.5 letters). The proportion of eyes achieving VA of 70 letters or more varied between 21.9 and 48.7% at 12 months. Median number of injections (visits) at each centre varied from 5 to 8 (9 to 12), with an overall median of 6 (11). Age, starting VA, number of injections, and visits, but not gender were significantly associated with variation in these VA outcomes (P<0.01). Significant variation between centres persisted even after adjusting for these factors.ConclusionThere are modest differences in VA outcomes between centres in the UK. These differences are influenced, but not completely explained, by factors such as patient age, starting VA, number of injections, and visits. These data provide an indication of the VA outcomes that are achievable in real-world settings.

  6. Visualizing vector field topology in fluid flows

    NASA Technical Reports Server (NTRS)

    Helman, James L.; Hesselink, Lambertus

    1991-01-01

    Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.

  7. Mapping receptive fields in primary visual cortex

    PubMed Central

    Ringach, Dario L

    2004-01-01

    Nearly 40 years ago, in the pages of this journal, Hubel and Wiesel provided the first description of receptive fields in the primary visual cortex of higher mammals. They defined two classes of cortical cells, ‘simple’ and ‘complex’, based on neural responses to simple visual stimuli. The notion of a hierarchy of receptive fields, where increasingly intricate receptive fields are constructed from more elementary ones, was introduced. Since those early days we have witnessed the birth of quantitative methods to map receptive fields and mathematical descriptions of simple and complex cell function. Insights gained from these models, along with new theoretical concepts, are refining our understanding of receptive field structure and the underlying cortical circuitry. Here, I provide a brief historical account of the evolution of receptive field mapping in visual cortex along with the associated conceptual advancements, and speculate on the shape novel theories of the cortex may take as a result these measurements. PMID:15155794

  8. Automated objective characterization of visual field defects in 3D

    NASA Technical Reports Server (NTRS)

    Fink, Wolfgang (Inventor)

    2006-01-01

    A method and apparatus for electronically performing a visual field test for a patient. A visual field test pattern is displayed to the patient on an electronic display device and the patient's responses to the visual field test pattern are recorded. A visual field representation is generated from the patient's responses. The visual field representation is then used as an input into a variety of automated diagnostic processes. In one process, the visual field representation is used to generate a statistical description of the rapidity of change of a patient's visual field at the boundary of a visual field defect. In another process, the area of a visual field defect is calculated using the visual field representation. In another process, the visual field representation is used to generate a statistical description of the volume of a patient's visual field defect.

  9. Transverse chromatic aberration across the visual field of the human eye

    PubMed Central

    Winter, Simon; Sabesan, Ramkumar; Tiruveedhula, Pavan; Privitera, Claudio; Unsbo, Peter; Lundström, Linda; Roorda, Austin

    2016-01-01

    The purpose of this study was to measure the transverse chromatic aberration (TCA) across the visual field of the human eye objectively. TCA was measured at horizontal and vertical field angles out to ±15° from foveal fixation in the right eye of four subjects. Interleaved retinal images were taken at wavelengths 543 nm and 842 nm in an adaptive optics scanning laser ophthalmoscope (AOSLO). To obtain true measures of the human eye's TCA, the contributions of the AOSLO system's TCA were measured using an on-axis aligned model eye and subtracted from the ocular data. The increase in TCA was found to be linear with eccentricity, with an average slope of 0.21 arcmin/degree of visual field angle (corresponding to 0.41 arcmin/degree for 430 nm to 770 nm). The absolute magnitude of ocular TCA varied between subjects, but was similar to the resolution acuity at 10° in the nasal visual field, encompassing three to four cones. Therefore, TCA can be visually significant. Furthermore, for high-resolution imaging applications, whether visualizing or stimulating cellular features in the retina, it is important to consider the lateral displacements between wavelengths and the variation in blur over the visual field. PMID:27832270

  10. Transverse chromatic aberration across the visual field of the human eye.

    PubMed

    Winter, Simon; Sabesan, Ramkumar; Tiruveedhula, Pavan; Privitera, Claudio; Unsbo, Peter; Lundström, Linda; Roorda, Austin

    2016-11-01

    The purpose of this study was to measure the transverse chromatic aberration (TCA) across the visual field of the human eye objectively. TCA was measured at horizontal and vertical field angles out to ±15° from foveal fixation in the right eye of four subjects. Interleaved retinal images were taken at wavelengths 543 nm and 842 nm in an adaptive optics scanning laser ophthalmoscope (AOSLO). To obtain true measures of the human eye's TCA, the contributions of the AOSLO system's TCA were measured using an on-axis aligned model eye and subtracted from the ocular data. The increase in TCA was found to be linear with eccentricity, with an average slope of 0.21 arcmin/degree of visual field angle (corresponding to 0.41 arcmin/degree for 430 nm to 770 nm). The absolute magnitude of ocular TCA varied between subjects, but was similar to the resolution acuity at 10° in the nasal visual field, encompassing three to four cones. Therefore, TCA can be visually significant. Furthermore, for high-resolution imaging applications, whether visualizing or stimulating cellular features in the retina, it is important to consider the lateral displacements between wavelengths and the variation in blur over the visual field.

  11. Visualization of 3-D tensor fields

    NASA Technical Reports Server (NTRS)

    Hesselink, L.

    1996-01-01

    Second-order tensor fields have applications in many different areas of physics, such as general relativity and fluid mechanics. The wealth of multivariate information in tensor fields makes them more complex and abstract than scalar and vector fields. Visualization is a good technique for scientists to gain new insights from them. Visualizing a 3-D continuous tensor field is equivalent to simultaneously visualizing its three eigenvector fields. In the past, research has been conducted in the area of two-dimensional tensor fields. It was shown that degenerate points, defined as points where eigenvalues are equal to each other, are the basic singularities underlying the topology of tensor fields. Moreover, it was shown that eigenvectors never cross each other except at degenerate points. Since we live in a three-dimensional world, it is important for us to understand the underlying physics of this world. In this report, we describe a new method for locating degenerate points along with the conditions for classifying them in three-dimensional space. Finally, we discuss some topological features of three-dimensional tensor fields, and interpret topological patterns in terms of physical properties.

  12. Photopsia and a temporal visual field defect.

    PubMed

    Marsiglia, Marcela; Odel, Jeffery G; Rudich, Danielle S; Tsang, Stephen H; Plant, Gordon T

    2016-01-01

    A 30-year-old woman presented with intermittent photopsia, a temporal visual field defect below the horizontal in her left eye, and flu-like symptoms. Slit-lamp and fundus examinations were unremarkable. Humphrey 30-2 threshold perimetry and 120-point screening visual field demonstrated blind spot enlargement of the left eye and a normal field in the right eye. Fundus autofluorescence, optical coherence tomography of the macula, full-field electroretinogram, electrooculogram, and multifocal electroretinogram were normal. Swept-source optical coherence tomography scan of the left optic nerve showed an intact outer retina, a remarkably thinned nerve fiber layer nasally, and peripapillary vitreous traction. Goldmann kinetic perimetry revealed a sector-shaped dense defect breaking out from the blind spot to the temporal periphery just below the horizontal in the left eye. The patient had nasal hypoplasia of the optic nerve and peripapillary vitreous traction.

  13. A computational theory of visual receptive fields.

    PubMed

    Lindeberg, Tony

    2013-12-01

    A receptive field constitutes a region in the visual field where a visual cell or a visual operator responds to visual stimuli. This paper presents a theory for what types of receptive field profiles can be regarded as natural for an idealized vision system, given a set of structural requirements on the first stages of visual processing that reflect symmetry properties of the surrounding world. These symmetry properties include (i) covariance properties under scale changes, affine image deformations, and Galilean transformations of space-time as occur for real-world image data as well as specific requirements of (ii) temporal causality implying that the future cannot be accessed and (iii) a time-recursive updating mechanism of a limited temporal buffer of the past as is necessary for a genuine real-time system. Fundamental structural requirements are also imposed to ensure (iv) mutual consistency and a proper handling of internal representations at different spatial and temporal scales. It is shown how a set of families of idealized receptive field profiles can be derived by necessity regarding spatial, spatio-chromatic, and spatio-temporal receptive fields in terms of Gaussian kernels, Gaussian derivatives, or closely related operators. Such image filters have been successfully used as a basis for expressing a large number of visual operations in computer vision, regarding feature detection, feature classification, motion estimation, object recognition, spatio-temporal recognition, and shape estimation. Hence, the associated so-called scale-space theory constitutes a both theoretically well-founded and general framework for expressing visual operations. There are very close similarities between receptive field profiles predicted from this scale-space theory and receptive field profiles found by cell recordings in biological vision. Among the family of receptive field profiles derived by necessity from the assumptions, idealized models with very good qualitative

  14. Increased Macular Pigment Optical Density and Visual Acuity following Consumption of a Buttermilk Drink Containing Lutein-Enriched Egg Yolks: A Randomized, Double-Blind, Placebo-Controlled Trial

    PubMed Central

    van der Made, Sanne M.; Kelly, Elton R.; Kijlstra, Aize; Plat, Jogchum

    2016-01-01

    Purpose. To study the effect of 1-year daily consumption of a dairy drink containing lutein-enriched egg yolks on macular pigment optical density (MPOD) and visual function parameters in elderly subjects with ocular drusen and/or retinal pigment abnormalities. Methods. One hundred and one subjects were recruited to participate in this randomized, double-blind, placebo-controlled parallel intervention trial. Statistical analyses were performed with 46 subjects in the lutein group and 43 in the control group. MPOD, best corrected visual acuity (BCVA, logMAR), and dark adaptation were measured at the start of the study, after 6 months and after 12 months. Plasma lutein and zeaxanthin concentrations were assessed at baseline and at the end of the study. Results. In the lutein group, plasma lutein concentrations increased significantly from 205 ng/mL at baseline to 399 ng/mL after twelve months of intervention. MPOD increased significantly from 0.45 to 0.52 and BCVA improved significantly from −0.04 to −0.09 LogMar. Differences in rod dark adaptation rate between both groups were not significant. Conclusion. Daily consumption of a dairy drink containing lutein-enriched egg yolks for one year improves visual acuity, MPOD, and plasma lutein concentration in elderly subjects with drusen and/or retinal pigment epithelial abnormalities. PMID:27064326

  15. A Pilot Study to Propose a "Harm Scale", a New Method to Predict Risk of Harm to the Corneal Endothelium Caused by Longitudinal Phacoemulsification, and the Subsequent Effect of Endothelial Damage on Post Operative Visual Acuity

    PubMed Central

    Sorrentino, Francesco Saverio; Bonifazzi, Claudio; Parmeggiani, Francesco; Perri, Paolo

    2016-01-01

    Purpose To study the effect of longitudinal phacoemulsification energy on corneal endothelium and to evaluate the relationship between changes of endothelial cells and postoperative visual acuity. Methods This prospective clinical observational cohort study included 50 patients with cataract who underwent longitudinal phacoemulsification. Sequential quantitative and qualitative morphometric endothelial cell analyses of the cornea were performed 4 weeks preoperatively and 6 weeks postoperatively using noncontact specular microscopy. Results There was a relationship between ECL percentage (ECL%) and the 5-score harm scale, well-described by a linear model (one-way ANOVA, R2 = 73.3%). Analyzing the distribution of ECL% Mean with Tukey post-hoc pairwise comparison test (P < 0.001), the value of ECL = 20% has been regarded as cut-off to discriminate patients who obtained an excellent postoperative best-corrected visual acuity (BCVA > 85 letters) from those who just had a good visual outcome (BCVA ≤ 85 letters). There was a significant correlation among the 5-score harm scale, phaco energy intraoperatively delivered, and average cell area postoperatively. Conclusions The 5-score harm scale, a new method that enables to pigeonhole cataracts taking into account nucleus hardness and phaco times, allows to predict the harm on corneal endothelium after longitudinal phacoemulsification. Assessment of ECL% permits to discriminate between patients with excellent BCVA and with just good BCVA, postoperatively. PMID:26761198

  16. Inhibition of Return in the Visual Field

    PubMed Central

    Bao, Yan; Lei, Quan; Fang, Yuan; Tong, Yu; Schill, Kerstin; Pöppel, Ernst; Strasburger, Hans

    2013-01-01

    Inhibition of return (IOR) as an indicator of attentional control is characterized by an eccentricity effect, that is, the more peripheral visual field shows a stronger IOR magnitude relative to the perifoveal visual field. However, it could be argued that this eccentricity effect may not be an attention effect, but due to cortical magnification. To test this possibility, we examined this eccentricity effect in two conditions: the same-size condition in which identical stimuli were used at different eccentricities, and the size-scaling condition in which stimuli were scaled according to the cortical magnification factor (M-scaling), thus stimuli being larger at the more peripheral locations. The results showed that the magnitude of IOR was significantly stronger in the peripheral relative to the perifoveal visual field, and this eccentricity effect was independent of the manipulation of stimulus size (same-size or size-scaling). These results suggest a robust eccentricity effect of IOR which cannot be eliminated by M-scaling. Underlying neural mechanisms of the eccentricity effect of IOR are discussed with respect to both cortical and subcortical structures mediating attentional control in the perifoveal and peripheral visual field. PMID:23820946

  17. Algorithm Visualization: The State of the Field

    ERIC Educational Resources Information Center

    Shaffer, Clifford A.; Cooper, Matthew L.; Alon, Alexander Joel D.; Akbar, Monika; Stewart, Michael; Ponce, Sean; Edwards, Stephen H.

    2010-01-01

    We present findings regarding the state of the field of Algorithm Visualization (AV) based on our analysis of a collection of over 500 AVs. We examine how AVs are distributed among topics, who created them and when, their overall quality, and how they are disseminated. There does exist a cadre of good AVs and active developers. Unfortunately, we…

  18. A Data Mining Project to Identify Cardiovascular Related Factors That May Contribute to Changes in Visual Acuity Within the US Astronaut Corps

    NASA Technical Reports Server (NTRS)

    Westby, Christian M.; Stein, Sydney P.; Platts, Steven H.

    2011-01-01

    clearly differentiated the two mission types. Statistical analysis confirmed that pulse pressure was significantly higher before [45.6; (42.1 to 49.1)] and after [50.7; (46.9 to 54.6)] time on station compared with their most recent shuttle flight [31.6 (27.8 to 35.4), and 32.2 (28.3 to 36.0) respectively] even after correcting differences in age and cumulative number of mission hours. Without knowing the identity of which long duration crewmembers demonstrated visual changes, we were limited to examining whether certain crew regulate components of pulse pressure, systolic and diastolic blood pressure, differently due to microgravity exposure. To that end, we stratified crew into tertiles based on either their pre-flight measure of systolic or diastolic blood pressure. Those crew in the highest tertile for both systolic (lower tertile (n=8; 103-111), middle tertile (n=7; 113-121), and upper tertile (n=5; 125-136) and diastolic blood pressure (lower tertile (n=8; 58-64), middle tertile (n=7; 67-73), and upper tertile (n=5; 75-81) demonstrated less variability in pulse pressure between R+0 and L-10 (Figure 2). Interestingly, those crewmembers with the highest resting systolic blood pressure demonstrated either no change or in some instances an increase in total peripheral resistance, where those in the lower tertiles had lower values of total peripheral resistance compared to pre-flight levels. In this study, it was found that crewmembers in the highest tertile for both systolic and diastolic blood pressure demonstrated less variability in pulse pressure and that the decrease in variability was due in part to lower levels of compliance as indicated by similar or higher levels of total peripheral resistance after compared with before flight levels. Whether there is a relation between blood pressure regulation and total peripheral resistance in crew presenting with negative changes in visual acuity remains unknown.

  19. Effects of posterior segment disorders on oscillatory displacement thresholds, and on acuities as measured using the potential acuity meter and laser interferometer.

    PubMed

    Barrett, B T; Davison, P A; Eustace, P E

    1994-04-01

    Oscillatory displacement thresholds (ODTs) were measured in 67 subjects with clear ocular media, but known posterior segment disorders. The ability of these thresholds to assess reduced visual function, as quantified by visual acuity deficits, was compared with that of the Potential Acuity Meter (PAM) and the Rodenstock Retinometer (RR). ODTs were found to be sensitive to acuity deficits which were retinal/neural in origin. Despite the fact that interferometric acuities are, unlike ODTs, a measure of resolution, the RR proved no more accurate in assessing the level of letter acuity which existed than did ODT measurement. As would be expected, the PAM provided for the most accurate means of assessing non-optical visual acuity deficits. However, the PAM proved to be less useful in eyes with: very poor levels of acuity, and certain anomalous conditions. The results have implications for the relative ability of each of the three tests to identify reduced visual function behind cataract.

  20. Visual Field Abnormalities among Adolescent Boys with Hearing Impairments

    PubMed Central

    KHORRAMI-NEJAD, Masoud; HERAVIAN, Javad; SEDAGHAT, Mohamad-Reza; MOMENI-MOGHADAM, Hamed; SOBHANI-RAD, Davood; ASKARIZADEH, Farshad

    2016-01-01

    The aim of this study was to compare the visual field (VF) categorizations (based on the severity of VF defects) between adolescent boys with hearing impairments and those with normal hearing. This cross-sectional study involved the evaluation of the VF of 64 adolescent boys with hearing impairments and 68 age-matched boys with normal hearing at high schools in Tehran, Iran, in 2013. All subjects had an intelligence quotient (IQ) > 70. The hearing impairments were classified based on severity and time of onset. Participants underwent a complete eye examination, and the VFs were investigated using automated perimetry with a Humphrey Visual Field Analyzer. This device was used to determine their foveal threshold (FT), mean deviation (MD), and Glaucoma Hemifield Test (GHT) results. Most (50%) of the boys with hearing impairments had profound hearing impairments. There was no significant between-group difference in age (P = 0.49) or IQ (P = 0.13). There was no between-group difference in the corrected distance visual acuity (P = 0.183). According to the FT, MD, and GHT results, the percentage of boys with abnormal VFs in the hearing impairment group was significantly greater than that in the normal hearing group: 40.6% vs. 22.1%, 59.4% vs. 19.1%, and 31.2% vs. 8.8%, respectively (P < 0.0001). The mean MD in the hearing impairment group was significantly worse than that in the normal hearing group (-0.79 ± 2.04 and -4.61 ± 6.52 dB, respectively, P < 0.0001), and the mean FT was also significantly worse (38.97 ± 1.66 vs. 35.30 ± 1.43 dB, respectively, P <0.0001). Moreover, there was a significant between-group difference in the GHT results (P < 0.0001). Thus, there were higher percentages of boys with VF abnormalities and higher mean MD, FT, and GHT results among those with hearing impairments compared to those with normal hearing. These findings emphasize the need for detailed VF assessments for patients with hearing impairments. PMID:28293650

  1. Visualization of a changing dose field.

    SciTech Connect

    Helm, T. M; Kornreich, D. E.

    2002-01-01

    To help visualize the results of dose modeling for nuclear materials processing opcrations, we have developed an integrated model that uses a simple dosc calculation tool to obtain estimates of the dose field in a complex geomctry and then post-process the data to produce a video of the now time-dependent data. We generate two-dimensional radiation fields within an existing physical cnvironment and then analyze them using three-dimensional visualization techniques. The radiation fields are generated for both neutrons and photons. Standard monoenergetic diffusion theory is used to estimate the neutron dosc fields. The photon dose is estimated using a point-kernel formalism, with photon shielding effects and buildup taken into account. The radiation field dynamics are analyzed by interleaving individual 3D graphic 'snapshots' into a smoothed, lime dependent, video-based display. In-the-room workers are 'seen' in the radiation fields via a graphical, 3D fly-through rendering of the room. Worker dose levels can reveal surprising dependencies on operational source placement, source types, worker alignment, shielding alignments, and indirect operations from external workers.

  2. Remaining Visual Field and Preserved Subjective Visual Functioning Prevent Mental Distress in Patients with Visual Field Defects

    PubMed Central

    Gall, Carolin; Brösel, Doreen; Sabel, Bernhard A.

    2013-01-01

    Background: Patients with visual field defects after visual pathway lesion may experience reduced vision-related quality of life (vrQoL). It has not been clarified how vrQoL impairments contribute to vision-related mental distress. Methods: One hundred and eight subjects with visual field defects caused by optic neuropathies (age M = 57.6; SD = 13.7 years) answered the National Eye Institute Visual-Functioning Questionnaire 39 (NEI-VFQ) for vrQoL and the SF-12 Short Form Health Survey for health-related quality of life. A 10 item composite of NEI-VFQ “visual functioning” and 5 items of “mental-health symptoms due to vision problems” were subjected to Rasch analysis. The test battery comprised static and High Resolution Perimetry (HRP). Regression and path analysis were used to investigate associations between QoL, mental distress, and perimetry results. Results: A higher level of “visual functioning” was associated with monocular impairment and a larger remaining visual field compared to binocular impairment. Subjective “visual functioning” but not visual field parameters predicted “mental-health symptoms due to vision problems” which was the only variable associated with the SF-12 mental component score. The SF-12 physical component score was less strongly associated with “mental-health symptoms due to vision problems.” Here, reaction time in HRP and mean threshold in perimetry were additional significant variables. Path analysis revealed a significant path from remaining visual field via visual functioning on mental health. Conclusion: Subjective consequences of visual impairments in everyday life impact mental health rather than “objective” visual function loss as measured by perimetry. Since a higher extent of vrQoL was related to lower levels of mental distress, the maintenance of vrQoL could reduce and prevent mental distress due to vision problems. Patients with persisting visual field defects may benefit from

  3. Relating Standardized Visual Perception Measures to Simulator Visual System Performance

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.; Sweet, Barbara T.

    2013-01-01

    Human vision is quantified through the use of standardized clinical vision measurements. These measurements typically include visual acuity (near and far), contrast sensitivity, color vision, stereopsis (a.k.a. stereo acuity), and visual field periphery. Simulator visual system performance is specified in terms such as brightness, contrast, color depth, color gamut, gamma, resolution, and field-of-view. How do these simulator performance characteristics relate to the perceptual experience of the pilot in the simulator? In this paper, visual acuity and contrast sensitivity will be related to simulator visual system resolution, contrast, and dynamic range; similarly, color vision will be related to color depth/color gamut. Finally, we will consider how some characteristics of human vision not typically included in current clinical assessments could be used to better inform simulator requirements (e.g., relating dynamic characteristics of human vision to update rate and other temporal display characteristics).

  4. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability was developed that makes it possible to apply to measured flow field data the visualization tools developed to display numerical solutions for computational fluid dynamic problems. The measurement monitor surface (MMS) procedure was applied to the analysis of flow field measurements within a low aspect ratio transonic axial flow fan rotor obtained with 2-D laser anemometry. The procedure generates input for the visualization tools developed to display numerical solutions for computational fluid dynamics problems. The relative Mach number contour plots obtained by this method resemble the conventional contour plots obtained by more traditional methods. The results show that the MMS procedure can be used to generate input for the multidimensional processing and analysis tools developed for data from numerical flow field simulations. They show that an experimenter can apply the MMS procedure to his data and then use an interactive graphics program to display scalar quantities like the Mach number by profiles, carpet plots, contour lines, and surfaces using various colors. Also, flow directionality can be shown by display of vector fields and particle traces.

  5. On using Vernier acuity to assess magnocellular sensitivity.

    PubMed

    Skottun, Bernt C; Skoyles, John R

    2010-03-01

    A recent study [Keri, S., & Benedek, G. (2009). Visual pathway deficit in female fragile x premutation carriers: A potential endophenotype. Brain and Cognition, 69, 291-295] has found Vernier acuity deficiencies together with contrast sensitivity defects consistent with a magnocellular deficit in female fragile x premutation carriers. This may appear to support the notion that Vernier acuity may serve as a test of magnocellular sensitivity. However, Vernier acuity deficiencies have been reported in other conditions (e.g., schizophrenia, amblyopia and cortical visual impairment) where there is little evidence for magnocellular deficits. The observation that Vernier acuity deficiencies can occur without magnocellular deficits indicates that Vernier acuity is not a reliable test of magnocellular sensitivity.

  6. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  7. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  8. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  9. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  10. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  11. Vision-related quality of life in first stroke patients with homonymous visual field defects

    PubMed Central

    2010-01-01

    Background To evaluate vision-related and health-related quality of life (VRQoL, HRQoL) in first stroke patients with homonymous visual field defects (VFD) with respect to the extent of the lesion. Since VFD occur in approximately 10% of stroke patients the main purpose of the study was to investigate the additional impact of VFD in stroke patients hypothesizing that VFD causes diminished VRQoL. Methods In 177 first stroke patients with persisting VFD 2.5 years after posterior-parietal lesions VRQoL was assessed by the National-Eye-Institute-Visual-Functioning-Questionnaire (NEI-VFQ) and HRQoL by the Medical-Outcome-Study Short-Form-36 Health-Survey (SF-36). Questionnaire results of VFD-patients were compared with age- and sex-matched healthy controls and with general non-selected stroke samples as published elsewhere. VFD-type and visual acuity were partially correlated with questionnaire results. Results Compared to healthy controls VFD-patients had lower NEI-VFQ scores except ocular pain (Z-range -11.34 to -3.35) and lower SF-36 scores except emotional role limitations (Z-range -7.21 to -3.34). VFD-patients were less impaired in SF-36 scores than general stroke patients one month post lesion (6/8 subscales) but had lower SF-36 scores compared to stroke patients six months post lesion (5/8 subscales). Visual acuity significantly correlated with NEI-VFQ scores (r-range 0.27 to 0.48) and VFD-type with SF-36 mental subscales (r-range -0.26 to -0.36). Conclusions VFD-patients showed substantial reductions of VRQoL and HRQoL compared to healthy normals, but better HRQoL compared to stroke patients one month post lesion. VFD-patients (although their lesion age was four times higher) had significantly lower HRQoL than a general stroke population at six months post-stroke. This indicates that the stroke-related subjective level of HRQoL impairment is significantly exacerbated by VFD. While VRQoL was primarily influenced by visual acuity, mental components of HRQoL were

  12. Anatomical Volume Visualization with Weighted Distance Fields.

    PubMed

    Kerwin, Thomas; Hittle, Brad; Shen, Han-Wei; Stredney, Don; Wiet, Gregory

    2010-01-01

    We describe the use of the weighted distance transform (WDT) to enhance applications designed for volume visualization of segmented anatomical datasets. The WDT is presented as a general technique to generate a derived characteristic of a scalar field that can be used in multiple ways during rendering. We obtain real-time interaction with the volume by calculating the WDT on the graphics card. Several examples of this technique as it applies to an application for teaching anatomical structures are detailed, including rendering embedded structures, fuzzy boundaries, outlining, and indirect lighting estimation.

  13. Flow field visualization about external axial corners

    NASA Technical Reports Server (NTRS)

    Talcott, N. A., Jr.

    1978-01-01

    An experimental investigation was conducted to visualize the flow field about external axial corners. The investigation was initiated to provide answers to questions about the inviscid flow pattern for continuing numerical investigations. Symmetrical and asymmetrical corner models were tested at a Reynolds number per meter of 60,700,000. Oil-flow and vapor-screen photographs were taken for both models at angle of attack and yaw. The paper presents the results of the investigation in the form of oil-flow photographs and the surrounding shock wave location obtained from the vapor screens.

  14. Analysis of visual field progression in glaucoma.

    PubMed Central

    Fitzke, F W; Hitchings, R A; Poinoosawmy, D; McNaught, A I; Crabb, D P

    1996-01-01

    BACKGROUND: Despite the widespread use of computerised perimetry the diagnosis of visual field deterioration in following glaucoma patients over time remains particularly difficult. A new method of analysis using a novel graphical display of longitudinal field data is presented. METHODS: A linear regression model of the luminance sensitivity at each stimulus location against time of follow up transforms the quantitative data from a series of fields into a colour coded form which illustrates the spatial configuration of change to aid the interpretation of field loss. The method of analysis and the developed computer software (PROGRESSOR) is described. Comparison with STATPAC-2 glaucoma change probability analysis is given including levels of agreement between the techniques using series of fields of 10 eyes from patients with normal tension glaucoma. RESULTS: Examples of this new method compare well with STATPAC-2 analysis. The level of agreement between the techniques to separate progressing from stable retinal locations is good (kappa = 0.62; SE = 0.04). CONCLUSIONS: This new technique, which combines the change in perimetric sensitivity over time with colour coding of significant change into one image may provide an efficient method to detect true progression in glaucomatous field loss. Images PMID:8664231

  15. [Relationship between visual field index and visual field morphological stages of glaucoma and their diagnostic value].

    PubMed

    Hou, X R; Qin, J Y; Ren, Z Q

    2017-02-11

    Objective: To investigate the rationality of visual field morphological stages of glaucoma, its relationship with visual field index and their diagnostic value. Methods: Retrospective series case study. Two hundred and seventy-four glaucoma patients and 100 normal control received visual field examination by Humphrey perimeter using standard automatic perimetry (SAP) program from March 2014 to September 2014. Glaucoma patients were graded into four stages according to characteristic morphological damage of visual field, distribution of mean defect (MD) and visual field index (VFI) of each stage were plotted and receiver operation characteristic curve (ROC) was used to explore its correlation with MD and VFI. The diagnostic value of MD and VFI was also compared. For the comparison of general data of subjects, categorical variables were compared using χ(2) test, numerical variables were compared using F test. MD and VFI were compared using ANOVA among stages according to visual field, followed by multiple comparisons using LSD method. The correlation between MD and VFI and different stages according to visual field defined their diagnostic value, and compared using area under the curve (AUC) of ROC. Results: No characteristic visual field damage was found in normal control group, and MD and VFI was (-0.06±1.24) dB and (99.15±0.76)%, respectively. Glaucomatous visual field damage was graded into early, medium, late and end stage according to morphological characteristic. MD for each stage were (-2.83±2.00) dB, (-9.70±3.68) dB, (-18.46±2.90) dB, and (-27.96±2.76) dB, respectively. VFI for each stage were (93.84±3.61)%, (75.16±10.85)%, (49.36±11.26)% and (17.65±10.59)%, respectively. MD and VFI of each stage of glaucomatous group and normal control group were all significantly different (F=1 165.53 and P<0.01 for MD; F=1 028.04 and P<0.01 for VFI). AUC of ROC was A(MD)=0.91 and Se(MD)=0.01 (95% confident interval was 0.89-0.94) for MD, and A(VFI)=0.97, Se

  16. The four-meter confrontation visual field test.

    PubMed

    Kodsi, S R; Younge, B R

    1992-01-01

    The 4-m confrontation visual field test has been successfully used at the Mayo Clinic for many years in addition to the standard 0.5-m confrontation visual field test. The 4-m confrontation visual field test is a test of macular function and can identify small central or paracentral scotomas that the examiner may not find when the patient is tested only at 0.5 m. Also, macular sparing in homonymous hemianopias and quadrantanopias may be identified with the 4-m confrontation visual field test. We recommend use of this confrontation visual field test, in addition to the standard 0.5-m confrontation visual field test, on appropriately selected patients to obtain the most information possible by confrontation visual field tests.

  17. Visualizing electromagnetic fields in metals by MRI

    NASA Astrophysics Data System (ADS)

    Chandrashekar, Chandrika Sefcikova; Shellikeri, Annadanesh; Chandrashekar, S.; Taylor, Erika A.; Taylor, Deanne M.

    2017-02-01

    Based upon Maxwell's equations, it has long been established that oscillating electromagnetic (EM) fields incident upon a metal surface, decay exponentially inside the conductor, leading to a virtual absence of EM fields at sufficient depths. Magnetic resonance imaging (MRI) utilizes radiofrequency (r.f.) EM fields to produce images. Here we present a visualization of a virtual EM vacuum inside a bulk metal strip by MRI, amongst several findings. At its simplest, an MRI image is an intensity map of density variations across voxels (pixels) of identical size (=Δ x Δ y Δ z ). By contrast in bulk metal MRI, we uncover that despite uniform density, intensity variations arise from differing effective elemental volumes (voxels) from different parts of the bulk metal. Further, we furnish chemical shift imaging (CSI) results that discriminate different faces (surfaces) of a metal block according to their distinct nuclear magnetic resonance (NMR) chemical shifts, which holds much promise for monitoring surface chemical reactions noninvasively. Bulk metals are ubiquitous, and MRI is a premier noninvasive diagnostic tool. Combining the two, the emerging field of bulk metal MRI can be expected to grow in importance. The findings here may impact further development of bulk metal MRI and CSI.

  18. [Status of center point thickness and correlation between anatomic and best corrected visual acuity changes after photocoagulation, in diabetic macular edema].

    PubMed

    Lima-Gómez, Virgilio; Razo Blanco-Hernández, Dulce Milagros

    2013-01-01

    Antecedentes: el grosor del punto central en pacientes con edema macular diabético cambia después del tratamiento, dependiendo del estado basal; se desconoce si esta variación reduce la correlación entre los cambios anatómicos y de capacidad visual. Objetivo: identificar la contribución del grosor del punto central basal a la correlación entre los cambios anatómicos y de capacidad visual, después de tratar el edema macular diabético. Material y métodos: estudio observacional, prospectivo, longitudinal y analítico, en diabéticos con edema macular tratados con fotocoagulación, estratificado por grupos: capacidad visual < 0.5 con (1) o sin engrosamiento central (2), y capacidad visual = 0.5 con (3) o sin engrosamiento central (4). Se identificó la correlación entre los cambios de grosor del punto central, volumen macular y capacidad visual (Spearman). Resultados: 79 ojos, 17 del grupo 1 (21.5%), 21 del 2 (26.6%), 14 del 3 (17.7%), 27 del 4 (34.2%). El grosor del punto central aumentó en los grupos 2 y 4, la capacidad visual disminuyó en el 3 y el volumen en todos. Las correlaciones entre el grosor del punto central y la capacidad visual en el grupo 3, y entre el volumen y la capacidad visual en el grupo 1 fueron negativas. La correlación de la muestra entre los cambios anatómicos y de capacidad visual fue baja (r= 0.14). Conclusiones: el aumento del grosor del punto central en ojos sin engrosamiento previo generó correlaciones opuestas entre grupos, y redujo la de la muestra. Estratificar conforme al grosor del punto central basal facilitaría identificar variables que afectan la respuesta terapéutica funcional.

  19. [Dependence of the sensitivity of the central visual field on hemoglobin-oxygen saturation].

    PubMed

    Brandl, H; Lachenmayr, B

    1994-04-01

    Retinal function is very sensitive to changes in hemoglobin oxygen saturation. Characteristic ophthalmological symptoms of oxygen deficiency are: changes in color perception, visual field defect, eye flickering, reduction of visual acuity, seeing double images, defects in neural image interpretation. To test the dependency of changes in the central visual field sensitivity on different degrees of oxygen saturation, 48 probands (48 monocular tests) 20-50 years of age were examined in the altitude simulation chamber of the Aviation Medicine Institute of German Air Force at zero altitude (= 500 m) and at 10,000 ft (ca. 3,500 m height). Three types of experiments were performed: determination of abnormal quotient using a Heidelberg anomaloscope; determination of changes in color vision by saturated and disaturated panel D-15 test; determination of differences in light sensitivity for white, red, blue and green light by a threshold test using a Humphrey Field Analyzer (640) as perimeter. At zero level (500 m) hemoglobin-oxygen saturation was 97% +/- 1%. At 10,000 ft this value decreased to 83% +/- 3%. Hypoxic hypoxia caused neither significant AQ changes nor did it induce reproducible changes in color vision by the panel D-15 test. However, anoxia resulted in significant (P < 0.01) differences in light sensitivity in phototopic range.

  20. Mechanisms Underlying Development of Visual Maps and Receptive Fields

    PubMed Central

    Huberman, Andrew D.; Feller, Marla B.; Chapman, Barbara

    2008-01-01

    Patterns of synaptic connections in the visual system are remarkably precise. These connections dictate the receptive field properties of individual visual neurons and ultimately determine the quality of visual perception. Spontaneous neural activity is necessary for the development of various receptive field properties and visual feature maps. In recent years, attention has shifted to understanding the mechanisms by which spontaneous activity in the developing retina, lateral geniculate nucleus, and visual cortex instruct the axonal and dendritic refinements that give rise to orderly connections in the visual system. Axon guidance cues and a growing list of other molecules, including immune system factors, have also recently been implicated in visual circuit wiring. A major goal now is to determine how these molecules cooperate with spontaneous and visually evoked activity to give rise to the circuits underlying precise receptive field tuning and orderly visual maps. PMID:18558864

  1. Visualizing individual microtubules by bright field microscopy

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Medina, Braulio; Block, Steven M.

    2010-11-01

    Microtubules are slender (˜25 nm diameter), filamentous polymers involved in cellular structure and organization. Individual microtubules have been visualized via fluorescence imaging of dye-labeled tubulin subunits and by video-enhanced, differential interference-contrast microscopy of unlabeled polymers using sensitive CCD cameras. We demonstrate the imaging of unstained microtubules using a microscope with conventional bright field optics in conjunction with a webcam-type camera and a light-emitting diode illuminator. The light scattered by microtubules is image-processed to remove the background, reduce noise, and enhance contrast. The setup is based on a commercial microscope with a minimal set of inexpensive components, suitable for implementation in a student laboratory. We show how this approach can be used in a demonstration motility assay, tracking the gliding motions of microtubules driven by the motor protein kinesin.

  2. Development of a Pediatric Visual Field Test

    PubMed Central

    Miranda, Marco A.; Henson, David B.; Fenerty, Cecilia; Biswas, Susmito; Aslam, Tariq

    2016-01-01

    Purpose We describe a pediatric visual field (VF) test based on a computer game where software and hardware combine to provide an enjoyable test experience. Methods The test software consists of a platform-based computer game presented to the central VF. A storyline was created around the game as was a structure surrounding the computer monitor to enhance patients' experience. The patient is asked to help the central character collect magic coins (stimuli). To collect these coins a series of obstacles need to be overcome. The test was presented on a Sony PVM-2541A monitor calibrated from a central midpoint with a Minolta CS-100 photometer placed at 50 cm. Measurements were performed at 15 locations on the screen and the contrast calculated. Retinal sensitivity was determined by modulating stimulus in size. To test the feasibility of the novel approach 20 patients (4–16 years old) with no history of VF defects were recruited. Results For the 14 subjects completing the study, 31 ± 15 data points were collected on 1 eye of each patient. Mean background luminance and stimulus contrast were 9.9 ± 0.3 cd/m2 and 27.9 ± 0.1 dB, respectively. Sensitivity values obtained were similar to an adult population but variability was considerably higher – 8.3 ± 9.0 dB. Conclusions Preliminary data show the feasibility of a game-based VF test for pediatric use. Although the test was well accepted by the target population, test variability remained very high. Translational Relevance Traditional VF tests are not well tolerated by children. This study describes a child-friendly approach to test visual fields in the targeted population. PMID:27980876

  3. Vector Field Visual Data Analysis Technologies for Petascale Computational Science

    SciTech Connect

    Garth, Christoph; Deines, Eduard; Joy, Kenneth I.; Bethel, E. Wes; Childs, Hank; Weber, Gunther; Ahern, Sean; Pugmire, Dave; Sanderson, Allen; Johnson, Chris

    2009-11-13

    State-of-the-art computational science simulations generate large-scale vector field data sets. Visualization and analysis is a key aspect of obtaining insight into these data sets and represents an important challenge. This article discusses possibilities and challenges of modern vector field visualization and focuses on methods and techniques developed in the SciDAC Visualization and Analytics Center for Enabling Technologies (VACET) and deployed in the open-source visualization tool, VisIt.

  4. Effect of early maternal docosahexaenoic acid intake on neuropsychological status and visual acuity at five years of age of breast-fed infants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We previously reported better psychomotor development at 30 months of age in infants whose mothers received a docosahexaenoic acid (DHA) supplement for the first 4 months of lactation. We now assess neuropsychological and visual function of the same children at 5 years of age. Breastfeeding women w...

  5. Visualization of second order tensor fields and matrix data

    NASA Technical Reports Server (NTRS)

    Delmarcelle, Thierry; Hesselink, Lambertus

    1992-01-01

    We present a study of the visualization of 3-D second order tensor fields and matrix data. The general problem of visualizing unsymmetric real or complex Hermitian second order tensor fields can be reduced to the simultaneous visualization of a real and symmetric second order tensor field and a real vector field. As opposed to the discrete iconic techniques commonly used in multivariate data visualization, the emphasis is on exploiting the mathematical properties of tensor fields in order to facilitate their visualization and to produce a continuous representation of the data. We focus on interactively sensing and exploring real and symmetric second order tensor data by generalizing the vector notion of streamline to the tensor concept of hyperstreamline. We stress the importance of a structural analysis of the data field analogous to the techniques of vector field topology extraction in order to obtain a unique and objective representation of second order tensor fields.

  6. Enhanced visual fields in hammerhead sharks.

    PubMed

    McComb, D M; Tricas, T C; Kajiura, S M

    2009-12-01

    Several factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the 'enhanced binocular field' hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than the bonnethead sharks (13 deg.) and carcharhinid species; however, the bonnethead shark did not differ from the carcharhinids. These results indicate that binocular overlap has increased with lateral head expansion in hammerhead sharks. The hammerhead species did not demonstrate greater eye rotation in the anterior or posterior direction. However, both the scalloped hammerhead and bonnethead sharks exhibited greater head yaw during swimming (16.9 deg. and 15.6 deg., respectively) than the lemon (15.1 deg.) and blacknose (15.0 deg.) sharks, indicating a behavioral compensation for the anterior blind area. This study illustrates the larger binocular overlap in hammerhead species relative to their carcharhinid sister taxa and is consistent with the 'enhanced binocular field' hypothesis.

  7. Rehabilitation of Reading and Visual Exploration in Visual Field Disorders: Transfer or Specificity?

    ERIC Educational Resources Information Center

    Schuett, Susanne; Heywood, Charles A.; Kentridge, Robert W.; Dauner, Ruth; Zihl, Josef

    2012-01-01

    Reading and visual exploration impairments in unilateral homonymous visual field disorders are frequent and disabling consequences of acquired brain injury. Compensatory therapies have been developed, which allow patients to regain sufficient reading and visual exploration performance through systematic oculomotor training. However, it is still…

  8. Effect of 1% Inspired CO2 During Head-Down Tilt on Ocular Structures, Cerebral Blood Flow, and Visual Acuity in Healthy Human Subjects

    NASA Technical Reports Server (NTRS)

    Laurie, S. S.; Hu, X.; Lee, S. M. C.; Martin, D. S.; Phillips, T. R.; Ploutz-Snyder, R.; Smith, S. M.; Stenger, M. B.; Taibbi, G.; Zwart, S. R.; Vizzeri, G.

    2016-01-01

    The cephalad fluid shift induced by microgravity has been hypothesized to elevate intracranial pressure (ICP) and contribute to the development of the visual impairment/intracranial pressure (VIIP) syndrome experienced by many astronauts during and after long-duration space flight. In addition, elevated ambient partial pressure of carbon dioxide (PCO2) on the International Space Station (ISS) has also been hypothesized to contribute to the development of VIIP. We seek to determine if an acute, mild CO2 exposure, similar to that occurring on the ISS, combined with the cephalad fluid shift induced by head-down tilt will induce ophthalmic and ICP changes consistent with the VIIP syndrome.

  9. The visual system of a palaeognathous bird: visual field, retinal topography and retino-central connections in the Chilean tinamou (Nothoprocta perdicaria).

    PubMed

    Krabichler, Quirin; Vega-Zuniga, Tomas; Morales, Cristian; Luksch, Harald; Marín, Gonzalo J

    2015-02-01

    Most systematic studies of the avian visual system have focused on Neognathous species, leaving virtually unexplored the Palaeognathae, comprised of the flightless ratites and the South American tinamous. We investigated the visual field, the retinal topography, and the pattern of retinal and centrifugal projections in the Chilean tinamou, a small Palaeognath of the family Tinamidae. The tinamou has a panoramic visual field with a small frontal binocular overlap of 20°. The retina possesses three distinct topographic specializations: a horizontal visual streak, a dorsotemporal area, and an area centralis with a shallow fovea. The maximum ganglion cell density is 61,900/ mm(2) , comparable to Falconiformes. This would provide a maximal visual acuity of 14.0 cycles/degree, in spite of relatively small eyes. The central retinal projections generally conform to the characteristic arrangement observed in Neognathae, with well-differentiated contralateral targets and very few ipsilateral fibers. The centrifugal visual system is composed of a considerable number of multipolar centrifugal neurons, resembling the "ectopic" neurons described in Neognathae. They form a diffuse nuclear structure, which may correspond to the ancestral condition shared with other sauropsids. A notable feature is the presence of terminals in deep tectal layers 11-13. These fibers may represent either a novel retinotectal pathway or collateral branches from centrifugal neurons projecting to the retina. Both types of connections have been described in chicken embryos. Our results widen the basis for comparative studies of the vertebrate visual system, stressing the conserved character of the visual projections' pattern within the avian clade.

  10. The strong connection between sensory and cognitive performance in old age: not due to sensory acuity reductions operating during cognitive assessment.

    PubMed

    Lindenberger, U; Scherer, H; Baltes, P B

    2001-06-01

    Cognitive aging research has documented a strong increase in the covariation between sensory and cognitive functioning with advancing age. In part, this finding may reflect sensory acuity reductions operating during cognitive assessment. To examine this possibility, the authors administered cognitive tasks used in prior studies (e.g., Lindenberger & Baltes, 1994) to middle-aged adults under age-simulation conditions of reduced visual acuity, auditory acuity, or both. Visual acuity was lowered through partial occlusion filters, and auditory acuity through headphone-shaped noise protectors. Acuity manipulations reduced visual acuity and auditory acuity in the speech range to values reaching or approximating old-age acuity levels, respectively, but did not lower cognitive performance relative to control conditions. Results speak against assessment-related sensory acuity accounts of the age-related increase in the connection between sensory and cognitive functioning and underscore the need to explore alternative explanations, including a focus on general aspects of brain aging.

  11. Distance stereo acuity improvement in intermittent exotropic patients following strabismus surgery.

    PubMed

    O'Neal, T D; Rosenbaum, A L; Stathacopoulos, R A

    1995-01-01

    To determine whether distance stereo acuity improved following strabismus surgery in patients with intermittent exotropia, we tested 20 patients (5 to 87 years old) preoperatively and postoperatively using the Mentor BVAT II Video acuity tester (Santa Barbara, Calif) and binocular visual system. Acuity improved in 75% as assessed by contour circles and in 45% as assessed by random dot E tests at distance. Our results suggest that surgical realignment of intermittent exotropia restores distance stereo acuity. We conclude that measuring distance stereo acuity offers valuable information in the evaluation of the intermittent exotropic patient.

  12. Standard-Fractionated Radiotherapy for Optic Nerve Sheath Meningioma: Visual Outcome Is Predicted by Mean Eye Dose

    SciTech Connect

    Abouaf, Lucie; Girard, Nicolas; Lefort, Thibaud; D'hombres, Anne; Tilikete, Caroline; Vighetto, Alain; Mornex, Francoise

    2012-03-01

    Purpose: Radiotherapy has shown its efficacy in controlling optic nerve sheath meningiomas (ONSM) tumor growth while allowing visual acuity to improve or stabilize. However, radiation-induced toxicity may ultimately jeopardize the functional benefit. The purpose of this study was to identify predictive factors of poor visual outcome in patients receiving radiotherapy for ONSM. Methods and Materials: We conducted an extensive analysis of 10 patients with ONSM with regard to clinical, radiologic, and dosimetric aspects. All patients were treated with conformal radiotherapy and subsequently underwent biannual neuroophthalmologic and imaging assessments. Pretreatment and posttreatment values of visual acuity and visual field were compared with Wilcoxon's signed rank test. Results: Visual acuity values significantly improved after radiotherapy. After a median follow-up time of 51 months, 6 patients had improved visual acuity, 4 patients had improved visual field, 1 patient was in stable condition, and 1 patient had deteriorated visual acuity and visual field. Tumor control rate was 100% at magnetic resonance imaging assessment. Visual acuity deterioration after radiotherapy was related to radiation-induced retinopathy in 2 patients and radiation-induced mature cataract in 1 patient. Study of radiotherapy parameters showed that the mean eye dose was significantly higher in those 3 patients who had deteriorated vision. Conclusions: Our study confirms that radiotherapy is efficient in treating ONSM. Long-term visual outcome may be compromised by radiation-induced side effects. Mean eye dose has to be considered as a limiting constraint in treatment planning.

  13. Effect of visual stimulus using central and peripheral visual field on postural control of normal subjects.

    PubMed

    Park, Du-Jin

    2016-06-01

    [Purpose] This study investigated the effects of visual stimulus using central and peripheral vision fields on postural control. [Subjects and Methods] The subjects consisted of 40 young adult volunteers (15 males, 25 females) who had been informed of the study purpose and procedure. The subjects were randomly divided into four groups of differing visual stimulus. Each group was given visual intervention in a standing position for 3 minutes. Postural control was evaluated before and after visual intervention. [Results] The results of the functional reach test and body sway test showed significant differences among the four groups. [Conclusion] The two-way peripheral vision-field group showed significantly more body sway after visual intervention than the other three groups. This finding may suggest two-way peripheral vision field is a more effective visual stimulus for training postural control and balance.

  14. Visual field interpretation with a personal computer based neural network.

    PubMed

    Mutlukan, E; Keating, D

    1994-01-01

    The Computer Assisted Touch Screen (CATS) and Computer Assisted Moving Eye Campimeter (CAMEC) are personal computer (PC)-based video-campimeters which employ multiple and single static stimuli on a cathode ray tube respectively. Clinical studies show that CATS and CAMEC provide comparable results to more expensive conventional visual field test devices. A neural network has been designed to classify visual field data from PC-based video-campimeters to facilitate diagnostic interpretation of visual field test results by non-experts. A three-layer back propagation network was designed, with 110 units in the input layer (each unit corresponding to a test point on the visual field test grid), a hidden layer of 40 processing units, and an output layer of 27 units (each one corresponding to a particular type of visual field pattern). The network was trained by a training set of 540 simulated visual field test result patterns, including normal, glaucomatous and neuro-ophthalmic defects, for up to 20,000 cycles. The classification accuracy of the network was initially measured with a previously unseen test set of 135 simulated fields and further tested with a genuine test result set of 100 neurological and 200 glaucomatous fields. A classification accuracy of 91-97% with simulated field results and 65-100% with genuine field results were achieved. This suggests that neural networks incorporated into PC-based video-campimeters may enable correct interpretation of results in non-specialist clinics or in the community.

  15. Visual functioning restoration developments in ARMD

    NASA Astrophysics Data System (ADS)

    Mumford, R. B.

    2006-09-01

    Recent progress in several fields has radically changed the expectations of low vision individuals. These changes augment existing prescription eye-care and electronic reading machines to improve recovery of visual function. Companies are reporting incidences of multi-line gains in visual acuity as their products for macular degeneration move through FDA approval stages. Funding for this research is rapidly increasing.

  16. Functional organization of telencephalic visual association fields in pigeons.

    PubMed

    Stacho, Martin; Ströckens, Felix; Xiao, Qian; Güntürkün, Onur

    2016-04-15

    Birds show remarkable visual abilities that surpass most of our visual psychophysiological abilities. In this study, we investigated visual associative areas of the tectofugal visual system in pigeons. Similar to the condition in mammals, ascending visual pathways in birds are subdivided into parallel form/color vs. motion streams at the thalamic and primary telencephalic level. However, we know practically nothing about the functional organization of those telencephalic areas that receive input from the primary visual telencephalic fields. The current study therefore had two objectives: first, to reveal whether these visual associative areas of the tectofugal system are activated during visual discrimination tasks; second, to test whether separated form/color vs. motion pathways can be discerned among these association fields. To this end, we trained pigeons to discriminate either form/color or motion stimuli and used the immediate early gene protein ZENK to capture the activity of the visual associative areas during the task. We could indeed identify several visual associative telencephalic structures by activity pattern changes during discriminations. However, none of these areas displayed a difference between form/color vs. motion sessions. The presence of such a distinction in thalamo-telencephalic, but not in further downstream visual association areas opens the possibility that these separate streams converge very early in birds, which possibly minimizes long-range connections due to the evolutionary pressure toward miniaturized brains.

  17. Variability in glaucomatous visual fields: implications for shared care schemes.

    PubMed

    Henson, D B; Spry, P G; Spencer, I C; Sparrow, J M

    1998-03-01

    The purpose of this study was to establish the extent of variability in the visual fields of patients with glaucoma using a suprathreshold perimetric test strategy. The visual fields of 104 patients (126 eyes) were measured twice, on separate days, with a Henson CFA3000 central visual field analyser. All eyes had a diagnosis of glaucoma and had a minimum of three stimuli missed at 12 dB above their threshold estimate derived at the beginning of the first suprathreshold examination. The perimeter tested 132 locations within the central 25 degrees with a multiple stimulus suprathreshold strategy. Data were analysed on the basis of the difference in the number of recorded missed stimuli between the two visits. Large amounts of variability were found in the visual field results. Variability was largest when all levels of defect were included (> = 5 dB) and was found to be independent of the overall extent of loss. Results from the superior hemifield were found to be more variable than those from the inferior hemifield. The results highlight the problem of differentiating real change in visual field status from the enhanced variability seen in patients with glaucomatous visual field loss. The results from this study can be used to establish return-referral criteria for shared care schemes. The advantages of duplicate measures of the visual field are highlighted.

  18. The role of perceptual reference frames in visual field asymmetries.

    PubMed

    Robertson, L C; Lamb, M R

    1988-01-01

    The direct access model of hemispheric asymmetry was tested in a letter reflection (normal of reflected) judgement task. In the baseline condition letters were presented in their upright orientation, and reaction times were faster to letters presented in the right visual field than to those presented in the left visual field. In two other conditions the slides, and thus the letters, were rotated +90 degrees clockwise (Rotated +90) from upright or -90 degrees counterclockwise (Rotated -90). This resulted in the letters in both rotated conditions being shown in the upper or lower visual field through the sagittal plane but rotated 90 degrees. Despite this fact a "right field" advantage was again found when the right field was defined relative to the orientation of the tops of the rotated letters (lower visual field in the Rotated +90 condition and upper visual field in the Rotated -90 condition). These results demonstrate that the internal representation of locations in space is more important in predicting visual field asymmetries, at least in the present task, than the field of stimulus presentation relative to the fovea.

  19. Variable acuity remote viewing system flight demonstration

    NASA Technical Reports Server (NTRS)

    Fisher, R. W.

    1983-01-01

    The Variable Acuity Remote Viewing System (VARVS), originally developed under contract to the Navy (ONR) as a laboratory brassboard, was modified for flight demonstration. The VARVS system was originally conceived as a technique which could circumvent the acuity/field of view/bandwidth tradeoffs that exists in remote viewing to provide a nearly eye limited display in both field of view (160 deg) and resolution (2 min arc) while utilizing conventional TV sensing, transmission, and display equipment. The modifications for flight demonstration consisted of modifying the sensor so it could be installed and flow in a Piper PA20 aircraft, equipped for remote control and modifying the display equipment so it could be integrated with the NASA Research RPB (RPRV) remote control cockpit.

  20. The neural correlates of learned motor acuity

    PubMed Central

    Yang, Juemin; Caffo, Brian; Mazzoni, Pietro; Krakauer, John W.

    2014-01-01

    We recently defined a component of motor skill learning as “motor acuity,” quantified as a shift in the speed-accuracy trade-off function for a task. These shifts are primarily driven by reductions in movement variability. To determine the neural correlates of improvement in motor acuity, we devised a motor task compatible with magnetic resonance brain imaging that required subjects to make finely controlled wrist movements under visual guidance. Subjects were imaged on day 1 and day 5 while they performed this task and were trained outside the scanner on intervening days 2, 3, and 4. The potential confound of performance changes between days 1 and 5 was avoided by constraining movement time to a fixed duration. After training, subjects showed a marked increase in success rate and a reduction in trial-by-trial variability for the trained task but not for an untrained control task, without changes in mean trajectory. The decrease in variability for the trained task was associated with increased activation in contralateral primary motor and premotor cortical areas and in ipsilateral cerebellum. A global nonlocalizing multivariate analysis confirmed that learning was associated with increased overall brain activation. We suggest that motor acuity is acquired through increases in the number of neurons recruited in contralateral motor cortical areas and in ipsilateral cerebellum, which could reflect increased signal-to-noise ratio in motor output and improved state estimation for feedback corrections, respectively. PMID:24848466

  1. Large Field Visualization with Demand-Driven Calculation

    NASA Technical Reports Server (NTRS)

    Moran, Patrick J.; Henze, Chris

    1999-01-01

    We present a system designed for the interactive definition and visualization of fields derived from large data sets: the Demand-Driven Visualizer (DDV). The system allows the user to write arbitrary expressions to define new fields, and then apply a variety of visualization techniques to the result. Expressions can include differential operators and numerous other built-in functions, ail of which are evaluated at specific field locations completely on demand. The payoff of following a demand-driven design philosophy throughout becomes particularly evident when working with large time-series data, where the costs of eager evaluation alternatives can be prohibitive.

  2. Visualizing Planetary Magnetic Fields (and Why You Should Care)

    NASA Astrophysics Data System (ADS)

    Fillingim, M.; Brain, D.; Peticolas, L.; Yan, D.; Fricke, K.

    2012-08-01

    Since they are invisible to our eyes, planetary magnetic fields are difficult to visualize. However, we can learn much about a planet, its interior, and its history from studying its magnetic field. A challenge, then, is how can we effectively communicate the structure of planetary magnetic fields to the public, i.e., how can we help the public visualize planetary magnetic fields. An additional challenge is how can we effectively communicate the importance of studying planetary magnetic fields to the public, or why should they care. We address these challenges by developing a series of presentations about magnetic fields and their importance given on visually engaging spherical displays. We are also creating scientifically accurate three-dimensional models of planetary magnetic fields.

  3. Visual fields, eye movements, and scanning behavior of a sit-and-wait predator, the black phoebe (Sayornis nigricans).

    PubMed

    Gall, Megan D; Fernández-Juricic, Esteban

    2010-01-01

    Foraging mode influences the dominant sensory modality used by a forager and likely the strategies of information gathering used in foraging and anti-predator contexts. We assessed three components of visual information gathering in a sit-and-wait avian predator, the black phoebe (Sayornis nigricans): configuration of the visual field, degree of eye movement, and scanning behavior through head-movement rates. We found that black phoebes have larger lateral visual fields than similarly sized ground-foraging passerines, as well as relatively narrower binocular and blind areas. Black phoebes moved their eyes, but eye movement amplitude was relatively smaller than in other passerines. Black phoebes may compensate for eye movement constraints with head movements. The rate of head movements increased before attacking prey in comparison to non-foraging contexts and before movements between perches. These findings suggest that black phoebes use their lateral visual fields, likely subtended by areas of high acuity in the retina, to track prey items in a three-dimensional space through active head movements. These head movements may increase depth perception, motion detection and tracking. Studying information gathering through head movement changes, rather than body posture changes (head-up, head-down) as generally presented in the literature, may allow us to better understand the mechanisms of information gathering from a comparative perspective.

  4. Visual fields and eye movements in herons (Ardeidae).

    PubMed

    Martin, G R; Katzir, G

    1994-01-01

    The visual fields and eye movements of three heron species (Ardeidae; Ciconiiformes): the cattle egret (Bubulcus ibis), the squacco heron (Ardeola ralloides), the western reef heron (Egretta gularis schistacea) were determined in alert, restrained birds using an ophthalmoscopic technique. All three species can gain panoramic visual coverage of the frontal field around the bill, and a bird standing with its bill horizontal can view its own feet binocularly. The region in which binocular overlap is possible is long (approximately 170 degrees) and narrow (maximum width approximately 20 degrees). Monocular field width in a horizontal plane is approximately 170 degrees. Retinal binocular overlap can be abolished by eye movements at all elevations in the frontal field. At the frontal margins of the monocular fields the retinal and optical field margins do not coincide; the retinal field margin lies between 9 degrees and 12.5 degrees inside the optical field margin. This results in a blind sector at the margin of each eye's optical field. Consequently the visually functional retinal binocular field widths are significantly narrower than the optical binocular fields. When retinal binocularity is abolished by eye movements, optical binocular fields are still retained. Thus, estimates of binocular overlap based only upon the appearance of the pupils will be erroneous. The comprehensive nature of vision beneath the bill is probably closely associated with the herons' visually guided, stealthy, foraging techniques, which result in the single-strike capture of mobile, highly evasive prey.

  5. Visual abilities in two raptors with different ecology.

    PubMed

    Potier, Simon; Bonadonna, Francesco; Kelber, Almut; Martin, Graham R; Isard, Pierre-François; Dulaurent, Thomas; Duriez, Olivier

    2016-09-01

    Differences in visual capabilities are known to reflect differences in foraging behaviour even among closely related species. Among birds, the foraging of diurnal raptors is assumed to be guided mainly by vision but their foraging tactics include both scavenging upon immobile prey and the aerial pursuit of highly mobile prey. We studied how visual capabilities differ between two diurnal raptor species of similar size: Harris's hawks, Parabuteo unicinctus, which take mobile prey, and black kites, Milvus migrans, which are primarily carrion eaters. We measured visual acuity, foveal characteristics and visual fields in both species. Visual acuity was determined using a behavioural training technique; foveal characteristics were determined using ultra-high resolution spectral-domain optical coherence tomography (OCT); and visual field parameters were determined using an ophthalmoscopic reflex technique. We found that these two raptors differ in their visual capacities. Harris's hawks have a visual acuity slightly higher than that of black kites. Among the five Harris's hawks tested, individuals with higher estimated visual acuity made more horizontal head movements before making a decision. This may reflect an increase in the use of monocular vision. Harris's hawks have two foveas (one central and one temporal), while black kites have only one central fovea and a temporal area. Black kites have a wider visual field than Harris's hawks. This may facilitate the detection of conspecifics when they are scavenging. These differences in the visual capabilities of these two raptors may reflect differences in the perceptual demands of their foraging behaviours.

  6. [Diagnostic difficulties in a case of constricted tubular visual field].

    PubMed

    Dogaru, Oana-Mihaela; Rusu, Monica; Hâncu, Dacia; Horvath, Kárin

    2013-01-01

    In the paper below we present the clinical case of a 48 year old female with various symptoms associated with functional visual disturbance -constricted tubular visual fields, wich lasts from 6 years; the extensive clinical and paraclinical ophthalmological investigations ruled out the presence of an organic disorder. In the present, we suspect a diagnosis of hysteria, still uncertain, wich represented over time a big challenge in psychology and ophthalmology. The mechanisms and reasons for hysteria are still not clear and it could represent a fascinating research theme. The tunnel, spiral or star-shaped visual fields are specific findings in hysteria for patients who present visual disturbance. The question of whether or not a patient with hysterical visual impairment can or cannot "see" is still unresolved.

  7. Visual field loss associated with vigabatrin: pathological correlations

    PubMed Central

    Ravindran, J; Blumbergs, P; Crompton, J; Pietris, G; Waddy, H

    2001-01-01

    Pathological changes are reported in the anterior visual pathways of a 41 year old man with complex partial seizures treated with vigabatrin who developed bilateral visual field constriction. There was peripheral retinal atrophy with loss of ganglion cells and loss of nerve fibres in the optic nerves, chiasm, and tracts. No evidence of intramyelinic oedema was seen. These findings suggest that the primary site of injury lies within the ganglion cells in the retina. The degree of atrophy seen would suggest that the visual field loss is irreversible.

 PMID:11385015

  8. Visual Outcomes, Visual Fields, and Optical Coherence Tomography in Paediatric Craniopharyngioma

    PubMed Central

    Mediero, Soraya; Noval, Susana; Bravo-Ljubetic, Luciano; Contreras, Inés; Carceller, Fernando

    2015-01-01

    ABSTRACT Ten patients with craniopharyngioma treated for the first time when younger than 18 were included. This study reviews the visual outcomes and provides information on visual field (VF) and optical coherence tomography (OCT) examination of craniopharyngioma. The best kappa concordance coefficients between VF and OCT parameters of atrophy were obtained for the ganglion cell (GC) thickness and the mean retinal nerve fibre layer (RNFL) thickness. The agreement between GC colour maps and VF defects was good. Optic nerve compression may be detected by RNFL measurement and GC analysis, and this may be valuable to predict visual recovery and in uncooperative patients to evaluate visual damage. PMID:27928346

  9. Recognizing patterns of visual field loss using unsupervised machine learning

    NASA Astrophysics Data System (ADS)

    Yousefi, Siamak; Goldbaum, Michael H.; Zangwill, Linda M.; Medeiros, Felipe A.; Bowd, Christopher

    2014-03-01

    Glaucoma is a potentially blinding optic neuropathy that results in a decrease in visual sensitivity. Visual field abnormalities (decreased visual sensitivity on psychophysical tests) are the primary means of glaucoma diagnosis. One form of visual field testing is Frequency Doubling Technology (FDT) that tests sensitivity at 52 points within the visual field. Like other psychophysical tests used in clinical practice, FDT results yield specific patterns of defect indicative of the disease. We used Gaussian Mixture Model with Expectation Maximization (GEM), (EM is used to estimate the model parameters) to automatically separate FDT data into clusters of normal and abnormal eyes. Principal component analysis (PCA) was used to decompose each cluster into different axes (patterns). FDT measurements were obtained from 1,190 eyes with normal FDT results and 786 eyes with abnormal (i.e., glaucomatous) FDT results, recruited from a university-based, longitudinal, multi-center, clinical study on glaucoma. The GEM input was the 52-point FDT threshold sensitivities for all eyes. The optimal GEM model separated the FDT fields into 3 clusters. Cluster 1 contained 94% normal fields (94% specificity) and clusters 2 and 3 combined, contained 77% abnormal fields (77% sensitivity). For clusters 1, 2 and 3 the optimal number of PCA-identified axes were 2, 2 and 5, respectively. GEM with PCA successfully separated FDT fields from healthy and glaucoma eyes and identified familiar glaucomatous patterns of loss.

  10. Comparison of the STYCAR and lighthouse acuity tests.

    PubMed

    Kastenbaum, S M; Kepford, K L; Holmstrom, E T

    1977-07-01

    In a study comparing the Screening Test for Young Children and Retardates (STYCAR) and the New York Lighthouse Flash Card Test, 50 preschool children (median age of 4.4 yr) were evaluated twice with each instrument. Results indicate that the Lighthouse test had higher reliability, better visual acuity scores, lower untestability rates, and shorter testing times than the STYCAR.

  11. On Using Vernier Acuity to Assess Magnocellular Sensitivity

    ERIC Educational Resources Information Center

    Skottun, Bernt C.; Skoyles, John R.

    2010-01-01

    A recent study [Keri, S., & Benedek, G. (2009). Visual pathway deficit in female fragile x premutation carriers: A potential endophenotype. "Brain and Cognition", 69, 291-295] has found Vernier acuity deficiencies together with contrast sensitivity defects consistent with a magnocellular deficit in female fragile x premutation carriers. This may…

  12. Visual Sample Plan (VSP) - FIELDS Integration

    SciTech Connect

    Pulsipher, Brent A.; Wilson, John E.; Gilbert, Richard O.; Hassig, Nancy L.; Carlson, Deborah K.; Bing-Canar, John; Cooper, Brian; Roth, Chuck

    2003-04-19

    Two software packages, VSP 2.1 and FIELDS 3.5, are being used by environmental scientists to plan the number and type of samples required to meet project objectives, display those samples on maps, query a database of past sample results, produce spatial models of the data, and analyze the data in order to arrive at defensible decisions. VSP 2.0 is an interactive tool to calculate optimal sample size and optimal sample location based on user goals, risk tolerance, and variability in the environment and in lab methods. FIELDS 3.0 is a set of tools to explore the sample results in a variety of ways to make defensible decisions with quantified levels of risk and uncertainty. However, FIELDS 3.0 has a small sample design module. VSP 2.0, on the other hand, has over 20 sampling goals, allowing the user to input site-specific assumptions such as non-normality of sample results, separate variability between field and laboratory measurements, make two-sample comparisons, perform confidence interval estimation, use sequential search sampling methods, and much more. Over 1,000 copies of VSP are in use today. FIELDS is used in nine of the ten U.S. EPA regions, by state regulatory agencies, and most recently by several international countries. Both software packages have been peer-reviewed, enjoy broad usage, and have been accepted by regulatory agencies as well as site project managers as key tools to help collect data and make environmental cleanup decisions. Recently, the two software packages were integrated, allowing the user to take advantage of the many design options of VSP, and the analysis and modeling options of FIELDS. The transition between the two is simple for the user – VSP can be called from within FIELDS, automatically passing a map to VSP and automatically retrieving sample locations and design information when the user returns to FIELDS. This paper will describe the integration, give a demonstration of the integrated package, and give users download

  13. Use of computer graphics for visualization of flow fields

    NASA Technical Reports Server (NTRS)

    Watson, Val; Buning, Pieter; Choi, Diana; Bancroft, Gordon; Merritt, Fergus; Rogers, Stuart

    1987-01-01

    A high-performance graphics workstation has been combined with software developed for flow-field visualization to yield a highly effective tool for analysis of fluid-flow dynamics. After the flow fields are obtained from experimental measurements or computer simulations, the workstation permits one to interactively view the dynamics of the flow fields; e.g., the viewer can zoom into a region or rotate his viewing position about the region to study it in more detail. Several techniques for visualization of flow fields with this workstation are described in this paper and illustrated with a videotape available from the authors. The computer hardware and software required to create effective flow visualization displays are discussed. Additional software and hardware required to create videotapes or 16mm movies are also described. Limitations imposed by current workstation performance is addressed and future workstation performance is forecast.

  14. Graphics and Flow Visualization of Computer Generated Flow Fields

    NASA Technical Reports Server (NTRS)

    Kathong, M.; Tiwari, S. N.

    1987-01-01

    Flow field variables are visualized using color representations described on surfaces that are interpolated from computational grids and transformed to digital images. Techniques for displaying two and three dimensional flow field solutions are addressed. The transformations and the use of an interactive graphics program for CFD flow field solutions, called PLOT3D, which runs on the color graphics IRIS workstation are described. An overview of the IRIS workstation is also described.

  15. Visual function affects prosocial behaviors in older adults.

    PubMed

    Teoli, Dac A; Smith, Merideth D; Leys, Monique J; Jain, Priyanka; Odom, J Vernon

    2016-02-01

    Eye-related pathological conditions such as glaucoma, diabetic retinopathy, and age-related macular degeneration commonly lead to decreased peripheral/central field, decreased visual acuity, and increased functional disability. We sought to answer if relationships exist between measures of visual function and reported prosocial behaviors in an older adult population with eye-related diagnoses. The sample consisted of adults, aged ≥ 60 years old, at an academic hospital's eye institute. Vision ranged from normal to severe impairment. Medical charts determined the visual acuities, ocular disease, duration of disease (DD), and visual fields (VF). Measures of giving help were via validated questionnaires on giving formal support (GFS) and giving informal support; measures of help received were perceived support (PS) and informal support received (ISR). ISR had subscales: tangible support (ISR-T), emotional support (ISR-E), and composite (ISR-C). Visual acuities of the better and worse seeing eyes were converted to LogMAR values. VF information converted to a 4-point rating scale of binocular field loss severity. DD was in years. Among 96 participants (mean age 73.28; range 60-94), stepwise regression indicated a relationship of visual variables to GFS (p < 0.05; Multiple R (2) = 0.1679 with acuity-better eye, VF rating, and DD), PS (p < 0.05; Multiple R (2) = 0.2254 with acuity-better eye), ISR-C (p < 0.05; Multiple R (2) = 0.041 with acuity-better eye), and ISR-T (p < 0.05; Multiple R (2) = 0.1421 with acuity-better eye). The findings suggest eye-related conditions can impact levels and perceptions of support exchanges. Our data reinforces the importance of visual function as an influence on prosocial behavior in older adults.

  16. Expansion of Severely Constricted Visual Field Using Google Glass.

    PubMed

    Trese, Matthew G J; Khan, Naheed W; Branham, Kari; Conroy, Erin Brown; Moroi, Sayoko E

    2016-05-01

    Google Glass (Google, Mountain View, CA) is a wearable technology with a computer and camera mounted on an eyeglass frame. The camera captures wide-angle video and projects it onto a prism located in the right superior temporal quadrant of the wearer's visual field. The authors present a case of an individual who used Google Glass' video projection feature to expand his severely constricted right visual field. This patient reported improved ambulatory navigation. Using Google Glass, the patient's peripheral vision, measured using Goldmann kinetic perimetry, expanded impressively. Based on these preliminary results, the authors propose further characterization on the potential utility of such head-mount display technology as a tool to improve the lives of patients with severely constricted visual fields. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:486-489.].

  17. Motor force field learning influences visual processing of target motion.

    PubMed

    Brown, Liana E; Wilson, Elizabeth T; Goodale, Melvyn A; Gribble, Paul L

    2007-09-12

    There are reciprocal connections between visual and motor areas of the cerebral cortex. Although recent studies have provided intriguing new insights, in comparison with volume of research on the visual control of movement, relatively little is known about how movement influences vision. The motor system is perfectly suited to learn about environmental forces. Does environmental force information, learned by the motor system, influence visual processing? Here, we show that learning to compensate for a force applied to the hand influenced how participants predicted target motion for interception. Ss trained in one of three constant force fields by making reaching movements while holding a robotic manipulandum. The robot applied forces in a null [null force field (NFF)], leftward [leftward force field (LFF)], or [rightward force field (RFF)] direction. Training was followed immediately with an interception task. The target accelerated from left to right and Ss's task was to stab it. When viewing time was optimal for prediction, the RFF group initiated their responses earlier and hit more targets, and the LFF group initiated their responses later and hit fewer targets, than the NFF group. In follow-up experiments, we show that motor learning is necessary, and we rule out the possibility that explicit force direction information drives how Ss altered their predictions of visual motion. Environmental force information, acquired by motor learning, influenced how the motion of nearby visual targets was predicted.

  18. Topographical estimation of visual population receptive fields by FMRI.

    PubMed

    Lee, Sangkyun; Papanikolaou, Amalia; Keliris, Georgios A; Smirnakis, Stelios M

    2015-02-03

    Visual cortex is retinotopically organized so that neighboring populations of cells map to neighboring parts of the visual field. Functional magnetic resonance imaging allows us to estimate voxel-based population receptive fields (pRF), i.e., the part of the visual field that activates the cells within each voxel. Prior, direct, pRF estimation methods(1) suffer from certain limitations: 1) the pRF model is chosen a-priori and may not fully capture the actual pRF shape, and 2) pRF centers are prone to mislocalization near the border of the stimulus space. Here a new topographical pRF estimation method(2) is proposed that largely circumvents these limitations. A linear model is used to predict the Blood Oxygen Level-Dependent (BOLD) signal by convolving the linear response of the pRF to the visual stimulus with the canonical hemodynamic response function. PRF topography is represented as a weight vector whose components represent the strength of the aggregate response of voxel neurons to stimuli presented at different visual field locations. The resulting linear equations can be solved for the pRF weight vector using ridge regression(3), yielding the pRF topography. A pRF model that is matched to the estimated topography can then be chosen post-hoc, thereby improving the estimates of pRF parameters such as pRF-center location, pRF orientation, size, etc. Having the pRF topography available also allows the visual verification of pRF parameter estimates allowing the extraction of various pRF properties without having to make a-priori assumptions about the pRF structure. This approach promises to be particularly useful for investigating the pRF organization of patients with disorders of the visual system.

  19. Spatial contrast sensitivity and grating acuity of barn owls.

    PubMed

    Harmening, Wolf M; Nikolay, Petra; Orlowski, Julius; Wagner, Hermann

    2009-07-22

    The eyes of barn owls (Tyto alba pratincola) display very little aberrations, and have thus excellent optical quality. In a series of behavioral experiments, we tested whether this presumably beneficial feature is also reflected at a perceptual level in this species. As fundamental indicators for visual performance, the spatial contrast sensitivity function (CSF) and grating acuity were measured in two barn owls with psychophysical techniques. Stimulus luminance was 2.7 cd/m(2). The CSF found here renders the typical band-limited, inverted U-shaped function, with a low maximum contrast sensitivity of 8-19 at a spatial frequency of 1 cyc/deg. Grating acuity was estimated from the CSF high frequency cut-off and yielded 3.0-3.7 cyc/deg. In a second experiment, in which contrast was held constant and spatial frequency was varied, grating acuity was measured directly (2.6-4.0 cyc/deg). These results put barn owls at the very low end of the visual acuity spectrum of birds, and demonstrate that visual resolution and sensitivity cannot be predicted by optical considerations alone.

  20. Multifocal pupillary light response fields in normal subjects and patients with visual field defects.

    PubMed

    Tan, L; Kondo, M; Sato, M; Kondo, N; Miyake, Y

    2001-04-01

    The optimal conditions for recording focal pupillary light responses with a multifocal stimulation technique were determined, and the technique was applied to normal subjects and patients with visual field defects. Thirty-seven hexagonal stimuli were presented on a TV monitor with a visual field of 40 degrees diameter under a constant background illumination. Using a slow (4.7 Hz) m-sequence, reliable focal responses were obtained in both normal subjects and patients. The pupillary field and visual field were well correlated in patients with retinal diseases, but the correlation was not strong in patients with optic-nerve diseases. Pupillary light responses were reduced in the blind hemifield in patients with post-geniculate lesions. These results indicate that the multifocal stimulation technique can be used clinically to obtain a pupillary field for objective visual field testing.

  1. Fixation behavior while walking: persons with central visual field loss.

    PubMed

    Turano, Kathleen A; Geruschat, Duane R; Baker, Frank H

    2002-10-01

    The aim of this study was to determine the effect of central visual field loss (CFL) on fixation patterns of a person walking towards a target. Subjects were four visually normal persons and 10 persons with CFL. Eye position on scene was recorded and classified into 20 scene categories. The distributions of fixations among scene categories were compared across the two subject groups. For all but two CFL subjects, who fixated primarily at the floor, the distributions of fixations for the CFL subjects ranged from being moderately to strongly correlated with that of the visually normal mean. An analysis of the similarity in the sequence of fixations (or gaze pattern) of the CFL subjects to the visually normal subjects showed a range of 7-66%. Excluding the one CFL subject who had a functioning fovea, sequence similarity was strongly correlated with the logarithm of the minimum angle of resolution (logMAR). The better a person's logMAR, the more closely his or her gaze pattern matched that of the visually normal subjects. Finally, the CFL data were tested against two current models of oculomotor strategy, visual salience and guided search. Similar to what was found with visually normal subjects, CFL subjects appear to use the expected features and general location of the target to guide their fixations, the guided-search strategy.

  2. Visual field and task influence illusory figure responses.

    PubMed

    Abu Bakar, Afiza; Liu, Lichan; Conci, Markus; Elliott, Mark A; Ioannides, Andreas A

    2008-11-01

    In normal viewing conditions, many objects are often hidden or occluded by others, therefore restricting the information that enters the eye. One ability that the human visual system has developed to compensate for this visual limitation is to relate the surrounding elements to globally interpret the whole scene. The appearance of illusory figures (IF) based on surrounding elements also relies on this similar function. In the present study, we hypothesized that different mechanisms may be used by the brain to process IF from the center and periphery of the visual field. We compared magnetoencephalographic responses to IFs presented at different parts of the visual field under three task loads. For central presentation, IF specific responses peaked first in V1/V2 (96-101 ms), and then in the lateral occipital complex (LOC; 132-141 ms), independent of task. For peripheral presentation, the relative modulation towards IF was markedly reduced in V1/V2 and LOC while prominent activation peaks now shifted to the Fusiform Gyrus (from 200 ms onwards). Additionally, the type of task influenced processing at early stages beginning in V1/V2 (87 ms). Our results show that retinal eccentricity plays a crucial role in IF processing: figural completion at the center of the visual field is achieved in an 'automatic' and seemingly effortless fashion whereas peripheral stimulus locations necessitate higher-order object completion stages which rely more heavily on attentional demands.

  3. Multiresolution and Explicit Methods for Vector Field Analysis and Visualization

    NASA Technical Reports Server (NTRS)

    Nielson, Gregory M.

    1997-01-01

    This is a request for a second renewal (3d year of funding) of a research project on the topic of multiresolution and explicit methods for vector field analysis and visualization. In this report, we describe the progress made on this research project during the second year and give a statement of the planned research for the third year. There are two aspects to this research project. The first is concerned with the development of techniques for computing tangent curves for use in visualizing flow fields. The second aspect of the research project is concerned with the development of multiresolution methods for curvilinear grids and their use as tools for visualization, analysis and archiving of flow data. We report on our work on the development of numerical methods for tangent curve computation first.

  4. Beyond blindsight: properties of visual relearning in cortically blind fields.

    PubMed

    Das, Anasuya; Tadin, Duje; Huxlin, Krystel R

    2014-08-27

    Damage to the primary visual cortex (V1) or its immediate afferents results in a dense scotoma, termed cortical blindness (CB). CB subjects have residual visual abilities, or blindsight, which allow them to detect and sometimes discriminate stimuli with high temporal and low spatial frequency content. Recent work showed that with training, discriminations in the blind field can become more reliable, and even reach consciousness. However, the narrow spatiotemporal bandwidth of blindsight limits its functional usefulness in everyday vision. Here, we asked whether visual training can induce recovery outside the spatiotemporal bandwidth of blindsight. Specifically, could human CB subjects learn to discriminate static, nonflickering stimuli? Can such learning transfer to untrained stimuli and tasks, and does double training with moving and static stimuli provide additional advantages relative to static training alone? We found CB subjects capable of relearning static orientation discriminations following single as well as double training. However, double training with complex, moving stimuli in a separate location was necessary to recover complex motion thresholds at locations trained with static stimuli. Subjects trained on static stimuli alone could only discriminate simple motion. Finally, both groups had approximately equivalent, incomplete recovery of fine orientation and direction discrimination thresholds, as well as contrast sensitivity. These results support two conclusions: (1) from a practical perspective, complex moving stimuli and double training may be superior training tools for inducing visual recovery in CB, and (2) the cortically blind visual system can relearn to perform a wider range of visual discriminations than predicted by blindsight alone.

  5. Sound Localization Acuity and its Relation to Vision in Large and Small Fruit-eating Bats: II. Non-echolocating Species, Eidolon helvum and Cynopterus brachyotis

    PubMed Central

    Heffner, R.S.; Koay, G.; Heffner, H.E.

    2008-01-01

    Passive sound-localization acuity for 100-msec noise bursts was determined behaviorally for two species of non-echolocating bats: the Straw-colored fruit bat, Eidolon helvum, a large frugivore, and the Dog-faced fruit bat, Cynopterus brachyotis, a small frugivore. The mean minimum audible angle for two E. helvum was 11.7°, and for two C. brachyotis was 10.5°. This places their passive sound-localization acuity near the middle of the range for echolocating bats as well as the middle of the range for other mammals. Sound-localization acuity varies widely among mammals, and the best predictor of this auditory function remains the width of the field of best vision (r = .89, p < .0001). Among echolocating and non-echolocating bats, as well as among other mammals, the use of hearing to direct the eyes to the source of a sound still appears to serve as an important selective factor for sound localization. Absolute visual acuity and the magnitude of the binaural locus cues available to a species remain unreliable predictors of sound-localization acuity. PMID:18571883

  6. The Optimal Viewing Position effect in the lower visual field.

    PubMed

    Yao-N'dré, Marina; Castet, Eric; Vitu, Françoise

    2013-01-14

    The Optimal Viewing Position (OVP) effect shows that word identification is best when the eyes first fixate near the centre of words. While this effect has been extensively studied in normal reading conditions, it has not been much investigated for words in the periphery. Here, we compared, in a perceptual identification task, the OVP effect for words presented either on the line of sight or in the lower visual field. Results confirmed the existence of an OVP effect for both central and vertically-shifted words but this effect was significantly weaker in the lower visual field. This finding provides further evidence for an important role of letter visibility in determining the shape of the OVP phenomenon. It also indicates that aligning the eyes with the centre of words is not as critical for vertically-shifted words. Implications for patients with central field loss who are forced to read in the periphery are discussed.

  7. Visualizing Vector Fields Using Line Integral Convolution and Dye Advection

    NASA Technical Reports Server (NTRS)

    Shen, Han-Wei; Johnson, Christopher R.; Ma, Kwan-Liu

    1996-01-01

    We present local and global techniques to visualize three-dimensional vector field data. Using the Line Integral Convolution (LIC) method to image the global vector field, our new algorithm allows the user to introduce colored 'dye' into the vector field to highlight local flow features. A fast algorithm is proposed that quickly recomputes the dyed LIC images. In addition, we introduce volume rendering methods that can map the LIC texture on any contour surface and/or translucent region defined by additional scalar quantities, and can follow the advection of colored dye throughout the volume.

  8. Semantic Data And Visualization Techniques Applied To Geologic Field Mapping

    NASA Astrophysics Data System (ADS)

    Houser, P. I. Q.; Royo-Leon, M.; Munoz, R.; Estrada, E.; Villanueva-Rosales, N.; Pennington, D. D.

    2015-12-01

    Geologic field mapping involves the use of technology before, during, and after visiting a site. Geologists utilize hardware such as Global Positioning Systems (GPS) connected to mobile computing platforms such as tablets that include software such as ESRI's ArcPad and other software to produce maps and figures for a final analysis and report. Hand written field notes contain important information and drawings or sketches of specific areas within the field study. Our goal is to collect and geo-tag final and raw field data into a cyber-infrastructure environment with an ontology that allows for large data processing, visualization, sharing, and searching, aiding in connecting field research with prior research in the same area and/or aid with experiment replication. Online searches of a specific field area return results such as weather data from NOAA and QuakeML seismic data from USGS. These results that can then be saved to a field mobile device and searched while in the field where there is no Internet connection. To accomplish this we created the GeoField ontology service using the Web Ontology Language (OWL) and Protégé software. Advanced queries on the dataset can be made using reasoning capabilities can be supported that go beyond a standard database service. These improvements include the automated discovery of data relevant to a specific field site and visualization techniques aimed at enhancing analysis and collaboration while in the field by draping data over mobile views of the site using augmented reality. A case study is being performed at University of Texas at El Paso's Indio Mountains Research Station located near Van Horn, Texas, an active multi-disciplinary field study site. The user can interactively move the camera around the study site and view their data digitally. Geologist's can check their data against the site in real-time and improve collaboration with another person as both parties have the same interactive view of the data.

  9. Population receptive field analysis of the primary visual cortex complements perimetry in patients with homonymous visual field defects.

    PubMed

    Papanikolaou, Amalia; Keliris, Georgios A; Papageorgiou, T Dorina; Shao, Yibin; Krapp, Elke; Papageorgiou, Eleni; Stingl, Katarina; Bruckmann, Anna; Schiefer, Ulrich; Logothetis, Nikos K; Smirnakis, Stelios M

    2014-04-22

    Injury to the primary visual cortex (V1) typically leads to loss of conscious vision in the corresponding, homonymous region of the contralateral visual hemifield (scotoma). Several studies suggest that V1 is highly plastic after injury to the visual pathways, whereas others have called this conclusion into question. We used functional magnetic resonance imaging (fMRI) to measure area V1 population receptive field (pRF) properties in five patients with partial or complete quadrantic visual field loss as a result of partial V1+ or optic radiation lesions. Comparisons were made with healthy controls deprived of visual stimulation in one quadrant ["artificial scotoma" (AS)]. We observed no large-scale changes in spared-V1 topography as the V1/V2 border remained stable, and pRF eccentricity versus cortical-distance plots were similar to those of controls. Interestingly, three observations suggest limited reorganization: (i) the distribution of pRF centers in spared-V1 was shifted slightly toward the scotoma border in 2 of 5 patients compared with AS controls; (ii) pRF size in spared-V1 was slightly increased in patients near the scotoma border; and (iii) pRF size in the contralesional hemisphere was slightly increased compared with AS controls. Importantly, pRF measurements yield information about the functional properties of spared-V1 cortex not provided by standard perimetry mapping. In three patients, spared-V1 pRF maps overlapped significantly with dense regions of the perimetric scotoma, suggesting that pRF analysis may help identify visual field locations amenable to rehabilitation. Conversely, in the remaining two patients, spared-V1 pRF maps failed to cover sighted locations in the perimetric map, indicating the existence of V1-bypassing pathways able to mediate useful vision.

  10. Volume Perimetry: measurement in depth of visual field loss

    PubMed Central

    Satgunam, PremNandhini; Apfelbaum, Henry L; Peli, Eli

    2012-01-01

    Purpose Volume scotomas are three-dimensional regions of space that are not visible to the observer. Volume perimetry maps volume scotomas. Volume scotomas predicted from combining monocular visual fields assume known fixation locus (mainly foveal). However fixation loci are not always known, especially with central field loss. Here we demonstrate methods for measuring and calculating volume scotomas and discuss their practical implications. Methods Three patients (bitemporal hemianopia, binasal scotoma, and central field loss (CFL)) were evaluated. Slices through the volume scotomas were measured at three distances: at the plane of fixation, at a plane anterior to fixation (representing anterior volume perimetry), and a plane posterior to fixation (representing posterior volume perimetry). For anterior volume perimetry, patients fixated on a screen 100cm away through a beamsplitter that reflected the perimetric stimulus (at 50cm). For posterior volume perimetry, patients fixated on a near target (50cm) while perimetric stimuli were presented on a screen 150cm beyond the fixation. At the plane of fixation, monocular visual fields under binocular viewing conditions were measured using a computerized dichoptic perimeter. Results Posterior and anterior volume scotomas were documented in patients with bitemporal hemianopia and binasal scotomas respectively. The CFL patient demonstrated both anterior and posterior volume scotomas. Scotoma magnitude was considered to determine its effect on visual function. Conclusions Direct measurement of volume scotomas can be performed. Anterior and posterior volume visual fields can vary substantially from conventional binocular perimetry measured at the fixation plane, revealing blind areas not otherwise identified. These volume scotomas are likely to impair functional vision such as driving (for bitemporal hemianopes) and near work with small hand tools (for binasal scotomas). Patients with CFL will have impaired functional vision

  11. [Neurons of the rabbit visual cortex with simple and complex visual fields].

    PubMed

    Supin, A Ia

    1978-01-01

    The receptive filelds of orientation-selective neurons were studied in the rabbit visual cortex. Two mechanisms of the selectivity were found: the mutual inhibition between on- and off-regions of the receptive field (simple type) and the orientation-dependent inhibition within the uniform region of the receptive field. The non-selective neurons could exhibit the lateral inhibition within the uniform region of the receptive field also. It is supposed that both "simple" and "complex" cells originate from the non-selective units.

  12. Impact of Visual Field Loss on Health-Related Quality of Life in Glaucoma

    PubMed Central

    McKean-Cowdin, Roberta; Wang, Ying; Wu, Joanne; Azen, Stanley P.; Varma, Rohit

    2016-01-01

    Purpose To examine the association between health-related quality of life (HRQOL) and visual field (VF) loss in participants with open-angle glaucoma (OAG) in the Los Angeles Latino Eye Study (LALES). Design Population-based cross-sectional study. Participants Two hundred thirteen participants with OAG and 2821 participants without glaucoma or VF loss. Methods Participants in the LALES—a population-based prevalence study of eye disease in Latinos 40 years and older, residing in Los Angeles, California—underwent a detailed eye examination including an assessment of their VF using the Humphrey Automated Field Analyzer (Swedish interactive thresholding algorithm Standard 24-2). Open-angle glaucoma was determined by clinical examination. Mean deviation scores were used to assess severity of VF loss. Health-related QOL was assessed by the Medical Outcomes Study 12-item Short-Form Health Survey (SF-12) and 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). Linear regression and analysis of covariance were used to assess the relationship between HRQOL scores and VF loss after adjusting for sociodemographic variables and visual acuity. Main Outcome Measures The 25-item NEI-VFQ and SF-12 scores. Results A trend of worse NEI-VFQ-25 scores for most subscales was observed with worse VF loss (using both monocular and calculated binocular data). Open-angle glaucoma participants with VF loss had lower scores than participants with no VF loss. This association was also present in participants who were previously undiagnosed and untreated for OAG (N = 160). Participants with any central VF loss had lower NEI-VFQ-25 scores than those with unilateral or bilateral peripheral VF loss. There was no significant impact of severity or location of VF loss on SF-12 scores. Conclusion Greater severity of VF loss in persons with OAG impacts vision-related QOL. This impact was present in persons who were previously unaware that they had glaucoma. Prevention of VF

  13. Enhancement and suppression in the visual field under perceptual load.

    PubMed

    Parks, Nathan A; Beck, Diane M; Kramer, Arthur F

    2013-01-01

    The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task-greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field.

  14. Visualizing 3D velocity fields near contour surfaces

    SciTech Connect

    Max, N.; Crawfis, R.; Grant, C.

    1994-03-01

    Vector field rendering is difficult in 3D because the vector icons overlap and hide each other. We propose four different techniques for visualizing vector fields only near surfaces. The first uses motion blurred particles in a thickened region around the surface. The second uses a voxel grid to contain integral curves of the vector field. The third uses many antialiased lines through the surface, and the fourth uses hairs sprouting from the surface and then bending in the direction of the vector field. All the methods use the graphite pipeline, allowing real time rotation and interaction, and the first two methods can animate the texture to move in the flow determined by the velocity field.

  15. Stream segregation with high spatial acuity

    PubMed Central

    Middlebrooks, John C.; Onsan, Zekiye A.

    2012-01-01

    Spatial hearing is widely regarded as helpful in recognizing a sound amid other competing sounds. It is a matter of debate, however, whether spatial cues contribute to “stream segregation,” which refers to the specific task of assigning multiple interleaved sequences of sounds to their respective sources. The present study employed “rhythmic masking release” as a measure of the spatial acuity of stream segregation. Listeners discriminated between rhythms of noise-burst sequences presented from free-field targets in the presence of interleaved maskers that varied in location. For broadband sounds in the horizontal plane, target-masker separations of ≥8° permitted rhythm discrimination with d′ ≥ 1; in some cases, such thresholds approached listeners’ minimum audible angles. Thresholds were the same for low-frequency sounds but were substantially wider for high-frequency sounds, suggesting that interaural delays provided higher spatial acuity in this task than did interaural level differences. In the vertical midline, performance varied dramatically as a function of noise-burst duration with median thresholds ranging from >30° for 10-ms bursts to 7.1° for 40-ms bursts. A marked dissociation between minimum audible angles and masking release thresholds across the various pass-band and burst-duration conditions suggests that location discrimination and spatial stream segregation are mediated by distinct auditory mechanisms. PMID:23231120

  16. New techniques in 3D scalar and vector field visualization

    SciTech Connect

    Max, N.; Crawfis, R.; Becker, B.

    1993-05-05

    At Lawrence Livermore National Laboratory (LLNL) we have recently developed several techniques for volume visualization of scalar and vector fields, all of which use back-to-front compositing. The first renders volume density clouds by compositing polyhedral volume cells or their faces. The second is a ``splatting`` scheme which composites textures used to reconstruct the scalar or vector fields. One version calculates the necessary texture values in software, and another takes advantage of hardware texture mapping. The next technique renders contour surface polygons using semi-transparent textures, which adjust appropriately when the surfaces deform in a flow, or change topology. The final one renders the ``flow volume`` of smoke or dye tracer swept out by a fluid flowing through a small generating polygon. All of these techniques are applied to a climate model data set, to visualize cloud density and wind velocity.

  17. Patterns in the sky: Natural visualization of aircraft flow fields

    NASA Technical Reports Server (NTRS)

    Campbell, James F.; Chambers, Joseph R.

    1994-01-01

    The objective of the current publication is to present the collection of flight photographs to illustrate the types of flow patterns that were visualized and to present qualitative correlations with computational and wind tunnel results. Initially in section 2, the condensation process is discussed, including a review of relative humidity, vapor pressure, and factors which determine the presence of visible condensate. Next, outputs from computer code calculations are postprocessed by using water-vapor relationships to determine if computed values of relative humidity in the local flow field correlate with the qualitative features of the in-flight condensation patterns. The photographs are then presented in section 3 by flow type and subsequently in section 4 by aircraft type to demonstrate the variety of condensed flow fields that was visualized for a wide range of aircraft and flight maneuvers.

  18. Invariance of visual operations at the level of receptive fields

    PubMed Central

    Lindeberg, Tony

    2013-01-01

    The brain is able to maintain a stable perception although the visual stimuli vary substantially on the retina due to geometric transformations and lighting variations in the environment. This paper presents a theory for achieving basic invariance properties already at the level of receptive fields. Specifically, the presented framework comprises (i) local scaling transformations caused by objects of different size and at different distances to the observer, (ii) locally linearized image deformations caused by variations in the viewing direction in relation to the object, (iii) locally linearized relative motions between the object and the observer and (iv) local multiplicative intensity transformations caused by illumination variations. The receptive field model can be derived by necessity from symmetry properties of the environment and leads to predictions about receptive field profiles in good agreement with receptive field profiles measured by cell recordings in mammalian vision. Indeed, the receptive field profiles in the retina, LGN and V1 are close to ideal to what is motivated by the idealized requirements. By complementing receptive field measurements with selection mechanisms over the parameters in the receptive field families, it is shown how true invariance of receptive field responses can be obtained under scaling transformations, affine transformations and Galilean transformations. Thereby, the framework provides a mathematically well-founded and biologically plausible model for how basic invariance properties can be achieved already at the level of receptive fields and support invariant recognition of objects and events under variations in viewpoint, retinal size, object motion and illumination. The theory can explain the different shapes of receptive field profiles found in biological vision, which are tuned to different sizes and orientations in the image domain as well as to different image velocities in space-time, from a requirement that the

  19. Age-Dependent Cortical Thinning of Peripheral Visual Field Representations in Primary Visual Cortex.

    PubMed

    Griffis, Joseph C; Burge, Wesley K; Visscher, Kristina M

    2016-01-01

    The cerebral cortex changes throughout the lifespan, and the cortical gray matter in many brain regions becomes thinner with advancing age. Effects of aging on cortical thickness (CT) have been observed in many brain regions, including areas involved in basic perceptual functions such as processing visual inputs. An important property of early visual cortices is their topographic organization-the cortical structure of early visual areas forms a topographic map of retinal inputs. Primary visual cortex (V1) is considered to be the most basic cortical area in the visual processing hierarchy, and is topographically organized from posterior (central visual representation) to anterior (peripheral visual representation) along the calcarine sulcus. Some studies have reported strong age-dependent cortical thinning in portions of V1 that likely correspond to peripheral visual representations, while there is less evidence of substantial cortical thinning in central V1. However, the effect of aging on CT in V1 as a function of its topography has not been directly investigated. To address this gap in the literature, we estimated the CT of different eccentricity sectors in V1 using T1-weighted MRI scans acquired from groups of healthy younger and older adults, and then assessed whether between-group differences in V1 CT depended on cortical eccentricity. These analyses revealed age-dependent cortical thinning specific to peripheral visual field representations in anterior portions of V1, but did not provide evidence for age-dependent cortical thinning in other portions of V1. Additional analyses found similar effects when analyses were restricted to the gyral crown, sulcul depth and sulcul wall, indicating that these effects are not likely due to differences in gyral/sulcul contributions to our regions of interest (ROI). Importantly, this finding indicates that age-dependent changes in cortical structure may differ among functionally distinct zones within larger canonical

  20. Age-Dependent Cortical Thinning of Peripheral Visual Field Representations in Primary Visual Cortex

    PubMed Central

    Griffis, Joseph C.; Burge, Wesley K.; Visscher, Kristina M.

    2016-01-01

    The cerebral cortex changes throughout the lifespan, and the cortical gray matter in many brain regions becomes thinner with advancing age. Effects of aging on cortical thickness (CT) have been observed in many brain regions, including areas involved in basic perceptual functions such as processing visual inputs. An important property of early visual cortices is their topographic organization—the cortical structure of early visual areas forms a topographic map of retinal inputs. Primary visual cortex (V1) is considered to be the most basic cortical area in the visual processing hierarchy, and is topographically organized from posterior (central visual representation) to anterior (peripheral visual representation) along the calcarine sulcus. Some studies have reported strong age-dependent cortical thinning in portions of V1 that likely correspond to peripheral visual representations, while there is less evidence of substantial cortical thinning in central V1. However, the effect of aging on CT in V1 as a function of its topography has not been directly investigated. To address this gap in the literature, we estimated the CT of different eccentricity sectors in V1 using T1-weighted MRI scans acquired from groups of healthy younger and older adults, and then assessed whether between-group differences in V1 CT depended on cortical eccentricity. These analyses revealed age-dependent cortical thinning specific to peripheral visual field representations in anterior portions of V1, but did not provide evidence for age-dependent cortical thinning in other portions of V1. Additional analyses found similar effects when analyses were restricted to the gyral crown, sulcul depth and sulcul wall, indicating that these effects are not likely due to differences in gyral/sulcul contributions to our regions of interest (ROI). Importantly, this finding indicates that age-dependent changes in cortical structure may differ among functionally distinct zones within larger canonical

  1. A metric for the evaluation of dense vector field visualizations.

    PubMed

    Matvienko, Victor; Krüger, Jens

    2013-07-01

    In this work, we present an intuitive image-quality metric that is derived from the motivation of DVF visualization. It utilizes the features of the resulting image and effectively measures the similarity between the output of the visualization method and the input flow data. We use the angle between the gradient direction and the original vector field as a measure of such similarity and the gradient magnitude as an importance measure. Our metric enables the automatic evaluation of images for a given vector field and allows the comparison of different methods, parameters sets, and quality improvement strategies for a specific vector field. By integrating the metric into the image-computation process, our approach can be used to generate improved images by choosing the best parameter set. To verify the effectiveness of our method, we conducted an extensive user study that demonstrated the metric’s applicability to various situations. For instance, our approach elucidated the robustness of a DVF visualization in the presence of data-altering filters, such as resampling.

  2. Assessment of visual space recognition in patients with visual field defects using head mounted display (HMD) system: case study with severe visual field defect.

    PubMed

    Sugihara, Shunichi; Tanaka, Toshiaki; Miyasaka, Tomoya; Izumi, Takashi; Shimizu, Koichi

    2013-01-01

    For the quantitative assessment of visual field defects of cerebrovascular patients, we developed a new measurement system that could present various kinds of visual information to the patient. In this system, we use a head mounted display as the display device. The quantitative assessment becomes possible by adding the capability to measure the eye movement and the head movement simultaneously by means of a video apparatus of motion analysis. In our study, we examined the effectiveness of this system by applying it to a patient with serious visual field defects. The visual image of the reduced test paper was presented to the patient, the effect on his/her spatial recognition and eye movement was investigated. The results indicated the increase in the ration of visual search in the reduced side. With the reduced image, the decrease of the angular velocity of eye movement was recognized in the visual search in the defected side. In the motion analysis, the head movement was not observed while the eye movements appeared corresponding to each different conditions. This fact led us to confirm that the patient coped with this kind of test by the eye movement. In this analysis, the effectiveness and the usefulness of the developed system were confirmed that enables us to evaluate the abnormal and compensation movement of the eyes.

  3. Visual Aids for Nonformal Education. A Field Guide to the Production and Use of Inexpensive Visual Aids in Nonformal Education.

    ERIC Educational Resources Information Center

    Vella, Jane Kathryn

    The effectiveness of visual aids in nonformal education depends on their relevance to the audience with which they are used, and this booklet provides a discussion of various factors for field workers to consider in designing and using simple visual aids in developing countries. Four specific types of visual aids are discussed in some…

  4. Binocular Glaucomatous Visual Field Loss and Its Impact on Visual Exploration - A Supermarket Study

    PubMed Central

    Aehling, Kathrin; Heister, Martin; Rosenstiel, Wolfgang; Schiefer, Ulrich; Papageorgiou, Elena

    2014-01-01

    Advanced glaucomatous visual field loss may critically interfere with quality of life. The purpose of this study was to (i) assess the impact of binocular glaucomatous visual field loss on a supermarket search task as an example of everyday living activities, (ii) to identify factors influencing the performance, and (iii) to investigate the related compensatory mechanisms. Ten patients with binocular glaucoma (GP), and ten healthy-sighted control subjects (GC) were asked to collect twenty different products chosen randomly in two supermarket racks as quickly as possible. The task performance was rated as “passed” or “failed” with regard to the time per correctly collected item. Based on the performance of control subjects, the threshold value for failing the task was defined as μ+3σ (in seconds per correctly collected item). Eye movements were recorded by means of a mobile eye tracker. Eight out of ten patients with glaucoma and all control subjects passed the task. Patients who failed the task needed significantly longer time (111.47 s ±12.12 s) to complete the task than patients who passed (64.45 s ±13.36 s, t-test, p<0.001). Furthermore, patients who passed the task showed a significantly higher number of glances towards the visual field defect (VFD) area than patients who failed (t-test, p<0.05). According to these results, glaucoma patients with defects in the binocular visual field display on average longer search times in a naturalistic supermarket task. However, a considerable number of patients, who compensate by frequent glancing towards the VFD, showed successful task performance. Therefore, systematic exploration of the VFD area seems to be a “time-effective” compensatory mechanism during the present supermarket task. PMID:25162522

  5. Visual Handicaps of Mentally Handicapped People.

    ERIC Educational Resources Information Center

    Ellis, David

    1979-01-01

    Recent literature concerning visual handicaps of mentally handicapped people is reviewed. Topic areas considered are etiology and epidemiology, visual acuity, color vision, and educational techniques. (Author)

  6. Three-dimensional imaging in degraded visual field

    NASA Astrophysics Data System (ADS)

    Oran, A.; Ozharar, S.; Ozdur, I.

    2016-04-01

    Imaging at degraded visual environments is one of the biggest challenges in today’s imaging technologies. Especially military and commercial rotary wing aviation is suffering from impaired visual field in sandy, dusty, marine and snowy environments. For example during landing the rotor churns up the particles and creates dense clouds of highly scattering medium, which limits the vision of the pilot and may result in an uncontrolled landing. The vision in such environments is limited because of the high ratio of scattered photons over the ballistic photons which have the image information. We propose to use optical spatial filtering (OSF) method in order to eliminate the scattered photons and only collect the ballistic photons at the receiver. OSF is widely used in microscopy, to the best of our knowledge this will be the first application of OSF for macroscopic imaging. Our experimental results show that most of the scattered photons are eliminated using the spatial filtering in a highly scattering impaired visual field. The results are compared with a standard broad area photo detector which shows the effectiveness of spatial filtering.

  7. The risk of pedestrian collisions with peripheral visual field loss

    PubMed Central

    Peli, Eli; Apfelbaum, Henry; Berson, Eliot L.; Goldstein, Robert B.

    2016-01-01

    Patients with peripheral field loss complain of colliding with other pedestrians in open-space environments such as shopping malls. Field expansion devices (e.g., prisms) can create artificial peripheral islands of vision. We investigated the visual angle at which these islands can be most effective for avoiding pedestrian collisions, by modeling the collision risk density as a function of bearing angle of pedestrians relative to the patient. Pedestrians at all possible locations were assumed to be moving in all directions with equal probability within a reasonable range of walking speeds. The risk density was found to be highly anisotropic. It peaked at ≈45° eccentricity. Increasing pedestrian speed range shifted the risk to higher eccentricities. The risk density is independent of time to collision. The model results were compared to the binocular residual peripheral island locations of 42 patients with forms of retinitis pigmentosa. The natural residual island prevalence also peaked nasally at about 45° but temporally at about 75°. This asymmetry resulted in a complementary coverage of the binocular field of view. Natural residual binocular island eccentricities seem well matched to the collision-risk density function, optimizing detection of other walking pedestrians (nasally) and of faster hazards (temporally). Field expansion prism devices will be most effective if they can create artificial peripheral islands at about 45° eccentricities. The collision risk and residual island findings raise interesting questions about normal visual development. PMID:27919101

  8. The effect of pilocarpine on the glaucomatous visual field.

    PubMed Central

    Webster, A R; Luff, A J; Canning, C R; Elkington, A R

    1993-01-01

    Patients with chronic open angle glaucoma are traditionally managed by medical therapy during the early stages of the disease. Pilocarpine is a well established topical agent, but suffers troublesome sequelae, the most apparent of which is pupillary constriction. This study assesses the effect of miosis (produced by one drop of 2% pilocarpine) on the static threshold perimetry of 20 subjects with chronic open angle glaucoma and documented visual field loss, using the 30-2 program of the Humphrey field analyser. Following miosis, the Statpac mean defect deteriorated by an average of -1.49 dB compared with baseline (p = 0.004). This dB deterioration is twice that reported in studies on younger normal subjects following miosis. The decrease in mean defect showed a positive correlation with the degree of pupillary constriction, the correlation being greater in those eyes with a miosed pupil diameter of 2 mm or less. There was no significant decrease in the other Statpac global indices following miosis. A parallel study using the fellow eye of the same glaucoma patients showed a high degree of intertest variability, but no significant learning or fatigue effect. We conclude that pilocarpine-induced miosis causes a significant deterioration in visual field in a population of patients with chronic open angle glaucoma: this factor should be considered when choosing therapy for glaucoma particularly in cases where field loss approaches the permitted legal minimum for driving. PMID:8280687

  9. Efficient visualization of unsteady and huge scalar and vector fields

    NASA Astrophysics Data System (ADS)

    Vetter, Michael; Olbrich, Stephan

    2016-04-01

    and methods, we are developing a stand-alone post-processor, adding further data structures and mapping algorithms, and cooperating with the ICON developers and users. With the implementation of a DSVR-based post-processor, a milestone was achieved. By using the DSVR post-processor the mentioned 3 processes are completely separated: the data set is processed in a batch mode - e.g. on the same supercomputer, which the data is generated on - and the interactive 3D rendering is done afterwards on the scientist's local system. At the actual status of implementation the DSVR post-processor supports the generation of isosurfaces and colored slicers on volume data set time series based on rectilinear grids as well as the visualization of pathlines on time varying flow fields based on either rectilinear grids or prism grids. The software implementation and evaluation is done on the supercomputers at DKRZ, including scalability tests using ICON output files in NetCDF format. The next milestones will be (a) the in-situ integration of the DSVR library in the ICON model and (b) the implementation of an isosurface algorithm for prism grids.

  10. Enhancement and suppression in the visual field under perceptual load

    PubMed Central

    Parks, Nathan A.; Beck, Diane M.; Kramer, Arthur F.

    2013-01-01

    The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task—greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field. PMID:23734135

  11. 38 CFR 4.76a - Computation of average concentric contraction of visual fields.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... concentric contraction of visual fields. 4.76a Section 4.76a Pensions, Bonuses, and Veterans' Relief... Sense § 4.76a Computation of average concentric contraction of visual fields. Table III—Normal Visual Field Extent at 8 Principal Meridians Meridian Normal degrees Temporally 85 Down temporally 85 Down...

  12. 38 CFR 4.76a - Computation of average concentric contraction of visual fields.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... concentric contraction of visual fields. 4.76a Section 4.76a Pensions, Bonuses, and Veterans' Relief... Sense § 4.76a Computation of average concentric contraction of visual fields. Table III—Normal Visual Field Extent at 8 Principal Meridians Meridian Normal degrees Temporally 85 Down temporally 85 Down...

  13. 38 CFR 4.76a - Computation of average concentric contraction of visual fields.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... concentric contraction of visual fields. 4.76a Section 4.76a Pensions, Bonuses, and Veterans' Relief... Sense § 4.76a Computation of average concentric contraction of visual fields. Table III—Normal Visual Field Extent at 8 Principal Meridians Meridian Normal degrees Temporally 85 Down temporally 85 Down...

  14. Simulation and visualization of velocity fields in simple electrokinetic devices

    NASA Astrophysics Data System (ADS)

    Mahanti, Prasun; Taylor, Thomas; Cochran, Douglas; Keebaugh, Michael; Hayes, Mark A.

    2013-12-01

    Capillary electrophoresis and similar techniques which use an electrified contracting-flow interface (gradient elution moving boundary electrophoresis, electrophoretic exclusion, for examples) are widely used, but the detailed flow dynamics and local electric field effects within this zone have only recently been quantitatively investigated. The motivating force behind this work is establishing particle flow based visualization tools enabling advances for arbitrary interfacial designs beyond this traditional flow/electric field interface. These tools work with pre-computed 2-dimensional fundamental interacting fields which govern particle and(or) fluid flow and can now be obtained from various computational fluid dynamics (CFD) software packages. The particle-flow visualization calculations implemented in the tool and are built upon a solid foundation in fluid dynamics. The module developed in here provides a simulated video particle observation tool which generates a fast check for legitimacy. Further, estimating the accuracy and precision of full 2-D and 3-D simulation is notoriously difficult and a centerline estimation is used to quickly and easily quantitate behaviors in support of decision points. This tool and the recent quantitative assessment of particle behavior within the interfacial area have set the stage for new designs which can emphasize advantageous behaviors not offered by the traditional configuration.

  15. Visual Basic VPython Interface: Charged Particle in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Prayaga, Chandra

    2006-12-01

    A simple Visual Basic (VB) to VPython interface is described and illustrated with the example of a charged particle in a magnetic field. This interface allows data to be passed to Python through a text file read by Python. The first component of the interface is a user-friendly data entry screen designed in VB, in which the user can input values of the charge, mass, initial position and initial velocity of the particle, and the magnetic field. Next, a command button is coded to write these values to a text file. Another command button starts the VPython program, which reads the data from the text file, numerically solves the equation of motion, and provides the 3d graphics animation. Students can use the interface to run the program several times with different data and observe changes in the motion.

  16. Human brain response to visual stimulus between lower/upper visual fields and cerebral hemispheres.

    PubMed

    Lee, Bumsuk; Kaneoke, Yoshiki; Kakigi, Ryusuke; Sakai, Yasujiro

    2009-11-01

    We studied the human brain response to visual stimulation in which a square area was randomly presented in upper and lower visual fields (VFs). Seven normal volunteers carried out a contrast-based visual search task. Magnetic responses were detected in the bilateral parietal regions at 200-250 ms after stimulus onset. We compared the response latencies and strengths of the essential single sensor and root mean square (RMS) of the regions. The former evaluates the strength of neural activity with relatively high spatial resolution, while the latter evaluates the global neural activity. The single sensor and RMS latencies for the lower left VF were significantly longer than that for the upper left (paired t-test, P<0.05). The strengths did not differ between the upper and lower left VFs. There was no significant difference in latency or strength between the upper right and lower right VFs. These findings suggest that only left VF has different response properties in the upper versus lower VF, and that both local and global extrastriate activities are responsible for this anisotropy.

  17. Identifying Areas of the Visual Field Important for Quality of Life in Patients with Glaucoma

    PubMed Central

    Murata, Hiroshi; Hirasawa, Hiroyo; Aoyama, Yuka; Sugisaki, Kenji; Araie, Makoto; Mayama, Chihiro; Aihara, Makoto; Asaoka, Ryo

    2013-01-01

    Purpose The purpose of this study was to create a vision-related quality of life (VRQoL) prediction system to identify visual field (VF) test points associated with decreased VRQoL in patients with glaucoma. Method VRQoL score was surveyed in 164 patients with glaucoma using the ‘Sumi questionnaire’. A binocular VF was created from monocular VFs by using the integrated VF (IVF) method. VRQoL score was predicted using the ‘Random Forest’ method, based on visual acuity (VA) of better and worse eyes (better-eye and worse-eye VA) and total deviation (TD) values from the IVF. For comparison, VRQoL scores were regressed (linear regression) against: (i) mean of TD (IVF MD); (ii) better-eye VA; (iii) worse-eye VA; and (iv) IVF MD and better- and worse-eye VAs. The rank of importance of IVF test points was identified using the Random Forest method. Results The root mean of squared prediction error associated with the Random Forest method (0.30 to 1.97) was significantly smaller than those with linear regression models (0.34 to 3.38, p<0.05, ten-fold cross validation test). Worse-eye VA was the most important variable in all VRQoL tasks. In general, important VF test points were concentrated along the horizontal meridian. Particular areas of the IVF were important for different tasks: peripheral superior and inferior areas in the left hemifield for the ‘letters and sentences’ task, peripheral, mid-peripheral and para-central inferior regions for the ‘walking’ task, the peripheral superior region for the ‘going out’ task, and a broad scattered area across the IVF for the ‘dining’ task. Conclusion The VRQoL prediction model with the Random Forest method enables clinicians to better understand patients’ VRQoL based on standard clinical measurements of VA and VF. PMID:23520528

  18. Incorporating Spatial Models in Visual Field Test Procedures

    PubMed Central

    Rubinstein, Nikki J.; McKendrick, Allison M.; Turpin, Andrew

    2016-01-01

    Purpose To introduce a perimetric algorithm (Spatially Weighted Likelihoods in Zippy Estimation by Sequential Testing [ZEST] [SWeLZ]) that uses spatial information on every presentation to alter visual field (VF) estimates, to reduce test times without affecting output precision and accuracy. Methods SWeLZ is a maximum likelihood Bayesian procedure, which updates probability mass functions at VF locations using a spatial model. Spatial models were created from empirical data, computational models, nearest neighbor, random relationships, and interconnecting all locations. SWeLZ was compared to an implementation of the ZEST algorithm for perimetry using computer simulations on 163 glaucomatous and 233 normal VFs (Humphrey Field Analyzer 24-2). Output measures included number of presentations and visual sensitivity estimates. Results There was no significant difference in accuracy or precision of SWeLZ for the different spatial models relative to ZEST, either when collated across whole fields or when split by input sensitivity. Inspection of VF maps showed that SWeLZ was able to detect localized VF loss. SWeLZ was faster than ZEST for normal VFs: median number of presentations reduced by 20% to 38%. The number of presentations was equivalent for SWeLZ and ZEST when simulated on glaucomatous VFs. Conclusions SWeLZ has the potential to reduce VF test times in people with normal VFs, without detriment to output precision and accuracy in glaucomatous VFs. Translational Relevance SWeLZ is a novel perimetric algorithm. Simulations show that SWeLZ can reduce the number of test presentations for people with normal VFs. Since many patients have normal fields, this has the potential for significant time savings in clinical settings. PMID:26981329

  19. Ultrafine spatial acuity of blind expert human echolocators

    PubMed Central

    Puri, Amrita; Whitney, David

    2013-01-01

    Echolocating organisms represent their external environment using reflected auditory information from emitted vocalizations. This ability, long known in various non-human species, has also been documented in some blind humans as an aid to navigation, as well as object detection and coarse localization. Surprisingly, our understanding of the basic acuity attainable by practitioners—the most fundamental underpinning of echoic spatial perception—remains crude. We found that experts were able to discriminate horizontal offsets of stimuli as small as ~1.2° auditory angle in the frontomedial plane, a resolution approaching the maximum measured precision of human spatial hearing and comparable to that found in bats performing similar tasks. Furthermore, we found a strong correlation between echolocation acuity and age of blindness onset. This first measure of functional spatial resolution in a population of expert echolocators demonstrates precision comparable to that found in the visual periphery of sighted individuals. PMID:22101568

  20. Binocular Coordination, Acuity, and Locomotion: Interacting with Objects in the Environment.

    ERIC Educational Resources Information Center

    Knowlton, Marie; Lee, Inkyung

    1995-01-01

    This article addresses issues of orientation and mobility for students with visual impairments, including the perception of motion, visual mechanisms of binocular coordination, perception of impending collision, and body movement to avoid collision. Emphasis is on the role of binocular coordination ability and acuity. These concepts were evaluated…

  1. Quantitative Analysis of the Displacement of the Anterior Visual Pathway by Pituitary Lesions and the Associated Visual Field Loss

    PubMed Central

    Boland, Michael V.; Lee, In Ho; Zan, Elcin; Yousem, David M.; Miller, Neil R.

    2016-01-01

    Purpose To evaluate quantitatively the relationship between the displacement of anterior visual pathway structures by pituitary tumors and visual field damage with the goal of improving diagnosis and management. Methods Subjects had pituitary macroadenomas and both magnetic resonance imaging (MRI) and static perimetry. Neuroradiologists measured the displacement of anterior visual pathway structures and right–left tumor asymmetry. To quantify the degree and laterality of visual field loss, we used algorithms from the neurologic hemifield test to analyze each right–left pair of visual fields with respect to temporal asymmetry, the proportion of loss that was temporal, total asymmetry, and total damage. We compared these metrics with the displacement of anterior visual pathway structures and tumor asymmetry. Results Of 114 subjects, 64 (56%) were male and the median age was 57 years (range, 14–88). The summation of vision loss in both eyes and the proportion of temporal loss were statistically significantly related to the maximum displacement of the anterior visual pathway (both P < 0.001 for fit of linear regression). The relationship between the asymmetry of visual field loss in the two eyes and the subjective assignment of tumor asymmetry on MRI did not achieve statistical significance (P = 0.06 by analysis of variance). Conclusions Displacement of the anterior visual pathway by pituitary tumors is associated with both the total amount of visual field loss and the proportion of temporal visual field loss. Although there was right–left asymmetry of vision loss in some subjects, it was not related to the subjective assessment of tumor asymmetry. PMID:27388050

  2. Mass Charge Interactions for Visualizing the Quantum Field

    NASA Astrophysics Data System (ADS)

    Baer, Wolfgang

    Our goal is to integrate the objective and subjective aspects of our personal experience into a single complete theory of reality. To further this endeavor we replace elementary particles with elementary events as the building blocks of an event oriented description of that reality. The simplest event in such a conception is an adaptation of A. Wheeler's primitive explanatory--measurement cycle between internal observations experienced by an observer and their assumed physical causes. We will show how internal forces between charge and mass are required to complete the cyclic sequence of activity. This new formulation of internal material is easier to visualize and map to cognitive experiences than current formulations of sub-atomic physics. In our formulation, called Cognitive Action Theory, such internal forces balance the external forces of gravity-inertia and electricity-magnetism. They thereby accommodate outside influences by adjusting the internal structure of material from which all things are composed. Such accommodation is interpreted as the physical implementation of a model of the external physical world in the brain of a cognitive being or alternatively the response mechanism to external influences in the material of inanimate objects. We adopt the deBroglie-Bohm causal interpretation of QT to show that the nature of space in our model is mathematically equivalent to a field of clocks. Within this field small oscillations form deBroglie waves. This interpretation allows us to visualize the underlying structure of empty space with a charge-mass separation field in equilibrium, and objects appearing in space with quantum wave disturbances to that equilibrium occurring inside material. Space is thereby associated with the internal structure of material and quantum mechanics is shown to be, paraphrasing Heisenberg, the physics of the material that knows the world.

  3. The Experiences of Parents of Students with Visual Impairments Who Are Professionals in the Field of Visual Impairment

    ERIC Educational Resources Information Center

    de Steiguer, Pamela B.; Erin, Jane N.; Topor, Irene L.; Rosenblum, L. Penny

    2008-01-01

    This survey examined the experiences of parents of individuals with visual impairments who acquired professional credentials in the field of visual impairment. The participants reported on such topics as the advantages and disadvantages of being a parent-professional, the types of support they seek, and advice to others who are balancing both…

  4. The Relationship between Central Visual Field Damage and Motor Vehicle Collisions in Primary Open-Angle Glaucoma Patients

    PubMed Central

    Yuki, Kenya; Asaoka, Ryo; Tsubota, Kazuo

    2014-01-01

    Purpose To investigate the relationship between visual field (VF) damage and history of motor vehicle collisions (MVCs) in subjects with primary open-angle glaucoma (POAG). Methods MVC history and driving habits were recorded using patient questionnaires in 247 POAG patients. Patients' driving attitudes (carefulness) were estimated using Rasch analysis. The relationship between MVC outcomes and 52 total deviation (TD) values of integrated binocular VF (IVF), better and worse visual acuities (VAs), age and gender was analyzed using principal component analysis and logistic regression. Results 51 patients had the history of MVCs. Significant difference was observed between patients with and without history of MVCs only for: better VA, a single TD value in the superior-right VF, and the typical distance driven in a week (unpaired t-test, p = 0.002, 0.015 and 0.006, respectively). There was not a significant relationship between MVCs and mean deviation (MD) of IVF (p = 0.41, logistic regression). None of the principal components were significantly correlated with MVC outcome (p>0.05, polynomial logistic regression analysis). There was a significant relationship between IVF MD and Rasch derived Person parameter (R2 = 0.023, p = 0.0095). There was also a significant positive relationship between MVCs and the distance driven in a week (p = 0.005, logistic regression). Conclusions In this study of POAG patients, MVCs were not related to central binocular VF damage. These results suggest the relationship between visual function and driving is not straightforward, and careful consideration should be given when predicting patients' driving ability using their VF. PMID:25545660

  5. Visualization of lithium ions by annular bright field imaging.

    PubMed

    Oshima, Yoshifumi; Lee, Soyeon; Takayanagi, Kunio

    2016-10-14

    The detection of lithium ions is required for characterization of lithium ion batteries, since the movement of lithium ions in the battery is one of the key ways to improve the performance. Annular bright field (ABF) imaging enables us to visualize individual lithium atomic columns simultaneously with heavy elements. Furthermore, it has been found that the number of lithium ions at the column is countable when the specimen is thin. These results suggest that movement of lithium ions in the material can be observed by taking consecutive ABF images during operation or in situ ABF observation. Actually, the spinel structure of L2V4O crystals was directly observed to be transformed into the defective NaCl structure at the moment when lithium ions were extracted from the original position during electron beam irradiation. We clarify the features of ABF imaging by comparing it with HAADF imaging in order to understand what information can be obtained by ABF imaging directly.

  6. Effect of palmitoylethanolamide on visual field damage progression in normal tension glaucoma patients: results of an open-label six-month follow-up.

    PubMed

    Costagliola, Ciro; Romano, Mario R; dell'Omo, Roberto; Russo, Andrea; Mastropasqua, Rodolfo; Semeraro, Francesco

    2014-09-01

    The purpose of this study is to assess the effect of palmitoylethanolamide (PEA) oral administration on intraocular pressure (IOP) and visual field damage progression in normal-tension glaucoma (NTG) patients. Thirty-two consecutive patients affected by NTG were enrolled and randomized in a 1:1 ratio to receive PEA treatment (group A) or no treatment (group B). Group A patients took ultramicronized 300 mg PEA tablets two times per day for six months. Best-corrected visual acuity (BCVA), IOP, and visual field test were evaluated at baseline and at the end of the six-month follow-up. No significant differences in clinical parameters between the two groups were observed at baseline. At six months, group A patients showed significant IOP reduction (from 14.4±3.2 mm Hg to 11.1±4.3 mm Hg, p<0.01). No statistically significant changes were seen in BCVA in either group. Visual field parameters significantly diminished in patients receiving PEA compared to baseline values (-7.65±6.55 dB vs. -4.55±5.31 dB, p<0.001; 5.21±4.08 dB vs. 3.81±3.02 dB, p<0.02; mean deviation [MD] and pattern standard deviation [PSD] respectively), while no significant changes were seen in group B. A generalized linear model demonstrated that the final IOP, MD, and PSD was affected only by the systemic PEA treatment (p<0.01 each) and not affected by demographic or clinical characteristic between the groups. Hence, systemic administration of PEA reduces IOP and improves visual field indices in individuals affected by NTG. Neither ocular nor systemic side effects were recorded during the study period.

  7. Division of labor in frontal eye field neurons during presaccadic remapping of visual receptive fields

    PubMed Central

    Shin, SooYoon

    2012-01-01

    Our percept of visual stability across saccadic eye movements may be mediated by presaccadic remapping. Just before a saccade, neurons that remap become visually responsive at a future field (FF), which anticipates the saccade vector. Hence, the neurons use corollary discharge of saccades. Many of the neurons also decrease their response at the receptive field (RF). Presaccadic remapping occurs in several brain areas including the frontal eye field (FEF), which receives corollary discharge of saccades in its layer IV from a collicular-thalamic pathway. We studied, at two levels, the microcircuitry of remapping in the FEF. At the laminar level, we compared remapping between layers IV and V. At the cellular level, we compared remapping between different neuron types of layer IV. In the FEF in four monkeys (Macaca mulatta), we identified 27 layer IV neurons with orthodromic stimulation and 57 layer V neurons with antidromic stimulation from the superior colliculus. With the use of established criteria, we classified the layer IV neurons as putative excitatory (n = 11), putative inhibitory (n = 12), or ambiguous (n = 4). We found that just before a saccade, putative excitatory neurons increased their visual response at the RF, putative inhibitory neurons showed no change, and ambiguous neurons increased their visual response at the FF. None of the neurons showed presaccadic visual changes at both RF and FF. In contrast, neurons in layer V showed full remapping (at both the RF and FF). Our data suggest that elemental signals for remapping are distributed across neuron types in early cortical processing and combined in later stages of cortical microcircuitry. PMID:22815407

  8. Visual agnosia.

    PubMed

    Álvarez, R; Masjuan, J

    2016-03-01

    Visual agnosia is defined as an impairment of object recognition, in the absence of visual acuity or cognitive dysfunction that would explain this impairment. This condition is caused by lesions in the visual association cortex, sparing primary visual cortex. There are 2 main pathways that process visual information: the ventral stream, tasked with object recognition, and the dorsal stream, in charge of locating objects in space. Visual agnosia can therefore be divided into 2 major groups depending on which of the two streams is damaged. The aim of this article is to conduct a narrative review of the various visual agnosia syndromes, including recent developments in a number of these syndromes.

  9. The Relationship between Better-Eye and Integrated Visual Field Mean Deviation and Visual Disability

    PubMed Central

    Arora, Karun S.; Boland, Michael V.; Friedman, David S.; Jefferys, Joan L.; West, Sheila K.; Ramulu, Pradeep Y.

    2013-01-01

    Objective To determine the extent of difference between better-eye visual field (VF) mean deviation (MD) and integrated VF (IVF) MD among Salisbury Eye Evaluation (SEE) subjects and a larger group of glaucoma clinic subjects and to assess how those measures relate to objective and subjective measures of ability/performance in SEE subjects. Design Retrospective analysis of population- and clinic-based samples of adults. Participants A total of 490 SEE and 7053 glaucoma clinic subjects with VF loss (MD ≤−3 decibels [dB] in at least 1 eye). Methods Visual field testing was performed in each eye, and IVF MD was calculated. Differences between better-eye and IVF MD were calculated for SEE and clinic-based subjects. In SEE subjects with VF loss, models were constructed to compare the relative impact of better-eye and IVF MD on driving habits, mobility, self-reported vision-related function, and reading speed. Main Outcome Measures Difference between better-eye and IVF MD and relationship of better-eye and IVF MD with performance measures. Results The median difference between better-eye and IVF MD was 0.41 dB (interquartile range [IQR], −0.21 to 1.04 dB) and 0.72 dB (IQR, 0.04–1.45 dB) for SEE subjects and clinic-based patients with glaucoma, respectively, with differences of ≥2 dB between the 2 MDs observed in 9% and 18% of the groups, respectively. Among SEE subjects with VF loss, both MDs demonstrated similar associations with multiple ability and performance metrics as judged by the presence/absence of a statistically significant association between the MD and the metric, the magnitude of observed associations (odds ratios, rate ratios, or regression coefficients associated with 5-dB decrements in MD), and the extent of variability in the metric explained by the model (R2). Similar associations of similar magnitude also were noted for the subgroup of subjects with glaucoma and subjects in whom better-eye and IVF MD differed by ≥2 dB. Conclusions The IVF

  10. Plate Scattering Visualization: Images, Near Fields, Currents, and Far Field Patterns

    NASA Technical Reports Server (NTRS)

    Shaeffer, John; Hom, Kam

    2004-01-01

    This paper presents a case study of a simple yet robust target for demonstration of the EM visualization process. A five lambda square plate exhibits many scattering mechanisms depending on excitation angle and polarization: specular scattering, leading and trailing edge diffraction, traveling wave, and edge wave scattering. Bistatic k space radiation images, currents maps, and near scattered / total fields are examined for each of these scattering mechanisms.

  11. Recovery of stereo acuity in adults with amblyopia

    PubMed Central

    Astle, Andrew T; McGraw, Paul V; Webb, Ben S

    2011-01-01

    Disruption of visual input to one eye during early development leads to marked functional impairments of vision, commonly referred to as amblyopia. A major consequence of amblyopia is the inability to encode binocular disparity information leading to impaired depth perception or stereo acuity. If amblyopia is treated early in life (before 4 years of age), then recovery of normal stereoscopic function is possible. Treatment is rarely undertaken later in life (adulthood) because declining levels of neural plasticity are thought to limit the effectiveness of standard treatments. Here, the authors show that a learning-based therapy, designed to exploit experience-dependent plastic mechanisms, can be used to recover stereoscopic visual function in adults with amblyopia. These cases challenge the long-held dogma that the critical period for visual development and the window for treating amblyopia are one and the same. PMID:22707543

  12. Stereopsis and positional acuity under dark adaptation.

    PubMed

    Livingstone, M S; Hubel, D H

    1994-03-01

    Though experience tells us we can perceive depth in dim light, it is not so obvious that one of the chief mechanisms for depth perception, stereopsis, is possible under scotopic conditions. The only studies on human stereopsis in the dark adapted state seem to be those of Nagel [(1902) Zeitschrift für Psychologie, 27, 264-266] and Mueller and Lloyd [(1948) Proceedings of the National Academy of Science, U.S.A., 34, 223-227], both of which used real objects or line stereograms. We tested stereopsis using both random-dot and line stereograms and, in agreement with these studies, found that stereopsis is indeed possible in dark adaptation. We also measured stereo acuity and positional acuity (both of which are examples of hyperacuity) and compared these with grating acuity at several levels of light and dark adaptation. At all illumination levels tested, acuities for stereopsis and relative line position were both higher than for grating acuity. As light levels decreased, positional and grating acuity declined in parallel fashion, whereas stereoacuity declined more steeply.

  13. Efficacy and complications of radiotherapy of anterior visual pathway tumors

    SciTech Connect

    Capo, H.; Kupersmith, M.J. )

    1991-02-01

    A progressive disturbance in visual acuity or visual field, along with an unexplained optic nerve atrophy, suggests the possibility of a tumor. Tumors that frequently affect the anterior visual pathway include primary optic nerve sheath meningiomas, intracranial meningiomas, optic gliomas, pituitary tumors, and craniopharyngiomas. The location of these tumors sometimes prohibits a complete surgical excision that might jeopardize the visual system. Radiation therapy, however, can be beneficial in these cases. This article reviews the indications for radiotherapy of tumors that involve the anterior visual pathway, along with the possible complications. Cases that present the effect of radiation therapy and radiation damage are presented.131 references.

  14. Splitting Attention across the Two Visual Fields in Visual Short-Term Memory

    ERIC Educational Resources Information Center

    Delvenne, Jean-Francois; Holt, Jessica L.

    2012-01-01

    Humans have the ability to attentionally select the most relevant visual information from their extrapersonal world and to retain it in a temporary buffer, known as visual short-term memory (VSTM). Research suggests that at least two non-contiguous items can be selected simultaneously when they are distributed across the two visual hemifields. In…

  15. Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task

    SciTech Connect

    Ragan, Eric D.; Bowman, Doug A.; Kopper, Regis; Stinson, Cheryl; Scerbo, Siroberto; McMahan, Ryan P.

    2015-02-13

    Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. The paper presents a framework for evaluating the effects of virtual reality fidelity based on an analysis of a simulation’s display, interaction, and scenario components. Following this framework, we conducted a controlled experiment to test the effects of fidelity on training effectiveness for a visual scanning task. The experiment varied the levels of field of view and visual realism during a training phase and then evaluated scanning performance with the simulator’s highest level of fidelity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual realism significantly affected target detection during training; higher field of view led to better performance and higher visual realism worsened performance. Additionally, the level of visual realism during training significantly affected learning of the prescribed visual scanning strategy, providing evidence that high visual realism was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training—evaluation in a more realistic setting may be necessary.

  16. Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task

    DOE PAGES

    Ragan, Eric D.; Bowman, Doug A.; Kopper, Regis; ...

    2015-02-13

    Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. The paper presents a framework for evaluating the effects of virtual reality fidelity based on an analysis of a simulation’s display, interaction, and scenario components. Following this framework, we conducted a controlled experiment to test the effects of fidelity on training effectiveness for a visual scanning task. The experiment varied the levels of field of view and visual realism during a training phase and then evaluated scanning performance with the simulator’s highestmore » level of fidelity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual realism significantly affected target detection during training; higher field of view led to better performance and higher visual realism worsened performance. Additionally, the level of visual realism during training significantly affected learning of the prescribed visual scanning strategy, providing evidence that high visual realism was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training—evaluation in a more realistic setting may be necessary.« less

  17. The accuracy of confrontation visual field test in comparison with automated perimetry.

    PubMed Central

    Johnson, L. N.; Baloh, F. G.

    1991-01-01

    The accuracy of confrontation visual field testing was determined for 512 visual fields using automated static perimetry as the reference standard. The sensitivity of confrontation testing excluding patchy defects was 40% for detecting anterior visual field defects, 68.3% for posterior defects, and 50% for both anterior and posterior visual field defects combined. The sensitivity within each group varied depending on the type of visual field defect encountered. Confrontation testing had a high sensitivity (75% to 100%) for detecting altitudinal visual loss, central/centrocecal scotoma, and homonymous hemianopsia. Confrontation testing was fairly insensitive (20% to 50% sensitivity) for detecting arcuate scotoma and bitemporal hemianopsia. The specificity of confrontation testing was high at 93.4%. The high positive predictive value (72.6%) and negative predictive value (75.7%) would indicate that visual field defects identified during confrontation testing are often true visual field defects. However, the many limitations of confrontation testing should be remembered, particularly its low sensitivity for detecting visual field loss associated with parasellar tumors, glaucoma, and compressive optic neuropathies. PMID:1800764

  18. Flow Charts: Visualization of Vector Fields on Arbitrary Surfaces

    PubMed Central

    Li, Guo-Shi; Tricoche, Xavier; Weiskopf, Daniel; Hansen, Charles

    2009-01-01

    We introduce a novel flow visualization method called Flow Charts, which uses a texture atlas approach for the visualization of flows defined over curved surfaces. In this scheme, the surface and its associated flow are segmented into overlapping patches, which are then parameterized and packed in the texture domain. This scheme allows accurate particle advection across multiple charts in the texture domain, providing a flexible framework that supports various flow visualization techniques. The use of surface parameterization enables flow visualization techniques requiring the global view of the surface over long time spans, such as Unsteady Flow LIC (UFLIC), particle-based Unsteady Flow Advection Convolution (UFAC), or dye advection. It also prevents visual artifacts normally associated with view-dependent methods. Represented as textures, Flow Charts can be naturally integrated into hardware accelerated flow visualization techniques for interactive performance. PMID:18599918

  19. Response time to colored stimuli in the full visual field

    NASA Technical Reports Server (NTRS)

    Haines, R. F.; Dawson, L. M.; Galvan, T.; Reid, L. M.

    1975-01-01

    Peripheral visual response time was measured in seven dark adapted subjects to the onset of small (45' arc diam), brief (50 msec), colored (blue, yellow, green, red) and white stimuli imaged at 72 locations within their binocular field of view. The blue, yellow, and green stimuli were matched for brightness at about 2.6 sub log 10 units above their absolute light threshold, and they appeared at an unexpected time and location. These data were obtained to provide response time and no-response data for use in various design disciplines involving instrument panel layout. The results indicated that the retina possesses relatively concentric regions within each of which mean response time can be expected to be of approximately the same duration. These regions are centered near the fovea and extend farther horizontally than vertically. Mean foveal response time was fastest for yellow and slowest for blue. Three and one-half percent of the total 56,410 trials presented resulted in no-responses. Regardless of stimulus color, the lowest percentage of no-responses occurred within 30 deg arc from the fovea and the highest within 40 deg to 80 deg arc below the fovea.

  20. Colour, face, and visuospatial imagery abilities in low-vision individuals with visual field deficits.

    PubMed

    Dulin, David; Cavezian, Céline; Serrière, Coline; Bachoud-Levi, Anne-Catherine; Bartolomeo, Paolo; Chokron, Sylvie

    2011-10-01

    This study investigates to what extent visual perception integrity is necessary for visual mental imagery. Sixteen low-vision participants with severe peripheral visual field loss, 16 with severe central field loss, 6 left brain-damaged patients with right homonymous hemianopia, 6 right brain-damaged patients with left homonymous hemianopia, and 16 normally sighted controls performed perceptual and imagery tasks using colours, faces, and spatial relationships. Results showed that (a) the perceptual and mental image>ry disorders vary according to the type of visual field loss, (b) hemianopics had no more difficulties imagining spatial stimuli in their contralesional hemispace than in their ipsilesional one, and (c) the only hemianopic participant to have perceptual and mental imagery impairments suffered from attentional deficits. Results suggest that (a) visual memory is not definitively established, but rather needs perceptual practice to be maintained, and (b) that visual mental imagery may involve some of the attentional-exploratory mechanisms that are employed in visual behaviour.

  1. Baseline Characteristics of the Infant Aphakia Treatment Study Population: Predicting Recognition Acuity at 4.5 Years of Age

    PubMed Central

    Hartmann, E. Eugenie; Lynn, Michael J.; Lambert, Scott R.

    2015-01-01

    Purpose. To identify patient baseline characteristics that predict recognition acuity at 4.5 years of age in the Infant Aphakia Treatment Study, a study of patients with monocular infantile cataracts. Methods. We analyzed baseline characteristics of the 114 infants enrolled in the Infant Aphakia Treatment Study to determine which were most predictive of visual outcome at 4.5 years of age. All infants underwent cataract surgery between 1 and 7 months of age. Monocular acuity was assessed at 4.5 years of age by a traveling examiner using the Amblyopia Treatment Study HOTV protocol. Results. Age at cataract surgery was weakly associated with visual acuity (Spearman rank correlation coefficient = 0.19, P = 0.041) with median visual acuity better among the younger patients (28–48 days: 0.50 logMAR, 49–210 days: 1.10 logMAR, P = 0.046). Patients from families with private insurance had significantly better median visual acuity (0.60 vs. 1.40 logMAR, P = 0.0004). No other baseline characteristic revealed a significant bivariate relationship with visual acuity. A multiple linear regression relating visual acuity to all baseline characteristics demonstrated that only the availability of private insurance was statistically significant, accounting for 12% of the variance. Conclusions. This analysis concurs with previous studies that early surgery is important for good visual outcomes in patients with unilateral infantile cataracts. The fact that only one baseline variable (private insurance) contributed to the multivariate analysis, accounting for 12% of the variance, suggests that predicting visual outcome for these patients is complicated at best, and cannot be estimated from baseline characteristics alone. (ClinicalTrials.gov number, NCT00212134.) PMID:25503455

  2. Contour interaction for foveal acuity targets at different luminances.

    PubMed

    Bedell, Harold E; Siderov, John; Waugh, Sarah J; Zemanová, Romana; Pluháček, František; Musilová, Lenka

    2013-08-30

    Single-letter visual acuity is impaired by nearby flanking stimuli, a phenomenon known as contour interaction. We showed previously that when foveal acuity is degraded by a reduction of letter contrast, both the magnitude and angular spatial extent of foveal contour interaction remain unchanged. In this study, we asked whether contour interaction also remains unchanged when foveal visual acuity is degraded by a reduction of the target's background luminance. Percent correct letter identification was measured for isolated, near-threshold black Sloan letters and for letters surrounded by 4 flanking bars in 10 normal observers, 5 at Anglia Ruskin University, UK (ARU) and 5 at Palacky University, Czech Republic (PU). A stepwise reduction in the background luminance over 3 log units resulted in an approximately threefold increase in the near-threshold letter size. At each background luminance, black flanking bars with a width equal to 1 letter stroke were presented at separations between approximately 0.45 and 4.5 min arc (ARU) or 0.32 and 3.2 min arc (PU). The results indicate that the angular extent of contour interaction remains unchanged at approximately 4 min arc at all background luminances. On the other hand, the magnitude of contour interaction decreases systematically as luminance is reduced, from approximately a 50% reduction to a 30% reduction in percent correct. The constant angular extent and decreasing magnitude of contour interaction with a reduction of background luminance suggest foveal contour interaction is mediated by luminance-dependent lateral inhibition within a fixed angular region.

  3. Tangent screen perimetry in the evaluation of visual field defects associated with ptosis and dermatochalasis

    PubMed Central

    Briceño, César A.; Nelson, Christine C.; Bradley, Elizabeth A.

    2017-01-01

    Purpose To determine if tangent visual fields gathered during assessment of superior visual field deficits caused by blepharoptosis and dermatochalasis offer good correlation to clinical exam in a time and cost efficient manner. Methods Prospective, observational case series. Subjects included all patients referred to a single surgeon (CCN) who underwent surgical correction of blepharoptosis and/or dermatochalasis. Preoperatively and postoperatively, upper margin-to-reflex distances were assessed. Tangent visual fields were performed in a timed fashion and analyzed for degrees of intact vision in the vertical meridian and degrees squared of area under the curve. Data were compared by Student t-tests and Pearson correlation coefficients. Results Mean preoperative superior visual fields with the eyelid in the natural position measured 8° in the vertical meridian. Measurements in the vertical meridian and area under the curve showed excellent correlation (r = 0.87). Patients with ptosis showed strong correlation between margin-to-reflex distance and superior visual fields. Patients completed field testing faster than reported times for automated or Goldmann testing. Finally, tangent screens were the least expensive type of equipment to purchase. Conclusions Tangent visual fields are a rapid and inexpensive way to test for functional loss of superior visual field in patients with upper eyelid malposition. Our data revealed potential differences between tangent screen results and published results for automated or Goldmann visual field testing which warrants further studies. PMID:28355310

  4. Investigation of aberration characteristics of eyes at a peripheral visual field by individual eye model.

    PubMed

    Lou, Qiqi; Wang, Yan; Wang, Zhaoqi; Liu, Yongji; Zhang, Lin; Zhai, Yi; Fang, Hui

    2015-07-01

    We propose a method of constructing an individual eye model with a large visual field, and then investigate aberration characteristics of eyes in peripheral fields with constructed models. Twelve eyes of different aberrations are selected from 89 myopic eyes. It is shown that astigmatism increases as visual field in a quadratic manner. The variation tendency of defocus can be expressed by the cubic curve for 50% of eyes. For most of the eyes, the variation of spherical aberration shows a quadratic rule within ±24° visual field. Coma exhibits obvious individual differences. The impact of high-order aberrations on vision is mainly at a smaller visual field, and it becomes negligible beyond 24° visual field.

  5. Visual prognosis following treatment of acute central retinal artery obstruction.

    PubMed Central

    Augsburger, J J; Magargal, L E

    1980-01-01

    The authors report the visual outcome in 34 consecutive cases of treated acute central retinal artery obstruction. Visual acuity equal to or better than 6/30 was recovered in 35% of the cases. The presenting visual acuity and duration of visual impairment appear to correlate with visual prognosis. PMID:7448144

  6. NAEP and the Visual Arts: Framework, Field Test, and Assessment.

    ERIC Educational Resources Information Center

    Vanneman, Alan; Goodwin, Mac Arthur

    1998-01-01

    The National Assessment of Educational Progress (NAEP) has developed a new generation of assessment tasks for assessing student achievement in the visual arts. Using paper-and-pencil and performance formats, these tasks draw on the concepts, skills, and processes used to create and understand visual images from a variety of world cultures and…

  7. Visual business ecosystem intelligence: lessons from the field.

    PubMed

    Basole, Rahul C

    2014-01-01

    Macroscopic insight into business ecosystems is becoming increasingly important. With the emergence of new digital business data, opportunities exist to develop rich, interactive visual-analytics tools. Georgia Institute of Technology researchers have been developing and implementing visual business ecosystem intelligence tools in corporate settings. This article discusses the challenges they faced, the lessons learned, and opportunities for future research.

  8. About the Role of Visual Field Defects in Pure Alexia

    ERIC Educational Resources Information Center

    Pflugshaupt, Tobias; Gutbrod, Klemens; Wurtz, Pascal; von Wartburg, Roman; Nyffeler, Thomas; de Haan, Bianca; Karnath, Hans-Otto; Mueri, Rene M.

    2009-01-01

    Pure alexia is an acquired reading disorder characterized by a disproportionate prolongation of reading time as a function of word length. Although the vast majority of cases reported in the literature show a right-sided visual defect, little is known about the contribution of this low-level visual impairment to their reading difficulties. The…

  9. 38 CFR 4.76a - Computation of average concentric contraction of visual fields.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Computation of average concentric contraction of visual fields. 4.76a Section 4.76a Pensions, Bonuses, and Veterans' Relief... Sense § 4.76a Computation of average concentric contraction of visual fields. Table III—Normal...

  10. Active Learning in Neuroscience: A Manipulative to Simulate Visual Field Defects

    ERIC Educational Resources Information Center

    Li, Andrew Yue-Lin; Carvalho, Helena

    2016-01-01

    Prevalent in 20-57% of stroke patients, visual field defects have been shown to impact quality of life. Studies have shown increased risk of falling, ambulatory difficulties, impaired reading ability, and feelings of panic in crowded or unfamiliar places in patients with visual field defects. Rehabilitation, independence, and mental health may…

  11. A Lack of Left Visual Field Bias when Individuals with Autism Process Faces

    ERIC Educational Resources Information Center

    Dundas, Eva M.; Best, Catherine A.; Minshew, Nancy J.; Strauss, Mark S.

    2012-01-01

    It has been established that typically developing individuals have a bias to attend to facial information in the left visual field (LVF) more than in the right visual field. This bias is thought to arise from the right hemisphere's advantage for processing facial information, with evidence suggesting it to be driven by the configural demands of…

  12. Visual Field Asymmetries in Attention Vary with Self-Reported Attention Deficits

    ERIC Educational Resources Information Center

    Poynter, William; Ingram, Paul; Minor, Scott

    2010-01-01

    The purpose of this study was to determine whether an index of self-reported attention deficits predicts the pattern of visual field asymmetries observed in behavioral measures of attention. Studies of "normal" subjects do not present a consistent pattern of asymmetry in attention functions, with some studies showing better left visual field (LVF)…

  13. Nonlinear population receptive field changes in human area V5/MT+ of healthy subjects with simulated visual field scotomas

    PubMed Central

    Papanikolaou, Amalia; Keliris, Georgios A.; Lee, Sangkyun; Logothetis, Nikos K.; Smirnakis, Stelios M.

    2016-01-01

    There is extensive controversy over whether the adult visual cortex is able to reorganize following visual field loss (scotoma) as a result of retinal or cortical lesions. Functional magnetic resonance imaging (fMRI) methods provide a useful tool to study the aggregate receptive field properties and assess the capacity of the human visual cortex to reorganize following injury. However, these methods are prone to biases near the boundaries of the scotoma. Retinotopic changes resembling reorganization have been observed in the early visual cortex of normal subjects when the visual stimulus is masked to simulate retinal or cortical scotomas. It is not known how the receptive fields of higher visual areas, like hV5/MT+, are affected by partial stimulus deprivation. We measured population receptive field (pRF) responses in human area V5/MT+ of 5 healthy participants under full stimulation and compared them with responses obtained from the same area while masking the left superior quadrant of the visual field (“artificial scotoma” or AS). We found that pRF estimations in area hV5/MT+ are nonlinearly affected by the AS. Specifically, pRF centers shift towards the AS, while the pRF amplitude increases and the pRF size decreases near the AS border. The observed pRF changes do not reflect reorganization but reveal important properties of normal visual processing under different test-stimulus conditions. PMID:26146195

  14. Visual field test simulation and error in threshold estimation.

    PubMed Central

    Spenceley, S E; Henson, D B

    1996-01-01

    AIM: To establish, via computer simulation, the effects of patient response variability and staircase starting level upon the accuracy and repeatability of static full threshold visual field tests. METHOD: Patient response variability, defined by the standard deviation of the frequency of seeing versus stimulus intensity curve, is varied from 0.5 to 20 dB (in steps of 0.5 dB) with staircase starting levels ranging from 30 dB below to 30 dB above the patient's threshold (in steps of 10 dB). Fifty two threshold estimates are derived for each condition and the error of each estimate calculated (difference between the true threshold and the threshold estimate derived from the staircase procedure). The mean and standard deviation of the errors are then determined for each condition. The results from a simulated quadrantic defect (response variability set to typical values for a patient with glaucoma) are presented using two different algorithms. The first corresponds with that normally used when performing a full threshold examination while the second uses results from an earlier simulated full threshold examination for the staircase starting values. RESULTS: The mean error in threshold estimates was found to be biased towards the staircase starting level. The extent of the bias was dependent upon patient response variability. The standard deviation of the error increased both with response variability and staircase starting level. With the routinely used full threshold strategy the quadrantic defect was found to have a large mean error in estimated threshold values and an increase in the standard deviation of the error along the edge of the defect. When results from an earlier full threshold test are used as staircase starting values this error and increased standard deviation largely disappeared. CONCLUSION: The staircase procedure widely used in threshold perimetry increased the error and the variability of threshold estimates along the edges of defects. Using

  15. Evaluation of Central and Peripheral Visual Field Concordance in Glaucoma

    PubMed Central

    Odden, Jamie L.; Mihailovic, Aleksandra; Boland, Michael V.; Friedman, David S.; West, Sheila K.; Ramulu, Pradeep Y.

    2016-01-01

    Purpose The purpose of this study was to characterize the extent to which central visual field (VF) loss reflects peripheral VF loss in patients with varying degrees of glaucoma severity. Methods A total of 232 patients with glaucoma or suspect glaucoma completed static central VF testing using the 24-2 pattern and peripheral VF testing using the suprathreshold 30-60 pattern. Points from 24-2 tests were reclassified as normal/abnormal based on pattern deviation values. Results Strong positive correlations (r ≥ 0.7) were observed between the proportion of abnormal central and peripheral points for the full VF, superior hemifield, and inferior hemifield, although the percentage of total central and peripheral abnormal points differed by ≥10% in 45% of eyes. In eyes with an average of 10%–40% abnormal points in the central and peripheral VFs, 12.0% more abnormal peripheral points were noted compared with the percentage of abnormal central points (P < 0.001; SD, 16.7%; range, 61% more to 37% less). In eyes with an average of 60%–90% abnormal points in the central and peripheral VFs, 16.4% fewer abnormal peripheral points were noted compared with the percentage of abnormal central points (P = 0.04; SD, 20.9%; range, 19% more to 49% less). Conclusions Central 24-2 testing generally reflects the extent of damage to the more peripheral VF in glaucoma, although significant disagreement exists for individual eyes. Further work is needed to determine whether integration of peripheral test points can improve detection of true VF loss in early glaucoma or be useful in monitoring progressive glaucomatous damage to areas of preserved VF in advanced glaucoma. PMID:27214688

  16. A comparison of the effects of ageing upon vernier and bisection acuity.

    PubMed

    Garcia-Suarez, Luis; Barrett, Brendan T; Pacey, Ian

    2004-05-01

    While most positional acuity tasks exhibit an age-related decline in performance, the effect of ageing upon vernier acuity continues to be the subject of some debate. In the present study we employed a stimulus design that enabled the simultaneous determination of bisection and vernier acuities in 36 subjects, aged between 22 and 84 years. This approach provided a means for directly testing the hypothesis that ageing affects bisection acuity but not vernier acuity by ensuring that differences in stimulus configuration and in the subject's task were kept to an absolute minimum. Optimum thresholds increased as a function of age for both bisection and vernier tasks. Inter-subject threshold variability also increased with age. Issues surrounding the comparison of absolute vernier thresholds across different studies are discussed and two important methodological factors are identified: the precise statistical method used to estimate thresholds, and the magnitude, in angular terms, of the smallest spatial offset of the elements of the vernier stimulus which can be displayed. Comparison with previously published data indicates that the discrepancy between this study and most previous investigations with respect to the effect of age upon vernier performance can be at least partly accounted for by differences in the minimum displayable vernier offset. Vernier thresholds do increase with age. The increased variability of vernier thresholds in older subjects would appear to limit the diagnostic value of the test as a means of enabling normal ageing to be distinguished from visual loss due to pathology of the eye or visual system.

  17. Relation between Approximate Number System Acuity and Mathematical Achievement: The Influence of Fluency

    PubMed Central

    Wang, Li; Sun, Yuhua; Zhou, Xinlin

    2016-01-01

    Previous studies have observed inconsistent relations between the acuity of the Approximate Number System (ANS) and mathematical achievement. In this paper, we hypothesize that the relation between ANS acuity and mathematical achievement is influenced by fluency; that is, the mathematical achievement test covering a greater expanse of mathematical fluency may better reflect the relation between ANS acuity and mathematics skills. We explored three types of mathematical achievement tests utilized in this study: Subtraction, graded, and semester-final examination. The subtraction test was designed to measure the mathematical fluency. The graded test was more fluency-based than the semester-final examination, but both involved the same mathematical knowledge from the class curriculum. A total of 219 fifth graders from primary schools were asked to perform all three tests, then given a numerosity comparison task, a visual form perception task (figure matching), and a series of other tasks to assess general cognitive processes (mental rotation, non-verbal matrix reasoning, and choice reaction time). The findings were consistent with our expectations. The relation between ANS acuity and mathematical achievement was particularly clearly reflected in the participants’ performance on the visual form perception task, which supports the domain-general explanations for the underlying mechanisms of the relation between ANS acuity and math achievement. PMID:28066291

  18. Relation between Approximate Number System Acuity and Mathematical Achievement: The Influence of Fluency.

    PubMed

    Wang, Li; Sun, Yuhua; Zhou, Xinlin

    2016-01-01

    Previous studies have observed inconsistent relations between the acuity of the Approximate Number System (ANS) and mathematical achievement. In this paper, we hypothesize that the relation between ANS acuity and mathematical achievement is influenced by fluency; that is, the mathematical achievement test covering a greater expanse of mathematical fluency may better reflect the relation between ANS acuity and mathematics skills. We explored three types of mathematical achievement tests utilized in this study: Subtraction, graded, and semester-final examination. The subtraction test was designed to measure the mathematical fluency. The graded test was more fluency-based than the semester-final examination, but both involved the same mathematical knowledge from the class curriculum. A total of 219 fifth graders from primary schools were asked to perform all three tests, then given a numerosity comparison task, a visual form perception task (figure matching), and a series of other tasks to assess general cognitive processes (mental rotation, non-verbal matrix reasoning, and choice reaction time). The findings were consistent with our expectations. The relation between ANS acuity and mathematical achievement was particularly clearly reflected in the participants' performance on the visual form perception task, which supports the domain-general explanations for the underlying mechanisms of the relation between ANS acuity and math achievement.

  19. Semi-automatic measurement of visual verticality perception in humans reveals a new category of visual field dependency.

    PubMed

    Kaleff, C R; Aschidamini, C; Baron, J; Di Leone, C N; Leone, C N; Canavarro, S; Vargas, C D

    2011-08-01

    Previous assessment of verticality by means of rod and rod and frame tests indicated that human subjects can be more (field dependent) or less (field independent) influenced by a frame placed around a tilted rod. In the present study we propose a new approach to these tests. The judgment of visual verticality (rod test) was evaluated in 50 young subjects (28 males, ranging in age from 20 to 27 years) by randomly projecting a luminous rod tilted between -18 and +18° (negative values indicating left tilts) onto a tangent screen. In the rod and frame test the rod was displayed within a luminous fixed frame tilted at +18 or -18°. Subjects were instructed to verbally indicate the rod's inclination direction (forced choice). Visual dependency was estimated by means of a Visual Index calculated from rod and rod and frame test values. Based on this index, volunteers were classified as field dependent, intermediate and field independent. A fourth category was created within the field-independent subjects for whom the amount of correct guesses in the rod and frame test exceeded that of the rod test, thus indicating improved performance when a surrounding frame was present. In conclusion, the combined use of subjective visual vertical and the rod and frame test provides a specific and reliable form of evaluation of verticality in healthy subjects and might be of use to probe changes in brain function after central or peripheral lesions.

  20. Effects of Binaural Sensory Aids on the Development of Visual Perceptual Abilities in Visually Handicapped Infants. Final Report, April 15, 1982-November 15, 1982.

    ERIC Educational Resources Information Center

    Hart, Verna; Ferrell, Kay

    Twenty-four congenitally visually handicapped infants, aged 6-24 months, participated in a study to determine (1) those stimuli best able to elicit visual attention, (2) the stability of visual acuity over time, and (3) the effects of binaural sensory aids on both visual attention and visual acuity. Ss were dichotomized into visually handicapped…

  1. Perception of heading speed from radial flow depends on visual field

    NASA Astrophysics Data System (ADS)

    Segawa, Kaori; Ujike, Hiroyasu; Okajima, Katsunori; Saida, Shinya

    2012-07-01

    We investigated the effects that the visual field has on the perception of heading speed. The stimulus was a radial flow pattern simulating a translational motion through a cylindrical tunnel. Observers evaluated the perception of heading speed by using a temporal two-alternative forced choice (2AFC) staircase method. In the first experiment, we manipulated the stimulus area by cutting the visual field along the longitudinal direction. The results showed that the perceived heading speed increases with the stimulus area. In the second experiment, we manipulated both the stimulus area and the eccentricity by cutting the visual field along the longitudinal direction. The results showed that the perception of heading speed increases when the stimulus occupies a large portion of the peripheral visual field. These findings suggest that the effect of eccentricity is a consequence of an incorrect translation of two-dimensional visual information into three-dimensional scaling.

  2. Multiple Visual Field Representations in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata)

    PubMed Central

    2016-01-01

    The visual wulst is the telencephalic target of the avian thalamofugal visual system. It contains several retinotopically organised representations of the contralateral visual field. We used optical imaging of intrinsic signals, electrophysiological recordings, and retrograde tracing with two fluorescent tracers to evaluate properties of these representations in the zebra finch, a songbird with laterally placed eyes. Our experiments revealed that there is some variability of the neuronal maps between individuals and also concerning the number of detectable maps. It was nonetheless possible to identify three different maps, a posterolateral, a posteromedial, and an anterior one, which were quite constant in their relation to each other. The posterolateral map was in contrast to the two others constantly visible in each successful experiment. The topography of the two other maps was mirrored against that map. Electrophysiological recordings in the anterior and the posterolateral map revealed that all units responded to flashes and to moving bars. Mean directional preferences as well as latencies were different between neurons of the two maps. Tracing experiments confirmed previous reports on the thalamo-wulst connections and showed that the anterior and the posterolateral map receive projections from separate clusters within the thalamic nuclei. Maps are connected to each other by wulst intrinsic projections. Our experiments confirm that the avian visual wulst contains several separate retinotopic maps with both different physiological properties and different thalamo-wulst afferents. This confirms that the functional organization of the visual wulst is very similar to its mammalian equivalent, the visual cortex. PMID:27139912

  3. Strength of visual percept generated by famous faces perceived without awareness: effects of affective valence, response latency, and visual field.

    PubMed

    Stone, Anna; Valentine, Tim

    2005-09-01

    Participants who were unable to detect familiarity from masked 17 ms faces (Stone and Valentine, 2004 and Stone and Valentine, in press-b) did report a vague, partial visual percept. Two experiments investigated the relative strength of the visual percept generated by famous and unfamiliar faces, using masked 17 ms exposure. Each trial presented simultaneously a famous and an unfamiliar face, one face in LVF and the other in RVF. In one task, participants responded according to which of the faces generated the stronger visual percept, and in the other task, they attempted an explicit familiarity decision. The relative strength of the visual percept of the famous face compared to the unfamiliar face was moderated by response latency and participants' attitude towards the famous person. There was also an interaction of visual field with response latency, suggesting that the right hemisphere can generate a visual percept differentiating famous from unfamiliar faces more rapidly than the left hemisphere. Participants were at chance in the explicit familiarity decision, confirming the absence of awareness of facial familiarity.

  4. Morphology, orthography, and the two hemispheres: A divided visual field study with Hindi/Urdu biliterates.

    PubMed

    Rao, Chaitra; Vaid, Jyotsna

    2016-07-25

    Although identical on the spoken level, Hindi and Urdu differ markedly on the written level in terms of reading/writing direction and orthographic depth, with discernible processing consequences. The present study used a divided field paradigm to study the impact of writing system characteristics of Hindi and Urdu on word naming latencies in skilled biliterate users of these languages. Hindi (read/written from left to right) was hypothesized to show a larger right field advantage than Urdu (read/written from right to left); Hindi words sharing form overlap with primes were expected to show a significant priming effect in the left visual field, but a significant right field effect for morphologically-primed naming. Both these expectations were confirmed. An overall right field advantage was obtained for one syllable Hindi and Urdu words; two syllable Urdu words showed either no visual field differences or a left field advantage, and the right field advantage for Hindi was significantly greater for two syllable than one syllable words. Further, Hindi words showed significant form priming (relative to control stimuli) in the left visual field and significant morphological priming (relative to form priming) in the right visual field. By contrast, Urdu words showed no significant form priming in either visual field, and significantly greater morphological than form priming in the left visual field. These results are taken to suggest that visual field asymmetries in word naming are sensitive to differences in reading habit-related scanning biases and to orthographic depth-related differences in word recognition processes.

  5. Neural Population Tuning Links Visual Cortical Anatomy to Human Visual Perception

    PubMed Central

    Song, Chen; Schwarzkopf, Dietrich Samuel; Kanai, Ryota; Rees, Geraint

    2015-01-01

    Summary The anatomy of cerebral cortex is characterized by two genetically independent variables, cortical thickness and cortical surface area, that jointly determine cortical volume. It remains unclear how cortical anatomy might influence neural response properties and whether such influences would have behavioral consequences. Here, we report that thickness and surface area of human early visual cortices exert opposite influences on neural population tuning with behavioral consequences for perceptual acuity. We found that visual cortical thickness correlated negatively with the sharpness of neural population tuning and the accuracy of perceptual discrimination at different visual field positions. In contrast, visual cortical surface area correlated positively with neural population tuning sharpness and perceptual discrimination accuracy. Our findings reveal a central role for neural population tuning in linking visual cortical anatomy to visual perception and suggest that a perceptually advantageous visual cortex is a thinned one with an enlarged surface area. PMID:25619658

  6. An Automated System for Comprehensive Assessment of Visual Field Sensitivity.

    DTIC Science & Technology

    1985-04-01

    act to degrade this basic configuration; e.g., pathology, such as glaucoma and retinitis pigmentosa ; environmental extremes, such as hypoxia...and B. Appleton. 1971. Effects of hypoxia on visual performance and retinal vascular state. Journal of Applied Physiology. 31: 357蘺. Kobrick, J. L

  7. Spatial Visualization Abilities of Field Dependent/Independent Preservice Teachers

    ERIC Educational Resources Information Center

    Yazici, Ersen

    2014-01-01

    Introduction: Spatial skills have been a significant area of research in educational psychology for more years and it has two major dimensions as spatial visualization and spatial orientation. Mathematics educators acknowledge the influence of cognitive styles in the learning of mathematics. There are various recognized cognitive styles in the…

  8. Synaptic and Network Mechanisms of Sparse and Reliable Visual Cortical Activity during Nonclassical Receptive Field Stimulation

    PubMed Central

    Haider, Bilal; Krause, Matthew R.; Duque, Alvaro; Yu, Yuguo; Touryan, Jonathan; Mazer, James A.; McCormick, David A.

    2011-01-01

    SUMMARY During natural vision, the entire visual field is stimulated by images rich in spatiotemporal structure. Although many visual system studies restrict stimuli to the classical receptive field (CRF), it is known that costimulation of the CRF and the surrounding nonclassical receptive field (nCRF) increases neuronal response sparseness. The cellular and network mechanisms underlying increased response sparseness remain largely unexplored. Here we show that combined CRF + nCRF stimulation increases the sparseness, reliability, and precision of spiking and membrane potential responses in classical regular spiking (RSC) pyramidal neurons of cat primary visual cortex. Conversely, fast-spiking interneurons exhibit increased activity and decreased selectivity during CRF + nCRF stimulation. The increased sparseness and reliability of RSC neuron spiking is associated with increased inhibitory barrages and narrower visually evoked synaptic potentials. Our experimental observations were replicated with a simple computational model, suggesting that network interactions among neuronal subtypes ultimately sharpen recurrent excitation, producing specific and reliable visual responses. PMID:20152117

  9. Attention modulates the visual field in healthy observers and parietal patients.

    PubMed

    Russell, Charlotte; Malhotra, Paresh; Husain, Masud

    2004-10-05

    Recent attention research suggests that factors other than low-level sensory processes modulate perception across the visual field, with right parieto-temporal cortex playing a critical role in directing visual attention to peripheral events. Here we examine how different degrees of attentional demand at fixation dynamically affect detection of abrupt visual onsets in the periphery. In young healthy subjects, peripheral detection was significantly disrupted bilaterally when there was high attention demand at fixation. Right parieto-temporal lesioned patients, tested with a simplified version of task, demonstrated bilateral shrinkage of their available visual field, worse to the contralesional side, under increased attentional demand at fixation. These findings demonstrate how the effective visual field is dynamically modulated by the deployment of attention in health and, more severely, following right parieto-temporal damage.

  10. Evaluation of vernier acuity near healed retinal laser lesions

    NASA Astrophysics Data System (ADS)

    Schmeisser, Elmar T.

    1997-05-01

    Seven Cynomolgus fasciculata who had graded laser lesions placed in own eye 6 years previously were evaluated for their vernier acuity by electrophysiologic recording techniques. In these experiments, 95 percent contrast vernier acuity targets were presented at high luminance levels to anesthetized primates. Visual evoked potentials were recorded by conventional means form scalp electrodes through hospital grade amplifiers. All animal testing was performed under IACUC approved protocols. The single q-switched pulses form a neodymium-YAG laser had produced lesions of 4 types: no visible change, minimal visible lesions, 'white dot' lesions and 'red dot' lesions in the eye at the time of placement. Single exposures had been made in four locations: 5 degrees superior, inferior and temporal to the fovea, and one foveally. Vernier recording proved somewhat successful in smaller animals with less than contained retinal hemorrhage lesions in the fovea. Initial analyses demonstrated a significant decrease of the pattern response signal/noise in the experimental eye overall, and an apparent relative loss of vernier signal in some lesioned eyes. Animals with the more severe lesions have somewhat degraded small patten responses and no recordable vernier response. Apparent lesser losses produced less effect.

  11. Resilience to the contralateral visual field bias as a window into object representations.

    PubMed

    Garcea, Frank E; Kristensen, Stephanie; Almeida, Jorge; Mahon, Bradford Z

    2016-08-01

    Viewing images of manipulable objects elicits differential blood oxygen level-dependent (BOLD) contrast across parietal and dorsal occipital areas of the human brain that support object-directed reaching, grasping, and complex object manipulation. However, it is unknown which object-selective regions of parietal cortex receive their principal inputs from the ventral object-processing pathway and which receive their inputs from the dorsal object-processing pathway. Parietal areas that receive their inputs from the ventral visual pathway, rather than from the dorsal stream, will have inputs that are already filtered through object categorization and identification processes. This predicts that parietal regions that receive inputs from the ventral visual pathway should exhibit object-selective responses that are resilient to contralateral visual field biases. To test this hypothesis, adult participants viewed images of tools and animals that were presented to the left or right visual fields during functional magnetic resonance imaging (fMRI). We found that the left inferior parietal lobule showed robust tool preferences independently of the visual field in which tool stimuli were presented. In contrast, a region in posterior parietal/dorsal occipital cortex in the right hemisphere exhibited an interaction between visual field and category: tool-preferences were strongest contralateral to the stimulus. These findings suggest that action knowledge accessed in the left inferior parietal lobule operates over inputs that are abstracted from the visual input and is contingent on analysis by the ventral visual pathway, consistent with its putative role in supporting object manipulation knowledge.

  12. Masked Priming Is Abstract in the Left and Right Visual Fields

    ERIC Educational Resources Information Center

    Bowers, Jeffrey S.; Turner, Emma L.

    2005-01-01

    Two experiments assessed masked priming for words presented to the left and right visual fields in a lexical decision task. In both Experiments, the same magnitude and pattern of priming was obtained for visually similar ("kiss"-"KISS") and dissimilar ("read"-"READ") prime-target pairs. These findings…

  13. Arm position does not attenuate visual loss in patients with homonymous field deficits.

    PubMed

    Smith, Daniel T; Lane, Alison R; Schenk, Thomas

    2008-01-01

    One of the most common and debilitating consequences of stroke is the loss of vision in the contralesional visual field. Clinicians typically regard this loss as irreversible and attempts at visual restoration have delivered only small and unreliable improvements. However, Schendel and Robertson [Schendel, K., & Robertson, L. C. (2004). Reaching out to see: Arm position can attenuate human visual loss. Journal of Cognitive Neuroscience, 16(6), 935-943] reported that the visual abilities of a hemianopic patient (WM) were significantly improved when the left arm was extended into the blind field. They suggest that visual stimuli near the arm recruited bimodal visual-tactile neurons, and this activity was sufficient to bring the stimulus into awareness. This result has enormous potential therapeutic value, but given that it is a single case study there are a number of reasons to be cautious about interpreting the data. Here, we investigate the effects of manipulating arm position on visual loss in a sample of five patients with homonymous field deficits. None of our patients showed any evidence of improved implicit or explicit visual ability in the blind field as a consequence of moving the arm. We suggest that WMs improvement was the consequence of a spatial bias towards the space containing his extended arm rather than the recruitment of bimodal neurons, and conclude that manipulating arm position is of little therapeutic value to patients with dense hemianopia.

  14. Right Visual Field Advantage for Perceived Contrast: Correlation with an Auditory Bias and Handedness

    ERIC Educational Resources Information Center

    Railo, H.; Tallus, J.; Hamalainen, H.

    2011-01-01

    Studies have suggested that supramodal attentional resources are biased rightward due to asymmetric spatial fields of the two hemispheres. This bias has been observed especially in right-handed subjects. We presented left and right-handed subjects with brief uniform grey visual stimuli in either the left or right visual hemifield. Consistent with…

  15. The effects of time, luminance, and high contrast targets: revisiting grating acuity in the domestic cat.

    PubMed

    Clark, Daria L; Clark, Robert A

    2013-11-01

    Based on optical clarity and retinal cone density, the cat has a potential acuity of 20-30 cycles per degree (cpd), yet most behavioral studies estimate feline acuity between 3 and 9 cpd. Those studies, however, were limited by restrictive experimental conditions that may have inadvertently lowered the estimated grating acuity. Two domestic cats previously trained on a two-choice visual discrimination task were retrained on a grating detection/discrimination task with unlimited time, high luminance, high contrast targets, and adequate space to prevent poor accommodation from affecting the results. Initially, vertical gratings of increasing cpd were tested until failure. Then, horizontal gratings of increasing cpd were tested until failure. Finally, the finest horizontal grating resolved was confirmed with a third test requiring 24 correct out of 36 consecutive trials, yielding a binomial probability less than 0.02 of non-random occurrence. M1, a 7-year-old male gray tabby with +2.00 OU refraction, tested for a grating detection acuity of 15 cpd for both vertical and horizontal gratings (binomial probability = 0.009). F1, a 2-year-old female gray tabby with +0.25 OU refraction, tested for a grating orientation discrimination acuity of 20 cpd for both vertical and horizontal gratings (binomial probability = 0.004). These results demonstrate that a young cat with good focus is capable of discriminating 20 cpd, in close agreement with the physiologic maximum. Uncorrected focusing errors appear to degrade visual performance. Optimum experimental conditions resulted in better grating acuity measurements than previously reported, emphasizing the importance of environmental factors in feline behavioral testing.

  16. Character Decomposition and Transposition of Chinese Compound Words in the Right and Left Visual Fields

    PubMed Central

    Cao, Hong-Wen; Yang, Kai-Fu

    2016-01-01

    This study investigated the character decomposition and transposition processes of Chinese two-character compound words (canonical and transposed words) and pseudowords in the right and left visual fields using a dual-target rapid serial visual presentation paradigm. The results confirmed a right visual field superiority for canonical words, but this advantage vanished for transposed words. The findings further indicated that the same quality of lexical processing could be obtained from the foveal and parafoveal regions of the right and left visual fields, regardless of the character order, but not in the periphery of the right visual field. Moreover, the proportion of order reversals peaked at the central position and the shortest exposure time, but it declined with increasing eccentricity and time interval. We concluded that the character transposition of Chinese compound words was significantly sensitive in the periphery of the right visual field. Furthermore, the character order errors were mainly encoded in the foveal vision with a duration of 100 ms, which suggested that the order of the foveally presented Chinese characters was more likely to be reversed at the early stage of visual word processing. PMID:27847584

  17. Reduced sampling efficiency causes degraded Vernier hyperacuity with normal aging: Vernier acuity in position noise.

    PubMed

    Li, Roger W; Brown, Brian; Edwards, Marion H; Ngo, Charlie V; Chat, Sandy W; Levi, Dennis M

    2012-01-01

    Vernier acuity, a form of visual hyperacuity, is amongst the most precise forms of spatial vision. Under optimal conditions Vernier thresholds are much finer than the inter-photoreceptor distance. Achievement of such high precision is based substantially on cortical computations, most likely in the primary visual cortex. Using stimuli with added positional noise, we show that Vernier processing is reduced with advancing age across a wide range of noise levels. Using an ideal observer model, we are able to characterize the mechanisms underlying age-related loss, and show that the reduction in Vernier acuity can be mainly attributed to the reduction in efficiency of sampling, with no significant change in the level of internal position noise, or spatial distortion, in the visual system.

  18. The subtlety of simple eyes: the tuning of visual fields to perceptual challenges in birds

    PubMed Central

    Martin, Graham R.

    2014-01-01

    Birds show interspecific variation both in the size of the fields of individual eyes and in the ways that these fields are brought together to produce the total visual field. Variation is found in the dimensions of all main parameters: binocular region, cyclopean field and blind areas. There is a phylogenetic signal with respect to maximum width of the binocular field in that passerine species have significantly broader field widths than non-passerines; broadest fields are found among crows (Corvidae). Among non-passerines, visual fields show considerable variation within families and even within some genera. It is argued that (i) the main drivers of differences in visual fields are associated with perceptual challenges that arise through different modes of foraging, and (ii) the primary function of binocularity in birds lies in the control of bill position rather than in the control of locomotion. The informational function of binocular vision does not lie in binocularity per se (two eyes receiving slightly different information simultaneously about the same objects from which higher-order depth information is extracted), but in the contralateral projection of the visual field of each eye. Contralateral projection ensures that each eye receives information from a symmetrically expanding optic flow-field from which direction of travel and time to contact targets can be extracted, particularly with respect to the control of bill position. PMID:24395967

  19. Comprehensive visual field test & diagnosis system in support of astronaut health and performance

    NASA Astrophysics Data System (ADS)

    Fink, Wolfgang; Clark, Jonathan B.; Reisman, Garrett E.; Tarbell, Mark A.

    Long duration spaceflight, permanent human presence on the Moon, and future human missions to Mars will require autonomous medical care to address both expected and unexpected risks. An integrated non-invasive visual field test & diagnosis system is presented for the identification, characterization, and automated classification of visual field defects caused by the spaceflight environment. This system will support the onboard medical provider and astronauts on space missions with an innovative, non-invasive, accurate, sensitive, and fast visual field test. It includes a database for examination data, and a software package for automated visual field analysis and diagnosis. The system will be used to detect and diagnose conditions affecting the visual field, while in space and on Earth, permitting the timely application of therapeutic countermeasures before astronaut health or performance are impaired. State-of-the-art perimetry devices are bulky, thereby precluding application in a spaceflight setting. In contrast, the visual field test & diagnosis system requires only a touchscreen-equipped computer or touchpad device, which may already be in use for other purposes (i.e., no additional payload), and custom software. The system has application in routine astronaut assessment (Clinical Status Exam), pre-, in-, and post-flight monitoring, and astronaut selection. It is deployable in operational space environments, such as aboard the International Space Station or during future missions to or permanent presence on the Moon and Mars.

  20. A Historical Review of the Representation of the Visual Field in Primary Visual Cortex with Special Reference to the Neural Mechanisms Underlying Macular Sparing

    ERIC Educational Resources Information Center

    Leff, Alexander

    2004-01-01

    This article comprises a historical review of the literature pertaining to the representation of the visual field in human primary visual cortex. A brief survey of the anatomy of the visual system is followed by a critical evaluation of the key studies that have informed both the issue of the disproportionate representation of central vision…

  1. Development of Techniques for Visualization of Scalar and Vector Fields in the Immersive Environment

    NASA Technical Reports Server (NTRS)

    Bidasaria, Hari B.; Wilson, John W.; Nealy, John E.

    2005-01-01

    Visualization of scalar and vector fields in the immersive environment (CAVE - Cave Automated Virtual Environment) is important for its application to radiation shielding research at NASA Langley Research Center. A complete methodology and the underlying software for this purpose have been developed. The developed software has been put to use for the visualization of the earth s magnetic field, and in particular for the study of the South Atlantic Anomaly. The methodology has also been put to use for the visualization of geomagnetically trapped protons and electrons within Earth's magnetosphere.

  2. Seeing without the occipito-parietal cortex: Simultagnosia as a shrinkage of the attentional visual field.

    PubMed

    Michel, François; Henaff, Marie-Anne

    2004-01-01

    Following bi-parietal lesions patient AT showed a severe inability to relocate her attention within a visual field which perimetry proved to be near-normal. An experimental approach with tasks testing visuo-spatial attention demonstrated a shrinkage of A.T.'s attentional visual field. With her visual attention narrowed to a kind of functional tunnel vision, the patient exhibited simultanagnosia (Wolpert, 1924), a symptom previously described in 1909 by Balint under the label of Psychic paralysis of "Gaze". In striking contrast AT showed an efficient and effortless perception of complex natural scenes, which, according to recent work in normal subjects, necessitate few if any attentional resources.

  3. Visual Population Receptive Fields in People with Schizophrenia Have Reduced Inhibitory Surrounds.

    PubMed

    Anderson, Elaine J; Tibber, Marc S; Schwarzkopf, D Sam; Shergill, Sukhwinder S; Fernandez-Egea, Emilio; Rees, Geraint; Dakin, Steven C

    2017-02-08

    People with schizophrenia (SZ) experience abnormal visual perception on a range of visual tasks, which have been linked to abnormal synaptic transmission and an imbalance between cortical excitation and inhibition. However, differences in the underlying architecture of visual cortex neurons, which might explain these visual anomalies, have yet to be reported in vivo Here, we probed the neural basis of these deficits using fMRI and population receptive field (pRF) mapping to infer properties of visually responsive neurons in people with SZ. We employed a difference-of-Gaussian model to capture the center-surround configuration of the pRF, providing critical information about the spatial scale of the pRFs inhibitory surround. Our analysis reveals that SZ is associated with reduced pRF size in early retinotopic visual cortex, as well as a reduction in size and depth of the inhibitory surround in V1, V2, and V4. We consider how reduced inhibition might explain the diverse range of visual deficits reported in SZ.SIGNIFICANCE STATEMENT People with schizophrenia (SZ) experience abnormal perception on a range of visual tasks, which has been linked to abnormal synaptic transmission and an imbalance between cortical excitation/inhibition. However, associated differences in the functional architecture of visual cortex neurons have yet to be reported in vivo We used fMRI and population receptive field (pRF) mapping to demonstrate that the fine-grained functional architecture of visual cortex in people with SZ differs from unaffected controls. SZ is associated with reduced pRF size in early retinotopic visual cortex largely due to reduced inhibitory surrounds. An imbalance between cortical excitation and inhibition could drive such a change in the center-surround pRF configuration and ultimately explain the range of visual deficits experienced in SZ.

  4. Visual Population Receptive Fields in People with Schizophrenia Have Reduced Inhibitory Surrounds

    PubMed Central

    Tibber, Marc S.; Schwarzkopf, D. Sam; Shergill, Sukhwinder S.; Fernandez-Egea, Emilio

    2017-01-01

    People with schizophrenia (SZ) experience abnormal visual perception on a range of visual tasks, which have been linked to abnormal synaptic transmission and an imbalance between cortical excitation and inhibition. However, differences in the underlying architecture of visual cortex neurons, which might explain these visual anomalies, have yet to be reported in vivo. Here, we probed the neural basis of these deficits using fMRI and population receptive field (pRF) mapping to infer properties of visually responsive neurons in people with SZ. We employed a difference-of-Gaussian model to capture the center-surround configuration of the pRF, providing critical information about the spatial scale of the pRFs inhibitory surround. Our analysis reveals that SZ is associated with reduced pRF size in early retinotopic visual cortex, as well as a reduction in size and depth of the inhibitory surround in V1, V2, and V4. We consider how reduced inhibition might explain the diverse range of visual deficits reported in SZ. SIGNIFICANCE STATEMENT People with schizophrenia (SZ) experience abnormal perception on a range of visual tasks, which has been linked to abnormal synaptic transmission and an imbalance between cortical excitation/inhibition. However, associated differences in the functional architecture of visual cortex neurons have yet to be reported in vivo. We used fMRI and population receptive field (pRF) mapping to demonstrate that the fine-grained functional architecture of visual cortex in people with SZ differs from unaffected controls. SZ is associated with reduced pRF size in early retinotopic visual cortex largely due to reduced inhibitory surrounds. An imbalance between cortical excitation and inhibition could drive such a change in the center-surround pRF configuration and ultimately explain the range of visual deficits experienced in SZ. PMID:28025253

  5. The effects of fixation and restricted visual field on vection-induced motion sickness

    NASA Technical Reports Server (NTRS)

    Stern, Robert M.; Hu, Senqi; Anderson, Richard B.; Leibowitz, Herschel W.; Koch, Kenneth L.

    1990-01-01

    Approximately 60 percent of healthy human subjects experience motion sickness when exposed to a rotating optokinetic drum. Here, the effects of certain visual factors on susceptibility to motion sickness were determined. Vection data (illusory self-motion), horizontal eye movement recordings, subjective motion sickness report, and a measure of gastric myoelectric activity were obtained from 45 subjects, who were randomly divided into the following three groups: a control group that observed the entire visual field with no fixation, a group that fixated on a central target, and a third group that had a visual field restricted to 15 deg. The experimental session was divided into three 12-min periods: baseline, drum rotation, and recovery. The results showed that fixation greatly reduced nystagmus and slightly reduced vection. The restricted visual field slightly reduced nystagmus and greatly reduced vection. Both of these manipulations significantly reduced symptoms of motion sickness and abnormal gastric myoelectric activity.

  6. Indoor Spatial Updating with Reduced Visual Information

    PubMed Central

    Legge, Gordon E.; Gage, Rachel; Baek, Yihwa; Bochsler, Tiana M.

    2016-01-01

    Purpose Spatial updating refers to the ability to keep track of position and orientation while moving through an environment. People with impaired vision may be less accurate in spatial updating with adverse consequences for indoor navigation. In this study, we asked how artificial restrictions on visual acuity and field size affect spatial updating, and also judgments of the size of rooms. Methods Normally sighted young adults were tested with artificial restriction of acuity in Mild Blur (Snellen 20/135) and Severe Blur (Snellen 20/900) conditions, and a Narrow Field (8°) condition. The subjects estimated the dimensions of seven rectangular rooms with and without these visual restrictions. They were also guided along three-segment paths in the rooms. At the end of each path, they were asked to estimate the distance and direction to the starting location. In Experiment 1, the subjects walked along the path. In Experiment 2, they were pushed in a wheelchair to determine if reduced proprioceptive input would result in poorer spatial updating. Results With unrestricted vision, mean Weber fractions for room-size estimates were near 20%. Severe Blur but not Mild Blur yielded larger errors in room-size judgments. The Narrow Field was associated with increased error, but less than with Severe Blur. There was no effect of visual restriction on estimates of distance back to the starting location, and only Severe Blur yielded larger errors in the direction estimates. Contrary to expectation, the wheelchair subjects did not exhibit poorer updating performance than the walking subjects, nor did they show greater dependence on visual condition. Discussion If our results generalize to people with low vision, severe deficits in acuity or field will adversely affect the ability to judge the size of indoor spaces, but updating of position and orientation may be less affected by visual impairment. PMID:26943674

  7. Detection of Visual Field Loss in Pituitary Disease: Peripheral Kinetic Versus Central Static.

    PubMed

    Rowe, Fiona J; Cheyne, Christopher P; García-Fiñana, Marta; Noonan, Carmel P; Howard, Claire; Smith, Jayne; Adeoye, Joanne

    2015-06-01

    Visual field assessment is an important clinical evaluation for eye disease and neurological injury. We evaluated Octopus semi-automated kinetic peripheral perimetry (SKP) and Humphrey static automated central perimetry for detection of neurological visual field loss in patients with pituitary disease. We carried out a prospective cross-sectional diagnostic accuracy study comparing Humphrey central 30-2 SITA threshold programme with a screening protocol for SKP on Octopus perimetry. Humphrey 24-2 data were extracted from 30-2 results. Results were independently graded for presence/absence of field defect plus severity of defect. Fifty patients (100 eyes) were recruited (25 males and 25 females), with mean age of 52.4 years (SD = 15.7). Order of perimeter assessment (Humphrey/Octopus first) and order of eye tested (right/left first) were randomised. The 30-2 programme detected visual field loss in 85%, the 24-2 programme in 80%, and the Octopus combined kinetic/static strategy in 100% of eyes. Peripheral visual field loss was missed by central threshold assessment. Qualitative comparison of type of visual field defect demonstrated a match between Humphrey and Octopus results in 58%, with a match for severity of defect in 50%. Tests duration was 9.34 minutes (SD = 2.02) for Humphrey 30-2 versus 10.79 minutes (SD = 4.06) for Octopus perimetry. Octopus semi-automated kinetic perimetry was found to be superior to central static testing for detection of pituitary disease-related visual field loss. Where reliant on Humphrey central static perimetry, the 30-2 programme is recommended over the 24-2 programme. Where kinetic perimetry is available, this is preferable to central static programmes for increased detection of peripheral visual field loss.

  8. Visualizing near-field coupling in terahertz dolmens

    NASA Astrophysics Data System (ADS)

    Halpin, Alexei; Mennes, Christiaan; Bhattacharya, Arkabrata; Gómez Rivas, Jaime

    2017-03-01

    Strong interactions between resonant structures in the near-field occur at length scales shorter than the wavelength, and can be exploited for modifying the propagation of electromagnetic radiation. Dolmen-like structures, formed by a rod supporting a dipolar (bright) resonance and two orthogonal rods with a quadrupolar (dark) resonance at the same frequency, represent a geometry of significant interest for near-field electromagnetic coupling. These structures demonstrate electromagnetically induced transparency (EIT) through coupling between these resonances, concurrently providing a sharp spectral selectivity in transmission and large group velocity reduction. We use near-field terahertz scanning microscopy to map the electric fields in the vicinity of a metallic dolmen in both amplitude and phase. In this way, we directly measure the interaction between bright and dark modes in the time-domain, revealing the physics resulting in EIT. We experimentally demonstrate the hybridization of bright and dark modes accompanying the near-field coupling, as well as the excitation of the dark mode at the frequency of the far-field transparency.

  9. Perceptual scaling of visual and inertial cues: effects of field of view, image size, depth cues, and degree of freedom.

    PubMed

    Correia Grácio, B J; Bos, J E; van Paassen, M M; Mulder, M

    2014-02-01

    In the field of motion-based simulation, it was found that a visual amplitude equal to the inertial amplitude does not always provide the best perceived match between visual and inertial motion. This result is thought to be caused by the "quality" of the motion cues delivered by the simulator motion and visual systems. This paper studies how different visual characteristics, like field of view (FoV) and size and depth cues, influence the scaling between visual and inertial motion in a simulation environment. Subjects were exposed to simulator visuals with different fields of view and different visual scenes and were asked to vary the visual amplitude until it matched the perceived inertial amplitude. This was done for motion profiles in surge, sway, and yaw. Results showed that the subjective visual amplitude was significantly affected by the FoV, visual scene, and degree-of-freedom. When the FoV and visual scene were closer to what one expects in the real world, the scaling between the visual and inertial cues was closer to one. For yaw motion, the subjective visual amplitudes were approximately the same as the real inertial amplitudes, whereas for sway and especially surge, the subjective visual amplitudes were higher than the inertial amplitudes. This study demonstrated that visual characteristics affect the scaling between visual and inertial motion which leads to the hypothesis that this scaling may be a good metric to quantify the effect of different visual properties in motion-based simulation.

  10. The role of the right frontal eye field in overt visual attention deployment as assessed by free visual exploration.

    PubMed

    Cazzoli, Dario; Jung, Simon; Nyffeler, Thomas; Nef, Tobias; Wurtz, Pascal; Mosimann, Urs P; Müri, René M

    2015-07-01

    The frontal eye field (FEF) is known to be involved in saccade generation and visual attention control. Studies applying covert attentional orienting paradigms have shown that the right FEF is involved in attentional shifts to both the left and the right hemifield. In the current study, we aimed at examining the effects of inhibitory continuous theta burst (cTBS) transcranial magnetic stimulation over the right FEF on overt attentional orienting, as measured by a free visual exploration paradigm. In forty-two healthy subjects, free visual exploration of naturalistic pictures was tested in three conditions: (1) after cTBS over the right FEF; (2) after cTBS over a control site (vertex); and, (3) without any stimulation. The results showed that cTBS over the right FEF-but not cTBS over the vertex-triggered significant changes in the spatial distribution of the cumulative fixation duration. Compared to the group without stimulation and the group with cTBS over the vertex, cTBS over the right FEF decreased cumulative fixation duration in the left and in the right peripheral regions, and increased cumulative fixation duration in the central region. The present study supports the view that the right FEF is involved in the bilateral control of not only covert, but also of overt, peripheral visual attention.

  11. Peripheral refraction along the horizontal and vertical visual fields in myopia.

    PubMed

    Atchison, David A; Pritchard, Nicola; Schmid, Katrina L

    2006-04-01

    Peripheral refractions were measured to 35 degrees eccentricity using a free-space autorefractor in young adult emmetropic and myopic subjects. Refractions were measured along horizontal and vertical visual fields for 116 subjects and a 43 subject subset, respectively. Along the horizontal visual field, peripheral myopic shifts in spherical equivalent M of emmetropes changed to relative hypermetropic shifts in the myopes, there were temporal-nasal asymmetries of 90 degrees to 180 degrees astigmatism J(180) which decreased as myopia increased, and 45 degrees to 135 degrees astigmatism J(45) was linearly related to field angle. Along the vertical visual field, both peripheral myopic shifts in peripheral M and J(180) asymmetry were unaffected by magnitude of myopia, and J(45) changed at three times the rate as for the horizontal visual field. Myopia has more effect on peripheral refraction of adult eyes along the horizontal than along the vertical visual field. The peripheral variations in refraction match well what is known about the shapes of emmetropic and myopic eyes.

  12. Hawk Eyes I: Diurnal Raptors Differ in Visual Fields and Degree of Eye Movement

    PubMed Central

    O'Rourke, Colleen T.; Hall, Margaret I.; Pitlik, Todd; Fernández-Juricic, Esteban

    2010-01-01

    Background Different strategies to search and detect prey may place specific demands on sensory modalities. We studied visual field configuration, degree of eye movement, and orbit orientation in three diurnal raptors belonging to the Accipitridae and Falconidae families. Methodology/Principal Findings We used an ophthalmoscopic reflex technique and an integrated 3D digitizer system. We found inter-specific variation in visual field configuration and degree of eye movement, but not in orbit orientation. Red-tailed Hawks have relatively small binocular areas (∼33°) and wide blind areas (∼82°), but intermediate degree of eye movement (∼5°), which underscores the importance of lateral vision rather than binocular vision to scan for distant prey in open areas. Cooper's Hawks' have relatively wide binocular fields (∼36°), small blind areas (∼60°), and high degree of eye movement (∼8°), which may increase visual coverage and enhance prey detection in closed habitats. Additionally, we found that Cooper's Hawks can visually inspect the items held in the tip of the bill, which may facilitate food handling. American Kestrels have intermediate-sized binocular and lateral areas that may be used in prey detection at different distances through stereopsis and motion parallax; whereas the low degree eye movement (∼1°) may help stabilize the image when hovering above prey before an attack. Conclusions We conclude that: (a) there are between-species differences in visual field configuration in these diurnal raptors; (b) these differences are consistent with prey searching strategies and degree of visual obstruction in the environment (e.g., open and closed habitats); (c) variations in the degree of eye movement between species appear associated with foraging strategies; and (d) the size of the binocular and blind areas in hawks can vary substantially due to eye movements. Inter-specific variation in visual fields and eye movements can influence behavioral

  13. Receptive field focus of visual area V4 neurons determines responses to illusory surfaces

    PubMed Central

    Cox, Michele A.; Schmid, Michael C.; Peters, Andrew J.; Saunders, Richard C.; Leopold, David A.; Maier, Alexander

    2013-01-01

    Illusory figures demonstrate the visual system’s ability to infer surfaces under conditions of fragmented sensory input. To investigate the role of midlevel visual area V4 in visual surface completion, we used multielectrode arrays to measure spiking responses to two types of visual stimuli: Kanizsa patterns that induce the perception of an illusory surface and physically similar control stimuli that do not. Neurons in V4 exhibited stronger and sometimes rhythmic spiking responses for the illusion-promoting configurations compared with controls. Moreover, this elevated response depended on the precise alignment of the neuron’s peak visual field sensitivity (receptive field focus) with the illusory surface itself. Neurons whose receptive field focus was over adjacent inducing elements, less than 1.5° away, did not show response enhancement to the illusion. Neither receptive field sizes nor fixational eye movements could account for this effect, which was present in both single-unit signals and multiunit activity. These results suggest that the active perceptual completion of surfaces and shapes, which is a fundamental problem in natural visual experience, draws upon the selective enhancement of activity within a distinct subpopulation of neurons in cortical area V4. PMID:24085849

  14. Field visual perspective during autobiographical memory recall is less frequent among patients with schizophrenia.

    PubMed

    Potheegadoo, Jevita; Berna, Fabrice; Cuervo-Lombard, Christine; Danion, Jean-Marie

    2013-10-01

    There is growing interest in clinical research regarding the visual perspective adopted during memory retrieval, because it reflects individuals' self-attitude towards their memories of past personal events. Several autobiographical memory deficits, including low specificity of personal memories, have been identified in schizophrenia, but visual perspective during autobiographical memory retrieval has not yet been investigated in patients. The aim of this study was therefore to investigate the visual perspective with which patients visualize themselves when recalling autobiographical memories and to assess the specificity of their memories which is a major determinant of visual perspective. Thirty patients with schizophrenia and 30 matched controls recalled personal events from 4 life periods. After each recall, they were asked to report their visual perspective (Field or Observer) associated with the event. The specificity of their memories was assessed by independent raters. Our results showed that patients reported significantly fewer Field perspectives than comparison participants. Patients' memories, whether recalled with Field or Observer perspectives, were less specific and less detailed. Our results indicate that patients with schizophrenia adopt Field perspectives less frequently than comparison participants, and that this may contribute to a weakened sense of the individual of being an actor of his past events, and hence to a reduced sense of self. They suggest that this may be related to low specificity of memories and that all the important aspects involved in re-experiencing autobiographical events are impaired in patients with schizophrenia.

  15. Visual field differences in visual word recognition can emerge purely from perceptual learning: evidence from modeling Chinese character pronunciation.

    PubMed

    Hsiao, Janet Hui-Wen

    2011-11-01

    In Chinese orthography, a dominant character structure exists in which a semantic radical appears on the left and a phonetic radical on the right (SP characters); a minority opposite arrangement also exists (PS characters). As the number of phonetic radical types is much greater than semantic radical types, in SP characters the information is skewed to the right, whereas in PS characters it is skewed to the left. Through training a computational model for SP and PS character recognition that takes into account of the locations in which the characters appear in the visual field during learning, but does not assume any fundamental hemispheric processing difference, we show that visual field differences can emerge as a consequence of the fundamental structural differences in information between SP and PS characters, as opposed to the fundamental processing differences between the two hemispheres. This modeling result is also consistent with behavioral naming performance. This work provides strong evidence that perceptual learning, i.e., the information structure of word stimuli to which the readers have long been exposed, is one of the factors that accounts for hemispheric asymmetry effects in visual word recognition.

  16. Effects of Visual Speech on Early Auditory Evoked Fields - From the Viewpoint of Individual Variance.

    PubMed

    Yahata, Izumi; Kawase, Tetsuaki; Kanno, Akitake; Hidaka, Hiroshi; Sakamoto, Shuichi; Nakasato, Nobukazu; Kawashima, Ryuta; Katori, Yukio

    2017-01-01

    The effects of visual speech (the moving image of the speaker's face uttering speech sound) on early auditory evoked fields (AEFs) were examined using a helmet-shaped magnetoencephalography system in 12 healthy volunteers (9 males, mean age 35.5 years). AEFs (N100m) in response to the monosyllabic sound /be/ were recorded and analyzed under three different visual stimulus conditions, the moving image of the same speaker's face uttering /be/ (congruent visual stimuli) or uttering /ge/ (incongruent visual stimuli), and visual noise (still image processed from speaker's face using a strong Gaussian filter: control condition). On average, latency of N100m was significantly shortened in the bilateral hemispheres for both congruent and incongruent auditory/visual (A/V) stimuli, compared to the control A/V condition. However, the degree of N100m shortening was not significantly different between the congruent and incongruent A/V conditions, despite the significant differences in psychophysical responses between these two A/V conditions. Moreover, analysis of the magnitudes of these visual effects on AEFs in individuals showed that the lip-reading effects on AEFs tended to be well correlated between the two different audio-visual conditions (congruent vs. incongruent visual stimuli) in the bilateral hemispheres but were not significantly correlated between right and left hemisphere. On the other hand, no significant correlation was observed between the magnitudes of visual speech effects and psychophysical responses. These results may indicate that the auditory-visual interaction observed on the N100m is a fundamental process which does not depend on the congruency of the visual information.

  17. Effects of Visual Speech on Early Auditory Evoked Fields - From the Viewpoint of Individual Variance

    PubMed Central

    Yahata, Izumi; Kanno, Akitake; Hidaka, Hiroshi; Sakamoto, Shuichi; Nakasato, Nobukazu; Kawashima, Ryuta; Katori, Yukio

    2017-01-01

    The effects of visual speech (the moving image of the speaker’s face uttering speech sound) on early auditory evoked fields (AEFs) were examined using a helmet-shaped magnetoencephalography system in 12 healthy volunteers (9 males, mean age 35.5 years). AEFs (N100m) in response to the monosyllabic sound /be/ were recorded and analyzed under three different visual stimulus conditions, the moving image of the same speaker’s face uttering /be/ (congruent visual stimuli) or uttering /ge/ (incongruent visual stimuli), and visual noise (still image processed from speaker’s face using a strong Gaussian filter: control condition). On average, latency of N100m was significantly shortened in the bilateral hemispheres for both congruent and incongruent auditory/visual (A/V) stimuli, compared to the control A/V condition. However, the degree of N100m shortening was not significantly different between the congruent and incongruent A/V conditions, despite the significant differences in psychophysical responses between these two A/V conditions. Moreover, analysis of the magnitudes of these visual effects on AEFs in individuals showed that the lip-reading effects on AEFs tended to be well correlated between the two different audio-visual conditions (congruent vs. incongruent visual stimuli) in the bilateral hemispheres but were not significantly correlated between right and left hemisphere. On the other hand, no significant correlation was observed between the magnitudes of visual speech effects and psychophysical responses. These results may indicate that the auditory-visual interaction observed on the N100m is a fundamental process which does not depend on the congruency of the visual information. PMID:28141836

  18. Characteristics of Fixational Eye Movements in Amblyopia: Limitations on Fixation Stability and Acuity?

    PubMed Central

    Kumar, Girish; Li, Roger W.; Levi, Dennis M.

    2015-01-01

    Persons with amblyopia, especially those with strabismus, are known to exhibit abnormal fixational eye movements. In this paper, we compared six characteristics of fixational eye movements among normal control eyes (n=16), the non-amblyopic fellow eyes and the amblyopic eyes of anisometropic (n=14) and strabismic amblyopes (n=14). These characteristics include the frequency, magnitude of landing errors, amplitude and speed of microsaccades, and the amplitude and speed of slow drifts. Fixational eye movements were recorded using retinal imaging while observers monocularly fixated a 1° cross. Eye position data were recovered using a cross-correlation procedure. We found that in general, the characteristics of fixational eye movements are not significantly different between the fellow eyes of amblyopes and controls, and that the strabismic amblyopic eyes are always different from the other groups. Next, we determined the primary factors that limit fixation stability and visual acuity in amblyopic eyes by examining the relative importance of the different oculomotor characteristics, adding acuity (for fixation stability) or fixation stability (for acuity), and the type of amblyopia, as predictive factors in a multiple linear regression model. We show for the first time that the error magnitude of microsaccades, acuity, amplitude and frequency of microsaccades are primary factors limiting fixation stability; while the error magnitude, fixation stability, amplitude of drifts and amplitude of microsaccades are the primary factors limiting acuity. A mediation analysis showed that the effects of error magnitude and amplitude of microsaccades on acuity could be explained, at least in part, by their effects on fixation stability. PMID:25668775

  19. Artificial neural network analysis of noisy visual field data in glaucoma.

    PubMed

    Henson, D B; Spenceley, S E; Bull, D R

    1997-06-01

    This paper reports on the application of an artificial neural network to the clinical analysis of ophthalmological data. In particular a 2-dimensional Kohonen self-organising feature map (SOM) is used to analyse visual field data from glaucoma patients. Importantly, the paper addresses the problem of how the SOM can be utilised to accommodate the noise within the data. This is a particularly important problem within longitudinal assessment, where detecting significant change is the crux of the problem in clinical diagnosis. Data from 737 glaucomatous visual field records (Humphrey Visual Field Analyzer, program 24-2) are used to train a SOM with 25 nodes organised on a square grid. The SOM clusters the data organising the output map such that fields with early and advanced loss are at extreme positions, with a continuum of change in place and extent of loss represented by the intervening nodes. For each SOM node 100 variants, generated by a computer simulation modelling the variability that might be expected in a glaucomatous eye, are also classified by the network to establish the extent of noise upon classification. Field change is then measured with respect to classification of a subsequent field, outside the area defined by the original field and its variants. The significant contribution of this paper is that the spatial analysis of the field data, which is provided by the SOM, has been augmented with noise analysis enhancing the visual representation of longitudinal data and enabling quantification of significant class change.

  20. Visualizing Special Relativity: The Field of An Electric Dipole Moving at Relativistic Speed

    ERIC Educational Resources Information Center

    Smith, Glenn S.

    2011-01-01

    The electromagnetic field is determined for a time-varying electric dipole moving with a constant velocity that is parallel to its moment. Graphics are used to visualize this field in the rest frame of the dipole and in the laboratory frame when the dipole is moving at relativistic speed. Various phenomena from special relativity are clearly…

  1. Abnormal visual field maps in human cortex: a mini-review and a case report.

    PubMed

    Haak, Koen V; Langers, Dave R M; Renken, Remco; van Dijk, Pim; Borgstein, Johannes; Cornelissen, Frans W

    2014-07-01

    Human visual cortex contains maps of the visual field. Much research has been dedicated to answering whether and when these visual field maps change if critical components of the visual circuitry are damaged. Here, we first provide a focused mini-review of the functional magnetic resonance imaging (fMRI) studies that have evaluated the human cortical visual field maps in the face of retinal lesions, brain injury, and atypical retinocortical projections. We find that there is a fair body of research that has found abnormal fMRI activity, but also that this abnormal activity does not necessarily stem from cortical remapping. The abnormal fMRI activity can often be explained in terms of task effects and/or the uncovering of normally hidden system dynamics. We then present the case of a 16-year-old patient who lost the entire left cerebral hemisphere at age three for treatment of chronic focal encephalitis (Rasmussen syndrome) and intractable epilepsy. Using an fMRI retinotopic mapping procedure and population receptive field (pRF) modeling, we found that (1) despite the long period since the hemispherectomy, the retinotopic organization of early visual cortex remained unaffected by the removal of an entire cerebral hemisphere, and (2) the intact lateral occipital cortex contained an exceptionally large representation of the center of the visual field. The same method also indicates that the neuronal receptive fields in these lateral occipital brain regions are extraordinarily small. These features are clearly abnormal, but again they do not necessarily stem from cortical remapping. For example, the abnormal features can also be explained by the notion that the hemispherectomy took place during a critical period in the development of the lateral occipital cortex and therefore arrested its normal development. Thus, caution should be exercised when interpreting abnormal fMRI activity as a marker of cortical remapping; there are often other explanations.

  2. Visualization and minimization of disruptive bubble behavior in ultrasonic field.

    PubMed

    Kim, Wonjung; Park, Keunhwan; Oh, Jongkeun; Choi, Jaehyuck; Kim, Ho-Young

    2010-08-01

    Although ultrasonic technology has been successfully adopted for semiconductor cleaning, a recent trend of extreme miniaturization of patterns calls for a novel process that can remove contaminant particles without damaging nanoscale patterns. Unstable bubble oscillations have been hypothesized to cause such surface damages, and here we show direct visualization results that a high acoustic pressure induces bubble instability leading to pattern damages. As a remedy for the conventional ultrasonic cleaning scheme, we introduce a novel cleaning system using dual transducers, in which one transducer generates bubbles with a high acoustic pressure in an acoustically isolated sub-chamber and the other drives the oscillation of bubbles around the cleaning area at a low acoustic pressure. The system is shown to achieve a high cleaning efficiency for submicron-sized particles while significantly suppressing the disruptive bubble instability thereby reducing the detachment of firmly attached nanoparticles. Comparison of the adhesion force of the firmly attached nanoparticles and the yield strength of nanopatterns allows us to anticipate that this scheme is capable of reducing damages of nanopatterns on semiconductor wafers and photomasks.

  3. The magnitude of the central visual field could be detected by active middle-late processing of ERPs.

    PubMed

    Li, Maojuan; Liu, Xiaoqin; Li, Qianqian; Ji, Mengmeng; Huang, Wenwen; Zhang, Mingyang; Wang, Tao; Luo, Chengliang; Wang, Zufeng; Chen, Xiping; Tao, Luyang

    2016-11-01

    This study investigated the changes in event-related potential (ERP) waveforms under different central visual field conditions using a three-stimulus oddball paradigm. Circular checkerboards were presented in the center of a computer screen with a visual angle of 5°, 10°, 20°, or 30°, which were regarded as target stimuli. The ERP waveforms were analyzed separately for different stimulus conditions. Participants responded more slowly and had lower accuracy for the 30° visual field level than the other three visual field levels. The ERP results revealed that the amplitudes of target P2 gradually increased from the 5° to 20° visual field conditions, while they decreased abruptly in the 30° visual field condition. Regional effects showed that the amplitudes of target P2 were larger from the occipital electrodes than that from the temporal sites. Besides the negative-going deflection of target N2 and visual mismatch negativity (vMMN) components having an increasing tendency with expansion of the visual field, there was also a trend that the amplitudes of target P3 were decreased and the peak latencies were prolonged with increasing visual field ranges. In addition, the latencies of the difference P3 had a similar trend to the latencies of the target P3, and all the differences were more obvious at the 30° visual field level. The study demonstrated that middle-late components of ERPs can reflect changes in the visual field to some extent.

  4. Development of the lateral eye of American horseshoe crabs: visual field and dioptric array.

    PubMed

    Shih, M J; Weiner, W W; Wheatley, K K; DePoncheau, J L; Sydlik, M A; Chamberlain, S C

    1995-01-01

    We used a precision two-circle goniometer mounted to the stage of a compound microscope to determine the optical alignment and to measure the entrance aperture diameter of individual cuticular cones in the dioptric array of the lateral eye of juvenile horseshoe crabs in order to learn about the development of the visual field. Our results show that the extent of the visual field of juvenile horseshoe crabs with prosomal lengths about 20% of adult size (14-21 mm) is about 70% that of the visual field of adult horseshoe crabs (prosomal lengths: 100+ mm). The visual field of such juvenile animals covers between 77 and 85 deg vertically and 140 and 145 deg horizontally. Assuming that the dioptric array is uniform and square packed, the average interommatidial angle of the juvenile animals is between 5.6 and 6.0 deg as compared to 4.6 deg for an adult animal. The diameter of the entrance aperture of individual cuticular cones increases markedly with increasing animal size. In addition, we noted a statistically significant trend for entrance aperture diameters to increase from anterior to posterior within the eye for animals of all sizes. There may be a slight trend for entrance aperture diameters to increase from dorsal to ventral within the eye. Our results indicate that the extent of the visual field and the resolution of the lateral eye approach adult values in advance of animals' reaching sexual maturity.

  5. Visual field bias in hearing and deaf adults during judgments of facial expression and identity

    PubMed Central

    Letourneau, Susan M.; Mitchell, Teresa V.

    2013-01-01

    The dominance of the right hemisphere during face perception is associated with more accurate judgments of faces presented in the left rather than the right visual field (RVF). Previous research suggests that the left visual field (LVF) bias typically observed during face perception tasks is reduced in deaf adults who use sign language, for whom facial expressions convey important linguistic information. The current study examined whether visual field biases were altered in deaf adults whenever they viewed expressive faces, or only when attention was explicitly directed to expression. Twelve hearing adults and 12 deaf signers were trained to recognize a set of novel faces posing various emotional expressions. They then judged the familiarity or emotion of faces presented in the left or RVF, or both visual fields simultaneously. The same familiar and unfamiliar faces posing neutral and happy expressions were presented in the two tasks. Both groups were most accurate when faces were presented in both visual fields. Across tasks, the hearing group demonstrated a bias toward the LVF. In contrast, the deaf group showed a bias toward the LVF during identity judgments that shifted marginally toward the RVF during emotion judgments. Two secondary conditions tested whether these effects generalized to angry faces and famous faces and similar effects were observed. These results suggest that attention to facial expression, not merely the presence of emotional expression, reduces a typical LVF bias for face processing in deaf signers. PMID:23761774

  6. Response Classification Images in Vernier Acuity

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Beard, B. L.; Ellis, Stephen R. (Technical Monitor)

    1997-01-01

    Orientation selective and local sign mechanisms have been proposed as the basis for vernier acuity judgments. Linear image features contributing to discrimination can be determined for a two choice task by adding external noise to the images and then averaging the noises separately for the four types of stimulus/response trials. This method is applied to a vernier acuity task with different spatial separations to compare the predictions of the two theories. Three well-practiced observers were presented around 5000 trials of a vernier stimulus consisting of two dark horizontal lines (5 min by 0.3 min) within additive low-contrast white noise. Two spatial separations were tested, abutting and a 10 min horizontal separation. The task was to determine whether the target lines were aligned or vertically offset. The noises were averaged separately for the four stimulus/response trial types (e.g., stimulus = offset, response = aligned). The sum of the two 'not aligned' images was then subtracted from the sum of the 'aligned' images to obtain an overall image. Spatially smoothed images were quantized according to expected variability in the smoothed images to allow estimation of the statistical significance of image features. The response images from the 10 min separation condition are consistent with the local sign theory, having the appearance of two linear operators measuring vertical position with opposite sign. The images from the abutting stimulus have the same appearance with the two operators closer together. The image predicted by an oriented filter model is similar, but has its greatest weight in the abutting region, while the response images fall to nonsignificance there. The response correlation image method, previously demonstrated for letter discrimination, clarifies the features used in vernier acuity.

  7. Visual field loss morphology in high- and normal-tension glaucoma.

    PubMed

    Iester, Michele; De Feo, Fabio; Douglas, Gordon R

    2012-01-01

    Purpose. To determine whether the patterns of visual field damage between high-tension glaucoma (HTG) and normal-tension glaucoma (NTG) are equivalent. Methods. In this retrospective cross-sectional study, fifty-one NTG and 57 HTG patients were recruited. For each recruited patient only the left eye was chosen. Glaucomatous patients had abnormal visual fields and/or glaucomatous changes at the optic nerve head. They were classified as HTG or NTG on the basis of intraocular pressure (IOP) measurements. Patients' visual fields were analyzed by using Humphrey Field Analyzer (HFA), program 30-2, full threshold. The visual field sensitivity values and the pattern deviation map values of the 72 tested points were considered. Then a pointwise analysis and an area analysis, based on the Glaucoma Hemifield test criteria, were performed, and a comparison between the two subgroups was made by Student's t test. Results. Between NTG and HTG, no significant difference was found pointwise for almost all the visual field points, except for two locations. One was under the blind spot, and the other was in the inferior hemifield around the twenty-degree position. When area analysis was considered, three areas showed a significantly different sensitivity between HTG and NTG. Conclusions. These data suggested that there was no relevant difference in the pointwise analysis between NTG and HTG; however, when visual field areas were compared, no difference in paracentral areas was found between NTG and HTG, but superior nasal step and inferior and superior scotomata showed to be deeper in HTG than in NTG.

  8. [Does music influence visual perception in campimetric measurements of the visual field?].

    PubMed

    Gall, Carolin; Geier, Jens-Stefan; Sabel, Bernhard A; Kasten, Erich

    2009-01-01

    21 subjects (mean age 28,4 +/- 10,9, M +/- SD) without any damage of the visual system were examined with computer-based campimetric tests of near threshold stimulus detection whereby an artificial tunnel vision was induced. Campimetry was performed in four trials in randomized order using a within-subjects-design: 1. classical music, 2. Techno music, 3. music for relaxation and 4. no music. Results were slightly better in all music conditions. Performance was best when subjects were listening to Techno music. The average increase of correctly recognized stimuli and fixation controls amounted to 3 %. To check the stability of the effects 9 subjects were tested three times. A moderating influence of personality traits and habits of listening to music was tested but could not be found. We conclude that music has at least no negative influence on performance in the campimetric measurement. Reasons for the positive effects of music can be seen in a general increase of vigilance and a modulation of perceptual thresholds.

  9. Automatic mapping of visual cortex receptive fields: a fast and precise algorithm.

    PubMed

    Fiorani, Mario; Azzi, João C B; Soares, Juliana G M; Gattass, Ricardo

    2014-01-15

    An important issue for neurophysiological studies of the visual system is the definition of the region of the visual field that can modify a neuron's activity (i.e., the neuron's receptive field - RF). Usually a trade-off exists between precision and the time required to map a RF. Manual methods (qualitative) are fast but impose a variable degree of imprecision, while quantitative methods are more precise but usually require more time. We describe a rapid quantitative method for mapping visual RFs that is derived from computerized tomography and named back-projection. This method finds the intersection of responsive regions of the visual field based on spike density functions that are generated over time in response to long bars moving in different directions. An algorithm corrects the response profiles for latencies and allows for the conversion of the time domain into a 2D-space domain. The final product is an RF map that shows the distribution of the neuronal activity in visual-spatial coordinates. In addition to mapping the RF, this method also provides functional properties, such as latency, orientation and direction preference indexes. This method exhibits the following beneficial properties: (a) speed; (b) ease of implementation; (c) precise RF localization; (d) sensitivity (this method can map RFs based on few responses); (e) reliability (this method provides consistent information about RF shapes and sizes, which will allow for comparative studies); (f) comprehensiveness (this method can scan for RFs over an extensive area of the visual field); (g) informativeness (it provides functional quantitative data about the RF); and (h) usefulness (this method can map RFs in regions without direct retinal inputs, such as the cortical representations of the optic disc and of retinal lesions, which should allow for studies of functional connectivity, reorganization and neural plasticity). Furthermore, our method allows for precise mapping of RFs in a 30° by 30

  10. Structural and functional correlates of visual field asymmetry in the human brain by diffusion kurtosis MRI and functional MRI.

    PubMed

    O'Connell, Caitlin; Ho, Leon C; Murphy, Matthew C; Conner, Ian P; Wollstein, Gadi; Cham, Rakie; Chan, Kevin C

    2016-11-09

    Human visual performance has been observed to show superiority in localized regions of the visual field across many classes of stimuli. However, the underlying neural mechanisms remain unclear. This study aims to determine whether the visual information processing in the human brain is dependent on the location of stimuli in the visual field and the corresponding neuroarchitecture using blood-oxygenation-level-dependent functional MRI (fMRI) and diffusion kurtosis MRI, respectively, in 15 healthy individuals at 3 T. In fMRI, visual stimulation to the lower hemifield showed stronger brain responses and larger brain activation volumes than the upper hemifield, indicative of the differential sensitivity of the human brain across the visual field. In diffusion kurtosis MRI, the brain regions mapping to the lower visual field showed higher mean kurtosis, but not fractional anisotropy or mean diffusivity compared with the upper visual field. These results suggested the different distributions of microstructural organization across visual field brain representations. There was also a strong positive relationship between diffusion kurtosis and fMRI responses in the lower field brain representations. In summary, this study suggested the