Avetisov, S E; Rybakova, E G; Egorova, G B; Churkina, M N; Borodina, N V; Boev, V I
A study aimed at assessing the efficiency of presbyopia correction by bifocal contact lenses (BCL) was undertaken; it envisaged a comprehensive evaluation of subjective data provided by patients and measurements of a number of functional parameters of the visual quality for far and near, including mono- and binocular measurements with BCL of different constructions versus a maximal sphero-cylindrical spectacle correction for far and for near. Soft Acuvue Bifocal BCL as well as soft and rigid BCL manufactured in the optical-and-mechanical laboratory of the Research Institute for Eye Disease of the Russian Academy of Medical Sciences and Russian-made and imported bifocal soft and rigid lenses, respectively, were made use of in the study. A reduced contrast sensitivity (mainly in high frequencies) to 7% with Russian-made BCL, to 12.5% with Acuvue Bifocal BCL, to 8.7% with monofocal BCL and to 13.4% with the "mono-vision" system was registered. A decreased visual working ability to 13% with soft bifocal Russian-made BCL, to 17.3% with Acuvue Bifocal BCL and to 20.7% with the "mono-vision" system was detected versus the spectacle correction. A reduction by 25% was noted in the stereoscopic vision indices with the "mono-vision" system. A study of sensitivity to dazzling did not show any statistically reliable differences between various correction types.
Aller, Thomas A; Liu, Maria; Wildsoet, Christine F
Most studies have reported only minimal reductions in myopia progression with bifocal or progressive multifocal spectacles, although somewhat larger, although mostly still clinically insignificant, effects have been reported in children with nearpoint esophoria and/or accommodative dysfunctions. The CONTROL study was a 1-year, prospective, randomized, clinical trial of bifocal contact lenses for control of myopia in children with eso fixation disparities at near. Eighty-six myopic subjects, aged 8 to 18 years, were enrolled in the study after passing the screening examination. Of these, 79 completed lens assignment and 78 completed the study. The mean refractive error of these 79 subjects was -2.69 ± 1.40D (SD), and all had progressed by -0.50D or more since their last examination. All subjects also had eso fixation disparity at near. Subjects were randomly assigned to wear either Vistakon Acuvue 2 (single-vision soft contact lenses [SVSCLs]) or Vistakon Acuvue Bifocal (bifocal soft contact lenses [BFSCLs]). Bifocal adds were selected to neutralize the associated phoria. Treatment outcomes included cycloplegic autorefraction and axial length, assessed in terms of changes after 6 and 12 months of treatment from pretreatment baseline values. The BFSCLs significantly slowed myopia progression, with statistically significant differences between the treatment groups after 6 months. After 12 months of treatment, the SVSCL group had progressed by -0.79 ± 0.43D compared with -0.22 ± 0.34D for the BFSCL group (cycloplegic objective spherical equivalent, average of two eyes). Corresponding axial length changes were 0.24 ± 0.17 mm and 0.05 ± 0.14 mm, respectively. All of these differences were found to be statistically significant (unpaired t-tests, p < 0.001). The distance center bifocal contact lenses tested in this study achieved greater control over myopia progression and axial elongation (>70%) compared with most published results with multifocal spectacles. Further
Toshida, Hiroshi; Takahashi, Kozo; Sado, Kazushige; Kanai, Atsushi; Murakami, Akira
Since people who wear contact lenses (CL) often continue using CL even when they develop presbyopia, there are growing expectations for bifocal CL. To understand actual state and problems, history, types, and their characteristics are summarized in this review. Bifocal CL have a long history over 70 years. Recently, bifocal CL have achieved remarkable progress. However, there still is an impression that prescription of bifocal CL is not easy. It should also be remembered that bifocal CL have limits, including limited addition for near vision, as well as the effects of aging and eye diseases in the aged, such as dry eye, astigmatism, cataract, etc. Analysis of the long-term users of bifocal CL among our patients has revealed the disappearance of bifocal CL that achieved unsatisfactory vision and poor contrast compared with those provided by other types of CL. Changing the prescription up to 3 times for lenses of the same brand may be appropriate. Lenses that provide poor contrast sensitivity, suffer from glare, or give unsatisfactory vision have been weeded out. The repeated replacement of products due to the emergence of improved or new products will be guessed. PMID:19668441
Young, G; Grey, C P; Papas, E B
We measured the modulation transfer functions (MTF's) of five simultaneous vision bifocal contact lenses: center-near (Alges, University Optical Products), center-distance (BiSoft, CIBA Vision), diffractive rigid gas-permeable (Diffrax, Pilkington Barnes-Hind), diffractive hydrogel (Hydron Echelon, Allergan), and varifocal center-near (PS-45, G. Nissel). MTF's were measured at various aperture sizes (1 to 7 mm) and at a wavelength of 546 nm. The soft diffractive bifocal MTF's were measured at various wavelengths. The results tended to confirm previous theoretical calculations. The optical performance of the concentric designs was highly sensitive to variations in aperture size. The optical performance of both the rigid and soft diffractive lenses was largely (but not entirely) independent of aperture size. The varifocal lens was sensitive to changes in aperture size with respect to both optical quality and optimal focus.
Kirschfeld, K; Land, M F
Bifocal or multifocal intraocular lenses (IOLs) can be used to replace natural lenses during cataract surgery. These lenses are recommended by cataract surgeons as the replacement lenses of choice when patients wish to avoid wearing spectacles. There are, however, drawbacks to these lenses: one drawback is that the contrast in the images of bifocal and multifocal lenses is reduced as documented in the ophthalmology literature. It is claimed that acuity is similar in multifocal compared to monofocal lenses, however, we show that any loss in contrast inevitably reduces visual acuity. The other drawback is that the sharp in-focus image is always seen superimposed on one or more blurred out of focus images of the same object. In the ophthalmology literature it is assumed that the brain can suppress the undesired blurred image and only perceive the sharp image. We argue that there are no known mechanisms that would make this possible. This means that vision with bifocal or multifocal implanted lenses cannot be as good as vision with monofocal implants supplemented by spectacles, and this should be explained to patients before undergoing surgery for lens replacement. The results also hold for bifocal and multifocal contact lenses.
Leube, Alexander; Kovats, Imre; Wahl, Siegfried; Sickenberger, Wolfgang
Pilot study to investigate the feasibility of an axis-free correction approach of regular astigmatism using soft, bifocal contact lenses (CL). The investigation covers an optical simulation and a pilot study for the assessment of visual performance (over refraction OR, monocular visual acuity VA). The power of the two zones was adjusted according to the power of the astigmatic meridians, individually. Subjective performance was assessed in 30 participants with a mean horizontal cylindrical component of J0=- 0.65±1.29 D (cylinder from -0.75 to -4.00 DC). OR and VA were measured directly after fitting the CL, after one hour and after 5days (3FUP). Evaluating the modulation transfer function, CL increased the Strehl ratio by 10% and the transferred spatial frequency was improved from 6.6 cpd to 21.3 cpd. Analysis of Sturm's interval revealed a residual astigmatism of DAst=0.73 D. OR revealed a statistically significant reduction of spherical error between baseline and all follow up (ΔM=-2.14 D, p<0.001) and between the J0 from baseline to 3FUP (ΔJ0=-0.46 D, p=0.04). Wearing the CL for 5days did not result in a significant difference of VA (ΔVA3FUP=+0.01 logMAR, p=0.99). Axis-free correction of astigmatism using bifocal CL resulted in reasonable performance based on computer simulation. Participants showed no clinically reduced visual acuity or contrast sensitivity. Further clinical studies are needed to show if this approach provides a good alternative to conventional astigmatic correction. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.
Kim, Eon; Bakaraju, Ravi C.; Ehrmann, Klaus
Purpose To evaluate the repeatability of power profiles measured on NIMO TR1504 (Lambda-X, Belgium) and investigate the effects of lens decentration on the power profiles for single vision (SV), bifocal (BF) and multifocal (MF) contact lenses. Methods Accuracy of the sphere power was evaluated using single vision BK-7 calibration glass lenses of six minus and six plus powers. Three SV and four BF/MF contact lenses – three lenses each, were measured five times to calculate the coefficients of repeatability (COR) of the instrument. The COR was computed for each chord position, lens design, prescription power and operator. One lens from each type was measured with a deliberate decentration up to ±0.5 mm in 0.1 mm steps. Results For all lenses, the COR varied across different regions of the half-chord position. In general, SV lenses showed lower COR compared to the BF/MF group lenses. There were no noticeable trends of COR between prescription powers for SV and BF/MF lenses. The shape of the power profiles was not affected when lenses were deliberately decentered for all SV and PureVision MF lenses. However, for Acuvue BF lenses, the peak to trough amplitude of the power profiles flattened up to 1.00 D. Conclusion The COR across the half-chord of the optic zone diameter was mostly within clinical relevance except for the central 0.5 mm half-chord position. COR were dependent on the lens type, whereby BF/MF group produced higher COR than SV lenses. The effects of deliberate decentration on the shape of power profiles were pronounced for lenses where the profiles had sharp transitions of power. PMID:26590009
Gál, J; Horváth, G; Clarkson, E N; Haiman, O
In this work we report on a unique and ancient type of eye, in which the lower surface of the upper calcite lens units possessed an enigmatic central bulge making the dioptric apparatus similar to a bifocal lens. This eye belonged to the trilobite Dalmanitina socialis, which became extinct several hundred million years ago. As far as we know, image formation by bifocal lenses of this kind did/does not occur in any other ancient or modern animal visual system. We suggest that the function of these bifocal lenses may be to enable the trilobite to see simultaneously both very near (e.g. floating food particles and tiny preys) and far (e.g. sea floor, conspecifics, or approaching enemies) in the optical environment through the central and peripheral lens region, respectively. This was the only reasonable function we could find to explain the puzzling lens shape. We admit that it is not clear whether bifocality was necessary for the animal studied. We show that the misleading and accidental resemblance of an erroneous correcting lens surface (designed by René DesCartes in 1637 [DesCartes, R. (1637). Oeuvres de DesCartes. La Géometrie. Livre 2. pp. 134. J. Maire, Leyden] to the correcting interface in the compound Dalmanitina lens may be the reason why the earlier students of the Dalmanitina lens did not recognize its possible bifocality.
Brezna, Wolfgang; Lux, Kirsten; Dragostinoff, Nikolaus; Krutzler, Christian; Plank, Nicole; Tobisch, Rainer; Boltz, Agnes; Garhöfer, Gerhard; Told, Reinhard; Witkowska, Katarzyna; Schmetterer, Leopold
Purpose The visual performance of monofocal, bifocal, and trifocal intraocular lenses was evaluated by human individuals using a vision simulator device. This allowed investigation of the visual impression after cataract surgery, without the need actually to implant the lenses. Methods The randomized, double-masked, three-way cross-over study was conducted on 60 healthy male and female subjects aged between 18 and 35 years. Visual acuity (Early Treatment Diabetic Retinopathy Study; ETDRS) and contrast sensitivity tests (Pelli-Robson) under different lighting conditions (luminosities from 0.14–55 cd/m2, mesopic to photopic) were performed at different distances. Results Visual acuity tests showed no difference for corrected distance visual acuity data of bi- and trifocal lens prototypes (P = 0.851), but better results for the trifocal than for the bifocal lenses at distance corrected intermediate (P = 0.021) and distance corrected near visual acuity (P = 0.044). Contrast sensitivity showed no differences between bifocal and trifocal lenses at the distant (P = 0.984) and at the near position (P = 0.925), but better results for the trifocal lens at the intermediate position (P = 0.043). Visual acuity and contrast sensitivity showed a strong dependence on luminosity (P < 0.001). Conclusions At all investigated distances and all lighting conditions, the trifocal lens prototype often performed better, but never worse than the bifocal lens prototype. Translational Relevance The vision simulator can fill the gap between preclinical lens development and implantation studies by providing information of the perceived vision quality after cataract surgery without implantation. This can reduce implantation risks and promotes the development of new lens concepts due to the cost effective test procedure. PMID:27777828
... Consumer Devices Consumer Products Contact Lenses Types of Contact Lenses Share Tweet Linkedin Pin it More sharing ... Orthokeratology (Ortho-K) Decorative (Plano) Contact Lenses Soft Contact Lenses Soft contact lenses are made of soft, ...
Scleral and corneal rigid lenses represented 100 per cent of the contact lens market immediately prior to the invention of soft lenses in the mid-1960s. In the United Kingdom today, rigid lenses comprise 2 per cent of all new lens fits. Low rates of rigid lens fitting are also apparent in 27 other countries which have recently been surveyed. Thus, the 1998 prediction of the author that rigid lenses--also referred to as 'rigid gas permeable' (RGP) lenses or 'gas permeable' (GP) lenses--would be obsolete by the year 2010 has essentially turned out to be correct. In this obituary, the author offers 10 reasons for the demise of rigid lens fitting: initial rigid lens discomfort; intractable rigid lens-induced corneal and lid pathology; extensive soft lens advertising; superior soft lens fitting logistics; lack of rigid lens training opportunities; redundancy of the rigid lens 'problem solver' function; improved soft toric and bifocal/varifocal lenses; limited uptake of orthokeratology; lack of investment in rigid lenses; and the emergence of aberration control soft lenses. Rigid lenses are now being fitted by a minority of practitioners with specialist skills/training. Certainly, rigid lenses can no longer be considered as a mainstream form of contact lens correction. May their dear souls (bulk properties) rest in peace.
... Ophthalmologist Patient Stories Español Eye Health / Glasses & Contacts Contact Lenses Sections Contact Lenses for Vision Correction Contact ... to Know About Contact Lenses Colored Contact Lenses Contact Lenses for Vision Correction Leer en Español: Lentes ...
... Real Lifesaver Kids Talk About: Coaches Glasses and Contact Lenses KidsHealth > For Kids > Glasses and Contact Lenses Print A A A What's in this ... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ...
Rajagopalan, Aruna S; Bennett, Edward S; Lakshminarayanan, Vasudevan
The purpose of this study is to assess the visual performance of subjects wearing gas-permeable (GP) multifocal contact lenses, soft bifocal contact lenses, GP monovision lenses and spectacles. The study included 32 subjects between the ages of 42 and 65 years wearing GP monovision, the Acuvue Bifocal (Vistakon), the Essentials GP Multifocal (Blanchard), and progressive addition lenses (PAL; spectacles group). There were eight subjects in each of these groups who were already wearing these modalities. Binocular low (18%) and high (95%) contrast acuities were recorded using the Bailey-Lovie chart; binocular contrast sensitivity from 1.5 to 18 cycles per degree (cpd) measured with the Vistech VCTS 6500 system, and monocular glare sensitivity at three luminance settings (400, 100, and 12 foot lamberts) was measured using the brightness acuity tester (BAT). Binocular near visual task performance (a modified version of letter counting method used in previous presbyopic studies) was also assessed. For the contact lens-wearing groups, subjects wearing GP multifocals provided the best binocular high and low contrast acuity followed by soft bifocal wearers. There was relative parity between the binocular high and low contrast acuity with PAL and GP multifocal wearers. Monovision acuity, measured binocularly, was determined to be lower than the other three groups with this difference being most significant with high contrast acuity. Among contact lens-wearing groups, it was observed that GP multifocal lens wearers experienced the lowest amount of monocular disability glare followed by soft bifocal wearers and monovision wearers. Subjects wearing soft bifocal lenses and monovision demonstrated slightly reduced binocular contrast sensitivity at all spatial frequencies. In the contact lens groups, GP multifocal lens wearers had the highest binocular contrast sensitivity at all spatial frequencies, on parity with PAL wearers, except at the highest spatial frequency (18 cpd) at
NAVAL SUBMARINE MEDICAL RESEARCH LABORATORY SUBMARINE BASE, GROTON, CONN. REPORT NUMBER 1048 CONTACT LENSES ON SUBMARINES... CONTACT LENSES ON SUBMARINES by James F. Socks, CDR, MSC, USN NAVAL SUBMARINE MEDICAL RESEARCH LABORATORY REPORT NUMBER 1048 NAVAL MEDICAL RESEARCH...DRSCHLAB Approved for public release; distribution unlimited SUMMARY PAGE PROBLEM To determine the feasibility of wearing contact lenses aboard
Spinell, M R
The introduction and development of soft lenses and rigid gas-permeable lenses has ushered in a new era in fitting athletes with contact lenses. Many of the well-known disadvantages associated with polymethylmethacrylate (PMMA)-type lenses have been either eliminated or minimized. Fitting athletes with contact lenses must still be viewed with caution, however, since athletes' visual needs are usually much more demanding than those of the general public. An indiscriminate choice of lens design can adversely affect athletic performance and may even create a hazardous situation. An intelligent choice of lens can provide some subtle advantages that may improve athletic performance and provide the margin for victory.
Sutherland, R. L.; VanLeeuwen, Wm. N.
A series of 55 patients were fitted with a new type of hydrophilic soft contact lens. These were found more comfortable than hard contact lenses and they had a protective and pain-relieving action in cases of chronic corneal disease. Vision was not as good as with hard contact lenses and a greater potential danger of infection was found. They are preferred by many patients despite the noticeable thick edge and the difficulty of obtaining an identical replacement. PMID:5042887
Kern, Seymour P.
A bifocal electronic molecular lens is described which can be switched between two foci without any grossly visible change in displacement, geometry, temperature or chemical composition. The lens requires very little power to change focus (on the order of tens to hundreds of nanoamps) so that long-term remote operation is anticipated. The principle of operation is based upon electronic control of optical polarization through a birefringent lens. Switching of focus is accomplished by controlling the molecular alignment of a film of liquid crystal molecules and thereby selecting between two orthogonal optical polarizations (P1 and P2). Polarization P1 is associated with focal point S1 and P2 is associated with focal point S2 through the birefringent lens. A number of useful new products are made possible by this lens. Specifically discussed are an electronic intraocular lens and electronic eyeglasses, both of which can be powered independently.
Kingston, David W.
Summarizes results of a three-item questionnaire returned by 43 Michigan institutions expressing views on wearing contact lenses in chemical laboratories. Questions focused on eye protection, type of protection, and use of contact lenses. (SK)
Bilbao-Calabuig, Rafael; González-López, Felix; Amparo, Ferrer; Alvarez, Gemma; Patel, Sunni R; Llovet-Osuna, Fernando
To investigate the visual outcomes between mix-and-match bifocal intraocular lenses (IOLs) (ReSTOR +2.50 and +3.00 diopters [D]; Alcon Laboratories, Inc., Fort Worth, TX) versus bilateral implantation of a trifocal IOL (FineVision; PhysIOL, Liège, Belgium). Twenty-three patients (average age: 56.3 ± 6.9 years; range: 45 to 71 years) referred for lens phacoemulsification and IOL implantation were included in this study. Patients were randomly assigned to two groups. The FineVision group was bilaterally implanted with the FineVision trifocal IOL and the ReSTOR group was implanted with mix-and-match bifocal ReSTOR +2.50 and +3.00 D IOLs. A 3-month postoperative check was performed, and manifest refraction and logMAR uncorrected (UDVA) and corrected (CDVA) distance and near visual acuities were recorded. Monocular and binocular defocus curve testing was performed under photopic (85 cd/m(2)) conditions in 0.50-D defocus steps. Contrast sensitivity was measured monocularly and binocularly under mesopic conditions at spatial frequencies of 3, 6, 12, and 18 cycles per degree using the CSV-1000 contrast test (VectorVision, Greenville, OH). There were no reported differences in monocular distance visual acuity or refractive outcomes between groups (P > .05). Furthermore, there were no significant differences in contrast sensitivity between the three IOLs (P > .05). The FineVision group achieved better monocular and binocular near and intermediate visual acuities under defocus curve testing than the ReSTOR group (P < .05). Binocular implantation of the FineVision trifocal IOL provided a better range of visual acuities at near and intermediate distances than mix-and-match bifocal IOL implantation. [J Refract Surg. 2016;32(10):659-663.]. Copyright 2016, SLACK Incorporated.
Lenkova, G. A.
Computer simulation was performed for the measurement process of the parameters of MIOL-Akkord bifocal diffractive-refractive lenses in which the central area of the diffractive element is reduced and spherical aberrations of the eye are compensated. The spatial-energy characteristics of an ideal diffractive lens are preliminarily calculated using existing formulas. The simulation of the process of controlling the intraocular lens parameters has shown that the intensity distribution along the optical axis does not characterize the diffraction efficiency, which is the total (integrated) intensity in the beam cross section at the focus. It has been found that due to the mutual influence of diffraction orders, it is difficult to measure the absolute diffraction efficiency and it is better to evaluate only the relative efficiency.
Hirohara, Yoko; Mihashi, Toshifumi; Suzaki, Asaki; Kuroda, Teruhito; Kelly, Jennifer Elise; Maeda, Naoyuki; Fujikado, Takashi
To assess optical characteristics of bifocal soft contact lenses (BCLs) in use, we measured wavefront aberrations of human eyes, of eyes with a monofocal soft contact lens (MCL), and of eyes with a BCL. Modulation transfer functions (MTFs), Strehl ratios, and simulated images for far and near vision were produced with the measured aberrations. High order aberrations of subject 1 were significantly smaller than those of subject 2 (t-test, P = 0.001). We found that wearing the BCL improved the optical quality of an eye in subject 1, expressed as the horizontal MTF from 2 to 48 cycles per degree (cpd) for near vision and the Strehl ratio (t-test, P = 0.009 for Strehl ratio). But we did not find the same effect in subject 2. This difference may be due to the difference in the aberrations of the eyes of the two subjects.
numerous military laboratory-based and field tests of contact lenses are reviewed. Military contact lens research has a history of almost 50 years. In...research has a history of almost 50 years. In 1944, Jaeckle reported the results of his investigation of what were unspecified but are presumed to be... histories of more than 10 years. Bachman (1988, 1990) provided the results of a study of extended wear rigid and soft lenses fitted on 44 rotary-wing
Ben Yaish, Shai; Zlotnik, Alex; Raveh, Ido; Yehezkel, Oren; Belkin, Michael; Lahav, Karen; Zalevsky, Zeev
We present novel technology for extension in depth of focus of imaging lenses for use in ophthalmic lenses correcting myopia, hyperopia with regular/irregular astigmatism and presbyopia. This technology produces continuous focus without appreciable loss of energy. It is incorporated as a coating or engraving on the surface for spectacles, contact or intraocular lenses. It was fabricated and tested in simulations and in clinical trials. From the various testing this technology seems to provide a satisfactory single-lens solution. Obtained performance is apparently better than those of existing multi/bifocal lenses and it is modular enough to provide solution to various ophthalmic applications.
Amaya, L G; Speedwell, L; Taylor, D
We prospectively studied for three years the optical correction by contact lenses of 83 aphakic infants (141 eyes) who generally also had systemic and other ocular anomalies: 85% of the patients tolerated the lens wear for the whole study period. Complications occurred in 46 eyes and led to cessation of lens wear in two cases. Ten patients abandoned the lenses for other reasons. Thirty-four eyes needed subsequent intraocular surgery, mostly minor, and nine patients had strabismus surgery. Contact lenses are a versatile, safe, successful, and cost effective treatment for aphakia in infancy against which, before their widespread introduction for primary optical correction of infant aphakia, other methods of aphakic treatment need to be compared. PMID:2322512
Artigas, José M; Felipe, Adelina; Diaz-Llopis, Manuel; Garcia-Delpech, Salvador; Navea, Amparo
The imaging quality provided by a piggyback integrated by a monofocal intraocular lens (IOL) + a bifocal IOL of zero power and +3.75 diopters of addition is compared with the optics quality of a simple multifocal IOL of the same power and addition. The imaging quality was evaluated by determining the modulation transfer function (MTF), using an artificial eye simulating in vivo conditions of the anterior chamber, including an artificial cornea and a wet cell containing physiologic solution where the IOL was positioned. The MTFs of the bifocal piggyback for near and distance vision were measured, with pupil diameters of 3 and 5 mm, and compared with the MTFs of an equivalent power of ReSTOR and TECNIS multifocal IOLs measured under the same conditions. The MTFs for distance and near focus of the bifocal piggyback are similar to the MTFs of the ReSTOR and TECNIS multifocal IOLs with the two diameters of pupil. A more accurate comparison, values of average modulation, and Strehl ratio show a greater similitude with ReSTOR than with TECNIS. The bifocal piggyback system provides a similar imaging quality to that obtained with a ReSTOR multifocal IOL and, like the ReSTOR, provides better performance in distance vision than in near vision, whereas the TECNIS multifocal IOL provides the best performance.
Shen, Zeren; Lin, Yuchen; Zhu, Yanan; Liu, Xin; Yan, Jie; Yao, Ke
To assess the visual effects of trifocal intraocular lenses (IOLs) compared to bifocal IOLs in cataract surgery, a meta-analysis of prospective comparative clinical trials (including 4 randomized controlled trials and 4 cohorts) was conducted. The defocus curves showed a better distance-corrected intermediate visual acuity (VA) for the trifocal group (MD −0.07; 95% CI, −0.10 to −0.05; p < 0.00001), while the VA outcomes showed no significant difference in distance VA (MD −0.03; 95% CI, −0.06 to 0.01; p = 0.13 for uncorrected distance VA and MD −0.00; 95% CI, −0.01 to 0.01; p = 0.78 for distance-corrected distance VA), near VA (MD −0.01; 95% CI, −0.07 to 0.04; p = 0.68 for uncorrected near VA and MD −0.01; 95% CI, −0.06 to 0.04; p = 0.66 for distance-corrected near VA) or refraction between the two groups. Contrast sensitivity and subjective visual quality yielded less conclusive results. Overall, a patient may achieve better intermediate VA with a trifocal IOL than with a bifocal IOL without any adverse effect on distance or near VA. The findings on contrast sensitivity and subjective visual quality were heterogeneous, with no clear results favoring either option.
Del Águila-Carrasco, Antonio J; Monsálvez-Romín, Daniel; Papadatou, Eleni
To present a methodology for evaluating the optical quality of rotationally symmetrical contact lenses (CLs) from a single power profile. Simulated rotationally symmetrical power profiles corresponding to different CLs designs (monofocal, two-zone center-near bifocal, and four-zone center-distance bifocal) were used to calculate the wavefront error profile by means of numerical integration. Then, each lens wavefront error profile was spun around the center to obtain the lens wavefront error surface. From the surface, monochromatic optical transfer functions (OTF), simulated images and the visual Strehl ratio based on the OTF (VSOTF) were obtained for different distances and pupil sizes (3 and 5.5mm) after performing a through-focus. VSOTF variations, taking into account both vergence and pupil size, were presented for the three CLs designs. The monofocal design showed excellent optical quality only for far vision, whereas the bifocal designs exhibited good optical quality for far and near vision. Modulation transfer function (MTF) from each lens design, pupil size, and work distance agreed with the previous results. The methodology presented here allows for a rapid and thorough assessment of the optical quality of rotationally symmetrical CLs by means of optical quality metrics, with a special interest in simultaneous image contact lenses. This methodology may be useful for choosing the most suitable lens for each subject's visual demands. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
By application of contact lenses destined for a extended wearing, for preservation of a normal structure and metabolism of the cornea a considerable permeability of the contact lens for oxygen is necessary (Dk/L 75-80). The actually most popular in the world soft contact lenses have no such parameters. The application of rigid lenses produced from materials of high permeability for oxygen enables the extended wearing without substantial disturbances of the corneal metabolism. The paper presents a new generation of fluoro-silicone acrylates used for the production of contact lenses permeable for oxygen. Discussed are the problems connected with the adjusting of these lenses, their tolerance and influence on the corneal metabolism.
The prevalence of myopia has been steadily rising, with 28 per cent of the global population said to be affected in 2010 and to rise to affect nearly 50 per cent by 2050. Increasing levels of myopia increase the risk of vision impairment and in particular, high myopia is associated with the risk of serious and permanent visual disability due to associated sight-threatening complications. To stem the burden associated with higher levels of myopia, there are efforts to slow the progression of myopia, and several optical and pharmaceutical strategies have been found useful in slowing myopia to varying degrees. More recently, numerous multifocal soft contact lenses and extended depth of focus soft contact lenses (collectively referred to as myopia control contact lenses) were found effective in slowing myopia. As opposed to overnight orthokeratology, myopia control contact lenses are worn during the day and the hypotheses proposed to explain the efficacy of these lenses are generally based on the premise that the stimulus for eye growth is a defocused retinal image with hyperopic blur either centrally or peripherally. Although the individual power profiles of the lenses vary, the contact lens generally incorporates 'positive power' to reduce the hyperopic blur and/or impose myopic defocus or in the case of the extended depth of focus lens, has a power profile designed to optimise retinal image quality for points on or in front of the retina. The use of soft contact lenses as a platform for myopia control offers an exciting and effective avenue to manage myopia but there is a need for further research on issues such as the mechanism underlying control of myopia, improving efficacy with lenses, and understanding rebound on discontinuation. More significantly, although contact lenses are generally safe and improve quality of life in older children, one of the major challenges for improved uptake and acceptance of contact lenses centres on the perceived risk of
Koos, D; Bitea, M J
The authors present their experience in using soft contact lenses in 33 eyes with keratoconus (18 patients). Adaptation was possible only when the doctor-patient collaboration was good. Visual acuity (VA) of 0.4-1 was obtained in 85% cases versus 42.5% when glasses were used. In the period under observation no case of VA decrease was recorded. The subjects tolerated well the contact lenses. The specialty literature contains data indicating not only the optical role of the contact lenses but also their therapeutic, tectorial role.
Muntz, Alex; Subbaraman, Lakshman N.; Sorbara, Luigina; Jones, Lyndon
Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses. PMID:25575892
Bradley, Arthur; Nam, Jayoung; Xu, Renfeng; Harman, Leslie; Thibos, Larry
Purpose To examine the separate and combined influences of zone geometry, pupil size, diffraction, apodisation and spherical aberration on the optical performance of concentric zonal bifocals. Methods Zonal bifocal pupil functions representing eye + ophthalmic correction were defined by interleaving wavefronts from separate optical zones of the bifocal. A two-zone design (a central circular inner zone surrounded by an annular outer-zone which is bounded by the pupil) and a five-zone design (a central small circular zone surrounded by four concentric annuli) were configured with programmable zone geometry, wavefront phase and pupil transmission characteristics. Using computational methods, we examined the effects of diffraction, Stiles Crawford apodisation, pupil size and spherical aberration on optical transfer functions for different target distances. Results Apodisation alters the relative weighting of each zone, and thus the balance of near and distance optical quality. When spherical aberration is included, the effective distance correction, add power and image quality depend on zone-geometry and Stiles Crawford Effect apodisation. When the outer zone width is narrow, diffraction limits the available image contrast when focused, but as pupil dilates and outer zone width increases, aberrations will limit the best achievable image quality. With two-zone designs, balancing near and distance image quality is not achieved with equal area inner and outer zones. With significant levels of spherical aberration, multi-zone designs effectively become multifocals. Conclusion Wave optics and pupil varying ocular optics significantly affect the imaging capabilities of different optical zones of concentric bifocals. With two-zone bifocal designs, diffraction, pupil apodisation spherical aberration, and zone size influence both the effective add power and the pupil size required to balance near and distance image quality. Five-zone bifocal designs achieve a high degree of
Dorronsoro, Carlos; Radhakrishnan, Aiswaryah; de Gracia, Pablo; Sawides, Lucie; Marcos, Susana
Bifocal contact or intraocular lenses use the principle of simultaneous vision to correct for presbyopia. A modified two-channel simultaneous vision simulator provided with an amplitude transmission spatial light modulator was used to optically simulate 14 segmented bifocal patterns (+ 3 diopters addition) with different far/near pupillary distributions of equal energy. Five subjects with paralyzed accommodation evaluated image quality and subjective preference through the segmented bifocal corrections. There are strong and systematic perceptual differences across the patterns, subjects and observation distances: 48% of the conditions evaluated were significantly preferred or rejected. Optical simulations (in terms of through-focus Strehl ratio from Hartmann-Shack aberrometry) accurately predicted the pattern producing the highest perceived quality in 4 out of 5 patients, both for far and near vision. These perceptual differences found arise primarily from optical grounds, but have an important neural component. PMID:27895981
Read, Michael Leonard; Morgan, Philip Bruce; Kelly, Jeremiah Michael; Maldonado-Codina, Carole
Contact angle measurements are used to infer the clinical wetting characteristics of contact lenses. Such characterization has become more commonplace since the introduction of silicone hydrogel contact lens materials, which have been associated with reduced in vivo wetting due to the inclusion of siloxane-containing components. Using consistent methodology and a single investigator, advancing and receding contact angles were measured for 11 commercially available silicone hydrogel contact lens types with a dynamic captive bubble technique employing customized, fully automated image analysis. Advancing contact angles were found to range between 20° and 72° with the lenses falling into six statistically discrete groupings. Receding contact angles fell within a narrower range, between 17° and 22°, with the lenses segregated into three groups. The relationship between these laboratory measurements and the clinical performance of the lenses requires further investigation.
Walline, Jeffrey J; Gaume Giannoni, Amber; Sinnott, Loraine T; Chandler, Moriah A; Huang, Juan; Mutti, Donald O; Jones-Jordan, Lisa A; Berntsen, David A
The Bifocal Lenses In Nearsighted Kids (BLINK) study is the first soft multifocal contact lens myopia control study to compare add powers and measure peripheral refractive error in the vertical meridian, so it will provide important information about the potential mechanism of myopia control. The BLINK study is a National Eye Institute-sponsored, double-masked, randomized clinical trial to investigate the effects of soft multifocal contact lenses on myopia progression. This article describes the subjects' baseline characteristics and study methods. Subjects were 7 to 11 years old, had -0.75 to -5.00 spherical component and less than 1.00 diopter (D) astigmatism, and had 20/25 or better logMAR distance visual acuity with manifest refraction in each eye and with +2.50-D add soft bifocal contact lenses on both eyes. Children were randomly assigned to wear Biofinity single-vision, Biofinity Multifocal "D" with a +1.50-D add power, or Biofinity Multifocal "D" with a +2.50-D add power contact lenses. We examined 443 subjects at the baseline visits, and 294 (66.4%) subjects were enrolled. Of the enrolled subjects, 177 (60.2%) were female, and 200 (68%) were white. The mean (± SD) age was 10.3 ± 1.2 years, and 117 (39.8%) of the eligible subjects were younger than 10 years. The mean spherical equivalent refractive error, measured by cycloplegic autorefraction was -2.39 ± 1.00 D. The best-corrected binocular logMAR visual acuity with glasses was +0.01 ± 0.06 (20/21) at distance and -0.03 ± 0.08 (20/18) at near. The BLINK study subjects are similar to patients who would routinely be eligible for myopia control in practice, so the results will provide clinical information about soft bifocal contact lens myopia control as well as information about the mechanism of the treatment effect, if one occurs.
Wahl, Siegfried; Fornoff, Luise; Ochakovski, G Alex; Ohlendorf, Arne
The study investigated the effect of the design of multifocal contact lenses on the sensitivity to contrast and disability glare. Contrast sensitivity was measured in 16 young adults (mean age: 25.5±2.5years) at a distance of 2m under two conditions: no-glare and glare. Two designs (Center Near and Center Distance) of the Biofinity soft contact lens were used to simulate correction for presbyopes, while a correction with single vision trial lenses and contact lenses acted as controls. The design of the used multifocal contact lenses had a significant influence on the log area under the curve of the contrast sensitivity function (AUC-CSF). Compared to the spectacle lens correction, the AUC-CSF was significantly reduced, in case CS was measured with the Center Near design lens, under the no-glare (p<0.001) and the glare condition (p: p<0.001). In case of the Center Distance design contact lens, the AUC-CSF was significantly smaller in case CS was tested under glare (p=0.001). Disability glare (DG) was depending on the spatial frequency and the design of the multifocal lens, while the Center Distance design produced higher amounts of DG (p<0.001), compared to the other used corrections. The optical design of a multifocal contact lenses has a significant impact on the contrast sensitivity as well as the disability glare. In order to dispense the best correction in terms of contact lenses, the sensitivity to contrast under no-glare and glare conditions should be tested a medium spatial frequencies. Copyright © 2017. Published by Elsevier Ltd.
Shcherbakova, Oksana; Kostarev, Konstantin; Kondyurin, Alexey
Contact lenses become widely used for vision correction. The modern contact lenses made of polymer materials have to satisfy a number of requirements: biocompatibility and non-toxicity, low elastic module, high oxygen permeability, good wettability, mechanical strength and stable shape. To following all these requirements, special polymer compositions and polymerization techniques are in development. One of the unique technology is based on polymerization process in microgravity. The synthesis of the polymer structures proceeds in low concentration solution and Earth gravity has a great influence on the polymerization kinetics and final properties of the gel. The microgravity conditions give a possibility to get a regular polymer network with specific macromolecular structure. The experiments on board of space station and theoretical models of the polymerization processes are considered for contact lenses application.
Donshik, P; Weinstock, F J; Wechsler, S; Asbell, P; Atwood, J; Davis, H; Farkas, B; Farris, R L; Gruber, E; Hartstein, J
Nine ophthalmologists and nine optometrists conducted a premarket study of the Acuvue disposable contact lens manufactured by Vistakon, Inc. Of the 812 patients offered the lens, 733 accepted it and were enrolled in the study. These patients were fitted with the lens and followed for a period of 8 months. Over 98% of these patients had 20/25 or better vision on initial fitting; and subjective ratings of lens comfort were very good. Only 3.7% (27 of 733) discontinued wearing their lenses during the study period. Thirty-four patients (5.6%) experienced a problem while wearing their contact lenses.
The purpose of this research was to examined the interactions of P. aeruginosa with hydrogel contact lenses and other substrata, and characterize adherence to lenses under various physiological and physicochemical conditions. Isolates adhered to polystyrene, glass, and hydrogel lenses. With certain lens types, radiolabeled cells showed decreased adherence with increasing water content of the lenses, however, this correlation with not found for all lenses. Adherence to rigid gas permeable lenses was markedly greater than adherence to hydrogels. Best adherence occurred near pH 7 and at a sodium chloride concentration of 50 mM. Passive adhesion of heat-killed cells to hydrogels was lower than the adherence obtained of viable cells. Adherence to hydrogels was enhanced by mucin, lactoferrin, lysozyme, IgA, bovine serum albumin, and a mixture of these macromolecules. Adherence to coated and uncoated lenses was greater with a daily-wear hydrogel when compared with an extended-wear hydrogel of similar polymer composition. Greater adherence was attributed to a higher concentration of adsorbed macromolecules on the 45% water-content lens in comparison to the 55% water-content lens.
Muntz, Alex; Subbaraman, Lakshman N; Sorbara, Luigina; Jones, Lyndon
Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.
Patients wearing contact lenses may present with a red eye which may be either of long-standing or of sudden onset. Causes of this redness range from those of a relatively minor nature to infection of such severity that it threatens the patient's sight. This paper describes the specific aspects of the history to be obtained and the examination to be undertaken in these cases. A comprehensive review is provided of the various causes of red eye in the contact lens wearer.
van der Worp, Eef; Bornman, Dina; Ferreira, Daniela Lopes; Faria-Ribeiro, Miguel; Garcia-Porta, Nery; González-Meijome, José M
Scleral contact lenses (ScCL) have gained renewed interest during the last decade. Originally, they were primarily used for severely compromised eyes. Corneal ectasia and exposure conditions were the primary indications. However, the indication range of ScCL in contact lens practices seems to be expanding, and it now increasingly includes less severe and even non-compromised eyes, too. All lenses that partly or entirely rest on the sclera are included under the name ScCL in this paper; although the Scleral Lens Education Society recommends further classification. When a lens partly rests on the cornea (centrally or peripherally) and partly on the sclera, it is called a corneo-scleral lens. A lens that rests entirely on the sclera is classified as a scleral lens (up to 25 mm in diameter maximum). When there is full bearing on the sclera, further distinctions of the scleral lens group include mini-scleral and large-scleral lenses. This manuscript presents a review of the current applications of different ScCL (all types), their fitting methods, and their clinical outcomes including potential adverse events. Adverse events with these lenses are rare, but the clinician needs to be aware of them to avoid further damage in eyes that often are already compromised. The use of scleral lenses for non-pathological eyes is discussed in this paper.
... https://medlineplus.gov/news/fullstory_167037.html Soft Contact Lenses Safe for Kids and Teens, Review Finds ... 2017 WEDNESDAY, July 5, 2017 (HealthDay News) -- Soft contact lenses are as safe for children and teens ...
... Home For Consumers Consumer Updates 'Colored' and Decorative Contact Lenses: A Prescription Is A Must Share Tweet ... care.” back to top Where NOT to Buy Contact Lenses FDA is aware that many places illegally ...
Refojo, M F
The transport of oxygen and carbon dioxide through contact lenses is important for maintaining normal corneal physiology. Gas permeation through a lens depends on the solubility and the diffusivity of the lens for that gas. Gases pass through spaces between the flexible polymer segments in plastics and rubbers. Gases diffuse through the water of hydration in hydrogel lenses, and gas permeation increases exponentially with hydration. The driving force behind gas permeation is the difference in partial pressure of the gas across the lens. The amount of gas passing through a given lens, in unit time, doubles by halving the lens thickness. Carbon dioxide permeation through any lens is several times greater than is oxygen permeation through that lens. Thus, it suffices to know the oxygen permeability in order to predict the physiological performance of a lens. The oxygen permeability coefficients of representative hard, hydrogel, and silicone rubber lenses are tabulated for easy reference.
Hales, R H
Gas-permeable cellulose acetate butyrate (CAB) contact lenses may often be worn succesfully by aphakic and other patients who are unable to wear hard contact lenses. The comfort characteristics of the CAB lenses are betweeen those of hard and soft contact lenses. They are much more permeable to O2 and CO2 than soft lenses and thus are less apt to cause edema. They are more flexible and more wettable than hard lenses. This study presents 50 patients who, having had to discontinue wearing hard contact lenses because of discomfort, diffuse central corneal edema, or visual problems, were fitted with CAB contact lenses. Thirty of the fifty were able to wear the CAB lenses successfully.
The current literature review was intended to investigate whether the use of silicone hydrogel contact lenses has resulted in improved comfort compared with that of hydrogel contact lenses when both are used for daily wear. The conclusion reached is that silicone hydrogel contact lenses, which were initially developed to eliminate hypoxia during overnight wear, have not significantly improved comfort compared with the comfort achieved with hydrogel contact lenses when worn on a daily wear basis, even though a body of the published literature would suggest to the contrary. A careful review and consideration of the literature demonstrates that the relative comfort achieved with the two types of contact lenses is in fact highly dependent on the study methodology: Although refitting studies have concluded enhanced comfort with silicone hydrogels, the more robust study designs involving concurrent controls and masking were not able to show a difference, and some even concluded an inferior performance. Evidence-based review has however clearly demonstrated that comfort cannot be considered in isolation but is contact lens specific and depends on the material surface and bulk properties, lens design characteristics, and modality of use of the contact lens, and may also be significantly influenced by the replacement frequency and interaction with any lens care system that may be used.
Łabuz, Grzegorz; López-Gil, Norberto; van den Berg, Thomas J T P; Vargas-Martín, Fernando
Multifocal contact lenses have been growing in popularity as a modality to correct presbyopic eyes, although visual side effects such as disability glare have been reported. The objective of this study was to investigate the effect of multifocal contact lenses on disability glare by means of ocular straylight. A prospective randomized, comparative study was performed that included 16 subjects free of ocular pathology. Straylight was measured using a commercial straylight meter with the natural and dilated pupil. Participants were fitted with Proclear Multifocal (Distance/Near), ACUVUE Oasys for Presbyopia, and Air Optix Aqua Multifocal randomized to the left or right eye. Straylight measurements were repeated with the contact lens in situ after the pupil dilation. Results obtained with the dilated pupil without contact lens acted as a control. Diameter of the natural and dilated pupil was 2.87 ± 0.40 mm and 7.45 ± 0.86 mm, respectively (P < .001). After pupil dilation, straylight increased from 0.92 ± 0.13 log(s) to 1.04 ± 0.11 log(s) (P < .001). Of the four studied lenses, a significant difference was only found between Air Optix and the control group (P = .006). The latter showed also slightly increased light scatter. A difference in measured straylight was found between the studied multifocal lenses. The observed variability and the straylight-pupil size dependency should be taken into account to avoid elevated straylight in multifocal contact lens wearers. The reason for the observed differences in straylight must be the subject of future studies.
Young, G; Allsopp, G; Inglis, A; Watson, S
A short-term clinical study was undertaken to compare and evaluate the fit and clinical behaviour of eight disposable hydrogel contact lenses. Thirty subjects were enrolled in a 1-day, randomised, double-masked study. The lenses compared were Vistakon Acuvue (8.80), Vistakon Surevue (8.80), Aspect Frequency-55, Bausch & Lomb Medalist (SeeQuence 2), Ciba Focus (8.90), Lunelle Rythmic, Pilkington Barnes Hind Precision-Wand Wesley Jessen Freshlook. Three of the eight designs, Acuvue (86.7%), Precision-UV (86.7%) and Frequency-55 (90%), achieved relatively high levels of fitting success. The Rythmic lenses achieved the lowest success rate (70%) showing significantly greater downward decentration than the other designs. Although all the lenses were designed to fit a wide variety of eyes, they exhibited widely varying fitting characteristics. Some were more successful than others. The study shows that it is necessary for practitioners to utilise a range of lens designs in order to fit satisfactorily the typical contact lens population.
Timucin, Ozgur Bulent; Karadag, Mehmet Fatih; Mehmet, Baykara
Clinical trials and electrophysiologic studies demonstrated increased perceptual sensitivity in patients suffering from migraines. At least, one triggering factor is described in 85% of migraine patients. The aim of this report was to investigate the relationship between contact lens (CL) usage and migraine attacks in two cases. Two patients who were diagnosed with migraine reported that the frequency of migraine attacks increased after they switched to using CL with different base curves (BCs). These two patients, who began using CL with different BCs experienced discomfort and dryness of the eye. The ocular complaints were followed by migraine attacks. CL intolerance was also developed during migraine attack in one of the cases. The frequency of migraine attacks decreased and allodynia relieved significantly when flatter BCs were selected. CL related stimulus could have triggered the migraine attack. CLs should be well fitted in migraine patients with allodynia.
Timucin, Ozgur Bulent; Karadag, Mehmet Fatih; Mehmet, Baykara
Clinical trials and electrophysiologic studies demonstrated increased perceptual sensitivity in patients suffering from migraines. At least, one triggering factor is described in 85% of migraine patients. The aim of this report was to investigate the relationship between contact lens (CL) usage and migraine attacks in two cases. Two patients who were diagnosed with migraine reported that the frequency of migraine attacks increased after they switched to using CL with different base curves (BCs). These two patients, who began using CL with different BCs experienced discomfort and dryness of the eye. The ocular complaints were followed by migraine attacks. CL intolerance was also developed during migraine attack in one of the cases. The frequency of migraine attacks decreased and allodynia relieved significantly when flatter BCs were selected. CL related stimulus could have triggered the migraine attack. CLs should be well fitted in migraine patients with allodynia. PMID:27433037
Contact lenses as a means to deliver pharmaceuticals to the eye have seen a significant increase in research interest in the past few years. This review will detail the in vitro experiments which have investigated use of these contact lenses in the context of the desired pharmacological treatment goals in the management of infectious, inflammatory, allergic and glaucomatous diseases of the eye. The techniques researchers have employed to modify and tailor drug release rates from these materials, including the use of vitamin E diffusion barriers, modified ionicity, molecular imprinting and incorporation of drug reservoirs, will be discussed, as well as their impact on drug release kinetics. Finally, the demonstration of the feasibility of these materials when applied in vivo in animal models as well as in humans with and without disease will be presented and their results discussed relating to their implications for the future of the field. © 2017 Optometry Australia.
Gifford, Paul; Gifford, Kate Louise
The growing incidence of pediatric myopia worldwide has generated strong scientific interest in understanding factors leading to myopia development and progression. Although contact lenses (CLs) are prescribed primarily for refractive correction, there is burgeoning use of particular modalities for slowing progression of myopia following reported success in the literature. Standard soft and rigid CLs have been shown to have minimal or no effect for myopia control. Overall, orthokeratology and soft multifocal CLs have shown the most consistent performance for myopia control with the least side effects. However, their acceptance in both clinical and academic spheres is influenced by data limitations, required off-label usage, and a lack of clear understanding of their mechanisms for myopia control. Myopia development and progression seem to be multifactorial, with a complex interaction between genetics and environment influencing myopigenesis. The optical characteristics of the individual also play a role through variations in relative peripheral refraction, binocular vision function, and inherent higher-order aberrations that have been linked to different refractive states. Contact lenses provide the most viable opportunity to beneficially modify these factors through their close alignment with the eye and consistent wearing time. Contact lenses also have potential to provide a pharmacological delivery device and a possible feedback mechanism for modification of a visual environmental risk. An examination of current patents on myopia control provides a window to the future development of an ideal myopia-controlling CL, which would incorporate the broadest treatment of all currently understood myopigenic factors. This ideal lens must also satisfy safety and comfort aspects, along with overcoming practical issues around U.S. Food and Drug Administration approval, product supply, and availability to target populations. Translating the broad field of myopia research
While gravity has its advantages in keeping us balanced and grounded here on Earth, scientists often find that they are at a disadvantage when trying to conduct research under its powerful, pulling influence. In these instances, the scientists prefer performing their studies in the weightless atmosphere of microgravity, where gravity is greatly reduced and solids, liquids, and gases behave differently. In 1993, Paragon Vision Sciences, Inc., of Mesa, Arizona, participated in a research project with NASA's Langley Research Center to perfect a process for developing contact lenses. The project called for three experiments that would fly onboard the Space Shuttle over the course of three separate missions, from 1993 to 1996. By unleashing contact lens materials to the microgravity settings of space, scientists from NASA and Paragon hoped to better understand how polymers - large molecules that make up plastics - are formed.
Chapman, J.M.; Cheeks, L.; Green, K. )
We measured the uptake and washout of benzalkonium chloride, using radioactive tracer, by representative hard and soft contact lenses. Uptake by soft contact lenses after 7 days of continuous exposure is high (30 to 56 micrograms/mg of lens weight), with a low percentage of washout in 24 hours (between 0.2% and 1.5% of total uptake). High-water content lenses absorb greater quantities of benzalkonium than do low-water content lenses. Hard lenses take up a much smaller quantity of benzalkonium but release between 30% and 60% of total uptake during washout for 24 hours. Fluorosilicone-acrylate polymer lenses adsorb and release the most preservative, while polymethylmethacrylate lenses (Paragon Optical Inc, Mesa, Ariz) adsorb and release the least. The released benzalkonium from either soft or hard lenses is of a sufficient concentration to be at or above the upper limits of safety.
Li, Lim; Moody, Kurt; Tan, Donald T H; Yew, Khoo Chong; Ming, Por Yong; Long, Quah Boon
Previous studies in the United States have evaluated the benefits of soft contact lenses (CLs) in 8- to 12-year-old children and 13- to 17-year-old teens. This study was undertaken in Singapore and evaluated the safety, efficacy, and physiologic performance of daily disposable soft lenses in a population of children. In this open-label, bilateral, 3-month dispensing study, 59 children (8-11 years) were fit with etafilcon A spherical or toric daily disposable lenses (1-DAY ACUVUE or 1-DAY ACUVUE for ASTIGMATISM, Vistakon, Jacksonville, FL). All subjects were neophytes requiring visual correction in both eyes. The refractive inclusion criteria were plano to -9.00 diopter (D) with astigmatism of < or =2.00DC in both eyes, or hyperopia of +0.50 to +6.00D with astigmatism of 0.75D or less. The subjects underwent follow-up evaluations, which included a questionnaire for parents and subjects, at 1 week, 1 month, and 3 months. Of the 59 subjects enrolled, 53 (90%) completed the study successfully. Six subjects were discontinued because of lens handling difficulties (four), unacceptable lens fit (one), and an adverse event (one). Adverse events were reported in three subjects, including the discontinuation, and in each case were due to a chalazion. Overall vision quality, overall comfort, and end-of-day comfort were graded significantly better at each of the follow-up visits compared with baseline with spectacles (P< or =0.0001). Both handling and reported symptoms improved during the course of the study. The questionnaire results indicated that most of both parents and subjects preferred CLs to spectacles across a wide variety of aspects including vision, comfort, handling, and appearance. Significantly, more limbal and bulbar hyperemia was noted at follow-up visits than at baseline (P=0.0001); however, no instances of hyperemia greater than grade 2 were noted at any visit. Significantly, more corneal staining was also noted at the 1- and 3-month follow-up visits than at
Moschos, Marilita M.; Nitoda, Eirini; Georgoudis, Panagiotis; Balidis, Miltos; Karageorgiadis, Eleftherios; Kozeis, Nikos
Background: Keratoconus is a chronic, bilateral, usuallly asymmetrical, non-inflammatory, ectatic disorder, being characterized by progressive steepening, thinning and apical scarring of the cornea. Initially, the patient is asymptomatic, but the visual acuity gradually decreases, resulting in significant vision loss due to the development of irregular astigmatism, myopia, corneal thinning and scarring. The classic treatment of visual rehabilitation in keratoconus is based on spectacles and contact lenses (CLs). Objective: To summarize the types of CLs used in the treatment of keratoconus. This is literature review of several important published articles focusing on the visual rehabilitation in keratoconus with CLs. Method: Gas permeable (GP) CLs have been found to achieve better best corrected visual acuity than spectacles, eliminating 3rd-order coma root-mean-square (RMS) error, 3rd-order RMS, and higher-order RMS. However, they have implicated in reduction of corneal basal epithelial cell and anterior stromal keratocyte densities. Soft CLs seem to provide greater comfort and lower cost, but the low oxygen permeability (if the lens is not a silicone hydrogel), and the inability to mask moderate to severe irregular astigmatism are the main disadvantages of them. On the other hand, scleral CLs ensure stable platforms, which eliminate high-order aberrations and provide good centration and visual acuity. Their main disadvantages include the difficulties in application and removal of these lenses along with corneal flattening and swelling. Result: The modern hybrid CLs are indicated in cases of poor centration, poor stability or intolerance with GP lenses. Finally, piggyback CL systems effectively ameliorate visual acuity, but they have been related to corneal neovascularization and giant papillary conjunctivitis. Conclusion: CLs seem to rehabilitate visual performance, diminishing the power of the cylinder and the high-order aberrations. The final choice of CLs is
Moschos, Marilita M; Nitoda, Eirini; Georgoudis, Panagiotis; Balidis, Miltos; Karageorgiadis, Eleftherios; Kozeis, Nikos
Keratoconus is a chronic, bilateral, usuallly asymmetrical, non-inflammatory, ectatic disorder, being characterized by progressive steepening, thinning and apical scarring of the cornea. Initially, the patient is asymptomatic, but the visual acuity gradually decreases, resulting in significant vision loss due to the development of irregular astigmatism, myopia, corneal thinning and scarring. The classic treatment of visual rehabilitation in keratoconus is based on spectacles and contact lenses (CLs). To summarize the types of CLs used in the treatment of keratoconus. This is literature review of several important published articles focusing on the visual rehabilitation in keratoconus with CLs. Gas permeable (GP) CLs have been found to achieve better best corrected visual acuity than spectacles, eliminating 3rd-order coma root-mean-square (RMS) error, 3rd-order RMS, and higher-order RMS. However, they have implicated in reduction of corneal basal epithelial cell and anterior stromal keratocyte densities. Soft CLs seem to provide greater comfort and lower cost, but the low oxygen permeability (if the lens is not a silicone hydrogel), and the inability to mask moderate to severe irregular astigmatism are the main disadvantages of them. On the other hand, scleral CLs ensure stable platforms, which eliminate high-order aberrations and provide good centration and visual acuity. Their main disadvantages include the difficulties in application and removal of these lenses along with corneal flattening and swelling. The modern hybrid CLs are indicated in cases of poor centration, poor stability or intolerance with GP lenses. Finally, piggyback CL systems effectively ameliorate visual acuity, but they have been related to corneal neovascularization and giant papillary conjunctivitis. CLs seem to rehabilitate visual performance, diminishing the power of the cylinder and the high-order aberrations. The final choice of CLs is based on their special features, the subsequent
Purpose. To characterize the effects on refractive error development and eye growth in young chicks of two-zone concentric lens designs, which differentially affect the defocus experiences of central and peripheral retinal regions. Methods. Monocular defocusing lenses were worn for 5 days from 17 days of age. Four two-zone concentric lens designs (overall optical zone diameter, 10 mm) combining plano with either −5- or +5-D power were used. Lens designs were as follows: (1) +5 D center (+5C), (2) +5 D periphery (+5P), (3) −5 D center (−5C), and (4) −5 D peripheral (−5P), with plano in periphery for all C-designs and in the center for P-designs. Five central zone diameters (CZDs) were tested, ranging from 2.5 to 6.5 mm in 1-mm increments. Plano, +5- and −5-D single-vision (SV) lenses were used as the control. A minimum of six birds were included in each lens group. Results. For the two-zone lenses, the P designs (i.e., peripheral defocus) had greater effects than the C designs (i.e., central defocus) on both on-axis eye growth and refractions. All but the 6.5-mm CZD +5P lens induced larger changes than the +5SV lens. The +5C lenses with CZD less than 5.5 mm had little effect. The two-zone −5-D lenses had less effect than the −5SV lens, and only the 6.5-mm CZD lens of the −5C series had a significant effect. Conclusions. The results demonstrate that peripheral defocus can influence both peripheral and central refractive development. The inhibitory effect on axial eye growth of the +5P lenses opens the possibility that appropriately designed concentric lenses may control the progression of human myopia. PMID:20861487
Wippermann, F. C.; Schreiber, P.; Bräuer, A.; Craen, P.
Miniaturized camera systems are an integral part of today's mobile phones which recently possess auto focus functionality. Commercially available solutions without moving parts have been developed using the electrowetting technology. Here, the contact angle of a drop of a conductive or polar liquid placed on an insulating substrate can be influenced by an electric field. Besides the compensation of the axial image shift due to different object distances, mobile phones with zoom functionality are desired as a next evolutionary step. In classical mechanically compensated zoom lenses two independently driven actuators combined with precision guides are needed leading to a delicate, space consuming and expansive opto-mechanical setup. Liquid lens technology based on the electrowetting effect gives the opportunity to built adaptive lenses without moving parts thus simplifying the mechanical setup. However, with the recent commercially available liquid lens products a completely motionless and continuously adaptive zoom system with market relevant optical performance is not feasible. This is due to the limited change in optical power the liquid lenses can provide and the dispersion of the used materials. As an intermediate step towards a continuously adjustable and motionless zoom lens we propose a bifocal system sufficient for toggling between two effective focal lengths without any moving parts. The system has its mechanical counterpart in a bifocal zoom lens where only one lens group has to be moved. In a liquid lens bifocal zoom two groups of adaptable liquid lenses are required for adjusting the effective focal length and keeping the image location constant. In order to overcome the difficulties in achromatizing the lens we propose a sequential image acquisition algorithm. Here, the full color image is obtained from a sequence of monochrome images (red, green, blue) leading to a simplified optical setup.
Socks, J F
Contact lenses are worn by many individuals in military and civilian populations. Anecdotal reports have described contact lenses "sticking" and "freezing" to the eye during extreme cold conditions. However, some articles indicate the advantages of wearing contact lenses in cold environments. Military operations frequently taken place in cold regions; therefore, we need to known whether contact lenses can be worn safely in extreme cold. Rabbits were fitted with hard (polymethyl methacrylate) contact lenses and exposed to -28.9 degrees C temperatures with winds up to 78 mph (125 km/hr) for 3-hr periods. The wind-chill factor in these conditions exceeded -67.8 degrees C. No effects of the cold or contact lenses were seen in 85% of the eyes. A few of the eyes, both with contact lenses and without, showed mild superficial fluorescein staining of the cornea which cleared within a few ours after exposure. Histologic examination of the corneas revealed no abnormalities attributable to the cold. Inasmuch as this study showed that rabbits wearing contact lenses in extreme cold suffered no acute deleterious effects to the eyes, the research can be expanded to include human subjects.
Chang, Chun-Li; Wu, Wen-Hong; Hwang, Chi-Chun
In general, the manufacture of contact lenses is conventionally labor intensive, requiring manual handling and inspection of the cast lens during production. This paper is to build an AOI (automatic optical inspection) system, which include suitable light source, camera and image processing algorithms, for contact lenses defect inspection. The mainly defect type are missing lens and surface defect on the contact lenses. An illumination system with fixed focal lens and charge coupled device (CCD) is used to capture the images of contact lenses. After images are captured, an algorithm is employed to check if there are flaws showed on the images. Five kinds of defect can be detected by the designed algorithm. A prototype of the AOI system for contact lenses inspection is implemented. The experimental result shows that the proposed system is robust for in-line inspection.
Peng, Cheng-Chun; Burke, Michael T; Carbia, Blanca E; Plummer, Caryn; Chauhan, Anuj
We combine laboratory-based timolol release studies and in vivo pharmacodynamics studies in beagle dogs to evaluate the efficacy of glaucoma therapy through extended wear contact lenses. Commercial contact lenses cannot provide extended delivery of ophthalmic drugs and so the studies here focused on increasing the release duration of timolol from ACUVUE TruEye contact lenses by incorporating vitamin E diffusion barriers. The efficacy of timolol delivered via extended wear contact lenses was then compared to eye drops in beagle dogs that suffer from spontaneous glaucoma. The lenses were either replaced every 24h or continuously worn for 4 days, and the pharmacodynamics effect of changes in the intraocular pressure (IOP) of timolol from the ACUVUE TruEye contact lenses can be significantly increased by incorporation of vitamin E. The in vivo studies showed that IOP reduction from baseline by pure contact lens on daily basis was comparable with that by eye drops but with only 20% of drug dose, which suggested higher drug bioavailability for contact lenses. In addition, by inclusion of vitamin E into the lenses, the IOP was reduced significantly during the 4-day treatment with continuous wear of lens.
Schurmans, L R; Boets, E P; van Best, J A
AIMS--The corneal epithelial permeability during extended wear of disposable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeability value than the daily wear of soft contact lenses. A higher permeability makes the cornea more vulnerable for bacterial infections and thus could explain the higher incidence of bacterial keratitis found in extended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. METHOD--The corneal epithelial permeability was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. Thereafter the determination was repeated in each volunteer after extended wear of disposable contact lenses for 1 month. The permeability in 34 healthy non-contact lens wearing volunteers was determined as a control. The permeability value was calculated from the amount of fluorescein that passed into the cornea after application by means of an eyebath. RESULTS--The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not significantly different (Wilcoxon paired test p > 0.5). The mean permeability for the non-contact lens wearing controls was 0.042 nm/s. CONCLUSION--The results do not sustain the explanation that a difference in permeability value is the main cause of the increased incidence of keratitis during extended wear of disposable contact lenses in comparison with daily wear. PMID:7742282
Efron, Nathan; Morgan, Philip B
Despite the current market popularity of silicone hydrogel contact lenses, conventional hydrogel lenses still represent a significant proportion of the overall contact lens market. Data gathered from annual UK contact lens fitting surveys over the past 13 years indicate that 64% of hydrogel lenses prescribed during this period were of low/medium water content (< or =60% water). Whereas, in the past, practitioners would choose the water content of a hydrogel lens to meet specific clinical needs, this choice appears today to be largely governed by product availability.
Wang, Yingming; Qian, Xuefeng; Zhang, Xiaofeng; Xia, Wei; Zhong, Lei; Sun, Zhengtai; Xia, Jing
Contact lens safety is an important topic in clinical studies. Corneal infections usually occur because of the use of bacteria-carrying contact lenses. The current study investigated the impact of plasma surface modification on bacterial adherence to rigid contact lenses made of fluorosilicone acrylate materials. Boston XO and XO2 contact lenses were modified using plasma technology (XO-P and XO2-P groups). Untreated lenses were used as controls. Plasma-treated and control lenses were incubated in solutions containing Staphylococcus aureus or Pseudomonas aeruginosa. MTT colorimetry, colony-forming unit counting method, and scanning electron microscopy were used to measure bacterial adhesion. MTT colorimetry measurements showed that the optical density (OD) values of XO-P and XO2-P were significantly lower than those of XO and XO2, respectively, after incubation with S. aureus (P < 0.01). The OD value of XO-P was also much lower than that of XO after incubation with P. aeruginosa (P < 0.01). Colony-forming unit counting revealed that a significantly lower number of bacterial colonies attached to the XO-P versus XO lenses and to the XO2-P versus XO2 lenses incubated with S. aureus (P < 0.01). Fewer bacterial colonies attached to the XO-P versus XO lenses incubated with P. aeruginosa (P < 0.01). Further, scanning electron microscopy suggested different bacterial adhesion morphology on plasma-treated versus control lenses. Plasma surface modification can significantly decrease bacterial adhesion to fluorosilicone acrylate contact lenses. This study provides important evidence of a unique benefit of plasma technology in contact lens surface modification.
Harris, M G; Chin, R S; Lee, D S; Tam, M H; Dobkin, C E; Dobkins, C E
With increasing scientific evidence demonstrating the harmful effects of ultraviolet (UV) radiation on different ocular tissues, contact lens manufacturers are incorporating UV blocking monomers into their contact lenses. This study evaluated the transmittance spectra of Vistakon's disposable soft contact lenses (1 Day Acuvue, Acuvue, Surevue, and Vistavue). All except Vistavue contain a UV blocking agent. Transmittance for each lens was recorded from 200 to 400 nm on a Shimadzu UV 160U Dual Beam Recording Spectrophotometer. The results indicate that lenses which incorporate the UV blocking monomer significantly reduced the transmission of W radiation while untreated lenses did not. Our findings indicate that 1 Day Acuvue, Surevue, and Acuvue meet the American National Standards Institution (ANSI) Standard Z80.20 for Class 2 UV blockers: a maximum of 30% transmittance of UVA wavelengths and 5% transmittance of UVB wavelengths. In contrast, the Vistavue lens demonstrated negligible UV blockage. Our technique, in which contact lenses were placed directly in front of a measuring beam, was accurate and simpler than previously reported methods and may be useful in future studies. We found that UV blocking soft contact lenses can be a viable alternative for spectacles in protecting internal ocular structures from UV radiation. However, the external structures of the eye remain at risk and would continue to benefit from the use of UV blocking sunglasses or spectacle lenses.
Acanthamoeba is a microbe that is very common in tap water. It has two forms: the trophozoite and the cyst. These trophozoites and cysts can stick to the surface of your contact lenses and then infect your eye.
Dumbleton, Kathy; Woods, Craig A; Jones, Lyndon W; Fonn, Desmond
Discontinuation or "dropout" from contact lens (CL) wear continues to afflict the CL industry. This study was conducted to determine whether the advent of new CL materials and designs has impacted the dropout rate and the reasons for discontinuation. Current and lapsed CL wearers residing in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 to 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed. Four thousand two hundred seven eligible surveys were received (64% female; median age 27 years). Forty percent had lapsed from lens wear for at least 4 months; however, 62% of the lapsed wearers (LWs) resumed wear. There were no differences between LWs and nonlapsed wearers (NLWs) with respect to gender; however, LWs were older, started lens wear when older, and had not worn lenses for as long as NLWs (all P<0.001). More NLWs than LWs wore silicone hydrogel CLs (49% vs. 38%, P<0.001) and more LWs than NLWs wore daily disposable lenses and hydrogel CLs (24% vs. 19% and 22% vs. 18%, respectively, P≤0.001). Primary reasons for discontinuation were discomfort (24%), dryness (20%), red eyes (7%), and expense (7%). Compliance with lens replacement was no different between LWs and NLWs (48% vs. 45%). About 23% of those surveyed had discontinued CL wear permanently. The primary reasons for dropping out continue to be discomfort and dryness. Dropout rates were lower in silicone hydrogel wearers.
Hickson-Curran, S B; Nason, R J; Becherer, P D; Davis, R A; Pfeifer, J; Stiegemeier, M J
In response to increasing scientific evidence which indicates that ultraviolet radiation (UVR) is a potential threat to ocular health, Acuvue contact lenses (Vistakon, Johnson & Johnson Vision Products Inc., Jacksonville, Florida) have been developed which incorporate an ultraviolet (UV) blocker within the lens polymer. Data are presented for the first clinical evaluation of Acuvue lenses with UV blocking characteristics. A double-masked, multicenter, prospective clinical trial involving 94 subjects was conducted. The study followed a randomized, parallel group design and consisted of 3 months of daily wear with two-weekly lens replacement. Two thirds of the subjects (61) wore the test lenses (Acuvue with UV blocker) and the remaining subjects (33) wore conventional Acuvue lenses (without UV blocker). Biomicroscopic evaluations indicated that the performance of the test and control lenses was clinically similar. No clinically relevant differences between the test and control lenses were noted in the subjective assessments of vision, comfort, or handling. In addition, no differences were shown for surface deposition, lens durability, visual acuity, and subjective symptoms. The study findings indicate that the addition of a UV blocker to Acuvue contact lenses has been achieved without affecting daily wear clinical performance. Because there is increasing evidence to suggest that the ocular tissues may be damaged by UVR, it is prudent for eye care practitioners to prescribe contact lenses that offer the benefits of both regular replacement and UV protection.
Tieppo, A; White, C J; Paine, A C; Voyles, M L; McBride, M K; Byrne, M E
In this paper, we demonstrate the successful in vivo extended release of a small molecular weight therapeutic, ketotifen fumarate (MW=425), from molecularly imprinted, therapeutic contact lenses. This is the first time that a steady, effective concentration of drug is maintained in the tear film from a contact lens for an extended period of time for the entire duration of lens wear. Poly(HEMA-co-AA-co-AM-co-NVP-co-PEG200DMA) soft contact lenses were prepared (100±5 μm thickness, diameter 11.8 mm, power zero), and a constant tear film concentration of 170±30 μg/mL was measured for up to 26 hrs in a New Zealand white rabbit model. The results showed a dramatic increase in ketotifen mean residence time (MRT) and bioavailability compared to topical drop therapy and drug soaked lenses. The MRT for imprinted lenses was 12.47±3.99 hrs, ~4 and 50 fold greater than non-imprinted lenses and 0.035% eye drops (Zaditor®), respectively. Furthermore, AUC(0-26 hrs) was 9 and 94 fold greater for imprinted lenses than non-imprinted lenses and eye drops, respectively. The results indicate that molecular imprinting provides an exciting rational engineering strategy for sustained release. It is clear that imprinted lenses are very promising combination devices and are much more effective and efficient delivery devices than eye drops.
Stevenson, R W
Gas permeable (GP) lenses can flex on some eyes producing unpredictable clinical results. A method of measuring the flexibility of hard GP materials has been developed and shown to be repeatable. Materials in the form of flats rather than lenses were used. Differences between materials were found and in general a linear relation was shown to exist between maximum flexing and quoted oxygen permeability (r = 0.78, p less than 0.05). It is recommended that flexibility be measured and reported in the data presented with all new GP polymers. The term "hard" rather than "rigid" in describing GP lenses is suggested.
Attempts to dispel rumors concerning contact lenses and tries to supply prudent-use practices for allowing contact lenses in industry and laboratories. Discusses federal regulations that impact the use of contact lenses in industry, policy statements from medical organizations on use of contact lenses in industrial environments, and the…
Attempts to dispel rumors concerning contact lenses and tries to supply prudent-use practices for allowing contact lenses in industry and laboratories. Discusses federal regulations that impact the use of contact lenses in industry, policy statements from medical organizations on use of contact lenses in industrial environments, and the…
Malone, James P.; Townsend, R. Reid
Purpose. To determine whether class 1 UV-blocking contact lenses protect against UVB radiation–induced damage in a human lens epithelial cell line (HLE B-3) and postmortem human lenses using a proteomics approach. Methods. HLE B-3 cells were exposed to 6.4 mW/cm2 UVB radiation at 302 nm for 2 minutes (768 mJ/cm2) with or without covering by senofilcon A class 1 UV-blocking contact lenses or lotrafilcon A non–UV-blocking (lotrafilcon A has some UV-blocking ability, albeit minimal) contact lenses. Control cells were not exposed to UVB radiation. Four hours after treatment, cells were analyzed by two-dimensional difference gel electrophoresis and tandem mass spectrometry, and changes in protein abundance were quantified. F-actin and microtubule cytoskeletons were examined by fluorescence staining. In addition, human donor lenses were exposed to UVB radiation at 302 nm for 4 minutes (1536 mJ/cm2). Cortical and epithelial cell proteins were scraped from lens surfaces and subjected to the same protein analyses. Results. Senofilcon A lenses were beneficial for protecting HLE B-3 cells against UVB radiation–induced changes in caldesmon 1 isoform, lamin A/C transcript variant 1, DEAD (Asp-Glu-Ala-Asp) box polypeptide, β-actin, glyceraldehyde 3-phosphate dehydrogenase (G3PDH), annexin A2, triose phosphate isomerase, and ubiquitin B precursor. These contact lenses also prevented actin and microtubule cytoskeleton changes typically induced by UVB radiation. Conversely, non–UV-blocking contact lenses were not protective. UVB-irradiated human lenses showed marked reductions in αA-crystallin, αB-crystallin, aldehyde dehydrogenase 1, βS-crystallin, βB2-crystallin, and G3PDH, and UV-absorbing contact lenses significantly prevented these alterations. Conclusions. Senofilcon A class 1 UV-blocking contact lenses largely prevented UVB-induced changes in protein abundance in lens epithelial cells and in human lenses. PMID:21873653
Qin, Guoting; Zhu, Zhiling; Li, Siheng; McDermott, Alison M; Cai, Chengzhi
In this work, we developed a simple method to load drugs into commercially available contact lenses utilizing fluorous chemistry. We demonstrated this method using model compounds including fluorous-tagged fluorescein and antibiotic ciprofloxacin. We showed that fluorous interactions facilitated the loading of model molecules into fluorocarbon-containing contact lenses, and that the release profiles exhibited sustained release. Contact lenses loaded with fluorous-tagged ciprofloxacin exhibited antimicrobial activity against Pseudomonas aeruginosa in vitro, while no cytotoxicity towards human corneal epithelial cells was observed. To mimic the tear turnover, we designed a porcine eye infection model under flow conditions. Significantly, the modified lenses also exhibited antimicrobial efficacy against Pseudomonas aeruginosa in the ex vivo infection model. Overall, utilizing fluorous chemistry, we can construct a drug delivery system that exhibits high drug loading capacity, sustained drug release, and robust biological activity.
Ji, Yong Woo; Cho, Young Joo; Lee, Chul Hee; Hong, Soon Ho; Chung, Dong Yong; Kim, Eung Kweon; Lee, Hyung Keun
To compare physical characteristics of cosmetic contact lenses (Cos-CLs) and conventional contact lenses (Con-CLs) that might affect susceptibility to bacterial adhesion on the contact lens (CL) surface. Surface characteristics of Cos-CLs and Con-CLs made from the same material by the same manufacturer were measured by atomic force microscopy (AFM) and scanning electron microscopy. To determine the extent and rate of bacterial adhesion, Cos-CL and Con-CL were immersed in serum-free Roswell Park Memorial Institute media containing Staphylococcus aureus or Pseudomonas aeruginosa. Additionally, the rate of removal of adherent bacteria was evaluated using hand rubbing or immersion in multipurpose disinfecting solutions (MPDS). The mean surface roughness (root mean square and peak-to-valley value) measured by AFM was significantly higher for Cos-CL than for Con-CL. At each time point, significantly more S. aureus and P. aeruginosa adhered to Cos-CL than to Con-CL, which correlated with the surface roughness of CL. In Cos-CL, bacteria were mainly found on the tinted surface rather than on the noncolored or convex areas. Pseudomonas aeruginosa attached earlier than S. aureus to all types of CL. However, P. aeruginosa was more easily removed from the surface of CL than S. aureus by hand rubbing or MPDS soaking. Increased surface roughness is an important physical factor for bacterial adhesion in Cos-CL, which may explain why rates of bacterial keratitis rates are higher in Cos-CL users in CL physical characteristics.
Douglas, J P; Lowder, C Y; Lazorik, R; Meisler, D M
Giant papillary conjunctivitis (GPC) is an external ocular inflammatory disorder associated with contact lens wear. GPC seems to occur less frequently with hard than with soft contact lens wear. The management of soft contact lens related GPC has included refitting with hard lenses, specifically the newer rigid gas permeable (RGP) lenses. We retrospectively studied 14 RGP lens wearers in whom GPC developed. Three patients had had GPC associated with soft contact lens wear and had been fitted with RGP lenses in an effort to restore contact lens tolerance. The interval of time between the initiation of RGP lens wear and the onset of GPC was inversely related to the lens oxygen transmissibility (DK value). Ophthalmologists should be aware of the association between GPC and rigid gas permeable lens wear.
Maulvi, Furqan A; Soni, Tejal G; Shah, Dinesh O
Contact lenses for ophthalmic drug delivery have become very popular, due to their unique advantages like extended wear and more than 50% bioavailability. To achieve controlled and sustained drug delivery from contact lenses, researchers are working on various systems like polymeric nanoparticles, microemulsion, micelle, liposomes, use of vitamin E, etc. Numerous scientists are working on different areas of therapeutic contact lenses to treat ocular diseases by implementing techniques like soaking method, molecular imprinting, entrapment of drug-laden colloidal nanoparticles, drug plate/film, ion ligand polymeric systems, supercritical fluid technology, etc. Though sustained drug delivery was achieved using contact lens, the critical properties such as water content, tensile strength (mechanical properties), ion permeability, transparency and oxygen permeability were altered, which limit the commercialization of therapeutic contact lenses. Also issues like drug stability during processing/fabrication (drug integrity test), zero order release kinetics (prevent burst release), drug release during monomer extraction step after fabrication (to remove un-reacted monomers), protein adherence, drug release during storage in packaging solution, shelf life study, cost-benefit analysis, etc. are still to be addressed. This review provides an expert opinion on different methodology to develop therapeutic contact lenses with special remark of their advantages and limitations.
Urgacz, Agnieszka; Mrukwa, Ewa
Allergy is the fifth leading chronic condition in industrialized countries among all ages, and the third most common chronic disease among children under 18 years old. Many of allergic patients also have problems with vision and want to improve their quality of life by wearing contact lenses. They are most frequently young and active individuals, for whom contact lenses provide greater convenience and more satisfying vision correction than spectacles. However, application of high quality and immunologically neutral products do not protect from allergic side reactions. Nowadays, eye-related allergy and contact lens wear concern larger and larger populations worldwide. The purpose of this review is to summarize the studies on ocular complications associated with wearing contact lenses. The article presents indications for allergic patients especially on the care system and wear schedule. PMID:26161062
Key, James E
The concept of applying a lens to the cornea as a refractive appliance was first proposed in the early 19th century. By 1888, glass scleral lenses for the correction of optical defects and irregularities were manufactured and used. New materials, especially soft hydrogel lenses and rigid gas-permeable lenses, became available in the 20th century and allowed comfortable contact lenses to be made in any design needed. By the 21st century, the increasing use of silicone hydrogel lenses to address the oxygen need of the cornea has led to increased worldwide use. Of the 125 million global contact lens wearers, most are female and relatively young. Soft lenses are by far the dominant modality used, with silicone hydrogel lenses taking an increasing share of new fittings, particularly for overnight wear. Microbial keratitis, although relatively uncommon, remains the most serious potential complication for these lens wearers. Ongoing basic research, more powerful antimicrobial agents, and the development of safer lens materials are helping to alleviate this problem.
Jung, Ji Won; Han, Sun Hyup; Kim, Sang Ah; Kim, Eung Kweon; Seo, Kyoung Yul; Kim, Tae-Im
The purpose of this study was to investigate efficient methods to evaluate the pigment layer location of tinted soft contact lenses and to assess various lens products on the market using those methods. Two types of tinted soft contact lenses with known pigment location embedded or back surface were manufactured and examined. Light microscopy (LM), focused ion beam milling and scanning electron microscopy (FIB-SEM), and Fourier-domain optical coherence tomography (FD-OCT) were used to examine the pigment layer. Lens surface roughness was also measured using atomic force microscopy. In the second part of the experiment, pigment location and surface roughness of a clear lens (Lens A) and eight commercially-available tinted soft contact lenses (Lens B-I) were evaluated using FIB-SEM and FD-OCT. Pigment location could be reliably determined with FIB-SEM and FD-OCT. With LM, 40% of the lens sections were broken or deformed during slide preparation. The pigment particles in Lens B were buried below the front surface and there were no significant differences of roughness between the front and back surfaces. However, all tinted lenses with surface pigment had significant difference of roughness between front and back surfaces at the pigmented area. The FIB-SEM and FD-OCT could reliably locate the pigment layer of tinted soft contact lenses. In addition, lens surface roughness was influenced by pigment layer location. Copyright © 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Zhang, Jiyan; Wang, Liru; Ma, Zhenya
A focimeter is one of the basic ophthalmic instruments used in every optometric practice, and verification of the accuracy and calibration of the instrument are of the utmost importance. For many years the International Standardization for Organization requires that calibrations for all kinds of focimeters shall be accomplished by using test lenses described in ISO 9342:1996. These test lenses must be of high quality and of nominal back vertex power that is known with high accuracy. With the development of science and technology, ISO 9342 was revised in 2005. A new part ISO 9342-2 had been drafted for test lenses used to calibrate focimeters with contact lens measurement, and the original ISO 9342 was turned into the current ISO 9342-1, which could only be used to calibrate fociemters with spectacle lens measurement. As one of the standard drafters, the background for the newly published ISO 9342-2 is introduced in this study, and comparison between test lenses of ISO 9342-1 and ISO 9342-2 is made. Further, the influence of tolerance and uncertainty in design and production of standard test lenses of ISO 9342-2 is analyzed. The paraxial approximation is used to relate the lens parameters with back vertex power and to calculate the uncertainty budget. Moreover, one set of test lenses conforming to ISO 9342-2 is manufactured and experiments are done with it. Results show that test lenses described in ISO 9342-2 can correct the measurement errors of focimeters used for measuring contact lenses well, especially for spherical aberration, and the correction is more effective for spherical contact lenses with high back vertex power.
Compañ, V; Andrio, A; López-Alemany, A; Riande, E; Refojo, M F
Oxygen transport through two extended wear (day and night) hydrogel contact lenses that contain organosilicon moieties (balafilcon A and lotrafilcon A) was studied in the hydrate (hydrogel) and dry (xerogel) states. The water uptake increased the oxygen permeability [(Dk)app] and transmissibility [Dk/L(av)] coefficients of the dry materials by about 70%. The (Dk)app for the hydrated lenses was determined following the so-called stack procedure. The values obtained were 107 +/- 4 barrer for balafilcon A and 141 +/- 5 barrer for lotrafilcon A, about 5-10 times larger than those previously reported for conventional (without organosilicon moieties) extended wear hydrogels contact lenses. The Dk/L(av) for -3.00 diopter lenses (harmonic average thickness, L(av) = 75 +/- 2 microm for lotrafilcon, and 85 +/- 2 microm for balafilcon) was 123 +/- 6 barrer/cm for balafilcon A and 183 +/- 8 barrer/cm for lotralicon A. The minimum oxygen transmissibility 87 barrer/cm stipulated by Holden and Mertz to avoid corneal edema with extended wear contact can be easily achieved with lotrafilcon and balafilcon lenses of diverse dioptric powers if the central and peripheral thickness of the lenses are kept below the critical level of oxygen transmissibility.
Badugu, Ramachandram; Lakowicz, Joseph R; Geddes, Chris D
We have developed a range of disposable and colorless tear glucose sensing contact lenses, using off-the-shelf lenses embedded with new water soluble, highly fluorescent and glucose sensitive boronic acid containing fluorophores. The new lenses are readily able to track tear glucose levels and therefore blood glucose levels, which are ideally suited for potential use by diabetics. The fluorescence responses from the lenses can be monitored using simple excitation and emission detection devices. The novelty of our approach is two fold. Firstly, the notion of sensing extremely low glucose concentrations in tears, which track blood levels, by our contact lens approach, and secondly, the unique compatibility of our new glucose signaling probes with the internal mildly acidic contact lens environment. The new lenses are therefore ideal for the non-invasive and continuous monitoring of tear glucose, with about 15-min response time, and a measured shelf life in excess of 3 months. In this review article, we show that fluorescence based signaling using plastic disposable lenses, which have already been industrially optimized with regard to vision correction and oxygen/analyte permeability etc, may a notable alternative to invasive and random finger pricking, the most widely used glucose monitoring technology by diabetics.
Rio, David; Woog, Kelly; Legras, Richard
We investigated the impact of lens centration, wearer aberrations, pupil size and age on the optics of two bifocal contact lenses using image simulation. Fourteen conditions (i.e. two optical profiles with two and eight concentric zones; two conditions of centration: centred and 0.77 mm decentred; and three conditions of aberrations: 0, 0.15 and 0.35 μm RMS; three pupil sizes: 3, 4.5 and 6 mm) were tested on two populations (i.e. 20-40 and 40-60 years old) using a numerical simulation method. For each condition, images were calculated for proximities ranging from -4D to + 2D with steps of 0.25D. Subjects graded the quality of each simulated image (i.e. a target 'HEV' of 0.4 logMAR) on a continuous scale from 0 to 5. To limit the effect of the observer's own aberrations, subjects viewed the displayed images through a 3-mm pupil and their optimal correction. Both populations reported similar image quality (i.e. average absolute difference of 0.23) except for sharp and low contrast images, which obtained slightly higher grades with younger subjects, probably due to a better contrast sensitivity in this population. Typical decentration had no effect on bifocal contact lenses wearers' vision, as the ratio between areas dedicated to near and distance vision did not change. Aberrations (i.e. mainly 0.24 μm of spherical aberration on a 4.5-mm pupil) reduced the addition of the two radial zones bifocal optics and introduced a hyperopic shift (i.e. 0.50D) of the through-focus image quality for the eight radial zone bifocal lens. The combination of typical aberrations with typical decentration created the same effect as typical aberrations alone, meaning that aberration impact was stronger than decentration impact. The two radial zone bifocal lens was dependent on the pupil whereas the eight radial zone lens was not. When fitting new bifocal optics, the aberrations of the patients, as well as their pupil diameter, are the main subject dependent parameters influencing
Dunn, J P; Mondino, B J; Weissman, B A; Donzis, P B; Kikkawa, D O
Four patients developed corneal ulcers associated with the use of disposable extended-wear hydrogel contact lenses. Bacteria were recovered from corneal ulcers in three of the patients. Three patients discarded their contact lenses after ten or more days of extended wear; the corneal ulcers in these patients developed toward the end of the wearing cycle. The fourth patient removed her contact lenses every two days for cleaning and disinfection and discarded them for a new pair on a weekly basis. Improper lens hygiene was noted in only one patient. All corneal ulcers responded to antibiotic treatment. In three patients visual acuity returned to normal, but scarring of one patient's cornea resulted in a visual acuity of 20/60.
Zambelli, Alison M.; Brothers, Kimberly M.; Hunt, Kristin M.; Romanowski, Eric G.; Nau, Amy C.; Dhaliwal, Deepinder K.; Shanks, Robert M. Q.
Objectives To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses in vitro. Methods Using an in vitro model, the diffusion of three antimicrobials through SH contact lenses was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of four hours. The amount of each diffused antimicrobial was determined by comparing the experimental value to a standard curve. A biological assay was performed to validate the contact lens diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least 4 independent replicates. Results Our data show detectable moxifloxacin and PHMB diffusion through SH contact lenses at 30 minutes, while amphotericin B diffusion remained below the limit of detection within the 4 hour experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 minutes on bacterial lawns, whereas PHMB and amphotericin B failed to demonstrate killing on microbial lawns over the course of the 60 minute experiment. Conclusions In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through silicone hydrogel contact lenses. Further studies regarding the clinical benefit of using these agents along with bandage contact lens use for corneal pathology are warranted. PMID:25806673
Girolamo, Nick Di; Chui, Jeanie; Wakefield, Denis; Coroneo, Minas T
Background This study was initiated after observation of some intriguing epithelial growth properties of contact lenses used as a bandage for patients after pterygium surgery. Aim To determine the efficacy of culturing human ocular surface epithelial cells on therapeutic contact lenses in autologous serum with a view of using this system to transfer epithelial cells to patients with persistent corneal or limbal defects. Methods Excess graft tissue resected from patients undergoing pterygium surgery (n = 3) consisting of limbal epithelium was placed on siloxane–hydrogel contact lenses (lotrafilcon A and balafilcon A). Limbal explants were cultured in media with 10% autologous serum. Morphology, proliferative capacity and cytokeratin profile were determined by phase contrast, light and electron microscopy, and immunohistochemical analysis. Results Lotrafilcon A contact lenses sustained proliferation and migration from limbal tissue. Cells became confluent after 10–14 days and consisted of 2–3 layers with a corneal phenotype (CK3+/CK12+/CK19−) and a propensity to proliferate (p63+). Electron microscopy showed microvilli on the apical surface with adhesive projections, indicating that these cells were stable and likely to survive for a long term. Growth was not observed from limbal explants cultured on balafilcon A contact lenses. Conclusion A method for culturing human ocular surface epithelium on contact lenses that may facilitate expansion and transfer of autologous limbal epithelial cells while avoiding the risks associated with transplanting allogeneic tissue has been developed. This technique may be potentially useful for the treatment of patients with limbal stem cell deficiency. PMID:16987897
Singh, Kishan; Nair, Anroop B; Kumar, Ashok; Kumria, Rachna
The success of ocular delivery relies on the potential to enhance the drug bioavailability by controlled and extended release of drug on the eye surface. Several new approaches have been attempted to augment the competence and diminish the intrinsic side effects of existing ocular drug delivery systems. In this contest, progress has been made to develop drug-eluting contact lens using different techniques, which have the potential to control and sustain the delivery of drug. Further, the availability of novel polymers have facilitated and promoted the utility of contact lenses in ocular drug delivery. Several research groups have already explored the feasibility and potential of contact lens using conventional drugs for the treatment of periocular and intraocular diseases. Contact lenses formulated using modern technology exhibits high loading, controlled drug release, apposite thickness, water content, superior mechanical and optical properties as compared to commercial lenses. In general, this review discus various factors and approaches designed and explored for the successful delivery of ophthalmic drugs using contact lenses as drug delivery device PMID:24826007
Maldonado-Codina, Carole; Efron, Nathan
Standard methods of contact angle analysis include sessile drop, captive bubble and Wilhelmy plate techniques; however, these methodologies are not particularly well suited for assessing the wettability of the surfaces of formed hydrogel contact lenses. This paper describes two methodologies that are adaptations of previously described techniques. The maximum adherent force method is an adaptation of the dynamic Wilhelmy plate technique that allows the assessment of whole, finished contact lenses. The dynamic photographic method allows the simultaneous assessment of the front and back surfaces of strip samples for the assessment of advancing and receding contact angles. Lenses investigated were made from polyhydroxyethyl methacrylate, hydroxyethyl methacrylate/methacrylic acid and hydroxyethyl methacrylate/glycerol methacrylate. The lenses were manufactured by lathing, spin-casting or cast-moulding techniques. Overall, both techniques demonstrated few differences between the wettability of different lens materials and no differences between materials of the 'same' lens type but manufactured by different methods. These findings are consistent with the results of clinical studies, which have shown little difference between contact lens surface wettability in vivo, which may be due to the apparent natural surface wettability-enhancing properties of the pre-lens tear film.
Aswad, M.I.; John, T.; Barza, M.; Kenyon, K.; Baum, J. )
The authors studied the adherence of Pseudomonas aeruginosa and Staphylococcus aureus to extended wear soft contact lenses (EWSCLs) with and without focal deposits using both a radiolabeling technique and electron microscopy. P. aeruginosa showed significant adherence to contact lenses in vitro. In contrast, S. aureus failed to show significant adherence to contact lenses in vitro (i.e., the radioactive uptake was not significantly above background). The extent of adherence of Pseudomonas was proportional to the number of focal deposits on the lenses. Results of electron microscopic examination showed the bacteria to be adherent primarily to large focal deposits (greater than or equal to 150 microns). There was no pseudomonal adherence to the small focal deposits (less than or equal to 50 microns) and little adherence to the areas in between the focal deposits. The authors hypothesize that worn lenses, especially those with large focal deposits, serve as a vehicle for the transport of P. aeruginosa to the cornea. This hypothesis could be a partial explanation for the high incidence of keratitis caused by P. aeruginosa in EWSCL patients.
... contact lenses and related issues. 456.5 Section 456.5 Commercial Practices FEDERAL TRADE COMMISSION TRADE... contact lenses and related issues. Rules applicable to prescriptions for contact lenses and related issues may be found at 16 CFR part 315 (Contact Lens Rule)....
... contact lenses and related issues. 456.5 Section 456.5 Commercial Practices FEDERAL TRADE COMMISSION TRADE... contact lenses and related issues. Rules applicable to prescriptions for contact lenses and related issues may be found at 16 CFR part 315 (Contact Lens Rule)....
... contact lenses and related issues. 456.5 Section 456.5 Commercial Practices FEDERAL TRADE COMMISSION TRADE... contact lenses and related issues. Rules applicable to prescriptions for contact lenses and related issues may be found at 16 CFR part 315 (Contact Lens Rule)....
ben Yaish, Shai; Zlotnik, Alex; Limon, Ofer; Lahav Yacouel, Karen; Doron, Ravid; Zalevsky, Zeev
In this communication we present the first dispensing medical trial in which we successfully report on testing of novel extended depth of focus rigid gas permeable (RGP) contact lenses having reduced halo and distinct focal peaks for near and far distance vision.
Rigid Gas-Permeable contact lenses is a less risky option for improving the quality of vision in corneal ectasias such as keratoconus. They reshape the corneal surface (flattens the cornea) so that in most cases, with a proper lens, the patient can reach a visual acuity of 20/20.
Tavazzi, Silvia; Ferraro, Lorenzo; Cozza, Federica; Pastori, Valentina; Lecchi, Marzia; Farris, Stefano; Borghesi, Alessandro
Drug-loaded contact lenses are emerging as the preferred treatment method for several ocular diseases, and efforts are being directed to promote extended and controlled delivery. One strategy is based on delivery induced by environmental triggers. One of these triggers can be hydrogen peroxide, since many platforms based on drug-loaded nanoparticles were demonstrated to be hydrogen-peroxide responsive. This is particularly interesting when hydrogen peroxide is the result of a specific pathophysiological condition. Otherwise, an alternative route to induce drug delivery is here proposed, namely the mechano-synthesis. The present work represents the proof-of-concept of the mechanosynthesis of hydrogen peroxide in siloxane-hydrogel contact lenses as a consequence of the cleavage of siloxane bonds at the interface between the polymer and water in aqueous phase. Their spongy morphology makes contact lenses promising systems for mechanical-to-chemical energy conversion, since the amount of hydrogen peroxide is expected to scale with the interfacial area between the polymer and water. The eyelid pressure during wear is sufficient to induce the hydrogen peroxide synthesis with concentrations which are biocompatible and suitable to trigger the drug release through hydrogen-peroxide-responsive platforms. For possible delivery on demand, the integration of piezoelectric polymers in the siloxane-hydrogel contact lenses could be designed, whose mechanical deformation could be induced by an applied wireless-controlled voltage.
WITH CONTACT Early Studies With PMMA Lenses Military contact lens research has a history of almost 50 Since the beginning of military aviation, vision...wearing histories of more than permeable lenses when they were worn by subjects exposed 10 years. to high +Gz. Their results showed that the spherical...available concerning Flynnr 3m"’ published reviews of the medical histories of 55 possible predisposing conditions, and the data may not be aviators
Selan, Laura; Palma, Stefano; Scoarughi, Gian Luca; Papa, Rosanna; Veeh, Richard; Di Clemente, Daniele; Artini, Marco
To compare silicone-hydrogel, poly(2-hydroxyethyl methacrylate) (pHEMA), and phosphorylcholine-coated (PC-C) contact lenses in terms of their susceptibility to biofilm formation by Staphylococcus epidermidis and Pseudomonas aeruginosa. Laboratory investigation. Biofilm formation on colonized test lenses was evaluated with confocal microscopy and in vitro antibiotic susceptibility assays. The results of the latter assays were compared with those performed on planktonic cultures of the same organism. For both microorganisms, sessile colonies on silicone-hydrogel and pHEMA lenses displayed lower antibiotic susceptibility than their planktonic counterparts. In contrast, the susceptibility of cultures growing on PC-C lenses was comparable with that for planktonic cultures. In particular, minimum inhibitory concentration for Tazocin (piperacillin plus tazobactam; Wyeth Pharmaceuticals, Aprilia, Italy; S. epidermidis) and gentamicin (P. aeruginosa) was identical, either in the presence of PC-C support or in planktonic cultures (Tazocin, = 0.2 mug/ml; gentamicin, 0.4 mug/ml). Minimum inhibitory concentration for imipenem (P. aeruginosa) was two-fold higher for PC-C lenses (0.4 mug/ml) with respect to planktonic cultures (0.2 mug/ml). Confocal microscopy of lenses colonized for 24 hours with P. aeruginosa green fluorescent protein-expressing cells revealed a sessile colonization on silicone-hydrogel lens and a few isolated bacterial cells scattered widely over the surface of the PC-C lens. An increase in antibiotic susceptibility of bacterial cultures was associated with diminished bacterial adhesion. Our results indicate that PC-C lenses seem to be more resistant than silicone-hydrogel and pHEMA lenses to bacterial adhesion and colonization. This feature may facilitate their disinfection.
Pérez-Prados, Roque; Piñero, David P; Pérez-Cambrodí, Rafael J; Madrid-Costa, David
Soft multifocal simultaneous image contact lenses have boomed in recent years due to the growing number of presbyopic patients demanding visual solutions, allowing them to maintain their current standard of living. The concept of 'simultaneous image' is based on blur interpretation and/or blur tolerance of superimposed multiple images on the retina formed by various powers of a contact lens. This is the basis for a specific type of multifocal contact lens developed for the compensation of presbyopia. Manufacturers have released a great variety of soft simultaneous image lens designs to meet different patient needs but their fitting is still unsatisfactory in some cases. Some presbyopes discontinue wearing contact lenses due to some limitations in visual quality and comfort that can be overcome with an appropriate contact lens selection based on a comprehensive pre-fitting evaluation. This paper aims to review the different types of soft multifocal contact lenses that are currently available for presbyopic correction and to define the steps and factors crucial for their fitting, such as pupil, aberrations, accommodation and centring. A discussion about useful tools to achieve a customised fitting leading to a successful outcome, such as the defocus curve, power profile and questionnaires, is performed.
Rao, B. L. J.
A bifocal dual reflector antenna is similar to and has better scan capability than classical cassegrain reflector antenna. The method used in determining the reflector surfaces is a modification of a design method for the dielectric bifocal lens. The three dimensional dual reflector is obtained by first designing an exact (in geometrical optics sense) two-point corrected two dimensional reflector and then rotating it around its axis of symmetry. A point by point technique is used in computing the reflector surfaces. Computed radiation characteristics of the dual reflector are compared with those of a cassegrain reflector. The results confirm that the bifocal antenna has superior performance.
Pitt, William G; Zhao, Yibei; Jack, Daniel R; Perez, Krystian X; Jones, Peter W; Marelli, Ryan; Nelson, Jared L; Pruitt, John D
Characterization of phospholipid release from an experimental reusable wear silicone hydrogel contact lens was performed to assess the possible use of these lenses for phospholipid delivery to increase eye comfort to patients who prefer reusable wear lenses. Contact lenses were loaded with 200 μg of radio-labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. To simulate 30 days of diurnal use with overnight cleaning, these lenses were eluted for 16 h at 35 °C into artificial tear fluid (ATF), and then eluted at room temperature (~22 °C) for 8 h in one of three commercial contact lens cleaning systems. This was repeated for 30 days. The elution of DMPC into ATF was greater on the first day, followed by a fairly constant amount of elution each day thereafter. The type of cleaning system had a statistically significant effect on the elution rate during daily exposure to ATF. The rate of elution into cleaning solutions did not show any enhanced elution on the first day; there was a fairly constant elution rate. Again, the type of cleaning system significantly influenced the elution rate into the nightly cleaner.
Ozkurt, Yelda; Rodop, Ozlen; Oral, Yeşim; Cömez, Arzu; Kandemir, Baran; Doğan, Omer Kamil
To investigate the effectiveness of silicone hydrogel soft contact lenses for therapeutic applications. The study included 37 patients who had bullous keratopathy (n=12), recurrent corneal erosion (n=9), filamentous keratitis (n=3), corneal melting after corneal surgery (n=4), lamellar lacerations (n=4), or chemical trauma (n=5) and were fitted with silicone hydrogel soft contact lenses between May 2000 and August 2003 in First Eye Clinic of Kartal Training and Research Hospital. Changes in corneal signs by slitlamp evaluation, judgment of pain relief, additional complications, and success of therapeutic lens treatment were reported. Appropriate medical therapy was given as required. A total of 83.78% of the patients had complete healing, and 8.1% of the patients showed at least partial improvement. Visual acuity improved in 56% of patients, and pain relief was achieved in 91.16% of the patients. No additional complications were reported in relation to the lenses. The use of high-Dk lotrafilcon A soft contact lenses for therapeutic purposes is safe, effective, and practical.
Mathews, Judith R.; And Others
Four young children were taught contact lens wear using a shaping procedure, which involved praise and tangibles for compliance and time-outs or restraint for noncompliance. At followup, levels of compliance were high for three children, while a subject with Down's syndrome showed low compliance with need for physical restraint throughout.…
Comparison of visual outcomes and subjective visual quality after bilateral implantation of a diffractive trifocal intraocular lens and blended implantation of apodized diffractive bifocal intraocular lenses
Gundersen, Kjell Gunnar; Potvin, Rick
Purpose To compare the visual acuity (VA) and quality of vision between bilateral implantation of a trifocal intraocular lens (IOL) and blended bifocal IOLs with an intermediate add in the dominant eye and a near add in the nondominant eye. Patients and methods Patients with either trifocal or blended bifocal IOLs implanted were recruited after surgery. Subjects returned for a single diagnostic visit between 3 and 24 months after surgery. VA was tested at various distances, including low-contrast acuity and acuity at their preferred reading distance. A binocular defocus curve was obtained, and subjective visual function and quality of vision were evaluated. Results Twenty-five trifocal subjects and 30 blended bifocal subjects were enrolled. There were no significant differences in low-contrast acuity, preferred reading distance, or acuity at that reading distance. Binocular vision at 4 m, 60 cm, and 40 cm was not statistically significantly different. The trifocal provided statistically significantly better visual acuity (P<0.05) at vergences from −0.5 to −1.5 D (from 2 m to 67 cm viewing distance, P<0.05). There was no statistically significant difference in the near vision subscale scores of the 39-question National Eye Institute Visual Function Questionnaire or the overall scores of the Quality of Vision questionnaire, though significantly more trifocal subjects reported that the observed visual disturbances were “bothersome” (P<0.05). Conclusion Both lens modalities provided subjects with excellent binocular near and distance vision, with similar low rates of visual disturbances and good reported functional vision. The trifocal IOL provided significantly better intermediate VA in the viewing distance range of 2 m to 67 cm, corresponding to viewing things such as a car dashboard or grocery shelf. VA was similar between groups at viewing distances from 60 to 40 cm, corresponding to computer or reading distance. PMID:27274184
Harris, M.G.; Rechberger, J.; Grant, T.; Holden, B.A. )
We evaluated the effectiveness of an in-office microwave disinfection procedure which allowed for the disinfection of up to 40 soft contact lenses at one time. Ciba AOSept cases filled with sterile unpreserved saline were contaminated with one of six FDA test challenge microorganisms at a concentration of approximately 10(3) colony forming units per milliliter (CFU/ml). Twenty cases were placed on the rotating plate of a standard 2450 MHz 650 W microwave oven in a 10-cm diameter circle. The cases were exposed to high intensity microwave irradiation for periods of 0 to 15 min. None of the 6 microorganisms evaluated survived 2 min or longer of microwave exposure. Our findings indicated that microwave irradiation can be a convenient, rapid, and effective method of disinfecting a number of soft contact lenses at one time and thus adaptable as an in-office soft contact lens disinfection procedure.
Plainis, Sotiris; Atchison, David A; Charman, W Neil
Many contact lens (CL) manufacturers produce simultaneous-image lenses in which power varies either smoothly or discontinuously with zonal radius. We present in vitro measurements of some recent CLs and discuss how power profiles might be approximated in terms of nominal distance corrections, near additions, and on-eye visual performance. Fully hydrated soft, simultaneous-image CLs from four manufacturers (Air Optix AQUA, Alcon; PureVision multifocal, Bausch & Lomb; Acuvue OASYS for Presbyopia, Vistakon; Biofinity multifocal- "D" design, Cooper Vision) were measured with a Phase focus Lens Profiler (Phase Focus Ltd., Sheffield, UK) in a wet cell and powers were corrected to powers in air. All lenses had zero labeled power for distance. Sagittal power profiles revealed that the "low" add PureVision and Air Optix lenses exhibit smooth (parabolic) profiles, corresponding to negative spherical aberration. The "mid" and "high" add PureVision and Air Optix lenses have bi-aspheric designs, leading to different rates of power change for the central and peripheral portions. All OASYS lenses display a series of concentric zones, separated by abrupt discontinuities; individual profiles can be constrained between two parabolically decreasing curves, each giving a valid description of the power changes over alternate annular zones. Biofinity lenses have constant power over the central circular region of radius 1.5 mm, followed by an annular zone where the power increases approximately linearly, the gradient increasing with the add power, and finally an outer zone showing a slow, linear increase in power with a gradient being almost independent of the add power. The variation in power across the simultaneous-image lenses produces enhanced depth of focus. The through-focus nature of the image, which influences the "best focus" (distance correction) and the reading addition, will vary with several factors, including lens centration, the wearer's pupil diameter, and ocular
Fogel, Joshua; Zidile, Chaya
Individuals are increasingly purchasing contact lenses over the Internet. No studies exist regarding Internet purchase of contact lenses and eye care health practices. One hundred fifty-one college students were surveyed regarding contact lenses purchase category (doctor's office, store, Internet). Pearson chi-square analyses compared purchase category with responses regarding U.S. Food and Drug Administration (FDA) recommendations for purchasing contact lenses online. Analysis of variance compared contact lenses purchase category with the Time Pressure Scale (TPS). Also, correlation analyses compared the TPS with Internet eye-health statements. Contact lens purchase categories included doctor's office (43.0%), store (55.0%), and Internet (22.5%), with individuals purchasing at multiple venues. With regard to the FDA recommendations, those who purchased contact lenses at a doctor's office more often adhered to the recommendations, whereas those who purchased contact lenses at a store or the Internet did so less often. Those who purchased contact lenses over the Internet had significantly higher TPS scores. In addition, higher TPS scores were significantly correlated with various statements regarding the Internet. Those who purchase contact lenses via the Internet or store do not follow a number of FDA contact lenses recommendations. Also, those with higher TPS scores trust possible non-evidence-based contact lenses Internet information. Implications with regard to the Fairness to Contact Lens Consumers Act are discussed.
White, Charles J.; DiPasquale, Stephen A.; Byrne, Mark E.
Purpose The majority of contact lens wearers experience a significant level of ocular discomfort associated with lens wear, often within hours of wear, related to dry lenses, inflammation, protein adhesion to the lens surface, etc. Application of controlled drug release techniques has focused on the incorporation and/or release of a single comfort molecule from a lens including high molecular weight comfort agents or pharmaceutical agents. Previous studies have sought to mitigate the occurrence of only single propagators of discomfort. Clinical studies with eye drop solutions have shown that a mixture of diverse comfort agents selected to address multiple propagators of discomfort provide the greatest and longest lasting sensations of comfort for the patient. In this paper, multiple propagators of discomfort are addressed through the simultaneous release of four molecules from a novel contact lens to ensure high level of lens wear comfort. Methods Silicone hydrogel contact lenses were engineered via molecular imprinting strategies to simultaneously release up to four template molecules including hydropropyl methylcellulose (HPMC), trehalose, ibuprofen, and prednisolone. Results By adjusting the ratio of functional monomer to comfort molecule, a high level of control was demonstrated over the release rate. HPMC, trehalose, ibuprofen, and prednisolone were released at therapeutically relevant concentrations with varying rates from a single lens. Conclusions The results indicate use as daily disposable lenses for single day release or extended-wear lenses with multiple day release. Imprinted lenses are expected to lead to higher efficacy for patients compared to topical eye drops by improving compliance and mitigating concentration peaks and valleys associated with multiple drops. PMID:26945177
Gritz, D.C.; Lee, T.Y.; McDonnell, P.J.; Shih, K.; Baron, N. )
Two sources of ultraviolet (UV) radiation with peak wavelengths in the UV-C or UV-B ranges were compared for their ability to sterilize contact lenses infected with Pseudomonas aeruginosa, Streptococcus pneumoniae, Acanthamoeba castellani, Candida albicans, and Aspergillus niger. Also examined was the effect of prolonged UV light exposure on soft and rigid gas permeable (RGP) contact lenses. The UV-C lamp (253.7 nm, 250 mW/cm2 at 1 cm) was germicidal for all organisms within 20 minutes but caused destruction of the soft lens polymers within 6 hours of cumulative exposure. UV-C caused damage to RGP lenses in less than 100 hours. The UV-B lamp (290-310 nm, 500 mW/cm2 at 1 cm) was germicidal for all organisms tested (except Aspergillus) with a 180-minute exposure and caused less severe changes in the soft lens polymers than did the UV-C lamp, although cumulative exposure of 300 hours did substantially weaken the soft lens material. RGP materials were minimally affected by exposure to 300 hours of UV-B. Ultraviolet light is an effective germicidal agent but is injurious to soft lens polymers; its possible utility in the sterilization of RGP lenses and lens cases deserves further study.
Tavazzi, Silvia; Rossi, Alessandra; Picarazzi, Sara; Ascagni, Miriam; Farris, Stefano; Borghesi, Alessandro
Soft contact lenses used for the correction of ametropia are often made of hydrogel and silicone-hydrogel materials. Since they are placed directly on the surface of the eye and they are hydrated by tears, eye cosmetics can compromise the lens performance and, even worse, can be transported from an external environment to the ocular surface through the contact lens. The diffusion of the dye component of a purple eyeshadow in soft contact lenses of different materials is here evaluated. Diffusivity is found to be typically higher in silicone-hydrogels than in hydrogels. In hydrogels, diffusivity is greater in the case of lower oxygen transmissibility. Despite differences between materials, absorbed mass of dye is much larger (10-100 times) than the expected mass by simple hydration and swelling of the contact lens. The most contaminated materials are also resistant to cleaning solutions. The results indicate that, notwithstanding the complexity of contact lens networks, diffusion of dye is found to follow Fick's law and it is driven by polymer-dye interaction, which governs lens hydration and swelling. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Martin, Raul; de Juan, Victoria; Rodriguez, Guadalupe; Martin, Sofia; Fonseca, Soraya
To compare the initial comfort afforded by silicone hydrogel lenses (lotrafilcon A) versus the comfort afforded by conventional hydrogel lenses (etafilcon A) in extended wear (EW). Prospective, double-masked and randomized controlled trial. Lotrafilcon A and etafilcon A contact lenses were eye randomly fitted on an EW basis for 7 days and nights in 20 subjects. A forced-choice subject preference questionnaire was made. Subjects were comfort, dryness, red eye and visual quality after night wear and at the end of the day. Subjective scored satisfaction (scale: 1-5) and lens preference were assessed. Lotrafilcon A proved more comfortable after night wear (60%, CI95% 38-82%) and at the end of the day (70%, CI95% 49-90%) than etafilcon A after night wear (10%, CI95% 0-23%, P<0.05) and at the end of the day (20%, CI95% 2-38%, P<0.05). The feeling of dryness was more marked with etafilcon A after night wear (50%, CI95% 27-72%) and at the end of the day (50%, CI95% 27-72%) than it was with lotrafilcon A (15%, CI95% 0%-31%) after night wear (P>0.05) and at the end of the day (25%, CI95% 5%-44%, P<0.05). General satisfaction with the lotrafilcon A lens was 3.65 points (CI95% 3-4.2) and with etafilcon A 2.95 points (CI95% 2.5-3.3, P<0.05). Eighty percent (CI95% 62%-98%) of subjects preferred lotrafilcon A (P<0.05) for EW. In EW, lotrafilcon A contact lenses were more comfortable and led to less dryness after night wear and at the end of the day than etafilcon A contact lenses.
Tavazzi, Silvia; Ferraro, Lorenzo; Fagnola, Matteo; Cozza, Federica; Farris, Stefano; Bonetti, Simone; Simonutti, Roberto; Borghesi, Alessandro
Molecular arrangement plays a role in the diffusion of water and solutes across soft contact lenses. In particular, the uptake of solutes in hydrated contact lenses can occur as long as free water is available for diffusion. In this work, we investigated the effect of mechanical vibrations of low frequency (200 Hz) on the solute uptake. Hyaluronan, a polysaccharide of ophthalmic use, was taken as example of solute of interest. For a specific water-hydrated hydrogel material, differential scanning calorimetry experiments showed that a large fraction of the hydration water accounted for loosely-bound water, both before and after one week of daily-wear of the lenses. The size (of the order of magnitude of few hundreds of nanometers) of hyaluronan in aqueous solution was found to be less than the size of the pores of the lens observed by scanning electron microscopy. However, solute uptake in already-hydrated lenses was negligible by simple immersion, while a significant increase occurred under mechanical vibrations of 200 Hz, thus providing experimental evidence of mechanically triggered enhanced solute uptake, which is attributed to the release of interfacial loosely-bound water. Also other materials were taken into consideration. However, the effectiveness of mechanical vibrations for hyaluronan uptake is restricted to lenses containing interfacial loosely-bound water. Indeed, loosely-bound water is expected to be bound to the polymer with bonding energies of the order of magnitude of 10-100 J/g, which are compatible with the energy input supplied by the vibrations.
Bacon, A S; Astin, C; Dart, J K
Silicone rubber contact lenses (SRCLs) are infrequently used because of the risk of developing unpredictable lens tightening, their poor availability, and their expense. However, their high oxygen transmissibility and nonabsorption of water make them valuable as therapeutic lenses. SRCLs are routinely used in our management of severely dry eyes, decompensated or vascularised corneas, and conditions where the corneal shape is flat or irregular. The records of 48 consecutive patients fitted with SRCLs between January 1989 and June 1990 were studied. The clinical history, indications, complications, success, and duration of SRCL wear were analysed. Therapeutic goals, which included epithelial healing, sealing of corneal perforations, and improved comfort and vision, were achieved in 53 of 62 eyes. The best corrected acuity was attained using SRCLs in 58 of 62 eyes. Failure of lens wear was due to lens tightening (four eyes), spoilation (two), discomfort, fornix shortening, handling problems, and decentration (one each). Infective keratitis complicated one case, but SRCL wear was resumed after successful treatment. With adequate follow-up, SRCLs have a low complication rate and are well tolerated even in severely compromised eyes, for which conventional lenses may be contraindicated. Their continued use as therapeutic lenses is advocated in carefully selected cases.
Bergmanson, J P; Pitts, D G; Chu, L W
Ultraviolet radiation (UVR) has been demonstrated to be harmful to the cornea, the lens and the retina. Recent research has indicated that, in addition to the epithelial trauma found in UVR-induced keratitis, the deeper corneal layers are also involved. Since trauma to keratocytes and endothelial cells can result in permanent damage or cell loss, it is imperative to protect eyes against excessive dosages of UVR. Standard hydrogel contact lenses (Vistamarc normal) and newly developed UV-filtering hydrogel lenses (Vistakon UV-BLOC) were fitted on five rabbits and compared in protection from harmful UVR (300 nm). The eyes that wore the UV-filtering lens maintained normal corneas; however, the eyes that wore the standard hydrogel lens showed pronounced epithelial, stromal and endothelial changes. We concluded that the UV-filtering lens effectively absorbed the hazardous UV radiation while the standard soft lens provided little protection.
Schnell, D; Khaireddin, R
The corneal metabolism during the use of contact lenses plays an important role for permanent corneal health, especially in competitive sports. Thus, it is important to understand the steps of corneal metabolism in general and during highly competitive sports activity in particular. The aim of this review is to summarize the current knowledge on physiological and biochemical effects of contact lens wear. Of the energy requirements of the cornea 75 % is supplied by aerobic processes; therefore, the eye needs the highest possible amount of oxygen and sufficient glucose which can be obtained from external air and to a lesser degree from within the anterior chamber. If the oxygen supply is too low this results in hypoxic edema. Fitting athletes with contact lenses must still be viewed with caution as the visual needs of athletes are usually much more demanding than those of the general public. An indiscriminate choice of lens design can adversely affect athletic performance and may even create a hazardous situation. An intelligent choice of contact lens can provide some subtle advantages that may improve athletic performance and provide the decisive margin for victory.
Lindskoog Pettersson, Anna; Wahlberg Ramsay, Marika; Lundström, Linda; Rosén, Robert; Nilsson, Maria; Unsbo, Peter; Brautaset, Rune
The aim of the present project was to investigate accommodative behavior in young adults and adolescents fitted with an aspheric multifocal (center distance) contact lens with focus on evaluating whether these lenses can be an alternative treatment for subjects in which a reduced level of blur and thereby accommodation in near vision is aimed at. Twenty normal subjects aged between 21 and 35 years participated in the study. Aberrometry was perfomed using a Zywave™ aberrometer, first on the uncorrected eyes of all subjects, and again while the subjects wore a multifocal contact lens with a +1.00 add. A Shin-Nippon N Vision-K 5001 Autoref-Keratometer was used to measure accommodative response with two different refractive corrections: (1) habitual spectacle correction only, and (2) habitual correction and a aspheric multifocal (center distance) contact lens. Four hours of adaptation to the lens was allowed. The lag when wearing only the habitual spectacles was compared with the lag while wearing both the habitual spectacles and the aspheric multifocal contact lens. The mean lag of accommodation for the subject group was 0.85 D (±0.57 SD) and 0.75 D (±0.52 SD) without and with the multifocal lens, respectively. Statistical analyses showed no difference in lag (t = 0.8479, p = 0.407) with and without the lens. In conclusion, young normal subjects do not relax accommodation when fitted with aspheric multifocal center distance lenses when the addition is +1.00. It is therefore unlikely that subjects with accommodative ability, in whom the treatment purpose is to reduce blur and thereby accommodation, can be effectively treated with such lenses.
Babaei Omali, Negar; Lada, Mark; Lakkis, Carol; Morgan, Philip B; Nichols, Jason J; Subbaraman, Lakshman N; Jones, Lyndon W
There remains only a small amount of data from human studies demonstrating the effect of contact lens/lens care solution combinations on the deposition of lipids. Therefore, information on the degree to which modern materials deposit lipids when used with contemporary care solutions would be valuable. The present study aims to determine the effect of lens care system combinations on levels of total lipid, cholesterol, and cholesteryl esters extracted from three different contact lenses (CLs) when used with four contemporary care systems. Experienced CL wearers were recruited to participate in this study. Combinations of three CLs (etafilcon A [ETA], galyfilcon A [GALY], and senofilcon A [SENO]) and four CL care solutions (Biotrue, ClearCare, OPTI-FREE PureMoist, and RevitaLens Ocutec) were investigated. A total of 791 CLs were analyzed. Subjects were randomized to one lens type and then used all four lens care solutions in random sequence for 10-14 days before the CLs were collected and analyzed for the amount of cholesterol, cholesteryl esters, and total lipids. The mean range of cholesterol recovered across the different care solutions was 0.34-2.77 μg/lens, 3.48-4.29 μg/lens, and 4.75-6.20 μg/lens for ETA, SENO, and GALY lenses, respectively. Use of OPTI-FREE PureMoist with ETA lenses led to a significantly greater amount of cholesterol being recovered when compared to the use of the other solutions with ETA lenses (P < .05). The mean range of cholesteryl esters recovered across different care solutions was 1.31-2.02 μg/lens, 6.43-7.19 μg/lens, and 7.96-10.13 μg/lens for ETA, SENO, and GALY lenses, respectively. There were no differences in the amount of cholesteryl esters and total lipids extracted for a given lens type when used with any of the four care solutions (P > .05). This study did not demonstrate conclusively that any of the solution/CL combinations were superior to any of the other combinations when the amounts of lipid deposition were compared
MacMillan, T F; Benjamin, W J
Most care regimens used with rigid contact lenses are composed of three solutions: 1) a "cleaning" solution; 2) a "combination" solution intended for storage, disinfection, and wetting prior to placement of rigid lenses on the eye; and 3) an in-eye "rewetting" or "lubricating" solution. While solutions (1) and (3) have only single functions, solution (2) must fulfill three fairly disparate functions. A "2-solution" care regimen is offered by Sherman Pharmaceuticals and consists of (a) a solution for cleaning, storage, and disinfection; and (b) a "wetting" solution that doubles as an in-eye lubricant. Through a more compatible and efficient matching of multiple functions within solutions, Sherman Pharmaceuticals claims to more adequately clean and prepare rigid gas-permeable (RGP) lens surfaces for wear. We investigated this strategy in terms of in-eye wettability of initially "ill-prepared" RGP lens surfaces, as measured with the in vivo contact angle technique. For this study, lenses were intentionally not cleaned of residues or solvents by the manufacturer at the end of production so as to create the well-known "first-day non-wetting syndrome." The ability of the 2-solution care regimen to even then provide wettable surfaces was compared to that of a saline control "regimen" and the most popular competing "3-solution" care system. We concluded that use of both care regimens dramatically enhanced in-eye wettability and, therefore, reduced the incidence of the "first-day non-wetting syndrome". However, the 2-solution care regimen provided significantly better wettability overall, lower incidence of functionally non-wetting surfaces, and more consistently wettable RGP lenses.
Kim, Eon; Bakaraju, Ravi C.; Ehrmann, Klaus
ABSTRACT Purpose To evaluate the optical power profiles of commercially available soft multifocal contact lenses and compare their optical designs. Methods The power profiles of 38 types of multifocal contact lenses—three lenses each—were measured in powers +6D, +3D, +1D, −1D, −3D, and −6D using NIMO TR1504 (Lambda-X, Belgium). All lenses were measured in phosphate buffered saline across 8 mm optic zone diameter. Refractive index of each lens material was measured using CLR 12-70 (Index Instruments, UK), which was used for converting measured power in the medium to in-air radial power profiles. Results Three basic types of power profiles were identified: center-near, center-distance, and concentric-zone ring-type designs. For most of the lens types, the relative plus with respect to prescription power was lower than the corresponding spectacle add. For some lens types, the measured power profiles were shifted by up to 1D across the power range relative to their labeled power. Most of the lenses were designed with noticeable amounts of spherical aberration. The sign and magnitude of spherical aberration can either be power dependent or consistent across the power range. Conclusions Power profiles can vary widely between the different lens types; however, certain similarities were also observed between some of the center-near designs. For the more recently released lens types, there seems to be a trend emerging to reduce the relative plus with respect to prescription power, include negative spherical aberration, and keep the power profiles consistent across the power range. PMID:27748699
Emina, Michael Osita; Idu, Faustina Kemdinum
Purpose This is to determine the prevalence of bacterial and parasitic flora in asymptomatic disposable and extended contact lens wearers in Lagos State, Nigeria. Methods The study was carried out on 156 contact lenses from 78 asymptomatic wearers between the ages of 12 to 38 years. Eighty two disposable daily wear (DWCL) and 74 extended wear (EWCL) contact lenses were examined. The contact lenses’ swabs and the trays were transferred to the laboratory for microbial examination. Results Fifty two (70.27 %) extended wear contact lenses and 50 (60.98 %) disposable contact lenses examined were contaminated. Streptococcus spp. (4.23 %) were found in extended contact lenses and (3.9 %) in disposable contact lenses. Escherichia coli (15.49 %) were more in the extended contact lenses and were in higher proportion (14.74 %) than the other microorganisms in all the contact lenses. Klebsiella spp. (12.99 %) were more in the disposable lenses than in the extended wear lenses (12.69 %). there were more disposable lenses (41.56 %) with ‘no growth’. Amoebae were isolated from (6.49 %) disposable and (4.23 %) extended wear contact lenses. Seventeen (32.69 %) DWCL had mixed flora. There were significant differences between disposable and extended contact lenses, p < 0.05. Conclusions EWCL present more microorganisms and pose threat to the users. DWCL had more amoebae, which calls for suitable lens care methods. Further studies may be needed to determine the level of care required for contact lens users in developing countries.
Walker, Jon; Young, Graeme; Hunt, Chris; Henderson, Terri
To evaluate the clinical performance of two daily disposable contact lenses: 1-DAY ACUVUE (1DA) (etafilcon A, Johnson & Johnson Vision Care) and FOCUS DAILIES with AquaComfort (FD) (nelfilcon A, CIBA Vision, Inc.), which contains a quickly released moisture enhancing agent, polyvinyl alcohol (PVA). This was a 1-week, daily wear, subject-masked, bilateral, parallel group study with subjects randomly assigned to one of two daily disposable soft contact lenses. Subjects were existing soft contact lens wearers in the age range 18-39 years with a spherical refraction between -0.50 and -6.00 D. Subjects were assessed at baseline and after 1 week. Assessments included both subjective (symptoms, wearing time, vision) and objective (lens fit and ocular health) outcomes. Twenty clinical sites enrolled 282 subjects (74% female) of whom 276 (98%) successfully completed the study. Significantly more 1DA wearers reported higher mean comfort scores than with FD (3.95 versus 3.41, respectively, P<0.0001). End-of-day comfort means were also significantly higher with the 1DA group compared to the FD group (3.3 versus 3.0, P=0.03). The 1DA group reported significantly longer mean overall wearing time (1DA was worn on average 0.66+/-0.30 h longer than FD, P=0.03) and longer mean comfortable wearing time (1DA was worn on average 1.73+/-0.35 h longer than FD, P<0.0001). The 1DA lens generally showed significantly better on-eye fitting in terms of movement in primary (P<0.0001) and upgaze (P<0.0001) and ease of removal from the eye (92% versus 63%, P<0.0001) compared to FD. There was significantly less corneal staining observed with the 1DA wearing eyes compared with the FD wearing eyes (23% versus 45%, respectively, P<0.0001). Finally, there was a weak correlation between corneal staining and comfort for FD (r=0.27, P=0.002, n=136), but not for 1DA (r=-0.11, P=0.18, n=140). Subjective and objective clinical performance differences between two commonly used daily disposable lenses
Read, Michael L; Morgan, Philip B; Maldonado-Codina, Carole
This work sought to undertake a comprehensive investigation of the measurement errors associated with contact angle assessment of curved hydrogel contact lens surfaces. The contact angle coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intralens COR, and interlens COR) was determined by measuring the contact angles (using both sessile drop and captive bubble methods) for three silicone hydrogel lenses (senofilcon A, balafilcon A, lotrafilcon A) and one conventional hydrogel lens (etafilcon A). Image analysis COR values were about 2 degrees , whereas intralens COR values (95% confidence intervals) ranged from 4.0 degrees (3.3 degrees , 4.7 degrees ) (lotrafilcon A, captive bubble) to 10.2 degrees (8.4 degrees , 12.1 degrees ) (senofilcon A, sessile drop). Interlens COR values ranged from 4.5 degrees (3.7 degrees , 5.2 degrees ) (lotrafilcon A, captive bubble) to 16.5 degrees (13.6 degrees , 19.4 degrees ) (senofilcon A, sessile drop). Measurement error associated with image analysis was shown to be small as an absolute measure, although proportionally more significant for lenses with low contact angle. Sessile drop contact angles were typically less repeatable than captive bubble contact angles. For sessile drop measures, repeatability was poorer with the silicone hydrogel lenses when compared with the conventional hydrogel lens; this phenomenon was not observed for the captive bubble method, suggesting that methodological factors related to the sessile drop technique (such as surface dehydration and blotting) may play a role in the increased variability of contact angle measurements observed with silicone hydrogel contact lenses.
Fowler, S A; Allansmith, M R
Scanning electron microscopy was used to investigate the effectiveness of surfactant and enzyme cleaners in removing coatings from soft contact lenses. We examined ten continuously worn lenses and 15 lenses worn and cleaned regularly for at six months. About 30% of the surface of continuously worn lenses cleaned with surfactant or enzyme was uncoated; smooth, matted coating covered the remainder. Continuously worn lenses cleaned with the combination surfactant and enzyme cleaner had similar deposits covering 50% of the surface. Lenses worn and cleaned regularly had more deposits after cleaning with surfactant or enzyme cleaner than after cleaning with combination cleaner. Approximately 25% of the surface of lenses cleaned with the combination was coated with deposits. The deposits on both types of lenses were about 30% less thick after use of the combination cleaner than with either single cleaner. The coating on worn contact lenses is not completely removed by any method we tested.
tion of temperature and wind produced wind-chill factors in the vicinity of -67.8°C, yet this acute exposure of the cornea to cold with and without...aqueous humor and intraocular temperature in rabbit and cat. Invest Ophthalmol Visual Sei 1978;17:1199-202. 6. Gülan JG. The cornea in Canada’s...5077 — "The effect of cold on the cornea while wearing contact lenses. It was submitted for review on 31 December 1980, approved for publication
Acar, Banu Torun; Vural, Ece Turan; Acar, Suphi
Because patients with keratoconus tend to wear contact lens for a long period of time, they are more prone to ocular surface changes induced by the lenses. This study aimed to compare immunohistochemical changes induced by two different types of contact lenses in patients with keratoconus. Twenty-four contact lens-naive keratoconus patients (30 eyes) were included in this prospective study. Group 1 comprised 14 eyes (12 patients) wearing piggyback lenses, and group 2 comprised 16 eyes (12 patients) wearing ClearKone hybrid lenses. The patients were analyzed for bulbar conjunctival impression cytology, tear interleukin-6 (IL-6) and IL-8 levels, and confocal microscopic changes of the cornea before and 6 months after wearing contact lenses. Six months after wearing contact lenses, the groups demonstrated similar epithelial metaplasia rates, tear IL-6 and IL-8 levels, and similar confocal microscopy findings (P>0.05 for all intergroup comparisons). Among the parameters tested in this study, only IL-6 and IL-8 levels and posterior keratocyte density on confocal microscopy showed an increase after 6 months when compared with baseline values but at a similar degree in the two groups. This small sample was not able to demonstrate a difference between the two types of lenses with regard to the variables examined, and further larger trials would be required to determine if differences truly exist or not. However, clinicians may still consider patient comfort and vision in selecting the lens type in patients with keratoconus.
and preferred them over glasses. Lens care and handling were cited as problems. APPLICATION Contact lenses offer some advantages over spectacles ...vision. Contact lenses were generally comfortable in the cold, but lens care is difficult. Since they do not fog and they offer protection from wind...driven ice and snow, contact lenses offer an important advantage over spectacles . ill It is estimated that 50.3% of all Americans wear glasses1
Xie, Zhuoying; Li, Linliang; Liu, Panmiao; Zheng, Fuyin; Guo, Liuyang; Zhao, Yuanjin; Jin, Lu; Li, Tingting; Gu, Zhongze
A circlular structural-colored contact lens is reported, which is fabricated by replicating self-assembled colloidal photonic crystal templates. The structural-colored contact lenses not only display variable and brilliant color under light illumination, but also avoid the addition of any colorants to the hydrogel lenses and prevent the potential harm posed by traditional colored contact lenses. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Altoaimi, Basal H; Almutairi, Meznah S; Kollbaum, Pete; Bradley, Arthur
Wearing aspheric contact lenses adds significant amounts of negative spherical aberration (SA). Also, when accommodated and converged to near targets, pupil size shrinks and SA shift from positive to more negative direction. Interestingly, in this study, pupil miosis was fully or partially able to compensate for the additional accommodation-induced negative SA. The present study aims to examine the accommodative response characteristics of young eyes fit with aspheric single vision contact lenses (SVCLs) that add significant negative SA to the eye responding to a wide range of accommodation stimuli. Using a Shack-Hartmann aberrometer, the accommodation behavior in eight young adult eyes (mean age and spherical equivalent is 27.25 ± 2.05 years and -1.75 ± 1.80D, respectively) was measured while subjects fixated binocularly and monocularly 20/40 letter E, which were moved from 2 m to 20 cm (0.5 to 5D) in 0.25D steps. Using natural pupils, refractive state was defined using three standard criteria: the dioptric power that (1) minimized the root mean square error (minRMS), (2) best-fit paraxial, and (3) provided the peak image quality (peak IQ). Wearing aspheric lenses with negative SA shifts the mean SA of the unaccommodated eyes from +0.05 μm (eyes only) to -0.029 μm (eyes + SVCL) and increases the negative SA for the eye + lens when accommodating from -0.029 to -0.07 μm for natural pupils. Aberration changes with accommodation were attenuated by the accommodative pupil miosis, which reduced binocular viewing pupil diameters from 3.9 to 3.3 mm. This alteration of the typical SA levels by the aspheric SVCL did not prevent accurate accommodation (mean ± standard deviation accommodative lag under binocular viewing were -0.08 ± 0.12D, -0.38 ± 0.12D, and -0.26 ± 0.08D for paraxial, minRMS, and peak IQ, respectively). These data clearly show that aspheric contact lenses designed to correct some or all of the unaccommodated eye's positive SA do not interfere with
Karlgard, C C S; Jones, L W; Moresoli, C
Hydrogel contact lenses can be used as bandage lenses to protect the corneal surface after injury. The use of novel silicon-based hydrogel lens materials as bandage lenses has not gained widespread acceptance. As a first step toward advocating their usefulness as bandage lenses, their interaction with ocular pharmaceuticals must be understood because topical agents are often administered in conjunction with bandage lenses. The in vitro uptake and release of ciprofloxacin from silicone-based hydrogel (SH) and conventional pHEMA-based (CH) hydrogel contact lenses was examined by spectrophotometric evaluation of the drug concentration in saline solution. The hydrogel contact lenses tested showed similar drug uptake (average 1800 microg/lens) but different levels of drug release. Multiphoton laser microscopy indicated that ciprofloxacin was distributed throughout the lens thickness, with higher levels of drug at the surface owing to drug precipitation. The drug adsorption onto the lenses was partially reversible. The SH lenses released a lower amount of drug than CH lenses (72 vs. 168 microg/lens). Ionic lenses released less drug than non-ionic lenses (127 vs. 151 microg/lens). The differences in ciprofloxacin uptake and release between SH and CH materials may not be clinically significant because the amount of drug released from all lenses would be above the MIC(90) of ciprofloxacin for common ocular pathogens. These results indicate that material properties have a significant impact on drug-lens interactions.
Freeman, M I
At the present time, nine lathe-cut lenses are FDA approved and commercially available in the United States. Complications of lathe-cut soft contact lenses cover a wide spectrum of problems. Five significant complications of lathe-cut lenses and their prevention and therapeutic management are discussed.
Bullimore, Mark A.
ABSTRACT Purpose There is increasing interest in fitting children with soft contact lenses. This review collates data from a range of studies to estimate the incidence of complications, specifically corneal infiltrative events and microbial keratitis, in patients under the age of 18 years. Methods Peer-review papers were identified using PubMed and the Web of Science. A broad range of studies are summarized including large-scale epidemiological studies of contact lens–related complications, hospital-based case series, long- and short-term prospective studies, and multicenter retrospective studies. Results Nine prospective studies representing 1800 patient years of wear in 7- to 19-year-olds include safety outcomes. In three large prospective studies representing between 159 and 723 patient years of soft contact lens wear in patients 8 to 14 years, the incidence of corneal infiltrative events is up to 136 per 10,000 years. Data from a large retrospective study show similar rates of corneal infiltrative events: 97 per 10,000 years in 8- to 12-year-olds (based on 411 patient years of wear) and 335 per 10,000 years in 13- to 17-year-olds (based on 1372 patient years of wear). None of the prospective studies report any cases of microbial keratitis. Five clinical studies where safety data are not reported constitute a further 493 patient years. One retrospective study found no cases of microbial keratitis occurred in 8- to 12-year-olds (411 patient years) and an incidence of 15 per 10,000 patient years in 13- to 17-year-olds (1372 patient years)—no higher than the incidence of microbial keratitis in adults wearing soft contact lenses on an overnight basis. Conclusions The overall picture is that the incidence of corneal infiltrative events in children is no higher than in adults, and in the youngest age range of 8 to 11 years, it may be markedly lower. PMID:28514244
Bengani, Lokendrakumar C; Leclerc, Jenna; Chauhan, Anuj
Protein binding in hydrogels adversely affects their performance and can interfere with their usage in several biomedical applications including contact lenses. In this study we focus on understanding and modeling the mechanisms of protein transport in hydrogels, specifically focusing on the effect of protein concentration and gel crosslinking on transport. Specifically, we focus on lysozyme, the most abundant protein in tear fluid, and hydrogels of poly-hydroxyethyl methacrylate (p-HEMA), a common contact lens material. Protein uptake experiments with gels of different thicknesses showed a time scale increase as the square of the thickness suggesting diffusion controlled transport. Partition coefficient was found to be dependent on the equilibrium concentration of lysozyme, and also on the degree of crosslinking. Since transport is related to mesh size, gel modulus was obtained for various crosslinkings and utilized to estimate the mesh size. The transport data were fitted to a diffusion model and the fitted diffusivity was compared to diffusivity predicted from a model based on hydrogel mesh size. Both protein absorption and desorption data fitted the diffusion model with the same value of diffusivity, but the experimentally measured diffusivities were significantly smaller than those estimated on the basis of the gel mesh size. Models were modified to take into account protein binding to the polymer but the modified predictions were still larger than the measured values. The results of this study could assist in the development of contact lens materials that exhibit minimal protein binding, in designing cleaning regimens for protein removal from contact lenses, and in applications related to protein binding in several other biomaterials. Copyright © 2012 Elsevier Inc. All rights reserved.
Stahler, D; Teubel, H; Karsten, H
Two accidents had been reported from abroad, within which contact lense users grew blind after staying quite near at electrical arcs. It is supposed that the contact lenses had been "welded" with the cornea by influence of the electromagnetic radiation. Removal of lenses shall have caused the cornea "ablation" and thus the subjects permanent blindness. Nilsson et al. (1, 2, 5) performed intensive animal tests which proved, that contact lenses get hot in special spectral ranges thus underlying a certain drying up. The "welding" between contact lenses and the cornea could not be confirmed by test animals, but partial glueing of contact lenses and cornea and surface lesions of the epithelium as well in some cases. Hüer and Conrads (3, 4) experimenting on enucleated pigs' eyes, reported on similar results.
Barbero, Sergio; Rubinstein, Jacob
When vision is affected simultaneously by presbyopia and myopia or hyperopia, a solution based on eyeglasses implies a surface with either segmented focal regions (e.g. bifocal lenses) or a progressive addition profile (PALs). However, both options have the drawback of reducing the field-of-view for each power position, which restricts the natural eye-head movements of the wearer. To avoid this serious limitation we propose a new solution which is essentially a bifocal power-adjustable optical design ensuring a wide field-of-view for every viewing distance. The optical system is based on the Alvarez principle. Spherical refraction correction is considered for different eccentric gaze directions covering a field-of-view range up to 45degrees. Eye movements during convergence for near objects are included. We designed three bifocal systems. The first one provides 3 D for far vision (myopic eye) and -1 D for near vision (+2 D Addition). The second one provides a +3 D addition with 3 D for far vision. Finally the last system is an example of reading glasses with +1 D power Addition.
Pitt, William G; Perez, Krystian X; Tam, Ngai Keung; Handly, Erika; Chinn, Joseph A; Liu, Xiaojun Michael; Maziarz, Edmond Peter
The introduction of silicone hydrogel (SiHy) contact lenses to the consumer marketplace necessitates study of the susceptibility of these lenses to spontaneous deposition by hydrophobic lipid components of ocular tears. The use of radioisotopes to measure lipid sorption on SiHy contact lenses gives precise and accurate results but requires institutional infrastructure and compels efficient lipid removal from the lens. This study compares three methods of quantitating phospholipid and cholesterol sorption on SiHy lenses using radiolabeled cholesterol and phosphatidylcholine that were sorbed on lenses from an artificial tear fluid. A triple extraction technique using n-propanol gives the most reliable results. Comparison of sorption on SiHy lenses shows that balafilcon A and senofilcon A lenses sorb similar amounts, while lotrafilcon B lenses sorb comparatively less.
Rimayanti, Ulfah; Kiuchi, Yoshiaki; Uemura, Shohei; Takenaka, Joji; Mochizuki, Hideki; Kaneko, Makoto
Purpose To evaluate the displacement of the central ocular surface during non-contact tonometry with and without soft contact lenses and determine the factors associated with the displacement of the central ocular surface and intraocular pressure (IOP) reading changes caused by wearing soft contact lenses (CLs). Methods One eye each in 21 subjects was studied. The cornea was photographed using a high-speed camera at 5,000 frames/sec during non-contact tonometry without contact lenses (NCL), with -5.0 diopters (D), -0.5 D and +5.0 D CL. The displacement of the ocular surface and the factors affecting displacement at the IOP reading and maximum displacement time were investigated. Results The IOP readings while wearing +5 D CL were significantly higher than those obtained while wearing -5 D CL. The ocular surface displacement between +5 D CL and other groups were significantly different. A significant positive correlation was found between the ocular surface displacement of subjects at the IOP reading time and the IOP obtained with the non-contact tonometer. A significant negative correlation was found between the ocular surface curvature and the IOP obtained using the non-contact tonometer. The radius of curvature of the ocular surface affected the displacement during the IOP reading and maximum displacement time. Conclusions Our results indicate that soft contact lens use changes the ocular surface behavior and IOP readings during non-contact tonometry. The radius of curvature of the eye affects the ocular surface displacement and IOP readings in this situation. PMID:24781212
Lee, Se Eun; Kim, So Ra; Park, Mijung
AIM To determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses. METHODS Two hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A) were used in the study. These lenses were incubated in phosphate-buffered saline (PBS) and borate-buffered saline (BBS) solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg), isotonic (310 mOsmol/kg) and hypertonic (380 mOsmol/kg) PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect. RESULTS Dk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality. CONCLUSION From the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers' physiological and/or pathological conditions. PMID:26558223
Kalsow, Carolyn M; Reindel, William T; Merchea, Mohinder M; Bateman, Kirk M; Barr, Joseph T
Purpose An increased risk of corneal infiltrative events has been noted with the use of certain contact lenses and multipurpose solutions (MPS). This study was designed to evaluate tear cytokine assay as a sensitive, objective, and quantitative measure of the ocular surface response to contact lens/MPS and to consider the assay’s clinical relevance in the context of other measures of ocular surface response. Methods Two MPS, ReNu® Fresh™ (RNF) and Opti-Free® RepleniSH (OFR), were used with daily wear silicone hydrogel contact lenses in a randomized, prospective crossover study involving 26 subjects. Clinical data collection (conjunctival hyperemia, ocular surface sensitivity, solution induced corneal staining (SICS) test score, and subjective responses) and tear cytokine assays were conducted masked. Responses were tracked as change from baseline throughout the experimental schedule. Results Similar response patterns for several inflammatory cytokines were seen throughout both phases: subjects who received OFR in Phase I had mean tear concentrations that were generally higher than those of the RNF Phase I group. OFR Phase I subjects had significant (P < 0.01) increases over baseline at day 1 and/or following washout for 13 cytokines (cc chemokine ligands [CCL] 3, CCL5, CCL11, granulocyte-macrophage colony-stimulating factor [GM-CSF], interferon [INF]-γ, interleukin [IL]-2, IL-4, IL-5, IL-6, IL-13, IL-15, IL-17, tumor necrosis factor [TNF]-α). These changes were not observed in RNF Phase I subjects, even though SICS test scores increased. Phase I OFR subjects also had increased dryness, while RNF Phase I subjects had decreased bulbar hyperemia. No changes were detected with respect to limbal hyperemia or surface sensitivity thresholds. Conclusion The tear cytokine assay can detect and differentiate contact lens/MPS induced increases in inflammatory cytokines. Changes in cytokine levels were consistent with measurement of hyperemia and dryness but not with
González-Chomón, Clara; Silva, Maite; Concheiro, Angel; Alvarez-Lorenzo, Carmen
Combination of the ability of contact lenses (CLs) to act as a physical barrier against airborne antigen and to serve as a sustained depot of antihistaminic drugs may improve the efficiency of treatments of some ocular allergic diseases. The aim of this work was to develop CLs that exhibit affinity to olopatadine by mimicking the composition of the natural H1-receptor for which olopatadine behaves as a selective antagonist. Functional monomers that match the chemical groups of the receptor and application of the molecular imprinting technology led to hydrogels able to load high amounts of olopatadine and to sustain the release once in contact with lachrymal fluid. Optimized hydrogels prepared with acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid and benzylmethacrylate as functional monomers provided in few hours olopatadine concentrations similar to those of commercially available eye drops but the levels could be sustained for a whole day, demonstrating their efficacy. Olopatadine-loaded CLs successfully passed the HET-CAM test of ocular irritancy and showed good compatibility with mast cells. They were able to inhibit the release of histamine and TNF-α from sensitized mast cells, proving their potential application in preventing and treating allergic conjunctivitis. Contact lenses (CLs) with affinity for antiallergic drugs may constitute an advantageous alternative to eye drops in management of ocular allergies for both contact lens wearers and patients who eventually use neutral CLs as therapeutic platforms. The present work represents a step forward in the state of the art of drug-CL combo products by (i) mimicking the composition of the human receptor of the drug, (ii) exploring combinations of functional monomers that include a monomer (2-acrylamido-2-methyl-1-propanesulfonic acid; AMPSA) with a strong acid group (pKa<4) able to enhance the interaction of the network with olopatadine in the saline environment of the lachrymal fluid, and (iii
Lopes-Ferreira, Daniela P; Neves, Helena I F; Faria-Ribeiro, Miguel; Queirós, António; Fernandes, Paulo R B; González-Méijome, José M
To evaluate the impact of eye and head rotation in the measurement of peripheral refraction with an open-field autorefractometer in myopic eyes wearing two different center-distance designs of multifocal contact lenses (MFCLs). Nineteen right eyes from 19 myopic patients (average central M ± SD = -2.67 ± 1.66 D) aged 20-27 years (mean ± SD = 23.2 ± 3.3 years) were evaluated using a Grand-Seiko autorefractometer. Patients were fitted with one multifocal aspheric center-distance contact lens (Biofinity Multifocal D(®)) and with one multi-concentric MFCL (Acuvue Oasys for Presbyopia). Axial and peripheral refraction were evaluated by eye rotation and by head rotation under naked eye condition and with each MFCL fitted randomly and in independent sessions. For the naked eye, refractive pattern (M, J0 and J45) across the central 60° of the horizontal visual field values did not show significant changes measured by rotating the eye or rotating the head (p > 0.05). Similar results were obtained wearing the Biofinity D, for both testing methods, no obtaining significant differences to M, J0 and J45 values (p > 0.05). For Acuvue Oasys for presbyopia, also no differences were found when comparing measurements obtained by eye and head rotation (p > 0.05). Multivariate analysis did not showed a significant interaction between testing method and lens type neither with measuring locations (MANOVA, p > 0.05). There were significant differences in M and J0 values between naked eyes and each MFCL. Measurements of peripheral refraction by rotating the eye or rotating the head in myopic patients wearing dominant design or multi-concentric multifocal silicone hydrogel contact lens are comparable. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Broich, J R; Weiss, L; Rapp, J
A method for elution of contaminants deposited onto soft contact lenses during wear utilizing a nondestructive cleaning procedure is presented. Twenty-five soft contact lenses supplied by American Optical Corp. were pooled and subjected to 20% H2O2 (hydrogen peroxide). The resulting wash was extracted with organic solvents, hydrolyzed, and re-extracted. The organic-soluble fraction was further divided into strong acids, intermediate acids, neutrals, and bases. Sequential separation, isolation, characterization, and confirmation of constituents were achieved with thin-layer chromatography, ultraviolet spectrophotometry, and microcrystallography. Photomicrographs before and after cleaning were obtained to assess the optical quality of the lenses. Initial emphasis has been to characterize naturally occurring, biologically active constituents and common environmental toxins of molecular weight 150 to 500. We find that nicotine, a common environmental pollutant and a significant component of the blood of people who smoke regularly, is one of the contaminants present on a worn soft contact lens.
Skipper, Richard S.; Spencer, Ian D.
The rapid and impressive growth of China has been achieved on the back of highly labour intensive industries, often in manufacturing, and at the cost of companies and jobs in Europe and America. Approaches that worked well in the 1990's to reduce production costs in the developed countries are no longer effective when confronted with the low labour costs of China and India. We have looked at contact lenses as a product that has become highly available to consumers here but as an industry that has reduced costs by moving to low labour cost countries. The question to be answered was, "Do we have the skill to still make the product in the UK, and can we make it cheap enough to export to China?" if we do not, then contact lens manufacture will move to China sooner or later. The challenge to enter the markets of the BRIC (Brazil, Russia, India and China) countries is extremely exciting as here is the new money, high growth and here is a product that sells to those with disposable incomes. To succeed we knew we had to be radical in our approach; the radical step was very simple: to devise a process in which each step added value to the customer and not cost to the product. The presentation examines the processes used by the major producers and how, by applying good manufacturing practice sound scientific principles to them, the opportunity to design a new low cost patented process was identified.
This dissertation presents progress toward the realization of functional contact lenses. Two primary goals of the functional contact lens project are to create displays for augmented reality and to create sensors to measure biomolecules in tears. First, work on contact lens displays is described, detailing the steps and process optimization required to fabricate fully functional contact lenses and culminating in the wireless activation of a single pixel contact lens display in vivo on a rabbit under general anesthesia. Next, solar cells designed to conform to a sphere for use with contact lens biosensors are described. To measure analytes in the tear film using electrochemical methods, contact lenses would require embedded sensors, electronics, antennas or LEDs for communication, and power sources. Ideally, a contact lens biosensor would be autonomous, provide regular readings, and operate during normal daily activity, thus requiring power continuously. Photovoltaic structures could provide continuous power for autonomous contact lens systems that could store sensor readings and communicate data when occasionally queried.
Maulvi, Furqan A; Soni, Tejal G; Shah, Dinesh O
Current dry eye treatment includes delivering comfort enhancing agents to the eye via eye drops, but low residence time of eye drops leads to low bioavailability. Frequent administration leads to incompliance in patients, so there is a great need for medical device such as contact lenses to treat dry eye. Studies in the past have demonstrated the efficacy of hyaluronic acid (HA) in the treatment of dry eyes using eye drops. In this paper, we present two methods to load HA in hydrogel contact lenses, soaking method and direct entrapment. The contact lenses were characterized by studying their optical and physical properties to determine their suitability as extended wear contact lenses. HA-laden hydrogel contact lenses prepared by soaking method showed release up to 48 h with acceptable physical and optical properties. Hydrogel contact lenses prepared by direct entrapment method showed significant sustained release in comparison to soaking method. HA entrapped in hydrogels resulted in reduction in % transmittance, sodium ion permeability and surface contact angle, while increase in % swelling. The impact on each of these properties was proportional to HA loading. The batch with 200-μg HA loading showed all acceptable values (parameters) for contact lens use. Results of cytotoxicity study indicated the safety of hydrogel contact lenses. In vivo pharmacokinetics studies in rabbit tear fluid showed dramatic increase in HA mean residence time and area under the curve with lenses in comparison to eye drop treatment. The study demonstrates the promising potential of delivering HA through contact lenses for the treatment of dry eye syndrome.
Merindano, M D; Canals, M; Saona, C; Costa, J
The anterior surface roughness of seven factory new rigid gas permeable (RGP) contact lenses has been studied by interferential shifting phase microscopy (ISPM) and scanning electron microscopy (SEM). Five lenses were fluorsilicone acrylate and two lenses were silicone acrylate. Their material Dk ranged from 14 to 210. ISPM is shown to be a reliable and non-destructive method to observe and measure the relief of the contact lens surface. Moreover, profile and contour data are easily stored for further quantitative studies. ISPM contour patterns of the studied lenses are qualitatively compared with those obtained by SEM for the same lenses. Results point out that ISPM gives similar accuracy but it is non-destructive and cheaper than SEM. Moreover, the quantitative study of surface roughness suggests that there is a relationship between surface roughness and Dk of the lens material: surface roughness increases with Dk and allows to distinguish between lenses with low, medium and high Dk.
Sulley, Anna; Hawke, Ryan; Lorenz, Kathrine Osborn; Toubouti, Youssef; Olivares, Giovanna
Rotational stability of toric soft contact lenses (TSCLs) is achieved using a range of designs. Designs utilising prism or peripheral ballast may result in residual prism in the optic zone. This study quantifies the vertical prism in the central 6mm present in TSCLs with various stabilisation methods. Vertical prism was computed using published refractive index and vertical thickness changes in the central optic zone on a full lens thickness map. Thickness maps were measured using scanning transmission microscopy. Designs tested were reusable, silicone hydrogel and hydrogel TSCLs: SofLens(®) Toric, PureVision(®)2 for Astigmatism, PureVision(®) Toric, Biofinity(®) Toric, Avaira(®) Toric, clariti(®) toric, AIR OPTIX(®) for ASTIGMATISM and ACUVUE OASYS(®) for ASTIGMATISM; with eight parameter combinations for each lens (-6.00DS to +3.00DS, -1.25DC, 90° and 180° axes). All TSCL designs evaluated had vertical prism in the optic zone except one which had virtually none (0.01Δ). Mean prism ranged from 0.52Δ to 1.15Δ, with three designs having prism that varied with sphere power. Vertical prism in ACUVUE OASYS(®) for ASTIGMATISM was significantly lower than all other TSCLs tested. TSCL designs utilising prism-ballast and peri-ballast for stabilisation have vertical prism in the central optic zone. In monocular astigmats fitted with a TSCL or those wearing a mix of toric designs, vertical prism imbalance could create or exacerbate disturbances in binocular vision function. Practitioners should be aware of this potential effect when selecting which TSCL designs to prescribe, particularly for monocular astigmats with pre-existing binocular vision anomalies, and when managing complaints of asthenopia in monocular astigmats. Copyright © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Lee, Dasom; Cho, Seungkwon; Park, Hwa Sung; Kwon, Inchan
Ocular drug delivery through hydrogel contact lenses has great potential for the treatment of ocular diseases. Previous studies showed that the loading of lipophilic vitamin E to silicone-hydrogel contact lenses was beneficial in ocular drug delivery. We hypothesized that vitamin E loading to another type of popular hydrogel contact lenses, pHEMA-hydrogel contact lenses, improves ocular drug delivery by increasing the drug loading or the duration of drug release. Loading of vitamin E to pHEMA-hydrogel contact lenses significantly increased the loading of a hydrophilic drug surrogate (Alexa Fluor 488 dye) and two hydrophilic glaucoma drugs (timolol and brimonidine) to the lenses by 37.5%, 19.1%, and 18.7%, respectively. However, the release duration time was not significantly altered. Next, we hypothesized that the lipophilic nature of vitamin E attributes to the enhanced drug loading. Therefore, we investigated the effects of co-loading of another lipophilic vitamin, vitamin A, on drug surrogate delivery. We found out that vitamin A loading also increased the loading of the drug surrogate to pHEMA-hydrogel contact lenses by 30.3%. Similar to vitamin E loading, vitamin A loading did not significantly alter the release duration time of the drug or drug surrogate.
Cheng, Yuan-Chieh; Chen, Jia-Hong; Chang, Rong-Jie; Wang, Chung-Yen; Hsu, Wei-Yao; Wang, Pei-Jen
Contact lenses are typically measured by the wet-box method because of the high optical power resulting from the anterior central curvature of cornea, even though the back vertex power of the lenses are small. In this study, an optical measurement system based on the Shack-Hartmann wavefront principle was established to investigate the aberrations of soft contact lenses. Fitting conditions were micmicked to study the optical design of an eye model with various topographical shapes in the anterior cornea. Initially, the contact lenses were measured by the wet-box method, and then by fitting the various topographical shapes of cornea to the eye model. In addition, an optics simulation program was employed to determine the sources of errors and assess the accuracy of the system. Finally, samples of soft contact lenses with various Diopters were measured; and, both simulations and experimental results were compared for resolving the controversies of fitting contact lenses to an eye model for optical measurements. More importantly, the results show that the proposed system can be employed for study of primary aberrations in contact lenses.
Lee, Dasom; Cho, Seungkwon; Park, Hwa Sung; Kwon, Inchan
Ocular drug delivery through hydrogel contact lenses has great potential for the treatment of ocular diseases. Previous studies showed that the loading of lipophilic vitamin E to silicone-hydrogel contact lenses was beneficial in ocular drug delivery. We hypothesized that vitamin E loading to another type of popular hydrogel contact lenses, pHEMA-hydrogel contact lenses, improves ocular drug delivery by increasing the drug loading or the duration of drug release. Loading of vitamin E to pHEMA-hydrogel contact lenses significantly increased the loading of a hydrophilic drug surrogate (Alexa Fluor 488 dye) and two hydrophilic glaucoma drugs (timolol and brimonidine) to the lenses by 37.5%, 19.1%, and 18.7%, respectively. However, the release duration time was not significantly altered. Next, we hypothesized that the lipophilic nature of vitamin E attributes to the enhanced drug loading. Therefore, we investigated the effects of co-loading of another lipophilic vitamin, vitamin A, on drug surrogate delivery. We found out that vitamin A loading also increased the loading of the drug surrogate to pHEMA-hydrogel contact lenses by 30.3%. Similar to vitamin E loading, vitamin A loading did not significantly alter the release duration time of the drug or drug surrogate. PMID:27678247
Fuentes, R.; Fernández, E.; Pascual, I.; García, C.
Protein deposition is one of the most frequent contaminants occurring on hydrophilic contact lenses and may modify the lens optical properties. The silicone-hydrogel contact lenses usually adsorb a lower amount of proteins than the conventional hydrogel ones. However it is important to study the influence of protein deposits on some silicone-hydrogel contact lenses properties, such as UV-Visible transmittance. In this study it is measured de UV-Visible properties of new and worn silicone-hydrogel contact lenses and the transmittance changes that can occur with wear are quantified. An optical fiber spectrometer has been used for measuring the transmittance of contact lenses. This spectrometer has the advantage that the lens can be positioned horizontally and the light beam passes through it perpendicularly. For the measurements, it was necessary to make a special cuvette to put inside the lens and keep it submerged in sterile saline solution. The contact lenses used were Biofinity®. They are manufactured by CooperVision with a material whose technical name is Comfilcon A. This material has not yet been analyzed for this purpose. Moreover, in this type of studies are commonly taken lenses of power -3.00D, however we have not limited to a single power value but we have extended the range to lower and higher values regarding to the standard power in order to see how this parameter affects.
Uçakhan, Ömür; Yanik, Özge
To evaluate the safety and efficacy of the use of the bandage contact lenses (BCLs) in adenoviral keratoconjunctivitis-related ocular surface problems. Fifteen eyes of 15 consecutive patients presenting at the Ankara University Medical Center, Cornea and Contact Lens Service, and requiring BCL use for adenoviral keratoconjunctivitis-related ocular surface problems were enrolled. Visual acuity, slitlamp examination findings, indication and duration of the BCL use, the total follow-up, and any adjuvant medication were recorded. All patients were followed regarding the success of treatment and adverse effects associated with BCL use. The average age at the time of presentation was 26.8±15.5 years. The major reasons for BCL use included epithelial defect (7 eyes), filamentous keratopathy (5 eyes), epithelial edema (1 eyes), and filamentous keratopathy together with epithelial defect (2 eyes). After the first appearance of conjunctivitis symptoms, the mean time to BCL application was 9.0±3.9 days. The mean duration of contact lens wear was 9.9±6.5 days, and the mean follow-up was 26.4±15.8 days. Preservative-free artificial tears and topical antibiotics were used in all cases. Besides, topical ganciclovir 0.15% gel (8 eyes), topical 0.4% povidone-iodine solution (9 eyes), and topical steroids (11 eyes) were used in various combinations. At the end of the follow-up period, the mean visual acuity improved from 0.23±0.32 logMAR units (∼0.6 Snellen line) to 0.0l±0.04 logMAR units (∼1.0 Snellen line) (P=0.042). No sight-threatening complication related to contact lens wear was encountered. Adjuvant use of BCLs seems to be safe and effective in the treatment of adenoviral keratoconjunctivitis-related ocular surface problems. Close follow-up and prophylactic use of topical antibiotics are rationalistic for prevention of secondary infections.
Dahl, A A; Brocks, E R
Forty-two aphakic eyes of 37 patients were fitted with oxygen-permeable silicone rubber corneal contact lenses. Thirty-four eyes had the lens after two to 11 months of continuous use. Visual results, comfort, and patient acceptance were good, but the deposition of mucus on the lenses remains a problem.
Atchison, D A; Smith, G
To investigate the feasibility of using gradient index media in contact lenses, we developed simple methods which we used to derive the power and aberrations associated with the contact lenses. In one method, we assume that the height of a ray does not change as it passes through the lens. We describe a second method in which the ray is assumed to follow a parabolic path as it passes through the lens. We use sophisticated third-order theory and finite raytracing for comparison with these methods. The methods are compared for contact lenses with parabolic radial gradient index media. Without the gradient index, these lenses would have zero power. The formula for power which assumes no change in ray height gives errors of approximally 0.8 and 1.5% for lenses of thicknesses 0.18 and 0.36 mm. However, the formula for third-order spherical aberration which uses the same assumption gives poor estimations. The method for calculating power using the parabolic ray path is very accurate. The sophisticated third-order aberration theory was reasonably accurate out to 2.5 mm ray height. The contact lenses with the gradient index media have much smaller aberration in air than do conventional contact lenses of the same powers, with the sign of the aberration being reversed. Our simple procedures give good estimations of powers of contact lenses with gradient index media. The approximate method, which assumes that the height of a ray does not change as it passes through the lens, should not be used for finding the spherical aberration of such a lens. Contact lenses with gradient index media have potential for minimizing spherical aberration.
Mrazovac, Danijela; Barisić Kutija, Marija; Vidas, Sania; Kuzman, Tomislav; Petricek, Igor; Jandroković, Sonja; Kalauz, Miro; Cerovski, Branimir
Keratoconus is a progressive, non-inflammatory corneal ectasia characterized by thinning and weakening of the corneal stroma which results in its' protrusion. The onset is during puberty and progresses until the fourth decade of life. In earlier stages, good visual acuity can be provided with spectacles. With progression, contact lenses are considered to be a better therapy. Aim of this study was to determine if there is statistically significant difference between best corrected visual acuity (BCVA) obtained by spectacles and contact lenses in newly diagnosed keratoconus patients, as well as to determine which type of contact lenses provide better BCVA in keratoconus patients. We conducted a 5-year retrospective study of all 2891 patients attending our Contact Lens Department for the first time, searching for patients newly diagnosed with keratoconus. Data were obtained on gender, age, education level, treated eyes, corneal changes, keratoconus severity, BCVA with spectacles, contact lenses and best fitted contact lens type. All patients underwent standard ophthalmic exam, refractometry and keratometry have been done, followed by a spectacles correction and lens fitting. Wilcoxon signed rank test was used for statistical analysis. Results showed that of all 2891 patients examined for the first time, 137 patients (4.74%) have been newly diagnosed with heratoconus, there was male bias (72.26%), mean age 27.7 +/- 9.9 years. Most patients had high school education (51.11%), 3.70% had present corneal changes, 50.37% had mild heratoconus. Majority had keratoconus on both eyes (36.3%) or keratoconus of right eye (26.67%). There was a statistically significant difference (p<0.001) between the BCVA obtained with contact lenses (0.82 +/- 0.21 Snellen chart) rather than spectacles (0.37 +/- 0.27 Snellen chart). The best corrected visual acuity was achieved with rigid gas permeable (RGP) lenses in majority of kera- toconus eyes (51.85%), with semi-gas permeable (SGP) lenses
Espy, J W
In a review of the literature, it became apparent that there were very few articles describing the advantages, as well as the fitting techniques, of lathe-cut hydrophilic contact lenses. Few practitioners, including those who fit other types of hydrophilic lenses and hard lenses, have had any experience with this lens, and considerable interest has been generated by fragmentary reports of good results. This paper describes in detail the geometry of the first lathe-cut hydrophilic lens approved by the Federal Drug Administration, the fitting methods utilizing trial lenses, and the results of 100 patients successfully fitted.
Ortiz, Carolina; Jiménez, Raimundo
To study the influence of iris-coloring soft contact lenses, designed for changing apparent iris color, on optical quality and vision. Eighty subjects were included in this study. All participants were classified as emmetropic, with monocular best-corrected visual acuity of 20/20 or better. For 40 subjects, we measured the optical quality (aberrations, the Strehl ratio, and the objective scattering index) and visual performance before and after wearing the cosmetic soft contact lenses. We also measured the optical quality and visual performance for the other 40 subjects but with a different kind of lens (fantasy soft contact lenses). Iris-coloring soft contact lenses significantly increased coma-like and total higher-order aberrations and objective scattering index (p < 0.05). We also found a significant deterioration in the Strehl ratio. The contrast sensitivity function significantly decreased only after wearing the fantasy soft contact lenses (p = 0.047). Iris-coloring soft contact lenses deteriorate the optical quality and worsen the contrast sensitivity function. Iris-coloring soft contact lens wearers should be informed about the effects on optical quality and visual function.
Cox, Stephanie M; Berntsen, David A; Bickle, Katherine M; Mathew, Jessica H; Powell, Daniel R; Little, B Kim; Lorenz, Kathrine Osborn; Nichols, Jason J
To assess whether patient-reported measures are improved with soft toric contact lenses (TCLs) compared with soft spherical contact lenses (SCLs) and whether clinical time needed to fit TCL is greater than SCL. Habitual contact lens wearers with vertexed spherical refraction +4.00 to +0.25 D or -0.50 to -9.00 D and cylinder -0.75 to -1.75 DC were randomly assigned to be binocularly fitted into a TCL or SCL, and masked to treatment assignment. Time to successful fit was recorded. After 5 days, the National Eye Institute Refractive Error Quality of Life Instrument (NEI-RQL-42) and modified Convergence Insufficiency Symptom Survey (CISS) were completed. After washout, subjects were fit into the alternative lens design (TCL or SCL). Outcomes were evaluated using linear mixed models for the time to fit and CISS score, generalized linear model for the successful fit, and Wilcoxon tests for the NEI-RQL-42. Sixty subjects (71.7% women, mean age [±SD] = 27.5±5.0 years) completed the study. The mean time to fit the TCL was 10.2±4.3 and 9.0±6.5 min for the SCL (least square [LS] mean difference (TCL-SCL)=1.2, P=0.22). Toric contact lens scored better than SCL in global NEI-RQL-42 score (P=0.006) and the clarity of vision (P=0.006) and satisfaction with correction subscales (P=0.006). CISS showed a 15% reduction in symptoms (LS mean difference [TCL-SCL]=-2.20, P=0.02). TCLs are a good option when trying to improve the vision of patients with low-to-moderate astigmatism given the subjective improvements in outcomes.
Wettable surfaces of a permanent nature can be produced on contact lenses by means of the technic of chemical deposition of an inorganic film on the...immersion resistance. Stepwise instructions are given for the preparation of hydrophilic surfaces on contact lenses . The equipment developed for this work is relatively simple and inexpensive. (Author)...lens surface. The process is simpler, both in apparatus and procedure, than the vacuum deposition technic designed earlier for producing wettable
Mýlková, M; Pluháček, F
Orthokeratology lenses present a special type of hard contact lenses, which is used especially for myopic correction. The lenses are applied during the night, when thanks to their special shape cause temporally (reversible) change of the cornea shape. During the day, there is not necessary to wear any other refractive correction. Due to the wearing regimen, there is, comparing to the classical contact lenses, higher risk of health complications. For their safe use, it is necessary to pay attention to the application of lenses of adequate parameters, follow up the care and hygiene precautions, regular controls and early treatment of possible problems. The application of contact lenses should be done by experienced and well-educated expert in contact lens fitting. In the Czech Republic, this method is practically not used. The aim of the case report was to follow up the course of concrete application of orthokeratology lenses for myopic correction from the optic (refractive) point of view, and to evaluate the optic changes in the system of the eye. In the followed up subject, there were measured subjective changes in refraction, visual acuity, corneal curvature, corneal and whole eye aberrations, and corneal thickness during the period of one month after the beginning of lens application (initial phase). The same parameters were followed-up during one-month period since the termination of lens wearing for three months (second phase). The subject was a woman, 24 years old, myopic, with the refractive error in the right eye -3.0 spherical diopters and astigmatism of -0.25 cylinder in the axis 90°, and in the left eye -2.75 spherical diopters without astigmatism; without ophthalmologic or systemic diseases. The full correction of the refractive error after the orthokeratology lenses application occurred approximately after four nights (wearing the lenses overnight). Concurrently, during the day, slight recurrence to original values was evident. With the decreased
Kang, Pauline; Fan, Yvonne; Oh, Kelly; Trac, Kevin; Zhang, Frank; Swarbrick, Helen A
To compare changes in peripheral refraction with single-vision (SV) and multifocal (MF) correction of distance central refraction with commercially available SV and MF soft contact lenses (SCLs) in young myopic adults. Thirty-four myopic adult subjects were fitted with Proclear Sphere and Proclear Multifocal SCLs to correct their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with the two different types of SCL correction. At baseline, refraction was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared with center at 30 and 35 degrees in the temporal visual field (VF) in low myopes, and at 30 and 35 degrees in the temporal VF, and 10, 30, and 35 degrees in the nasal VF in moderate myopes. Single-vision and MF distance correction with Proclear Sphere and Proclear Multifocal SCLs, respectively, caused a hyperopic shift in refraction at all locations in the horizontal VF. Compared with SV correction, MF SCL correction caused a significant relative myopic shift at all locations in the nasal VF in both low and moderate myopes and also at 35 degrees in the temporal VF in moderate myopes. Correction of central refractive error with SV and MF SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. Single-vision SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction to experience an absolute hyperopic defocus. Multifocal SCL correction resulted in a relative myopic shift in peripheral refraction compared with SV SCL correction. This myopic shift may explain recent reports of reduced myopia progression rates with MF SCL correction.
Kang, Pauline; Fan, Yvonne; Oh, Kelly; Trac, Kevin; Zhang, Frank; Swarbrick, Helen
To investigate changes in peripheral refraction with under-, full, and over-correction of central refraction with commercially available single vision soft contact lenses (SCLs) in young myopic adults. Thirty-four myopic adult subjects were fitted with Proclear Sphere SCLs to under-correct (+0.75 DS), fully correct, and over-correct (-0.75 DS) their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with different levels of SCL central refractive error correction. The uncorrected refractive error was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared to center at 30 and 35° in the temporal visual field (VF) in low myopes and at 30 and 35° in the temporal VF and 10, 30, and 35° in the nasal VF in moderate myopes. All levels of SCL correction caused a hyperopic shift in refraction at all locations in the horizontal VF. The smallest hyperopic shift was demonstrated with under-correction followed by full correction and then by over-correction of central refractive error. An increase in relative peripheral hyperopia was measured with full correction SCLs compared with no correction in both low and moderate myopes. However, no difference in relative peripheral refraction profiles were found between under-, full, and over-correction. Under-, full, and over-correction of central refractive error with single vision SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. All levels of SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction, to experience absolute hyperopic defocus. This peripheral hyperopia may be a possible cause of myopia progression reported with different types and levels of myopia correction.
Vreugdenhil, W; Eggink, F A; Beekhuis, W H; Theeuwes, A
The relation between corneal thickness changes and the Dk value of rigid contact lenses was investigated in 42 patients who were fitted with contact lenses for the first time. These 42 patients were divided into 4 groups that were fitted with contact lenses of different Dk values. Corneal thickness in the open-eye state was measured (mid-afternoon) before contact lens fitting and after 6 weeks of daily contact lens wear. The changes in corneal thickness were not significantly different among the 4 contact lens materials (Dk values 8, 26, 54, and 92). We conclude that for daily wear use the lower Dk materials meet corneal requirements. However, there is a significant trend; the higher Dk values result in a thinner cornea. Causes for this phenomenon are discussed.
Moore, Linda; Ferreira, Jannie T
The ultraviolet (UV) transmittance spectra of daily wear hydrogel and disposable silicone hydrogel contact lenses were measured. Average transmittance percentages were calculated for each lens for the entire UV spectrum and individually for the UVC, UVB and UVA portions of the spectrum. The significance of the differences in transmittance spectra obtained for the lenses was analysed using a one-way ANOVA planned comparisons test (alpha=0.05). The transmittance data were then used to calculate a UV protection factor (PF) for each contact lens brand tested. The PFs for 1-DAY ACUVUE MOIST (6.22), ACUVUE ADVANCE (10.02) and ACUVUE OASYS (11.96) contact lenses show that these contact lenses have superior UV-blocking capabilities. The PFs for Focus DAILIES (1.79), SofLens 1-day disposables (1.72), NIGHT & DAY (1.84), O2 Optix (1.99) and Purevision (2.62) show that these contact lenses posses more modest UV-blocking characteristics. This paper reviews the importance of protection of the anterior ocular surface from UV damage and quantifies the protection afforded by selected commercially available disposable contact lenses.
Taibbi, Giovanni; Wang, Zhong I; Dell’Osso, Louis F
We investigated the effects of contact lenses in broadening and improving the high-foveation-quality field in a subject with infantile nystagmus syndrome (INS). A high-speed, digitized video system was used for the eye-movement recording. The subject was asked to fixate a far target at different horizontal gaze angles with contact lenses inserted. Data from the subject while fixating at far without refractive correction and at near (at a convergence angle of 60 PD), were used for comparison. The eXpanded Nystagmus Acuity Function (NAFX) was used to evaluate the foveation quality at each gaze angle. Contact lenses broadened the high-foveation-quality range of gaze angles in this subject. The broadening was comparable to that achieved during 60 PD of convergence although the NAFX values were lower. Contact lenses allowed the subject to see “more” (he had a wider range of high-foveation-quality gaze angles) and “better” (he had improved foveation at each gaze angle). Instead of being contraindicated by INS, contact lenses emerge as a potentially important therapeutic option. Contact lenses employ afferent feedback via the ophthalmic division of the V cranial nerve to damp INS slow phases over a broadened range of gaze angles. This supports the proprioceptive hypothesis of INS improvement. PMID:19668758
Radhakrishnan, Aiswaryah; Dorronsoro, Carlos; Sawides, Lucie; Marcos, Susana
Simultaneous vision is an increasingly used solution for the correction of presbyopia (the age-related loss of ability to focus near images). Simultaneous Vision corrections, normally delivered in the form of contact or intraocular lenses, project on the patient's retina a focused image for near vision superimposed with a degraded image for far vision, or a focused image for far vision superimposed with the defocused image of the near scene. It is expected that patients with these corrections are able to adapt to the complex Simultaneous Vision retinal images, although the mechanisms or the extent to which this happens is not known. We studied the neural adaptation to simultaneous vision by studying changes in the Natural Perceived Focus and in the Perceptual Score of image quality in subjects after exposure to Simultaneous Vision. We show that Natural Perceived Focus shifts after a brief period of adaptation to a Simultaneous Vision blur, similar to adaptation to Pure Defocus. This shift strongly correlates with the magnitude and proportion of defocus in the adapting image. The magnitude of defocus affects perceived quality of Simultaneous Vision images, with 0.5 D defocus scored lowest and beyond 1.5 D scored “sharp”. Adaptation to Simultaneous Vision shifts the Perceptual Score of these images towards higher rankings. Larger improvements occurred when testing simultaneous images with the same magnitude of defocus as the adapting images, indicating that wearing a particular bifocal correction improves the perception of images provided by that correction. PMID:24664087
Papadatou, Eleni; Del Águila-Carrasco, Antonio J.; Esteve-Taboada, José J.; Madrid-Costa, David; Cerviño-Expósito, Alejandro
AIM To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses. METHODS Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device (LAMBDA-X, Belgium). Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance (far, intermediate, and near) and pupil size was also analyzed. RESULTS The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about −3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens. CONCLUSION In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient's visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome. PMID:28149785
Vishnubhatla, Sravya; Borchman, Douglas; Foulks, Gary N
Accelerated evaporation of tears may contribute to dry eye symptoms. It is not clear whether contact lenses decrease or increase the rate of evaporation of tears. In this study, the rates of evaporation through contact lenses (ERTCL) were measured in vitro to gain insight to this question. Contact lenses were equilibrated with various solutions to determine if they influenced ERTCL in vitro. ERTCL was measured gravimetrically. ERTCL measured in vitro for used contact lenses was about 20% faster than for buffer alone suggesting that natural tear components bound to the lenses changed the ERTCL. One natural tear component that binds to contact lenses is waxes. Equilibration of contact lenses with wax increased the ERTCL by about 30% suggesting that waxes might potentially increase ERTCL in vivo. Squalene, found in sebum and possibly meibum was infused into the contact lenses as a step toward decreasing the ERTCL. Squalene decreased ERTCL by over 60% in vitro. Soaking a contact lens in DuraSite(®) with benzalkonium chloride (BAK) did not alter the ERTCL. ERTCL were about 40% higher than the evaporation rate of DuraSite(®) alone or without BAK. In addition to lowering the ERTCL, the squalene in contact lenses could be a source of terpenoids to replace the terpenoids deficient in patients with MGD. If the ERTCL could be minimized in vivo, contact lenses could potentially be used to relieve dry eye symptoms in patients with evaporative dry eye. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Rahmani, Saeed; Mohammadi Nia, Mohadeseh; Akbarzadeh Baghban, Alireza; Nazari, Mohammad Reza; Ghassemi-Broumand, Mohammad
Three major parts of sunlight consist of visible, ultraviolet and infrared radiation. Exposure to ultraviolet radiation (UVR) can result in a spectrum of skin and ocular diseases. UV-blocking contact lenses help provide protection against harmful UV radiation. We studied the ultraviolet and visible light rays transmission in some soft UV-blocking contact lenses. Four available tinted soft lenses (Acuvue Moist, Zeiss CONTACT Day 30 Air spheric, Pretty Eyes and Sauflon 56 UV) have been evaluated for UV and visible transmission. One-way ANOVA testing was performed to establish is there a statistically significant difference between the UV regions and visible spectra means for the contact lenses (α=0.05). Pretty Eyes, Zeiss CONTACT, Acuvue Moist and Sauflon 56 UV showed UV-B transmittance value of 0.65%, 10.69%, 1.22%, and 5.78%, respectively. Pretty Eyes and Acuvue Moist had UV-A transmittance values of 32% and 34%, Sauflon 56 UV and Zeiss CONTACT had transmittance values of 48% and 43%, respectively. All of the studied lenses transmitted at least 94.6% on the visible spectrum. The results of the one-way ANOVA statistical analysis show that a statistically significant difference exists within the group of contact lenses tested for the visible (p<0.001), UV-B (p<0.001) and UV-A (p<0.001) portions of the spectrum (α=0.05). Acuvue Moist has the best UV-blocking property and also visible transmission between other tested contact lenses in this study. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Advanced manual lensometry techniques are required when automated lensometry may not be appropriate for reading special lenses or rigid contact lenses. These advanced techniques are challenging but provide accurate diagnostic and lens verification data. One should never assume that the glasses the patient is wearing match what the doctor prescribed. The prescription should be checked at least once, even when there are no patient complaints. If possible, learn and practice these special procedures under the supervision of an optician or ophthalmic clinical trainer. This will help to verify that you are performing these special techniques correctly.
Grzech, Adam; Misiuk-Hojło, Marta
Contact lenses are a modern method of refraction defects correction. Polymers of different kind are a basic material for contact lenses. Only with such a sophisticated material can a functional, yet safe for the eye, contact lens be made. Contact lens must be oxygen-permeable to provide nutrition for cornea which has no own vascular net. In the past decade hydrogel lenses are being replaced with silicone-hydrogels. A new generation of contact lenses does not disturb the physiology of a cornea as much as the old one. Since the introduction of silicone-hydrogel lenses much less side effects have been reported. They can also be used continuously with less risk, over longer period of time. Traditional measures such as oxygen permeability and transmissibility seem inadequate with silicone-hydrogel lenses. Therefore a new measure, an oxygen flux, has been introduced. It is more physiological and more suitable in higher oxygen transfer range. It refers to quantity of oxygen reaching the surface of a cornea.
Vermeltfoort, Pit B J; van der Mei, Henny C; Busscher, Henk J; Hooymans, Johanna M M; Bruinsma, Gerda M
The aim of this study was to determine the transfer of Pseudomonas aeruginosa No. 3 and Staphylococcus aureus 835 from contact lenses to surfaces with different hydrophobicity and roughness. Bacteria were allowed to adhere to contact lenses (Surevue, PureVision, or Focus Night & Day) by incubating the lenses in a bacterial suspension for 30 min. The contaminated lenses were put on a glass, poly(methylmethacrylate), or silicone rubber substratum, shaped to mimic the eye. After 2 and 16 h, lenses were separated from the substrata and bacteria were swabbed off from the respective surfaces and resuspended in saline. Appropriate serial dilutions of these suspensions were made, from which aliquots were plated on agar for enumeration. Bacterial transfer varied between 4 and 60%, depending on the combination of strain, contact time, contact lens, and substratum surface. For P. aeruginosa No. 3, transfer was significantly higher after 16 h than after 2 h, whereas less increase with time was seen for S. aureus 835. Bacterial transfer from all tested contact lenses was least to silicone rubber, the most hydrophobic and roughest substratum surface included.
Omali, Negar Babaei; Subbaraman, Lakshman N; Coles-Brennan, Chantal; Fadli, Zohra; Jones, Lyndon W
Within a few minutes of wear, contact lenses become rapidly coated with a variety of tear film components, including proteins, lipids, and mucins. Tears have a rich and complex composition, allowing a wide range of interactions and competitive processes, with the first event observed at the interface between a contact lens and tear fluid being protein adsorption. Protein adsorption on hydrogel contact lenses is a complex process involving a variety of factors relating to both the protein in question and the lens material. Among tear proteins, lysozyme is a major protein that has both antibacterial and anti-inflammatory functions. Contact lens materials that have high ionicity and high water content have an increased affinity to accumulate lysozyme during wear, when compared with other soft lens materials, notably silicone hydrogel lenses. This review provides an overview of tear film proteins, with a specific focus on lysozyme, and examines various factors that influence protein deposition on contact lenses. In addition, the impact of lysozyme deposition on various ocular physiological responses and bacterial adhesion to lenses and the interaction of lysozyme with other tear proteins are reviewed. This comprehensive review suggests that deposition of lysozyme on contact lens materials may provide a number of beneficial effects during contact lens wear.
Gavara, Rafael; Compañ, Vicente
Oxygen permeability, diffusion coefficient of the sodium ions and water flux and permeability in different conventional hydrogel (Hy) and silicone-hydrogel (Si-Hy) contact lenses have been measured experimentally. The results showed that oxygen permeability and transmissibility requirements of the lens have been addressed through the use of siloxane containing hydrogels. In general, oxygen and sodium chloride permeability values increased with the water content of the lens but there was a percolation phenomenon from a given value of water uptake mainly in the Si-Hy lenses which appeared to be related with the differences between free water and bound water contents. The increase of ion permeability with water content did not follow a unique trend indicating a possible dependence of the chemical structure of the polymer and character ionic and non-ionic of the lens. Indeed, the salt permeability values for silicone hydrogel contact lenses were one order of magnitude below those of conventional hydrogel contact lenses, which can be explained by a diffusion of sodium ions occurring only through the hydrophilic channels. The increase of the ionic permeability in Si-Hy materials may be due to the confinement of ions in nanoscale water channels involving possible decreased degrees of freedom for diffusion of both water and ions. In general, ionic lenses presented values of ionic permeability and diffusivity higher than most non-ionic lenses. The tortuosity of the ionic lenses is lower than the non-ionic Si-Hy lenses. Frequency 55 and PureVision exhibited the highest water permeability and flux values and, these parameters were greater for ionic Si-Hy lenses than for ionic conventional hydrogel lenses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2218-2231, 2017. © 2016 Wiley Periodicals, Inc.
Gaiser, Hilary; Ho, Connie; Janier, Nicole; Wee, Amy; Johnson, Catherine; Watanabe, Ronald
To describe practitioner experiences regarding ocular complications in patients wearing decorative contact lenses, and to investigate the compliance of unauthorized distributors of decorative contact lenses to current Food and Drug Administration (FDA) and Federal Trade Commission (FTC) regulations. Also, to provide data to support a more targeted public health approach to reducing the incidence of illegal contact lens sales and associated ocular complications. An institutional review board-approved online survey was distributed through mass email to a list of 98 optometrists in the Boston, MA area. Concurrently, an empirical evaluation of independent, online decorative contact lens sellers who were not associated with FDA-approved contact lens manufacturers was performed to determine their adherence to FDA and FTC guidelines. The first 18 noncoincidental websites that resulted from a Google search for "costume contact lens sellers" and "cosmetic contact lens sellers" were examined as to the brands and parameters of lenses being sold, whether or not a valid prescription was required or verified, and if consumer education was provided. Twenty-two optometrists completed the online survey. Seventy-seven percent of respondents reported having patients with complications from decorative contact lenses that were purchased both legally and illegally. The most common age group for complications was 18 to 25 years (61%). One third of complications were seen in first-time lens wearers, half of whom never received proper care instructions or were unaware that care instructions existed. One quarter of the lenses were purchased illegally with unlicensed stores being the most common place of purchase. Of the 18 online sites examined, 72% of sellers failed to adhere to FTC and FDA regulations. A significant number of individuals who obtain contact lenses illegally from unauthorized sources are young adults. Most unauthorized sellers reviewed did not adhere to the proper protocol
Lee, Se Eun; Kim, So Ra; Park, Mijung
Purpose. To investigate the effect of tear protein deposition on the change in oxygen permeability (Dk) of soft contact lenses (SCL). Methods. Three hydrogel lenses (polymacon, nelfilcon A, and etafilcon A) and two silicon hydrogel lenses (lotrafilcon A and balafilcon A) were investigated. Etafilcon A lenses were incubated in artificial tear solution for 1, 6, 12, and 48 h, whereas the other SCL were incubated for 1, 3, 7, and 14 days. Oxygen permeability was measured using the polarographic method, and lenses were stacked in four layers to correct the boundary effect. Results. The Dk of all investigated SCL was decreased by the protein deposition. Silicone hydrogel lenses showed a smaller deposition of artificial tear proteins than conventional hydrogel lenses. However, their Dk was reduced twofold than those of 3 conventional hydrogel lenses when compared at the same level of protein deposition. Despite a large amount of total deposited protein in etafilcon A lenses, their Dk was more stable than other SCL. Conclusions. From the results, it was revealed that the Dk of SCL is different from the value provided by manufacturers because of the tear protein deposition on surface and/or in pore of SCL; however, the degree of Dk change in SCL was not simply correlated with the amount of tear protein deposition. Thus, it is considered that the correlation between tear protein deposition and properties of lens materials affects Dk change.
Purpose. To investigate the effect of tear protein deposition on the change in oxygen permeability (Dk) of soft contact lenses (SCL). Methods. Three hydrogel lenses (polymacon, nelfilcon A, and etafilcon A) and two silicon hydrogel lenses (lotrafilcon A and balafilcon A) were investigated. Etafilcon A lenses were incubated in artificial tear solution for 1, 6, 12, and 48 h, whereas the other SCL were incubated for 1, 3, 7, and 14 days. Oxygen permeability was measured using the polarographic method, and lenses were stacked in four layers to correct the boundary effect. Results. The Dk of all investigated SCL was decreased by the protein deposition. Silicone hydrogel lenses showed a smaller deposition of artificial tear proteins than conventional hydrogel lenses. However, their Dk was reduced twofold than those of 3 conventional hydrogel lenses when compared at the same level of protein deposition. Despite a large amount of total deposited protein in etafilcon A lenses, their Dk was more stable than other SCL. Conclusions. From the results, it was revealed that the Dk of SCL is different from the value provided by manufacturers because of the tear protein deposition on surface and/or in pore of SCL; however, the degree of Dk change in SCL was not simply correlated with the amount of tear protein deposition. Thus, it is considered that the correlation between tear protein deposition and properties of lens materials affects Dk change. PMID:28280635
Maulvi, Furqan A; Desai, Ankita R; Choksi, Harsh H; Patil, Rahul J; Ranch, Ketan M; Vyas, Bhavin A; Shah, Dinesh O
The effect of surfactant chain lengths [sodium caprylate (C8), Tween 20 (C12), Tween 80 (C18)] and the molecular weight of block copolymers [Pluronic F68 and Pluronic F 127] were studied to determine the stability of the microemulsion and its effect on release kinetics from cyclosporine-loaded microemulsion-laden hydrogel contact lenses in this work. Globule size and dilution tests (transmittance) suggested that the stability of the microemulsion increases with increase in the carbon chain lengths of surfactants and the molecular weight of pluronics. The optical transmittance of direct drug-laden contact lenses [DL-100] was low due to the precipitation of hydrophobic drugs in the lenses, while in microemulsion-laden lenses, the transmittance was improved when stability of the microemulsion was achieved. The results of in vitro release kinetics revealed that drug release was sustained to a greater extent as the stability of microemulsion was improved as well. This was evident in batch PF127-T80, which showed sustained release for 15days in comparison to batch DL-100, which showed release up to 7days. An in vivo drug release study in rabbit tear fluid showed significant increase in mean residence time (MRT) and area under curve (AUC) with PF-127-T80 lenses (stable microemulsion) in comparison to PF-68-SC lenses (unstable microemulsion) and DL-100 lenses. This study revealed the correlation between the stability of microemulsion and the release kinetics of drugs from contact lenses. Thus, it was inferred that the stable microemulsion batches sustained the release of hydrophobic drugs, such as cyclosporine from contact lenses for an extended period of time without altering critical lens properties.
Willcox, M D; Power, K N; Stapleton, F; Leitch, C; Harmis, N; Sweeney, D F
The aim of this paper was to determine the possible contamination sources of contact lenses during wear. Potential sources of the microbiota that colonized hydrogel contact lenses during wear were examined. The microorganisms that colonize contact lenses were grown, identified, and compared to those microorganisms that colonized the lower lid margins, upper bulbar conjunctiva, hands, and contact lens cases of contact lens wearers. In addition, the incidence of contamination of the domestic water supply in the Sydney area was obtained, and this was compared to the incidence of colonization of contact lenses by microorganisms in general and gram-negative bacteria in particular. There was a wide diversity of bacteria that were isolated from each site sampled. Coagulase-negative staphylococci and Propionibacterium spp. were the most common isolates from all ocular sites examined, and constituted the normal ocular microbiota. Other bacteria, including members of the families Enterobacteriaceae and Pseudomonadaceae, were isolated infrequently from all sites, but most frequently from contact lens cases. Statistical analysis revealed that there was a correlation between the isolation of bacteria from the contact lens and the lower lid margin (p < 0.001). Analysis of this correlation revealed that this was true for the normal microbiota. A correlation was also noted between the colonization of contact lenses by gram-negative bacteria and contamination of the domestic water supply. This study has demonstrated that the likely route for the normal ocular microbiota colonizing contact lenses is via the lid margins, whereas colonization by gram-negative bacteria, including potential agents of microbial keratitis, is likely to be from the domestic water supply.
Hsu, Kuan-Hui; Fentzke, Richard C; Chauhan, Anuj
Cystinosis is an inherited genetic disease characterized by the accumulation of cystine crystals in several tissues including the cornea. The corneal manifestations of cystinosis are treated by hourly instillation of cysteamine eye drops each day while awake. The high frequency of eye drop instillation along with the long duration of treatment leads to poor compliance in many patients. We have combined in vitro experiments with mathematical modeling to investigate the feasibility of daily use of cysteamine loaded contact lenses to replace the hourly instillation of drops. Our approach was based on incorporation of vitamin E diffusion barriers into commercially available contact lenses to increase the duration of drug release. Contact lenses were first soaked in a solution of vitamin E in ethanol. Subsequently, the lenses were soaked in an aqueous solution of cysteamine to load the drug. The drug release profiles from vitamin E treated lenses were measured under sink conditions. In addition, drug oxidation rates were measured after exposing drug loaded contact lenses to humidified room air. To study further the feasibility of using contact lenses for the delivery of cysteamine, a mass transfer model was used to determine the rates at which the drug loaded in the lens is delivered to the cornea. The results show that vitamin E loading increases the release duration from 10 min to about 3 h in solution, thus allowing the possibility of extended drug delivery. In addition to improving the release profiles, vitamin E loading also improved the drug stability by reducing the oxidation rates. The mathematical modeling of drug transport in the eye suggested that the vitamin E loaded contact lens can provide the daily therapeutic dose without causing toxicity, while significantly increasing the bioavailability compared to eye drops. Based on the in vitro experimental results and the mathematical modeling, it is likely that a single contact lens worn for about 2h could
Choo, Jennifer; Vuu, Kathy; Bergenske, Peter; Burnham, Kara; Smythe, Jennifer; Caroline, Patrick
A number of reports have indicated an association between swimming with contact lenses and subsequent eye infection. This study tests whether a hydrophilic contact lens worn while swimming accumulates bacteria present in the water. It was of interest to determine whether lens type (silicone hydrogel vs. hydrogel) affected the result. Fifteen healthy noncontact lens wearers swam for 30 minutes with a silicone hydrogel lens (PureVision, Bausch & Lomb, Rochester, NY) on one eye and a hydrogel lens (Acuvue 2, Vistakon Inc., Jacksonville, FL) on the other. Lenses were removed aseptically and placed in sterile vials 10 minutes after the subjects left the water. Microbial growth was enumerated for total numbers of colonies and categorized by species present. Numbers of colonies were compared between the two lens groups and with a water sample taken from the pool at the time of the experiment. Eight of the subjects returned on a different day and wore new lenses for 50 minutes in normal room conditions. Two lenses were lost while swimming. Twenty-seven of the remaining 28 lenses worn while swimming showed colonization, principally with Staphylococcus epidermidis, which was also by far the most common species identified from the water itself. Small numbers of Staphylococcus aureus and Streptococcus salivarius were also present in the water and on the lenses. Numbers of colonies varied among subjects (range, 0 to 230), but no differences were observed between the two lens groups. Lenses removed after 30 minutes of wear without swimming were mostly sterile, with 3 of 16 lenses showing just two colonies each. It appears that wearing a hydrophilic lens while swimming allows accumulation of microbial organisms on or in the lens, regardless of lens material. Swimmers should be advised to wear tight-fitting goggles if lenses are worn while swimming, and thorough disinfection of the lenses before overnight wear seems prudent.
Filipecki, J; Sitarz, M; Kocela, A; Kotynia, K; Jelen, P; Filipecka, K; Gaweda, M
Determination of free volume holes of the hydrogel and silicone-hydrogel polymer contact lenses were investigated. Two types of polymer contact lenses were used as materials: the first is a hydrogel contact lenses Proclear family (Omafilcon A), while the second is a silicone-hydrogel contact lens of the family Biofinity (Comfilcon A). Positron annihilation lifetime spectroscopy PALS was used to characterize geometrical sizes and fraction of the free volume holes in the investigated samples. There is a clear difference in the free volume sizes and their fractions between silicone-hydrogel and polymer hydrogel contact lenses which in turn are connected with oxygen permeability in these lenses. Apart from that, spectroscopic (middle infrared) MIR and Raman examinations were carried out in order to demonstrate the differences of the water content in the test contact lenses.
Hsu, Kuan-Hui; Carbia, Blanca E; Plummer, Caryn; Chauhan, Anuj
Glaucoma patients frequently instill eye drops multiple times each day, which is a cause for reduced compliance. Additionally, eye drops suffer from other limitations including low bioavailability, which can lead to side effects. We propose to develop drug-eluting contact lenses for managing glaucoma with increased bioavailability and improved compliance. Contact lenses are developed for extended simultaneous release of timolol and dorzolamide, both of which are commonly prescribed hydrophilic drugs. The extended release is achieved by loading lenses with vitamin E barriers. In vitro release studies are performed with control and vitamin E loaded lenses for both drugs loaded separately and then together in the same lens. The safety and efficacy of combination therapy by contacts are demonstrated in a Beagle model of glaucoma. Simultaneous loading of timolol and dorzolamide increases the release duration of both drugs. Also vitamin E incorporation is highly effective in increasing the release durations of both drugs to about 2-days. The lenses loaded with both drugs exhibited superior IOP reduction compared to eye drops with about 6-fold lower drug loading. More importantly, combination therapy by continuous wear of vitamin E loaded contact for 2-days, followed by a new set of contacts for another two days, reduced IOP during the 4days of wear time and for another 8days after removal of the contacts. Vitamin E loading is very effective for providing combination therapy by contact lenses due to the increase in release durations of several drugs. The contact lens based therapy reduces IOP with lower drug dose compared to eye drops and may significantly improve the compliance as the effect of the therapy lasts significantly longer than the wear-duration.
In 3 patients with status after Fuchs-Steven-Johnson syndrome highly hydrophilic contact lenses (72% H2O-up take) were adapted and worn permanently. 2 patients had worn already for a long time usual HEMA-lenses. The lenses showed themselves to be favorable against mechanical irritation from cilia and accessory eyelashes and from scarring conjunctival conditions, and they affected favorably the signs of dessication of the cornea. Corneal defects healed, and the patients had subjectively no complaints. It is sometimes necessary to replace the tears. An increase in the corneal vascularisation already present could not be observed during the 18 months observation time.
Tsukiyama, Junko; Miyamoto, Yuko; Kodama, Aya; Fukuda, Masahiko; Shimomura, Yoshikazu
Previous reports showed that cosmetic cleansing oil for removing makeup, which contains mineral oil and surfactant, can deform some silicone hydrogel contact lenses (SHCLs) when applied directly to the lenses, although plasma-coated SHCLs (lotrafilcon A and B) were not affected. In the present study, we investigated hydrogel lenses and SHCLs in both wet and dry conditions. Several brands of hydrogel and SHCLs were immersed in a cleansing oil solution containing Sudan Black B for 5 min under wet and dry conditions. The lenses under the wet condition were simply picked up from the saline, whereas those under the dry condition were blotted with paper wipes. After immersing, the excess solution remaining on the lenses was removed by finger rubbing with a multipurpose solution. The lenses were then examined using a stereomicroscope, and their mean brightness was measured and compared. The cosmetic cleansing oil was not absorbed by the hydrogel lenses under wet or dry conditions. However, four of seven brands of SHCLs absorbed the cosmetic cleansing oil under both conditions (dry and wet), whereas asmofilcon A absorbed it only under the dry condition. Lotrafilcon B and delefilcon A did not absorb cleansing oil even under the dry condition. Hydrogel lenses resist cosmetic cleansing oil. However, SHCLs have different degrees of resistance depending on the lens material. Some SHCLs absorbed cosmetic cleansing oil more under dry conditions than under wet conditions.
It is well established that both acute and chronic ultraviolet (UV) exposure can lead to various ophthalmic pathologic conditions in the anterior segment. Several scientific studies have demonstrated that after UV exposure, the unprotected cornea is vulnerable to damage in the epithelial, stromal, and endothelial cellular layers. DNA damage, apoptosis, and altered protease expression are all examples of harmful changes that can occur within the cornea after irradiation. Beyond the cornea, damage associated with UV exposure, such as decreased antioxidant levels and increased reactive oxygen species production, has been noted in the aqueous humor and crystalline lens. Ultraviolet-blocking contact lenses have the potential to provide protection against such exposure to harmful UV radiation. Experimental use of UV-absorbing contact lenses prevented detrimental cellular changes to the cornea and maintained corneal clarity after UV exposure. Additionally, studies suggest that shielding the aqueous humor and crystalline lens from irradiation with UV-absorbing contact lenses aids in protection against precataractous changes. Despite ongoing research, to date, neither chronic nor clinical studies have been performed in humans to demonstrate that wearing UV-blocking contact lenses reduces the risk of developing cataracts or other ocular disorders within the anterior segment. This article will discuss the impact of UV exposure on ocular tissue and the need for adequate UV protection, with particular emphasis on UV-blocking contact lenses.
Smith, Kyle A; Carrell, James D
The authors describe a case of a keratoconic patient with Intacs fitted with a high-Dk piggyback contact lens system. A 41-year-old man presented to the clinic 1 week after Intacs surgery for keratoconus with complaints of poor visual acuity (VA) and monocular polyopia OU. The patient was corrected to 20/30 in both eyes with rigid gas permeable contact lenses but could not tolerate the lenses for more than 8 hours OD and 2 hours OS. The patient was then successfully fit with a high-Dk piggyback contact lens system. The patient was able to wear the piggyback contact lenses comfortably 12 to 18 hours per day and was corrected to 20/25 OD, 20/30 OS, and 20/20 OU. Patients with Intacs for keratoconus may require a combination of soft and rigid contact lenses for the best possible VA. Contact lens fitting with a high-Dk piggyback contact lens system can provide optimal comfort, corneal health, and VA for patients with Intacs for keratoconus.
Reverey, Julia F; Fromme, Roland; Leippe, Matthias; Selhuber-Unkel, Christine
To compare the potential of different soft contact lenses to be contaminated with Acanthamoeba castellanii as a function of material parameters and cleaning procedures. Different unworn soft hydrogel and silicone hydrogel contact lenses were incubated with human pathogenic A. castellanii. The adhesion of the acanthamoebae was investigated on the contact lenses and put into relation to their material parameters. The efficacy of a recommended contact lens cleaning procedure in reducing A. castellanii adhesion was investigated. We found that material parameters such as elastic modulus, silicone content, ionic properties and swelling do not influence the adhesion of acanthamoebae to soft contact lenses. A material parameter that influenced adhesion significantly was the water content of the lens. With increasing water content, the adhesion of acanthamoebae increased. By following the cleaning instructions of the manufacturer the contamination of the lenses with A. castellanii could be reduced to a minimum, as shown both on contact lenses and in control experiments. With this study we show that for the tested lenses, the adhesion of A. castellanii to contact lenses is independent of the silicone content of the lens, but depends nonlinearly on the water content of the lens. Furthermore, we demonstrate that applying proper lens cleaning procedures minimizes the risk of acanthamoebae adhesion to contact lenses. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Lövsund, P; Nilsson, S E; Lindh, H; Oberg, P A
Because of reports of risks associated with the use of contact lenses during exposure to welding arcs, the temperature changes in soft contact lenses were recorded in connection with certain types of welding [manual metal arc (MMA) welding, tungsten inert-gas (TIG) welding, and metal inert-gas (MIG) welding], both with free-hanging lenses and lenses applied to the eyes of anesthetized rabbits. A great increase in temperature was noted, especially with MMA welding. At a distance of 0.4 m the temperature of a lens on a rabbit eye rose from about 35 to 50 degrees C within 6 min, whereas the air temperature only increased from 23 to 30 degrees C. The increase was the greatest at the beginning of the welding period. Most of the lenses completely dried out during the experiment, and there would seem to be a potential risk that the lens would adhere to the cornea. One safety glass screen (DIN 10 A) proved effective in preventing the rise in temperature in contact lenses during MMA welding. Even though it is impossible to direct the eyes at the arc for a prolonged period of time, the use of contact lenses in connection with at least certain types of welding is not to be recommended without the use of a suitable safety glass screen (or safety glasses). With regard to the large number of particles in the welding environment, also a risk factor for contact lens wearers, it is doubtful whether even safety glasses or screens are satisfactory unless they fit closely.
Pucker, Andrew D.; Thangavelu, Mirunalni
Purpose. The purpose of this work was to develop an enzymatic method of quantification of cholesterol and cholesterol esters derived from contact lenses, both in vitro and ex vivo. Methods. Lotrafilcon B (O2 Optix; CIBA Vision, Inc., Duluth, GA) and galyfilcon A (Acuvue Advance; Vistakon, Inc., Jacksonville, FL) silicone hydrogel contact lenses were independently incubated in cholesterol oleate solutions varying in concentrations. After incubation, the lenses were removed and underwent two separate 2:1 chloroform-methanol extractions. After in vitro studies, 10 human subjects wore both lotrafilcon B and galyfilcon A contact lenses for 7 days. The lenses also underwent two separate 2:1 chloroform-methanol extractions. All in vitro and ex vivo samples were quantified with a cholesterol esterase enzymatic reaction. Results. Calibration curves from quantifications of in vitro contact lens samples soaked in successively decreasing concentrations of cholesterol oleate yielded coefficients of determination (R2) of 0.99 (lotrafilcon B) and 0.97 (galyfilcon A). For in vitro contact lens samples, galyfilcon A was associated with an average cholesterol oleate extraction of 39.85 ± 48.65 μg/lens, whereas lotrafilcon B was associated with 5.86 ± 3.36 μg/lens (P = 0.05) across both extractions and all incubation concentrations. For ex vivo contact lens samples, there was significantly more cholesterol and cholesterol esters deposited on galyfilcon A (5.77 ± 1.87 μg/lens) than on lotrafilcon B (2.03 ± 1.62 μg/lens; P = 0.0005). Conclusions. This is an efficient and simple method of quantifying total cholesterol extracted from silicone hydrogel contact lenses and, potentially, the meibum and/or tear film. Certain silicone hydrogel materials demonstrate more affinity for cholesterol and its esters than do others. PMID:20089871
Pucker, Andrew D; Thangavelu, Mirunalni; Nichols, Jason J
The purpose of this work was to develop an enzymatic method of quantification of cholesterol and cholesterol esters derived from contact lenses, both in vitro and ex vivo. Lotrafilcon B (O2 Optix; CIBA Vision, Inc., Duluth, GA) and galyfilcon A (Acuvue Advance; Vistakon, Inc., Jacksonville, FL) silicone hydrogel contact lenses were independently incubated in cholesterol oleate solutions varying in concentrations. After incubation, the lenses were removed and underwent two separate 2:1 chloroform-methanol extractions. After in vitro studies, 10 human subjects wore both lotrafilcon B and galyfilcon A contact lenses for 7 days. The lenses also underwent two separate 2:1 chloroform-methanol extractions. All in vitro and ex vivo samples were quantified with a cholesterol esterase enzymatic reaction. Calibration curves from quantifications of in vitro contact lens samples soaked in successively decreasing concentrations of cholesterol oleate yielded coefficients of determination (R(2)) of 0.99 (lotrafilcon B) and 0.97 (galyfilcon A). For in vitro contact lens samples, galyfilcon A was associated with an average cholesterol oleate extraction of 39.85 +/- 48.65 microg/lens, whereas lotrafilcon B was associated with 5.86 +/- 3.36 microg/lens (P = 0.05) across both extractions and all incubation concentrations. For ex vivo contact lens samples, there was significantly more cholesterol and cholesterol esters deposited on galyfilcon A (5.77 +/- 1.87 microg/lens) than on lotrafilcon B (2.03 +/- 1.62 microg/lens; P = 0.0005). This is an efficient and simple method of quantifying total cholesterol extracted from silicone hydrogel contact lenses and, potentially, the meibum and/or tear film. Certain silicone hydrogel materials demonstrate more affinity for cholesterol and its esters than do others.
Erdogan, Gizem; Ross, Arun
Recent research in iris recognition has established the impact of non-cosmetic soft contact lenses on the recognition performance of iris matchers. Researchers in Notre Dame demonstrated an increase in False Reject Rate (FRR) when an iris without a contact lens was compared against the same iris with a transparent soft contact lens. Detecting the presence of a contact lens in ocular images can, therefore, be beneficial to iris recognition systems. This study proposes a method to automatically detect the presence of non-cosmetic soft contact lenses in ocular images of the eye acquired in the Near Infrared (NIR) spectrum. While cosmetic lenses are more easily discernible, the problem of detecting non-cosmetic lenses is substantially difficult and poses a significant challenge to iris researchers. In this work, the lens boundary is detected by traversing a small annular region in the vicinity of the outer boundary of the segmented iris and locating candidate points corresponding to the lens perimeter. Candidate points are identified by examining intensity profiles in the radial direction within the annular region. The proposed detection method is evaluated on two databases: ICE 2005 and MBGC Iris. In the ICE 2005 database, a correct lens detection rate of 72% is achieved with an overall classification accuracy of 76%. In the MBGC Iris database, a correct lens detection rate of 70% is obtained with an overall classification accuracy of 66:8%. To the best of our knowledge, this is one of the earliest work attempting to detect the presence of non-cosmetic soft contact lenses in NIR ocular images. The results of this research suggest the possibility of detecting soft contact lenses in ocular images but highlight the need for further research in this area.
Kim, Joohee; Kim, Minji; Lee, Mi-Sun; Kim, Kukjoo; Ji, Sangyoon; Kim, Yun-Tae; Park, Jihun; Na, Kyungmin; Bae, Kwi-Hyun; Kyun Kim, Hong; Bien, Franklin; Young Lee, Chang; Park, Jang-Ung
Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on an actual ocular contact lens. It was also designed to monitor glucose within tears, as well as intraocular pressure using the resistance and capacitance of the electronic device. Furthermore, in-vivo and in-vitro tests using a live rabbit and bovine eyeball demonstrated its reliable operation. Our developed contact lens sensor can measure the glucose level in tear fluid and intraocular pressure simultaneously but yet independently based on different electrical responses.
Kim, Joohee; Kim, Minji; Lee, Mi-Sun; Kim, Kukjoo; Ji, Sangyoon; Kim, Yun-Tae; Park, Jihun; Na, Kyungmin; Bae, Kwi-Hyun; Kyun Kim, Hong; Bien, Franklin; Young Lee, Chang; Park, Jang-Ung
Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on an actual ocular contact lens. It was also designed to monitor glucose within tears, as well as intraocular pressure using the resistance and capacitance of the electronic device. Furthermore, in-vivo and in-vitro tests using a live rabbit and bovine eyeball demonstrated its reliable operation. Our developed contact lens sensor can measure the glucose level in tear fluid and intraocular pressure simultaneously but yet independently based on different electrical responses. PMID:28447604
Kim, Joohee; Kim, Minji; Lee, Mi-Sun; Kim, Kukjoo; Ji, Sangyoon; Kim, Yun-Tae; Park, Jihun; Na, Kyungmin; Bae, Kwi-Hyun; Kyun Kim, Hong; Bien, Franklin; Young Lee, Chang; Park, Jang-Ung
Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on an actual ocular contact lens. It was also designed to monitor glucose within tears, as well as intraocular pressure using the resistance and capacitance of the electronic device. Furthermore, in-vivo and in-vitro tests using a live rabbit and bovine eyeball demonstrated its reliable operation. Our developed contact lens sensor can measure the glucose level in tear fluid and intraocular pressure simultaneously but yet independently based on different electrical responses.
Lin, Meng C.; Svitova, Tatyana F.
Purpose To investigate the release of surface-active agents (surfactants) from unworn soft contact lenses and their influence on the lens surface wettability in vitro. Methods Surface tension (ST) of blister pack solutions was measured by pendant-drop technique. STs at the air-aqueous interface and contact angles (CAs) of four conventional and seven silicone hydrogel (SiH) soft contact lenses (SCLs) were evaluated in a dynamic-cycling regime using a modified captive-bubble tensiometer-goniometer. Measurements were performed immediately after removal from blister packs, and after soaking in a glass vial filled with a surfactant-free solution, which was replaced daily for one week. Lens surface wettability was expressed as adhesion energy (AE) according to Young’s equation. Results STs of all blister pack solutions were lower than the reference ST of pure water (72.5 mN/m), indicating the presence of surfactants. When lenses were depleted of surfactants by soaking, the STs of all studied lenses and advancing CAs of selected lenses increased (p < 0.001). Receding CAs of all studied lenses were 12° ± 5° and were not affected by the presence of surfactants. For most of the conventional lenses, the surface wettability was largely dependent on surfactants, and reduced significantly after surfactant depletion. In contrast, most SiH lenses exhibited stable and self-sustained surface wettability in vitro. Conclusions The manufacturer-added surfactants affected wetting properties of all studied SCLs, although to different degrees. PMID:20400924
Roth, H W
Use of a computer connected with a slit-lamp-video-camera detected changes in the cornea topography after wearing contact lenses on a daily basis. Also subtle surface changes were observed within the upper portion of the areas measured. These appeared to be spiral-shaped or cloudlike patterns as a result of wearing hard or soft contact lenses respectively. The changes observed appeared to have resulted from movement of the contact lens. However, this device has also been used to determine changes that are similar in early keratokonus. The computer can store data from 1600 sites on the surface; there sites are distributed over a 4-mm diameter area in the central cornea. On command the computer can display an image of the corneal surface. Images from hour 0 and 6 weeks later were compared to determine the topographic differences. The surface patterns observed after 6 weeks of wearing lenses appeared to be involve numerous small depressions.
Efron, N; Carney, L G
The oxygen tension, which can also be stated as the equivalent oxygen percentage (EOP), was measured beneath a variety of hard and soft gas-permeable contact lenses following static and dynamic wearing conditions. The significant increases in EOP beneath rigid lenses upon blinking were to be expected in view of the tear pumping mechanisms known to exist with such lenses. However, blinking was found to have a minimal effect on the EOP beneath hydrogen lenses, confirming earlier predictions.
López-Alemany, Antonio; Compañ, Vicente; Refojo, Miguel F
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevisiontrade mark (balafilcon A) and Focus(R)Night&Daytrade mark (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence(R)), medium (Acuvue(R)), and high water content (Precision UV(R)) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO(2), and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observed on the front and back surfaces, and in their bulk. The average diameter of the macropores appears to be much larger, from one to several orders of magnitude, than the network porosity of standard hydrogel lenses. The macropores might contribute to the gas and water permeability of these lenses, as well as to their mobility on the cornea.
Jung, Hyun Jung; Abou-Jaoude, Michelle; Carbia, Blanca E; Plummer, Caryn; Chauhan, Anuj
Glaucoma is the second major cause of blindness in the world after cataract. Glaucoma management through eye drops that reduce the intraocular pressure (IOP) has major deficiencies including low patient compliance and low bioavailability. Extended wear contact lenses that deliver glaucoma drugs for extended periods could increase patient compliance, while also increasing the bioavailability. To develop extended wear contact lenses that can also provide extended glaucoma therapy, we disperse nanoparticles of PGT (propoxylated glyceryl triacylate) that contain a glaucoma drug timolol. The particles can also be loaded into prefabricated lenses by soaking the lenses in a solution of particles in ethanol. The particle loaded gels can release timolol in phosphate buffered saline (PBS) for about a month at room temperature. The most likely rate controlling mechanism is hydrolysis of the ester bond that links timolol to the PGT matrix, but other mechanisms such as water and drug diffusion, drug dissolution, drug-polymer chain cleavage, time-dependent drug permeability within the polymeric matrix, etc. may also be important. Nanoparticle incorporation in the silicone hydrogels results in reduction in ion and oxygen permeabilities, and an increase in modulus, and the impact on each of these properties is proportional to the particle loading. A gel with 5% particle loading can deliver timolol at therapeutic doses for about a month at room temperature, with a minimal impact on critical lens properties. Preliminary animal studies in Beagle dogs conducted with lenses in which particles are loaded by soaking the lenses in ethanol show a reduction in IOP.
Jones, L; Franklin, V; Evans, K; Sariri, R; Tighe, B
Twelve subjects were fitted with a high water content, nonionic contact lens (Pilkington Barnes-Hind "Precision UV"), which was either replaced every month for 3 months or worn for 3 consecutive months before replacement occurred. Visual quality, high and low contrast acuity, and comfort were unaltered with either replacement schedule, but overall satisfaction was significantly greater with the shorter replacement schedule (p = 0.04). Front surface wettability revealed a large amount of intersubject variability and was reduced at the 3-month visit with the longer replacement period lenses (p = 0.003). Visible deposits also increased with longer replacement times (p < 0.05). Laboratory-based analytical results showed that both gross lipid and gross extractable protein significantly increased in the 3-month lenses compared with the 1-month lenses, with 44% less lipid accumulation and 60% less protein deposition occurring with the shorter replacement time. The results support the replacement of high water content lenses on a monthly basis.
Hall, Brad; Forrest, James A; Jones, Lyndon
To compare and critically evaluate a variety of techniques to measure the quantity and biological activity of protein sorption to contact lenses over short time periods. A literature review was undertaken investigating the major techniques to measure protein sorption to soft contact lens materials, with specific reference to measuring protein directly on lenses using in situ, ex situ, protein structural, and biological activity techniques. The use of in situ techniques to measure protein quantity provides excellent sensitivity, but many are not directly applicable to contact lenses. Many ex situ techniques struggle to measure all sorbed proteins, and these measurements can have significant signal interference from the lens materials themselves. Techniques measuring the secondary and tertiary structures of sorbed proteins have exhibited only limited success. There are a wide variety of techniques to measure both the amount of protein and the biological activity of protein sorbed to soft contact lens materials. To measure the mass of protein sorbed to soft contact lenses (not just thin films) over short time periods, the method of choice should be I radiolabeling. This technique is sensitive enough to measure small amounts of deposited protein, provided steps are taken to limit and measure any interaction of the iodine tracer with the materials. To measure the protein activity over short time periods, the method of choice should be to measure the biological function of sorbed proteins. This may require new methods or adaptations of existing ones.
Milton, Harry E.; Gleeson, Helen F.; Morgan, Philip B.; Goodby, John W.; Cowling, Stephen; Clamp, John H.
The inability of the eye to focus on nearby objects, presbyopia, is suffered by ~100% of people over the age of 50. Liquid crystal (LC) spectacle lenses have shown great potential for correcting presbyopia. However, correcting presbyopia in contact lens users has proven elusive and existing commercial options suffer significant compromises in vision and comfort. We describe a novel contact lens that includes a liquid crystal element that offers to correct presbyopia without the compromises associated with other technologies. We fabricated variable focus lenses using a balanced optical system, providing the additional optical power presbyopes require for near vision (typically +1.00 D to +2.00 D). The system uses positive optical power from the two substrates and variable negative optical power from the LC layer to form a balanced optical system which, when unpowered, corrects distance vision. Upon voltage application, the liquid crystal layer decreases in refractive index, resulting in additional optical power in the system, offering correction equivalent to reading glasses. Our new technology is based on a traditional contact lens material which could be placed directly on the eye. The liquid crystal lens employed is well suited to the small optical areas associated with contact lenses. We compare several different LC materials and geometries which are suitable for our application, and discuss the influence of material and geometry on switching times, optical quality and operating voltage. Our contact lenses typically switch +/-2.00D in response to < 10 Vrms with response times of the order of a second.
Paradiso, Patrizia; Serro, Ana Paula; Saramago, Benilde; Colaço, Rogério; Chauhan, Anuj
Symptoms of bacterial and fungal keratitis are typically treated through the frequent application of antibiotic and antifungal eye drops. The high frequency of half hourly or hourly eye drop administration required to treat these indications is tedious and could reduce compliance. Here, we combine in vitro experiments with a mathematical model to develop therapeutic soft contact lenses to cure keratitis by extended release of suitable drugs. We specifically focus on increasing the release duration of levofloxacin and chlorhexidine from 1-DAY ACUVUE(®) TrueEye™ and ACUVUE OASYS(®) contact lenses by incorporating vitamin E diffusion barriers. Results show that 20% of vitamin E loading in the contact lens increases the release duration of levofloxacin to 100 h and 50 h from 1-DAY ACUVUE(®) TrueEye™ and ACUVUE OASYS(®), respectively, which is a 3- and 6-fold increase, respectively, for the 2 lenses. For chlorhexidine, the increase is 2.5- and 10-fold, for the TrueEye™ and OASYS(®), respectively, to 130 h and 170 h. The mass of drug loaded in the lenses can be controlled to achieve a daily release comparable to the commonly prescribed eye drop therapy. The vitamin E-loaded lenses retain all critical properties for in vivo use.
Kollbaum, Pete S.; Bradley, Arthur; Thibos, Larry N.
Purpose The purpose of the current study was to examine the on- and off-eye optical performance of two types of soft contact lenses (hydrogel and silicone hydrogel). Methods The monochromatic aberrations (lambda = 850 nm) of contact lenses were measured on-eye using a clinical Shack-Hartmann ocular aberrometer. Additionally, we used an off-eye single-pass contact lens aberrometer (lambda = 540 nm) in which the soft contact lens was placed within a wet cell. Comparison of the lower and higher order aberrations measured with these two methods required compensation for different wavelengths and knowledge of the refractive index of the contact lens materials. Results The measured on-eye sphere and spherical aberration values were generally similar to those measured off-eye and those specified by the lens manufacturers for both types of soft contact lenses. However, there were notable differences, especially for high plus-powered lenses, which typically exhibited lower sphere power on the eye than expected from the lens specifications and from the off-eye measured powers, both of which were almost identical. Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometrical optics theory. Longitudinal spherical aberration measurements on- and off-eye, however, deviated significantly from that expected of a thin lens with spherical surfaces due to surface asphericities. The difference between on- and off-eye optics can be modeled as a tear lens, or as relative lens thickness changes caused by lens flexure. Conclusions The results of the current study reveal that the major difference between the on-eye lens optics and the manufacturers’ specifications are not due to lens errors, but due to eye-lens interactions, which could be either lens flexure or a tear lens forming behind the soft contact lens. PMID:23969894
Maulvi, Furqan A; Choksi, Harsh H; Desai, Ankita R; Patel, Akanksha S; Ranch, Ketan M; Vyas, Bhavin A; Shah, Dinesh O
In the present work a novel cyclosporine-loaded Eudragit S100 (pH-sensitive) nanoparticles-laden contact lenses were designed to provide sustained release of cyclosporine at therapeutic rates, without leaching of drug during sterilization and storage period (shelf life). The nanoparticles were prepared by Quasi-emulsion solvent diffusion technique using different weight ratios of cyclosporine to Eudragit S100. The contact lenses with direct drug entrapment were also fabricated (DL-50) for comparison. The percentage swelling and optical transparency of nanoparticles-laden contact lenses were improved in comparison to DL-50 lenses. The nanoparticles-laden contact lenses showed sustained drug release profiles, with inverse relationship to the amount of nanoparticles loaded in the contact lenses. It was interesting to note that nanoparticles form nanochannels/cavities after dissolution of Eudragit S 100 in tear fluid pH=7.4 (in vitro release study). This followed the precipitation of drug in hydrogel matrix of contact lenses. As the amount of nanoparticles loading increased, more number of cavities were formed, which caused the formation of large cavities in contact lens matrix. This in turn precipitated the drug. The nanoparticles-laden contact lenses with 1:1 (drug: Eudragit) weight ratio showed the most promising results of sustaining the drug release up to 156h, without affecting optical and physical properties of contact lenses. Packaging study confirmed that the drug was not leached in packaging solution (buffer, pH=6.5) from nanoparticles-laden lenses during shelf life period. In-vivo study in rabbit tear fluid showed sustained release up to 14days. The study revealed the application of pH-sensitive nanoparticles-laden contact lenses for controlled release of cyclosporine without altering the optical and physical properties of lens material. Copyright © 2017 Elsevier B.V. All rights reserved.
Stork, Wilhelm; Wagner, Armin; Kreiner, Christine F.; Mueller-Glaser, Klaus-Dieter
Intraocular lenses IOLs allow the vision restoration of cataract patients. However the ability of accommodation is lost after cataract surgery. Multifocal lenses show two or more foci with different refractive powers. Far and near objects can be at focus simultaneously. No additional spectacles are necessary. Bifocal lenses can be fabricated as multizone or as diffractive lenses. Diffractive multifocal lenses show in contrast to multi zone multifocal lenses no change of the brightness ratio for the far and near focus with change of the pupil diameter. Diffractive lenses show a saw tooth like microscopic shape with a geometrical height of the teeth in the order of microns. The lens was fabricated with a mold technique in a flexible silicone material. The molds have been lathed in metal with a ultra precision diamond lathe machine. For the test of the optical performance a MTF-measurement machine was constructed for multifocal lenses. With this machine the imaging quality and the intensity ratio of the two foci were measured. The optical quality of the lens turned out to be diffraction limited. At the University Hospital of Giessen, Germany a first clinical evaluation with 23 patients has been performed and proved for the high quality of the manufactured IOLs.
Pult, H; Khaireddin, R
This review is intended to give supportive information for beginners in contact lens fitting who are interested in providing a quality-related service to customers and patients. In Germany the proportion of contact lens wearers is significantly lower than in most other countries; therefore, there is a potentially fast growing market. The aim of this paper is to provide comprehensive guidelines for practitioners to develop and improve contact lens fitting practice and minimize unnecessary or preventable complications. The fundamental requirement for starting in contact lens fitting is to have correct education in the field and for the practice to be appropriately equipped. The key to providing a safe a reliable contact lens fitting practice is to continually update knowledge in the field and to maintain the practice to the highest professional standards.
Sankaridurg, P R; Willcox, M D; Sharma, S; Gopinathan, U; Janakiraman, D; Hickson, S; Vuppala, N; Sweeney, D F; Rao, G N; Holden, B A
Ten episodes of adverse responses to contact lens wear, including contact lens-induced acute red eye (CLARE), in which Haemophilus influenzae was isolated from contact lenses and/or from one of the external ocular sites at the time of the event, are described. All episodes occurred in patients wearing disposable hydrogel lenses on a 6-night extended-wear schedule. Two of the patients had recurrent episodes. H. influenzae was usually isolated in large numbers, and other bacteria or fungi colonizing the contact lens or the external ocular surface were usually present in low numbers. Those patients who were colonized with H. influenzae were more than 100 times as likely to have had a CLARE or infiltrative response than those subjects who were not colonized with this bacterium. H. influenzae colonization of the contact lens and eye may be subsequent to colonization of the nasopharynx because four of the seven patients presented with fever at the time of the event, with concurrent upper respiratory tract infection. Contact lens wearers should be made aware of the potential risk of CLARE associated with the wearing of contact lenses for extended periods during and subsequent to upper respiratory tract infection. PMID:8880493
Grobe, G L; Valint, P L; Ammon, D M
The surface chemistry and topography of cast-molded Etafilcon-A and doubled-sided lathed Etafilcon-A soft contact lenses were determined to be significantly different. The variations in surface chemical and morphologic structure between the two lenses were the result of contact lens manufacturing methods. The surface of the cast-molded Etafilcon-A had a consistently less rough surface compared to the doubled sided lathed Etafilcon-A as determined by atomic force microscopy. The surface of the doubled sided lathed Etafilcon-A contained primarily silicone and wax contamination in addition to minute amounts of HEMA. The cast-molded Etafilcon-A had an elemental and chemical content which was consistent with the polymer stoichiometry. Contact angle wettability profiles revealed inherent wettability differences between the two lenses types. The cast-molded Etafilcon-A had an inherently greater water wettability, polarity, and critical surface tension. This means that these two lenses cannot be compared as similar or identical lens materials in terms of surface composition. The manufacturing method used to produce a soft contact lens directly determines the surface elemental and chemical structure as well as the morphology of the finished lens material. These results suggest possible differences in the clinical comfort, spoilage, and lubricity felt during patient wear.
Weissman, B A
A method to calculate areal average thickness of rigid contact lenses is shown. The method involves division of lens volume, which is determined from lens design specifications or derived from measured lens weight, by the area of the lens back surface. Areal average thickness may then be used with known oxygen permeability to generate oxygen transmissibility values.
Wei, Xiaojia; Aliwarga, Yulina; Carnt, Nicole A.; Garrett, Qian; Willcox, Mark D.P.
Purpose Previous studies have demonstrated deposition of tear proteins onto worn contact lenses. In this study, we used proteomic techniques to analyze the protein deposits extracted from worn daily wear silicone hydrogel contact lenses in combination with different lens care solutions. Methods Worn lenses were collected and protein deposits extracted using urea and surfactant. Protein extracts were desalted, concentrated, and then separated using one-dimensional gel electrophoresis. Individual protein components in extracts were identified using liquid chromatography combined with tandem mass spectrometry (LC-MS-MS) after trypsin digestion. Results One-dimensional gel electrophoresis revealed that lysozyme and other small proteins (around 20 kDa) were the most abundant proteins in the extracts. LC-MS-MS revealed a wide array of proteins in lens extracts with lysozyme and lipocalin 1 being the most commonly identified in deposit extracts. Conclusions Worn contact lenses deposit a wide array of proteins from tear film and other sources. Protein deposit profiles varied and were specific for each contact lens material. PMID:18989384
independent of contact lens wear. All cases involved subjects wearing soft lenses. One case of acute, localized ulcerative keratitis has been confirmed. The ... ulcer (and its secondary scar) was located superiorly off the visual axis, so visual acuity was unaffected. The individual was on Duty Not to Include
Williams, C E
Gas permeable rigid lens materials offer the opportunity to reevaluate contact lens design. This paper presents the rationale and procedures followed in the development of a design concept for the Polycon lens material.
Cornish, R; Sulaiman, S
To test the hypothesis that thinner rigid gas permeable (RGP) contact lenses provide superior initial comfort, RGP lenses of 3 center thicknesses, 0.08, 0.12, and 0.16 mm, in otherwise matched parameters, were worn for 30 min by 17 unadapted subjects in a controlled, double masked, randomized study. Comfort ratings (0 to 100) after 30 min of wear were 42 +/- 30, 55 +/- 27, and 57 +/- 28 for the 0.08-, 0.12-, and 0.16-mm thick lenses, respectively (p = 0.04, multiple analysis of variance (MANOVA)), and 93 +/- 13 for the hydrogel control lens. The thinnest RGP lens was significantly less comfortable than its thicker counterparts (p = 0.03, Univariate F-test). There were no differences among the test lenses in edge shape, front surface wettability, or static lens fittings, and small differences in movement, vertical decentration, and front surface geometry were not significantly related to comfort. We hypothesize that the greater flexibility of the thinnest lens resulted in greater deformation of the lens during a blink cycle, causing transient peripheral lens lifting and interaction with the upper eyelid, thereby reducing comfort. In conclusion we found that thinner RGP lenses do not provide an initial comfort advantage and that very thin and, as a corollary, very flexible, RGP lenses can actually be less comfortable initially than stiffer, but otherwise matched, designs.
Quesnel, N M; Fares, F; Verret, E; Giasson, C
Increasing evidence suggesting deleterious effects of ultraviolet radiation (UVR) on the eye has prompted manufacturers to develop UV-absorbing disposable contact lenses. The spectral transmittances of a sample of these lenses were measured in order to determine if they provide adequate protection from UVR. Four types of UV-absorbing disposable lenses were studied (Acuvue [Vistakon, Jacksonville, FL], Precision UV [Wesley-Jessen, Des Plaines, IL], Specialty Sport [Specialty UltraVision, Sunnyvale, CA], and Surevue [Vistakon]). For comparison, a lens without UV-absorbing properties (Acuvue), a conventional soft lens (Permaflex UV [Cooper Vision, San Jose, CA]) and an RGP lens (Boston ES [Polymer Technology, Rochester, NY]) were also evaluated. The tested lens was placed in a silica wet cell filled with saline. Spectral transmittance was measured over the 200-800 nm waveband. Each disposable lens exhibited a transmittance window in the 240-320 nm waveband. Computing indices of protection factor and safe exposure duration allowed for the assessment of the level of protection afforded by each lens. Among disposable lenses studied, the Surevue performed best with a transmittance of less than 1% in the waveband 280-348 nm and the longest safe exposure duration, while the Specialty Sport had the highesttransmittance of UVB (290-315 nm). All UV-absorbing lenses studied provided a better level of protection from UVR exposure than lenses without UV absorber. These results will help the eyecare practitioner in prescribing the most appropriate UV-blocking lens for each patient.
Koch, J M; Refojo, M F; Leong, F L
Elastofilcon A silcone rubber contact lenses induce less corneal swelling than no lens wear during sleep, and increasing the central thickness and volume of the lens does not influence its overnight performance. We sought to elucidate whether a silicone rubber lens can promote the distribution of atmospheric O2 on the cornea through a small interpalpebral opening under closed-eye conditions. Three groups of rabbit eyes comprised 12 eyes wearing Silflex (Dk 79.8 barrer) lenses, 12 with elastofilcon A (Dk 340 barrer) lenses, and 12 without lenses. All eyes were surgically closed overnight; six eyes in each group had a complete lid closure and six eyes had a partial tarsorrhaphy that left a small, central gap approximately 3 mm in length. When the lids were opened the next morning, the partially closed elastofilcon A eyes showed less corneal swelling (6.2 +/- 1.4%) than the partially closed no-lens eyes did (9.6 +/- 1.3%) (p less than 0.01), whereas the partially closed Silflex eyes were significantly more swollen (12.8 +/- 2.1%) (p = 0.01) than the other two partially closed groups were. The completely closed eyes showed no significant difference in corneal swelling among the groups. These results indicate that small lid gaps during sleep may lead to less corneal swelling when elastofilcon A lenses are used than with no lenses.
in visual acuity , keratometric readings, and post-lens removal refractions? Appropriate statistical analysis of the data would be used to determine the...study. Visual acuities had to be correctable to 20/20 or better in each eye by both spectacles and contact lens. Participation in this study required...eye. This was done before and after lens removal. 4. Distant Snellen visual acuity --measured through contact lenses with a • -: Meanco projector and an
Willcox, Mark; Sharma, Savitri; Naduvilath, Thomas J; Sankaridurg, Padmaja R; Gopinathan, Usha; Holden, Brien A
To determine whether carriage of microbes on the contact lens or ocular surfaces during extended wear (EW) with soft hydroxyethyl methacrylate (HEMA)-based contact lenses predisposes the wearer to adverse events. Participants (non-contact lens wearers) were enrolled in a clinical study involving wear of HEMA-based hydrogel lenses on a six night EW basis with weekly replacement. Type and number of bacteria colonizing the lower lid margins, upper bulbar conjunctiva, and contact lenses during EW after one night, 1 week, 1 month, and thereafter every 3 months for 3.5 years were determined. The association of bacteria with adverse responses was compared between carriers (defined as having significant microbes cultured from two or more samples with 1 year) and noncarriers, and the strength of the association was estimated using multivariate logistic regression. Carriers of gram-positive bacteria on lenses (particularly coagulase negative staphylococci or Corynebacterium spp.) were approximately three and eight times more likely to develop contact lens-induced peripheral ulcers (CLPUs) and asymptomatic infiltrates (AIs), respectively. Staphylococcus aureus was most frequently isolated from lenses during CLPU. Carriers of gram-negative bacteria on lenses were five times more likely to develop contact lens-induced acute red eye (CLARE). Haemophilus influenzae was isolated most frequently from lenses during CLARE and AI events. Bacterial carriage on contact lenses during EW predisposes the wearer to the development of corneal inflammatory events including CLARE, CLPU, and AI.
Cho, P; Woo, G C
Distance and near visual acuity of 13 low astigmats were determined in a double-masked experiment through thick and thin (centre thickness 0.12 mm and 0.06 mm, respectively) spherical lathe-cut soft lenses. For each lens type, distance and near LogMAR VA and over-refraction were assessed with different logMAR VA charts. For 70% of the subjects, the residual astigmatism was significantly lower than the refractive astigmatism with thicker lenses. No statistically significant differences in the distance and near logMAR VA was found between the two lens types using any of the charts used, though, in general, logMAR VA obtained through the thicker lens was better than logMAR VA through the thinner lens. The variabilities in distance and near logMAR VA between the two lens types increased with decreased contrast. The variabilities in distance logMAR VA were greater with Chinese charts than with English charts, and LogMAR VA with Chinese charts were significantly worse for both lens types. Based on the results of this study, we concluded that thicker spherical lathe-cut soft lenses provide better vision in low astigmats. The Snellen acuity test is inadequate for vision assessment of soft contact lens wearers. When a patient wearing thin soft contact lenses complains of poor vision in spite of 6/6 or 6/5 Snellen acuity, changing to thicker lenses may be considered.
Versura, P.; Maltarello, M.C.; Roomans, G.M.; Caramazza, R.; Laschi, R.
The deposits accumulated on the surfaces of soft contact lenses are a cause of problems for the wearer of these lenses, as the deposits are never completely removed by the available washing solutions. Therefore it appears of interest to investigate the composition of these deposits. In this paper we review the major findings in the literature and, in addition, present our personal experience. We have studied new, continuously and daily worn soft contact lenses by scanning electron microscopy (SEM), X-ray microanalysis and immunohistochemistry. We have carefully evaluated preparative methods, and we can conclude that SEM and X-ray microanalysis are best carried out on unfixed, air-dried lenses. The deposits present consist mainly of mucus, especially on the tarsal side of the lenses. Chloride and potassium, coming from the tear fluid, as well as sulfur, derived from proteins, were found. Calcium was very rarely detected. IgG, IgA, IgE and C3c complement fractions were found only on the outer surfaces and not within the lens. We believe that the best characterization of the deposits is achieved by means of correlative techniques on the same lens. In fact, this approach integrates morphology and composition.
Temporarily implanted devices, such as drug-loaded contact lenses, are emerging as the preferred treatment method for ocular diseases like glaucoma. Localizing the delivery of glaucoma drugs, such as timolol maleate (TM), can minimize adverse effects caused by systemic administration. Although eye drops and drug-soaked lenses allow for local treatment, their utility is limited by burst release and a lack of sustained therapeutic delivery. Additionally, wet transportation and storage of drug-soaked lenses result in drug loss due to elution from the lenses. Here we present a nanodiamond (ND)-embedded contact lens capable of lysozyme-triggered release of TM for sustained therapy. We find that ND-embedded lenses composed of enzyme-cleavable polymers allow for controlled and sustained release of TM in the presence of lysozyme. Retention of drug activity is verified in primary human trabecular meshwork cells. These results demonstrate the translational potential of an ND-embedded lens capable of drug sequestration and enzyme activation. PMID:24506583
Momeni-Moghaddam, Hamed; Naroo, Shehzad A; Askarizadeh, Farshad; Tahmasebi, Fatemeh
To compare lens orientation and rotational recovery of five currently available soft toric lenses. Twenty subjects were recruited and trialed with each of the study lenses in a random order. Study lenses were PureVision(®) Toric (B&L), Air Optix(®) for Astigmatism (Alcon), Biofinity(®) Toric (CooperVision), Acuvue(®) Advance for Astigmatism (Vistakon), and Proclear(®) Toric (CooperVision). Lens orientation in primary position to determine the lens rotation form the vertical position and rotational recovery to primary gaze orientation following a 45° manual misorientation for the different lenses was compared. The Biofinity Toric showed the lowest rotation from the vertical position and the Proclear Toric the highest. Also, the highest and the lowest reorientation speed were related to the Biofinity Toric and the Acuvue Advance for Astigmatism, respectively. The Repeated Measures ANOVA showed a significant difference in the lens rotation (P=0.004) and rotational recovery (P<0.001) among different contact lenses and the performed multiple comparisons indicated differences in rotation and also in reorientation speed were only seen between the Biofinity Toric when compared to four other lenses (P<0.05). Although there was appropriate fitting, based upon lens orientation and reorientation speed, with each of the study lenses it would appear that the optimized ballast technique used in the design of the Biofinity Toric helps reduce lens rotation and improve rotational recovery compared to others. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Hill, J F
The purpose of this study was to compare the clinical acceptability of polymacon spin-cast to polymacon lathe-cut hydrophilic contact lenses. Ten patients successfully wearing polymacon spin-cast lenses were studied. Each patient had one eye refitted with polymacon lathe-cut lenses. Comparison of the two types of lenses was then made. Objective evaluation included centration, movement, visual acuity, and over-refraction. Subjective criteria were based on patient comfort and stability and quality of vision. Results indicate that lathe-cut lenses can be just as clinically satisfactory as the spincast ones.
Komori, Yasuka; Kobayashi, Daisuke; Murase, Yosuke; Enomoto, Itaru; Takagi, Hideki; Kono, Ichiro
This study investigated the extent of contact-lens use in Japanese college water-polo male players over 20 years (1991-2011, once every five years). Information about the use of contact lenses during play and the types of contact lens was obtained through a self-report questionnaire. The proportion of contact lens use among the players while playing water polo differed from 1991 to 2011 (χ2(4) = 25.28, P < 0.001, Cohen's d = 0.63). Fifty-four per cent of the players used contact lenses while playing in 1991 (P < 0.001); more than 74% in 1996; 89% in 2001; 84% in 2006; and 86% in 2011. While 96% of the contact lenses used by the players in 1991 were the soft type, 74%, 92%, 86%, and 88% of the contact lenses used in 1996, 2001, 2006, and 2011, respectively, were the disposable type. These findings indicated a high percentage of players were using contact lenses while playing water polo between 1996 and 2011. This could be because the majority of players used disposable lenses. The results suggest that increasing use of contact lenses by water-polo players is beneficial.
Xu, Jinku; Li, Xinsong; Sun, Fuqian
The purpose of this work was to evaluate the usefulness of silicone hydrogel contact lenses loaded with ketotifen fumarate for ocular drug delivery. First, silicone contact lenses were prepared by photopolymerization of bitelechelic methacrylated polydimethylsiloxanes macromonomer, 3-methacryloxypropyltris(trimethylsiloxy)silane, and N,N-dimethylacrylamide using ethylene glycol dimethacrylate as a cross-linker and Darocur 1173 as an initiator followed by surface plasma treatment. Then, the silicone hydrogel matrices of the contact lenses were characterized by equilibrium swelling ratio (ESR), tensile tests, ion permeability, and surface contact angle. Finally, the contact lenses were loaded with ketotifen fumarate by pre-soaking in drug solution to evaluate drug loading capacity, in vitro and in vivo release behavior of the silicone contact lenses. The results showed that ESR and ion permeability increase, and the surface contact angle and tensile strength decreased with the increase of DMA component in the silicone hydrogel. The drug loading and in vitro releases were dependent on the hydrogel composition of hydrophilic/hydrophobic phase of the contact lenses. In rabbit eyes, the pre-soaked contact lenses sustained ketotifen fumarate release for more than 24 h, which leads to a more stable drug concentration and a longer mean retention time in tear fluid than that of eye drops of 0.05%.
Yen, Chih-Ta; Ye, Jhe-Wen
The design of complex contact lenses involves numerous uncertain variables. How to help an optical designer to first design the optimal contact lens to reduce discomfort when wearing a pair of glasses is an essential design concern. This study examined the impact of aberrations on contact lenses to optimize a contact lens design for myopic and astigmatic eyes. In general, two aspherical surfaces can be assembled in an optical system to reduce the overall volume size. However, this design reduces the spherical aberration (SA) values at wide contact radii. The proposed optimization algorithm with optical design can be corrected to improve the SA value and, thus, reduce coma aberration (TCO) values and enhance the modulation transfer function (MTF). This means integrating a modified genetic algorithm (GA) with a neural network (NN) to optimize multiple-quality characteristics, namely the SA, TCO, and MTF, of contact lenses. When the proposed optional weight NN-GA is implemented, the weight values of the fitness function can be varied to adjust system performance. The method simplifies the selection of parameters in the optimization of optical systems. Compared with the traditional CODE V built-in optimal scheme, the proposed scheme is more flexible and intuitive to improve SA, TCO, and MTF values by 50.03%, 45.78%, and 24.7%, respectively.
Valley, Pouria; Reza Dodge, Mohammad; Schwiegerling, Jim; Peyman, Gholam; Peyghambarian, N
We report on a novel zoom lens with no moving parts in the form of a switchable Galilean telescope. This zoom telescope consists of two flat liquid-crystal diffractive lenses with apertures of 10mm that can each take on the focal lengths of -50 and +100cm, with a spacing of 50cm and, hence, a zoom ratio of 4x. The lenses are driven using a low-voltage ac source with 1.6V and exhibit millisecond switching times. The spectral characteristic of this diffractive zoom system is evaluated for light sources of various bandwidths. Potential applications for this technology include a zoom lens with no moving parts for camera phones and medical imaging devices.
Pucker, Andrew D.; Nichols, Jason J.
PURPOSE To determine the impact of the rinse step in “no rub” contact lens care systems relative to its ability to assist in removing loosely associated and bound tear film proteins from a worn silicone hydrogel lens. METHODS After informed consent, subjects were fitted with lotrafilcon B contact lenses (CIBA Vision, Inc). If the fit was acceptable, subjects were asked to wear the lenses on a daily wear basis for 5 (+2, −0) days for an outcome visit. Subjects were instructed to use AQuify Multi-Purpose Disinfecting Solution (CIBA Vision, Inc) following the manufacturer's “no rub” instructions. At the outcome visit, contact lenses were then collected by a gloved examiner, with a sterile metal forceps, who rinsed the right lens but did not rinse the left lens upon removal from the eyes. Protein was extracted with a 50:50 0.2% trifluoroacetic acid-acetonitrile solution and quantified using a Bradford analyses. RESULTS Twenty contact lens wearers were enrolled in this study. For the non-rinsed lenses, the first extraction yielded 13.4 ± 9.2 µg/lens of protein, while the second extraction yielded 5.8 ± 2.8 µg/lens of protein. For the rinsed lenses, first extraction yielded an average of 3.0 ± 1.9 µg/lens of protein, while the second extraction yielded an average of 4.0 ± 2.3 µg/lens. Repeated measures ANOVA showed a significant interaction (F-statistic = 18.9, p< 0.0001) between the rinse of a lens and extraction number. CONCLUSIONS Rinsing a contact lens following removal from the eye removes well over one-half of the protein associated with it. Further, in order to biochemically recover all protein from a silicone hydrogel lens, it may be important to perform more than one chemical extraction from it. PMID:19609231
Atabek Yigit, Elif; Ercal, Nuran
To investigate the use of contact lenses to release N-acetylcysteine (NAC) and N-acetylcysteine amide (NACA) that have frequently used for the treatment of some eye diseases. Three commercial contact lenses were used: Soflens Multi-Focal, 1-Day ACUVUE TruEye, and Frequency 55. All contact lenses were individually kept for 3 days in 10 mL of 3 mM NAC or NACA solutions in phosphate-buffered saline (PBS). After the loading period, the lenses were removed from the solution and put into 5 mL of PBS for 3 days (static mode). During this period, samples were taken at specified times and analyzed by high-pressure liquid chromatography. From the release profiles of NAC and NACA, it was found that both NAC and NACA could be released from the lenses within 72 hours. Frequency 55 released 95.9%±2.7% of loaded NAC and 60.0%±2.1% of loaded NACA in 24 hours, whereas 1-Day ACUVUE TruEye released 80.9%±1.2% of loaded NAC and 54.0%±1.9% of loaded NACA and Soflens Multi-Focal released 72.8%±2.8% of loaded NAC and 51.9%±2.3% of loaded NACA during that same period. The lenses could achieve the appropriate delivery of drugs during their intended time of wear. The amount of released NACA was less than that of NAC because of the more hydrophobic structure of NACA. According to the power law, the values of the exponential constant n were found to be below 0.5, indicating that the behavior observed was "less Fickian".
Port, M; Refson, K; Minards, J
A Nissel +1.75 D PS45 lens' label power seems to be made up of about +0.75 D distance and +0.75 D near addition. There are individual variations which will depend on pupil size, corneal shape, lens position and ocular aberrations. When a +0.75 Bausch & Lomb U3 lens was used as a control, there was also a significant increase in 'accommodation' measured (+0.75 D), but this could not be explained. When two other lenses with an aspheric surface were studied, they also showed a near addition effect. In this supplementary study the changes were explained by changes in spectacle accommodation. A lens with two spherical surfaces did not show the expected increase in spectacle accommodation. Astigmatism, as a general rule, was not corrected by the PS45 lens, although the very occasional case did show some reduction. Visual acuity and contrast sensitivity at 8 cpd and 3 cpd were not significantly affected when compared to the control lens.
Uzunel, Umut Duygu; Kusbeci, Tuncay; Yuce, Berna; Yüksel, Bora
The aim was to evaluate the effect of irregular astigmatism on the retinal nerve fibre layer (RNFL), macular thickness and ganglion cell analysis obtained by spectral domain optical coherence tomography (OCT) in eyes with keratoconus. Fifty-two eyes of 31 patients (20 females) with keratoconus that required correction of irregular astigmatism with rigid gas-permeable (RGP) contact lenses were included to this study. The average, superior, nasal, inferior, temporal and 12 clock hour sector's RNFL, ganglion cell and macular thickness analyses before and 30 minutes after RGP contact lens (Rose K2 -Menicon Z material, David Thomas Contact Lenses Ltd, Northampton, United Kingdom) wear were performed to all patients with Cirrus HD spectral domain optical coherence tomography. The average thickness of the retinal nerve fibre layer, the thickness at the nasal quadrants and 1-2-3-4 o'clock hour sectors and mean signal strength were increased significantly by RGP contact lens wearing independent of the stage of keratoconus. Central sub-field thickness increased after correction with RGP contact lens (p = 0.037). After wearing RGP contact lenses, changes on ganglion cell analysis were not significant (all p values ≥ 0.111). OCT is a widely used device for retinal nerve fibre layer and macular thickness evaluation in patients with glaucoma and macular diseases. The study demonstrates that OCT parameters such as retinal nerve fibre layer, central sub-field thickness and mean signal strength are affected by irregular astigmatism. Correction of irregular astigmatism with RGP contact lenses should be recommended before analysing keratoconic eyes to obtain optimum results on OCT measurements. © 2015 The Authors. Clinical and Experimental Optometry © 2015 Optometry Australia.
Carracedo, Gonzalo; Carballo, Jesús; Loma, Elena; Felipe, Gema; Cacho, Isabel
Purpose The aim of this pilot study was to test whether retinitis pigmentosa patients would benefit from filter contact lenses as an effective optical aid against glare and photophobia. Methods Fifteen subjects with retinitis pigmentosa were enrolled in this study. All of them were evaluated with filter soft contact lenses (MaxSight), filter glasses (CPF 527) and without filters (control). All patients were assessed for the three aid conditions by means of best corrected visual acuity (BCVA), contrast sensitivity (without glare and with central and peripheral glare)(CSV-1000) and a specific subjective questionnaire about quality of vision. Results BCVA was slightly better with filters than without filter but the differences were not statistically significant. Contrast sensitivity without glare improved significantly with the contact lenses (p < 0.05). The central glare had significant differences for the frequencies of 3 cpd and 18 cpd between the contact lens filter and the control group (p = 0.021 and p = 0.044, respectively). For the peripheral glare contrast sensitivity improved with contact lens versus control group for highest frequencies, 12 and 18 cpd (p < 0.001 and p = 0.045, respectively). According to the questionnaire the contact lens filter gave them more visual comfort than the glasses filter under the scenarios of indoors glare, outdoors activities and indoors comfort. Conclusion The filter contact lenses seem to be a good option to improve the quality of vision of patients with retinitis pigmentosa.
Szczotka-Flynn, Loretta; Chalmers, Robin
Contact lens-associated corneal infiltrative events (CIEs) are presumed sterile events that have complicated contact lens wear for more than 30 years. There is consistent evidence that silicone hydrogel soft contact lenses increase CIE risk by twofold compared with low Dk hydrogel materials. The incidence of CIEs during silicone hydrogel extended wear ranges from 2% to 6% for symptomatic events and from 6% to 25% when asymptomatic events are included. For daily wear, with silicone hydrogels, the incidence of CIEs ranges from 2% to 3% for symptomatic events and from 7% to 20% when asymptomatic events are included. Despite the increased rate of CIEs with silicone hydrogels, the benefits of these lenses largely outweigh this risk for many patients. Most risk factors for CIEs observed with silicone hydrogels are consistent with CIE risk factors reported earlier with hydrogel lenses, such as bacterial bioburden on lens surfaces, and young age among others. Limiting the transfer of bacterial bioburden from the skin to lenses, lens cases and eventually to the eye is an obvious step forward for the prevention of CIEs across all lens types.
Fink, B A; Carney, L G; Hill, R M
Differences between corneal oxygen uptake rates measured after 5 min of static (without blinking) and 5 min of dynamic (with blinking once every 5 s) non-gas permeable (polymethyl methacrylate) contact lens wear, referenced to the oxygen uptake rates of the normal open eye, were used as indications of tear pump efficiencies associated with each of seven contact lens back vertex powers (-9.00 to +9.00 D, in 3.00 D steps). Measurements were made in vivo on six human corneas showing with-the-rule (0.25 to 0.87 D) toricity. Lens overall diameter was 8.8 mm, optic zone diameter was 7.4 mm, and base curve radius was fitted "on K." Lens center thickness was 0.14 mm for all minus-powered lenses, and 0.19, 0.26, 0.34, and 0.41 mm for the plano, +3.00, +6.00, and +9.00 D lenses, respectively, maintaining an edge thickness of 0.11 mm. Under both static and dynamic wearing conditions, no significant differences were found among the corneal oxygen uptake rates associated with the various contact lens back vertex powers; however, the difference between the static and dynamic condition data, an indication of tear pump efficiency, was greatest for the -3.00 D lens. The difference values associated with the +9.00 and +6.00 D lenses were significantly lower than those associated with the minus power lenses.
Rad, Maryam Shayani; Sajadi Tabassi, Sayyed Abolghasem; Moghadam, Maryam Hassanpour; Mohajeri, Seyed Ahmad
Betamethasone (BMZ) is an effective drug which is commonly used as an eye drop for the management of ophthalmic inflammations. Due to low ocular bioavailability, it is necessary to prepare and optimize an ocular drug delivery system for BMZ. In this study we tried to use vitamin E diffusion barrier for sustaining BMZ release. Three commercial contact lenses were soaked in vitamin E solutions and swelling percentage, diameter, transmittance, binding capacity and release amount and time were evaluated in comparison with non-vitamin E-loaded pure lenses. The results showed that vitamin E significantly decreased water content of contact lenses whereas, increased the lens diameter in both dry and wet states. It effectively blocked UV radiation which is harmful for the eye surface while had no significant effect on visible transmittance. BMZ loading capacity enhanced and release rate remarkably decreased after using vitamin E as a hydrophobic diffusion barrier. This study revealed that vitamin E can be applied as a hydrophobic diffusion barrier for controlling and sustaining BMZ release from silicone-based soft contact lenses into the lachrymal fluid. It can also protect eye tissues as an antioxidant by blocking the UV radiation.
Ovechkin, I G; Rosliakov, V A; Aleksandrova, L A
The development of effective methods for preventing and correcting myopia in pilots is one of the most important problems of aeronautic ophthalmology. The majority of Russian and foreign aeronautic ophthalmologists agree that contact correction is the principal method for repair of occupational vision of myopic pilots. Experiments with soft contact lenses with 38 and 70% humor content were carried out. The methodology was based on comprehensive examinations of the vision status and status of the organ of vision under common conditions on the Earth and during simulation of unfavorable flight factors. The results indicate that contact lenses are a safe means for correcting myopia in pilots. This is confirmed by the absence of unfavorable changes in the main visual functions and in the status of the anterior segment of the eye, by a constant level of visual working capacity, and by the absence of negative subjective sensations.
Arman, Ayşegül; Demirseren, D Deniz; Akoglu, Gulsen
Purpose. Numerous ocular side effects have been reported with the use of systemic isotretinoin therapy. Herein, we presented two contact lens user patients who did not have contact lens intolerance during systemic isotretinoin therapy. Methods. 25-year-old male and 20-year-old female patients with severe acne vulgaris who were using highly wettable silicone hydrogel contact lenses which increase tear film stability were examined. Tear film function tests including Schirmer tests and tear break up time (TBUT) test and ocular surface staining with fluorescein were done. Subjective ocular complaints were scored with ocular surface disease index (OSDI) questionnaire. Patients were followed up monthly and examinations were repeated at each visit. Results. Both patients completed the therapy after a cumulative dose of 140 mg/kg isotretinoin in 6 months. The OSDI score and tear film function tests before and after treatment were all within normal limits. Discussion. Highly wettable contact lenses that provide increase in the tear film stability may be used during systemic retinoid therapy under close followups. Although isotretinoin affects ocular glands, the differences between tolerances to this retinoid therapy need to be investigated in larger patient groups using contact lenses.
Arman, Ayşegül; Demirseren, D. Deniz
Purpose. Numerous ocular side effects have been reported with the use of systemic isotretinoin therapy. Herein, we presented two contact lens user patients who did not have contact lens intolerance during systemic isotretinoin therapy. Methods. 25-year-old male and 20-year-old female patients with severe acne vulgaris who were using highly wettable silicone hydrogel contact lenses which increase tear film stability were examined. Tear film function tests including Schirmer tests and tear break up time (TBUT) test and ocular surface staining with fluorescein were done. Subjective ocular complaints were scored with ocular surface disease index (OSDI) questionnaire. Patients were followed up monthly and examinations were repeated at each visit. Results. Both patients completed the therapy after a cumulative dose of 140 mg/kg isotretinoin in 6 months. The OSDI score and tear film function tests before and after treatment were all within normal limits. Discussion. Highly wettable contact lenses that provide increase in the tear film stability may be used during systemic retinoid therapy under close followups. Although isotretinoin affects ocular glands, the differences between tolerances to this retinoid therapy need to be investigated in larger patient groups using contact lenses. PMID:24707422
Lunardi, Letícia Helena; Arroyo, Danielle; Andrade Sobrinho, Marcelo Vicente de; Lipener, César; Rosa, Juliana Maria da Silva
Keratoconus is characterized by bilateral asymmetrical corneal ectasia that leads to inferior stromal thinning and corneal protrusion. There is currently a lack of consensus regarding the most efficacious method for fitting contact lenses in patients with keratoconus, given the various topographical patterns and evolution grades observed in affected populations. The purpose of the present study was to evaluate the association between keratoconus evolution grade and topography pattern and the type and design of fitted contact lens. We performed a retrospective analysis of contact lenses fitted in a total of 185 patients with keratoconus (325 eyes). Keratoconus was classified as either grade I, II, III, or IV based on keratometry and cone morphology (nipple, oval, globus, or indeterminate) results. A total of 325 eyes were evaluated in the present study. Of the 62 eyes classified as grade I, 66.1% were fitted with monocurve contact lenses. Of the 162 eyes classified as grade I and II, 51%, 30%, and 19% were fitted with adapted monocurve rigid gas-permeable contact lenses (RGPCL), bicurve lenses, and others lens types, respectively. Bicurve lenses were fitted in 52.1% and 62.2% of eyes classified as grade III and IV, respectively. Of the eyes classified as grade III and IV, monocurve and bicurve RGPCL were fitted in 26% and 55%, respectively. In eyes with oval keratoconus, 45%, 35%, and 20% were fitted with monocurve lenses, bicurve lenses, and other lens types, respectively. In eyes with round cones (nipple morphology), 55%, 30%, and 15% were fitted with bicurve lenses, monocurve lenses, and other lens types, respectively. Monocurve RGPCL were most frequently fitted in patients with mild to moderate keratoconus and oval cones morphology, while bicurve lenses were more frequently fitted in patients with severe and advanced keratoconus. This was probably because bicurve lenses are more appropriate for round cones due to increased corneal asphericity.
Morgan, Philip B; Chamberlain, Paul; Moody, Kurt; Maldonado-Codina, Carole
To evaluate the performance of a silicone hydrogel daily disposable lens in neophyte subjects over 12 months. Seventy four subjects with no previous contact lens experience were randomised to wear narafilcon A (1 DAY ACUVUE(®) TruEye™) lenses (LW group) or to wear no contact lenses (NLW group) for 12 months. Biomicroscopy (performed by a masked investigator), visual acuity and subjective response scores were recorded at an initial visit and six follow-up visits, in addition to lens fit and surface evaluation for the LW group. Comfort was recorded with SMS messaging. Fifteen of the LW group discontinued before the end of the study, compared with six of the NLW group. Measured visual acuity was about half a line better for the NLW group as these subjects were provided with their full sphero-cylindrical over-refraction, compared to the LW group in their best spherical corrected contact lenses; subjective scores for vision were similar for the two groups. Bulbar conjunctival hyperaemia, limbal hyperaemia, corneal staining, conjunctival staining and papillary conjunctivitis were clinically equivalent for the two groups whereas conjunctival staining was higher in the LW group. Comfort scores assessed by SMS were equivalent for the LW and NLW groups; there was a measurable improvement in comfort during the first month of wear for the LW group. This work has demonstrated that modern soft lenses (narafilcon A daily disposable silicone hydrogel lenses) offer an excellent, comfortable form of vision correction, and are able to exhibit minimal alterations to ocular physiology. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Montés-Micó, Robert; Belda-Salmerón, Lurdes; Ferrer-Blasco, Teresa; Albarrán-Diego, César; García-Lázaro, Santiago
To quantify the optical quality of various daily disposable contact lenses in vivo and to ascertain its variation in terms of wearing time by means of objective non-invasive determination of wavefront patterns. The crx1 adaptive-optics system was used to measure the wavefront aberrations in 15 myopic eyes before and at 2-h intervals after contact lens fitting, over a 12-h wearing period. Seven types of contact lenses having different material, water content and lens design were evaluated in this study: Dailies Total1, Dailies AquaComfort Plus, Proclear 1 Day, 1-Day Acuvue TruEye, 1-Day Acuvue moist, SofLens daily disposable and Clariti 1-Day. The aberration data were analysed by fitting Zernike polynomials up to the 5th-order for 3 and 5-mm pupils. The optical quality under each condition and at each point in time was described by means of the Root-Mean-Square (RMS) value of wavefront aberration, Modulation Transfer Function (MTF), Point Spread Function and cut-off spatial frequency. A RMS increase was observed after contact lens fitting as well as over time, both for a 3-mm and a 5-mm pupil. Each type of lens induced a different amount of wavefront aberrations, which vary over time also in a different manner. Dailies Total1 showed the lowest RMS values both at baseline and at the end of the day. In addition, Dailies Total1 provided the best MTF out of all the contact lenses that were assessed. These observations were reflected in higher cut-off spatial frequencies and visual resolution both at baseline and after 12 h of wearing time. Aberrometry makes it possible to analyse accurately and in vivo the optical quality of contact lenses and to assess how lenses having different characteristics - such as material or water content - behave for different wearing times. These variations across contact lenses may result in differences in visual performance. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.
Vincent, Stephen J
Ocular pathology that manifests at an early age has the potential to alter the vision-dependent emmetropisation mechanism, which co-ordinates ocular growth throughout childhood. The disruption of this feedback mechanism in children with congenital or early-onset visual impairment often results in the development of significant ametropia, including high levels of spherical refractive error, astigmatism and anisometropia. This review examines the use of contact lenses as a refractive correction, low vision aid and therapeutic intervention in the rehabilitation of patients with bilateral, irreversible visual loss due to congenital ocular disease. The advantages and disadvantages of the use of contact lenses for increased magnification (telescopes and microscopes) or field expansion (reverse telescopes) are discussed, along with the benefits and practical considerations for the correction of pathological high myopia. The historical and present use of therapeutic tinted contact lenses to reduce photosensitivity and nystagmus in achromatopsia, albinism and aniridia are also presented, including clinical considerations for the contact lens practitioner. In addition to the known optical benefits in comparison to spectacles for high levels of ametropia (an improved field of view for myopes and fewer inherent oblique aberrations), contact lenses may be of significant psycho-social benefit for patients with low vision, due to enhanced cosmesis and reduced conspicuity and potential related effects of improved self-esteem and peer acceptance. The contact lens correction of patients with congenital vision impairment can be challenging for both practitioner and patient but should be considered as a potential optical or therapeutic solution in modern low vision rehabilitation. © 2017 Optometry Australia.
Rocha, Guilherme Andrade do Nascimento; Miziara, Patrícia Oliveira Braga; Castro, Ana Clara Vieira de; Rocha, Arthur Andrade do Nascimento
To report the visual rehabilitation outcomes and complications of patients fitted with mini-scleral rigid gas-permeable (RGP) contact lenses (mini-SCLs) after penetrating keratoplasty. We retrospectively reviewed 27 eyes (21 patients) that were fitted with mini-SCLs between October 2013 and December 2014. We analyzed demographic data, previous corneal disorders, visual outcomes, interval from keratoplasty to contact lens fitting, topographic and specular microscope data, fitted contact lens parameters, and complications. The patients were divided into two groups according to the elapsed time since surgery: Group A, grafts with <10 years (n=14 eyes); and Group B, grafts with ≥10 years (n=13 eyes). Lens use was discontinued in four eyes, and microbial keratitis developed in one eye during follow-up. No corneal graft rejection was observed. The mean interval between grafting and initial contact lens fitting was 10.6 ± 7.3 years (range: 1-29 years). The most frequent reason for keratoplasty was keratoconus (22 eyes, 81.4%). The mean contact lens-corrected visual acuity (CLCVA) was 0.09 ± 0.12 logMar (range: 0.50-0.00 logMar). The average topographic astigmatism, mean steepest keratometry (Kmax), and average cellularity on specular microscopy were 6.19 ± 3.49 diopters (D), 58.4 ± 7.8 D, and 1,231 ± 723 cells/mm2, respectively. Mini-SCL use allowed successful visual rehabilitation after corneal keratoplasty, particularly in patients who required corrective lenses for low visual acuity and were unable to wear RGP contact lenses. Our results indicate that mini-scleral lenses may be an option for the treatment of corneal irregularities, such as those associated with keratoplasty.
Leibowitz, H M; Berrospi, A R
A hydrophilic contact lens was used as the initial mode of therapy in 5 cases of descemetocele. The lens was left in place over the descemetocele continuously for periods ranging from 2 to 15 months. Corneal perforation did not occur, and the anterior chamber remained formed in all cases. The device seemingly provides sufficient structural reinforcement to Descemet's membrane to prevent its distension by the intraocular pressure. It also maintains Descemet's membrane in a moist state and protects the descemetocele from the trauma of the lid margins during blinking. This series of cases indicates that a hydrophilic contact lens can be a very effective temporizing measure for the treatment of descemetocele, enabling the surgeon initially to cope with an ocular emergency in a very simple manner, and to convert the ultimate surgical repair to a scheduled, carefully planned procedure with a much greater potential for success.
Zsebik, Barbara; Ujlaky-Nagy, László; Losonczy, Gergely; Vereb, György; Takács, Lili
Purpose/Aim: Autologous cultivated oral mucosal (OM) epithelial transplantation has been successfully used as corneal epithelial replacement in bilateral limbal stem cell deficiency. Recently, lotrafilcon A contact lens (CL) surface was described as a suitable carrier for cultured stem cells in corneal epithelial transplantation. Our aim was to establish explant cultures from human OM on CL carriers that are free of animal-derived materials and feeder cells.
Zimmerman, Aaron B; Marks, Amanda
To report a case of neurotrophic keratitis in which scleral contact lenses improved vision from 20/100 to 20/20, however, due to poor lens care, an incident of microbial keratitis developed. A 64-year-old man with an ocular history of neurotrophic keratitis secondary to herpes simplex in each eye was successfully fit with scleral lenses. He subsequently developed microbial keratitis due to a number of risk factors. The lesion was culture negative, yet was very responsive to treatment with moxifloxacin. The lesion fully healed, and the patient did not suffer additional vision loss. This case demonstrates the ability of scleral lenses to correct visual impairments secondary to poor epithelial integrity and illustrates the importance of the practitioner providing detailed lens care instruction.
Boles, S F; Refojo, M F; Leong, F L
After 7 days of continuous wear, Acuvue (Vistakon, Jacksonville, FL, U.S.A.; etafilcon A) lenses were soaked in a Pseudomonas aeruginosa suspension (1.4 x 10(8) cfu/ml). New Acuvue lenses served as controls. A single strain of P aeruginosa harvested from a human corneal ulcer was used throughout the experiment. Lenses were examined by culture and scanning electron microscopy (SEM). We found significantly greater (p less than 0.05) bacterial attachment to new Acuvue lenses [culture, 3.1 x 10(4) (+/- 0.82 x 10(4)) cfu/mm2; SEM, 2.6 x 10(4) (+/- 0.47 x 10(4)) bacteria/mm2] compared with those previously worn [culture, 1.0 x 10(4) (+/- 0.17 x 10(4)) cfu/mm2; SEM, 0.73 x 10(4) (+/- 0.21 x 10(4)) bacteria/mm2]. No statistical difference was found among the individuals. Our findings demonstrate that the biological coating resulting from 1 week of continuous contact lens wear restricts P. aeruginosa attachment to the Acuvue lens when comparing new and used lenses.
Fonn, D; Holden, B A
A clinical trial was conducted to compare the extended wear performance of rigid gas-permeable (RGP) contact lenses with that of soft lenses. Subjects were fitted with a RGP lens (Boston IV) in one eye and a soft lens (Bausch & Lomb "O" series) in the other eye, and wore them on an extended wear basis for up to 3 months. No subjects developed any acute adverse reactions in the RGP lens-wearing eye. After the initial adaptation period, subject acceptance of RGP extended wear in terms of vision and comfort was superior. The RGP lenses also induced less chronic hypoxic stress than hydrogel lenses of comparable Dk/L, as evidenced by the presence of epithelial microcysts. Several complications of RGP extended wear were observed including lens binding, blepharoptosis, transient pupil size increases, and corneal staining. As hypoxia-induced corneal changes, such as microcysts and striae, were observed in the RGP lens-wearing eyes, we consider that these particular RGP lenses do not have adequate oxygen transmissibility for successful long-term extended wear. However, if RGP lens materials of higher oxygen transmissibility and better designs can be attained, the potential of RGP extended wear would appear promising.
Dillehay, Sally M; Miller, Marian B
The silicone hydrogel lens O2OPTIX with a Dk/t of 138 (at -3.00 diopters [D]) was evaluated and compared with patients' habitual low-Dk/t lenses. This large, multisite (United States and Canada), single-masked study enrolled experienced daily-wear, low-Dk/t, 2-week replacement soft contact lens wearers. Subjects underwent baseline evaluations and were fitted with O2OPTIX lenses for a 2-week period. After 2 weeks, subjects returned for assessment versus their habitual lenses. Data for 760 subjects were analyzed. The overall average habitual contact lens power was -3.13 D, and the average O2OPTIX lens power was -3.22 D. Biomicroscopy evaluations showed improvements in signs related to corneal health with O2OPTIX. Conjunctival and limbal redness, corneal neovascularization, corneal edema, and corneal and conjunctival staining all decreased significantly from baseline. O2OPTIX lenses performed better than habitual lenses in terms of comfort, symptoms, and overall preference. When wearing O2OPTIX lenses, significantly fewer subjects reported problems compared to their habitual lenses, including uncomfortable lens wear (-20.3%), redness (-44.5%), dryness during the day (-40.2%), and dryness at the end of the day (-34.4%); 47.9% reported that they could wear O2OPTIX lenses longer than their habitual lenses. At the end of study, among those with a preference, a significantly greater proportion of patients (60.3%) preferred O2OPTIX lenses to their habitual lenses. Daily wear of O2OPTIX lenses resulted in improvements in corneal signs of health and patient symptoms and provided excellent vision and comfort. O2OPTIX lenses were preferred by subjects over their habitual lenses.
HAJIALILO, Elham; NIYYATI, Maryam; SOLAYMANI, Mohammad; REZAEIAN, Mostafa
Background: Free-living amoeba (FLA)-related keratitis is a progressive infection of the cornea with poor prognosis. The present study aimed to investigates the contact lenses of patients with keratitis for pathogenic free-living amoebae. Methods: Overall, 62 contact lenses and their paraphernalia of patients with keratitis cultured and tested for the presence of free-living amoebae using morphological criteria. Unusual plates including plates containing mix amoebae and Vermamoeba were submitted to molecular analysis. Results: Out of 62 plates, 11 revealed the outgrowth of free living amoeba of which 9 were Acanthamoeba, one plates contained mix amoebae including Acanthamoeba and Vermamoeba and one showed the presence of Vermamoeba. These two latter plates belonged to patients suffered from unilateral keratitis due to the misused of soft contact lenses. One of the patients had mix infection of Acanthamoeba (T4) and V. vermiformis meanwhile the other patient was infected with the V. vermiformis. Conclusion: Amoebic keratitis continues to rise in Iran and worldwide. To date, various genera of free-living amoebae such as Vermamoeba could be the causative agent of keratitis. Soft contact lens wearers are the most affected patients in the country, thus awareness of high-risk people for preventing free-living amoebae related keratitis is of utmost importance. PMID:26811719
Kumbar, Tukaram; Shyam Sunder, T; Swati, Jawalkar; Fathima, Asma; Addepally, U K; Rao, Harsha L; Rathi, Varsha M
To investigate the accuracy of Back Optic Zone Radius (BOZR, base curve) measurements with manual keratometer for spherical polymethylmethacrylate (PMMA) lenses. 100 spherical PMMA contact lenses were selected randomly from the trial sets. One investigator measured the BOZR with radiuscope. The second investigator measured the BOZR with keratometer. The two investigators were masked to each other's readings. As the keratometer is designed to measure a convex corneal surface, the BOZR readings are less than actual radii. A correction factor of 0.025 was used to have corrected keratometers readings. There was a high correlation between the BOZR measurement with radiuscope and the uncorrected (Pearson's correlation coefficient, r=0.99) and corrected (r=0.99) measurements with keratometer. The mean difference between BOZR measurement with radiuscope and the uncorrected and corrected measurements with keratometer were 0.003 mm (p=0.62) and -0.024 mm (p<0.001) respectively. The 95% limits of agreement for the BOZR measurements with radiuscope and the uncorrected and corrected measurements with keratometer were -0.11 to 0.11 mm and -0.14 to 0.09 mm respectively. We found that the uncorrected BOZR measurements with keratometer were similar to the BOZR measurements with radiuscope. With unavailability of radiuscope in majority of contact lens practice, keratometer can be used to measure the BOZR of contact lenses. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Hickson-Curran, Sheila; Chalmers, Robin L; Riley, Colleen
To review important aspects of contact lens compliance and to survey contact lens replacement frequency, steps in lens care and hygiene and replacement of the lens storage case via online surveys. Random US samples (n=645 and 787) of frequent replacement contact lens wearers answered questions on contact lens wear in online, sponsor-masked surveys. Wearers of lenses prescribed by their practitioner for 2 weekly replacement reported that they replaced lenses as follows: within 2 weeks 45%, within 3 weeks (minor stretching) 68%, within 4 weeks 89%, ≥8 weeks (extreme stretching) 4%, compared to Monthly wearers who reported: within 4 weeks 37%, within 5 weeks (minor stretching) 57%, ≥8 weeks 23% (≥8 weeks extreme stretching, Chi-square p=0.001). Median frequency for cleaning lens storage case was 2-3 times per week, while 33% reported cleaning monthly or less often. Median lens storage case replacement was every 4-6 months, while 48% reported annual replacement or less often. Most patients cleaned their lens case with hot or cold tap water (72%). These internet surveys revealed significant non-compliance with lens care steps, case hygiene and lens replacement schedule. More than half of the contact lens wearers surveyed were not compliant with their 2-weekly or monthly schedule. Lenses prescribed for longer replacement intervals can lead to more extreme stretching of lens life. To encourage better patient habits, eye care providers should reinforce their recommended frequency of replacement of lenses and storage cases and should reinforce care and hygiene steps at each patient visit. Copyright © 2010. Published by Elsevier Ltd.
Heynen, Miriam; Luensmann, Doerte; Jones, Lyndon
Purpose To determine the impact of incubation solution composition on protein deposition to silicone hydrogel (SH) contact lenses using a simplistic and a complex model of the tear film. Methods Three SH materials – senofilcon A (SA), lotrafilcon B (LB), and balafilcon A (BA) – were incubated in two different solutions; Solution A was a simplistic augmented buffered saline solution containing a single protein, whereas Solution B was a complex artificial tear solution (ATS), containing the augmented buffered saline solution in addition to proteins, lipids, and mucins (pH=7.4). The proteins of interest (lysozyme, lactoferrin, albumin) were radiolabeled with Iodine-125 (2% protein of interest) and the accumulation of the conjugated protein to the lens materials was determined after 1, 7, 14, and 28 days of incubation. Protein deposition was measured using a gamma counter and the raw data were translated into absolute amounts (µg/lens) via extrapolation from standards. Results After 28 days, lysozyme uptake was significantly lower on BA lenses when incubated in Solution A (33.7 μg) compared to Solution B (56.2 μg), p<0.001. SA lenses deposited similar amounts of lysozyme when incubated in either Solution A (2.6 μg) or Solution B (4.1 μg), p>0.05. LB lenses also deposited similar amounts of lysozyme for both solutions (Solution A: 5.0 μg, Solution B: 4.7 μg, p>0.05). After 28 days, BA lenses accumulated approximately twice the amount of lactoferrin than the other lens materials, with 30.3 μg depositing when exposed to Solution A and 22.0 μg with Solution B. The difference between the two solutions was statistically significant (p<0.001). LB materials deposited significantly greater amounts of lactoferrin when incubated in Solution A (16.6 μg) compared to Solution B (10.3 μg), p<0.001. Similar amounts of lactoferrin were accumulated onto SA lenses regardless of incubation solution composition (Solution A: 8.2 μg, Solution B: 11.2 μg, p>0.05). After 28
López-Alemany, Antonio; González-Méijome, José M; Almeida, José B; Parafita, Manuel A; Refojo, Miguel F
To investigate the apparent oxygen transmissibility of various piggyback systems using conventional and silicone hydrogel soft contact lenses of different water content and permeability, rigid poly(methyl methacrylate), and rigid gas-permeable lenses of medium, high, and ultrahigh oxygen permeability. The aim of the study was to establish which material (rigid or hydrogel) is more representative of the resulting oxygen performance of piggyback systems. The apparent oxygen transmissibility of 66 piggyback systems was measured with an electrochemical method. Eighteen of these combinations involved the use of silicone hydrogel contact lenses currently available. One hyperpermeable rigid gas-permeable contact lens (tisilfocon A) was also included in the study. Measured apparent transmissibility correlates with rigid lens permeability (r = 0.403; SE = +/-3.03 barrer/cm; P < 0.001) and hydrogel lens permeability (r = 0.334; SE = +/-3.2 barrer/cm; P < 0.001). As expected, a linear model comprising permeability values from both rigid and soft materials gave a more precise estimation of the piggyback transmissibility (r = 0.736; SE = +/-2.02 barrer/cm; P < 0.001). The highest values of apparent oxygen transmissibility were found for the combination of tisilfocon A rigid material with any of the 3 silicone hydrogel lenses. Tisilfocon A material significantly improved the transmissibility of all piggyback systems even when conventional hydrogels are involved. The combination of hypertransmissible rigid gas permeable lenses with silicone hydrogel soft materials should result in normal corneal function under daily wear conditions. When fitting piggyback systems, clinicians must be aware of material selection to optimize oxygen performance. This is of particular importance in already compromised corneas.
Lorenz, Kathrine Osborn; Kakkassery, Joseph; Boree, Danielle; Pinto, David
Background Limbal ring (also known as ‘circle’) contact lenses are becoming increasingly popular, especially in Asian markets because of their eye-enhancing effects. The pigment particles that give the eye-enhancing effects of these lenses can be found on the front or back surface of the contact lens or ‘enclosed’ within the lens matrix. The purpose of this research was to evaluate the pigment location and surface roughness of seven types of ‘circle’ contact lenses. Methods Scanning electron microscopic (SEM) analysis was performed using a variable pressure Hitachi S3400N instrument to discern the placement of lens pigments. Atomic force microscopy (Dimension Icon AFM from Bruker Nano) was used to determine the surface roughness of the pigmented regions of the contact lenses. Atomic force microscopic analysis was performed in fluid phase under contact mode using a Sharp Nitride Lever probe (SNL-10) with a spring constant of 0.06 N/m. Root mean square (RMS) roughness values were analysed using a generalised linear mixed model with a log-normal distribution. Least square means and their corresponding 95% confidence intervals were estimated for each brand, location and pigment combination. Results SEM cross-sectional images at 500× and 2,000× magnification showed pigment on the surface of six of the seven lens types tested. The mean depth of pigment for 1-DAY ACUVUE DEFINE (1DAD) lenses was 8.1 μm below the surface of the lens, while the remaining lens types tested had pigment particles on the front or back surface. Results of the atomic force microscopic analysis indicated that 1DAD lenses had significantly lower root mean square roughness values in the pigmented area of the lens than the other lens types tested. Conclusions SEM and AFM analysis revealed pigment on the surface of the lens for all types tested with the exception of 1DAD. Further research is required to determine if the difference in pigment location influences on-eye performance. PMID
Lorenz, Kathrine Osborn; Kakkassery, Joseph; Boree, Danielle; Pinto, David
Limbal ring (also known as 'circle') contact lenses are becoming increasingly popular, especially in Asian markets because of their eye-enhancing effects. The pigment particles that give the eye-enhancing effects of these lenses can be found on the front or back surface of the contact lens or 'enclosed' within the lens matrix. The purpose of this research was to evaluate the pigment location and surface roughness of seven types of 'circle' contact lenses. Scanning electron microscopic (SEM) analysis was performed using a variable pressure Hitachi S3400N instrument to discern the placement of lens pigments. Atomic force microscopy (Dimension Icon AFM from Bruker Nano) was used to determine the surface roughness of the pigmented regions of the contact lenses. Atomic force microscopic analysis was performed in fluid phase under contact mode using a Sharp Nitride Lever probe (SNL-10) with a spring constant of 0.06 N/m. Root mean square (RMS) roughness values were analysed using a generalised linear mixed model with a log-normal distribution. Least square means and their corresponding 95% confidence intervals were estimated for each brand, location and pigment combination. SEM cross-sectional images at 500× and 2,000× magnification showed pigment on the surface of six of the seven lens types tested. The mean depth of pigment for 1-DAY ACUVUE DEFINE (1DAD) lenses was 8.1 μm below the surface of the lens, while the remaining lens types tested had pigment particles on the front or back surface. Results of the atomic force microscopic analysis indicated that 1DAD lenses had significantly lower root mean square roughness values in the pigmented area of the lens than the other lens types tested. SEM and AFM analysis revealed pigment on the surface of the lens for all types tested with the exception of 1DAD. Further research is required to determine if the difference in pigment location influences on-eye performance. © 2014 The Authors. Clinical and Experimental
Ziak, P; Ondriska, F; Mrva, M
The case history of a 39-year patient suffering from a deep inflammation of cornea and not responding to conventional antibiotic treatment is presented. The patient was using soft contact lenses during the period of initial symptoms; moreover, he was bathing in thermal bathing pool. A cultivation examination of smears from the area of corneal defect revealed the presence of Acanthamoeba lugdunensis in combination with bacterial infection by Pseudomonas aeruginosa. The available data indicate that it is the first case of acanthamoeba karatitis (AK) after the application of contact lenses in Slovakia. A long-term local treatment with propamidin isethionate (Brolene gtt, ung.) resulted in healing up. The subsequent vision after 16 months since the initial symptoms proved to be 6/12 (0.5). The healing of the centrally localized defect changed the curvature of cornea with consequent hypermetropic shift. The defect completely corrected the patient's myopia (-8.5). The paper describes present possibilities of AK therapy.
Malet, Florence; Schnider, Cristina M
This study examines what effects replacement schedule and care regimen have on overall patient satisfaction with daily wear frequent-replacement contact lenses. Over 3000 patients were recruited from 313 ophthalmologic practices in France to participate in a 1-month prospective observational clinical study. Subjects included 2108 experienced and 957 novice users of the predominantly prescribed soft contact lenses and care systems in France. All subjects were required to use ACUVUE 2 (Vistakon, Jacksonville, FL) brand contact lenses, replaced once every 2 weeks, and using COMPLETE brand multipurpose solution (Allergan, Irvine, CA) during the study. Practitioners assessed lens fit, and refractive and ocular physiological status. Subjects were surveyed about various subjective attributes at the baseline examination and at the end of the study. Patient satisfaction with the test lenses and care system was found to be excellent for the majority of patients, as evidenced by high subjective satisfaction ratings and the desire of approximately 9 of 10 subjects to continue using the test products after completing the study. Significant improvements were noted with the test lenses and solution compared to previous lenses and solutions for overall satisfaction and comfort variables. Replacing lenses once every 2 weeks combined with a multipurpose care system incorporating ingredients designed for lens conditioning contributed to significant improvements in lens wearing comfort. Thus, lens replacement frequency and lens-and-solution compatibility should be considered in addition to lens material and design when prescribing contact lenses for new or existing wearers.
Costa, Manuel F. M.
Optical triangulation as a non-destructive test method extensively proved its usefulness on the dimensional and topographic inspection of a large range of objects and surfaces. In this communication the issue of microtopographic and thickness inspection of hard contact lenses (RPG) is addressed. The use of optical triangulation is discussed based on the results of the application of our MICROTOP.03.MFC microtopographer to this kind of tasks will be presented.
Butt, Thomas; Crossland, Michael D; West, Peter; Orr, Shepley W; Rubin, Gary S
Background/aims The National Institute for Health and Care Excellence (NICE) has recommended the use of ranibizumab for neovascular age-related macular degeneration (AMD) and for diabetic macular oedema (DMO) as part of its health technology appraisal process. In the economic evaluations of both interventions, utility values were derived from members of the general public wearing contact lenses with a central opacity that was meant to simulate the blind spot experienced by many patients with advanced retinal disease. This paper tests the validity of the contact lens simulation, and finding it to be invalid, explores the impact on prior economic evaluations. Methods Visual acuity, contrast sensitivity and visual fields were assessed with and without simulation lenses in five healthy subjects with normal vision. Results We identified important differences between the contact lens simulation and vision loss experienced by patients with AMD. The contact lens simulator did not cause the central scotoma which is characteristic of late-stage AMD and which leads to severe difficulty with everyday activities such as reading or recognising faces and objects. The contact lens instead caused a reduction in retinal illumination experienced by the subjects as a general dimming across the retina. Conclusions A contact lens with a central opacity does not simulate a central scotoma. The clinical differences between simulated and actual AMD suggest there has been an underestimation of the severity of AMD health states. This brings into question the validity of the economic evaluations of treatments for AMD and DMO used by NICE. PMID:25351679
Heynen, Miriam; Liu, Lina; Sheardown, Heather; Jones, Lyndon
Purpose To investigate the efficiency of lysozyme and albumin removal from silicone hydrogel and conventional contact lenses, using a polyhexamethylene biguanide multipurpose solution (MPS) in a soaking or rubbing/soaking application and a hydrogen peroxide system (H2O2). Methods Etafilcon A, lotrafilcon B and balafilcon A materials were incubated in protein solutions for up to 14 days. Lenses were either placed in radiolabeled protein to quantify the amount deposited or in fluorescent-conjugated protein to identify its location, using confocal laser scanning microscopy (CLSM). Lenses were either rinsed with PBS or soaked overnight in H2O2 or MPS with and without lens rubbing. Results After 14 days lysozyme was highest on etafilcon A (2,200 μg) >balafilcon A (50 µg) >lotrafilcon B (9.7 µg) and albumin was highest on balafilcon A (1.9 µg) =lotrafilcon B (1.8 µg) >etafilcon A (0.2 µg). Lysozyme removal was greatest for balafilcon A >etafilcon A >lotrafilcon B, with etafilcon A showing the most change in protein distribution. Albumin removal was highest from etafilcon A >balafilcon A >lotrafilcon B. H2O2 exhibited greater lysozyme removal from etafilcon A compared to both MPS procedures (p<0.001) but performed similarly for lotrafilcon B and balafilcon A lenses (p>0.62). Albumin removal was solely material specific, while all care regimens performed to a similar degree (p>0.69). Conclusions Protein removal efficiency for the regimens evaluated depended on the lens material and protein type. Overall, lens rubbing with MPS before soaking did not reduce the protein content on the lenses compared to nonrubbed lenses (p=0.89). PMID:20098668
Campos-Rodríguez, Rafael; Oliver-Aguillón, Gabriela; Vega-Pérez, Luz M; Jarillo-Luna, Adriana; Hernández-Martínez, Dolores; Rojas-Hernández, Saúl; Rodríguez-Monroy, Marco A; Rivera-Aguilar, Víctor; González-Robles, Arturo
Specific anti-Acanthamoeba IgA antibodies have been detected in the serum and tears of patients and healthy individuals. However, the role of human secretory IgA antibodies in inhibiting the adherence of Acanthamoeba had not been previously investigated. Therefore, the purpose of this study was to purify secretory IgA from human colostrum and analyze its effect on the adherence of Acanthamoeba trophozoites to contact lenses and Madin-Darby canine kidney (MDCK) cells. IgA antibodies to Acanthamoeba polyphaga in colostrum of healthy women as well as in saliva and serum of healthy subjects were analyzed by ELISA and Western blot analysis. In serum, saliva, and colostrum, we detected IgA antibodies that recognized several antigens of A. polyphaga. In addition, colostrum and IgA antibodies purified from it inhibited adherence of A. polyphaga trophozoites to contact lenses and MDCK cells. These results suggest that IgA antibodies may participate in the resistance to the amoebic infection, probably by inhibiting the adherence of the trophozoites to contact lenses and corneal epithelial cells.
Sandri, Giuseppina; Bonferoni, Maria Cristina; Rossi, Silvia; Delfino, Alessio; Riva, Federica; Icaro Cornaglia, Antonia; Marrubini, Giorgio; Musitelli, Giorgio; Del Fante, Claudia; Perotti, Cesare; Caramella, Carla; Ferrari, Franca
Hemoderivative tear substitutes contain various ephiteliotrophic factors, such as growth factors (GF), involved in ocular surface homeostasis without immunogenic properties. The aim of the present work was the loading of platelet lysate into contact lenses to improve the precorneal permanence of platelet lysate growth factors on the ocular surface to enhance the treatment of corneal lesions. To this purpose, chondroitin sulfate, a sulfated glycosaminoglycan, which is normally present in the extracellular matrix, was associated with platelet lysate. In fact, chondroitin sulfate is capable of electrostatic interaction with positively charged growth factors, in particular, with bFGF, IGF, VEGF, PDGF and TGF-β, resulting in their stabilization and reduced degradation in solution. In the present work, various types of commercially available contact lenses have been loaded with chondroitin sulfate or chondroitin sulfate in association with platelet lysate to achieve a release of growth factors directly onto the corneal surface lesions. One type of contact lenses (PureVision(®)) showed in vitro good proliferation properties towards corneal cells and were able to enhance cut closure in cornea constructs.
Thibos, Larry N; Cheng, Xu; Bradley, Arthur
The concept of the wave-front guided design of contact lenses is presented from three vantage points: ray optics, wave front aberrations, and optical path-length errors. We argue that the goal of contact lenses is to make all of the optical paths from a distant object to the retina equal in length, regardless of where the path intersects the plane of the eye's pupil. The aberration map of an eye is a prescription for such a lens. Unfortunately, variability of measured aberration maps is a fundamental limit to our knowledge of the true aberration structure of an eye. Variability arises because the eye is a biologic system that changes over time for normal, physiologic reasons. Furthermore, uncertainty in our measurement of the aberration map because of such variable factors, such as alignment of the aberrometer to the eye by the clinician or small fixation errors committed by the patient, will make it difficult to achieve a full measure of success with aberration-correcting contact lenses. The clinical implication of these findings is that multiple measurements of the aberration map should be collected using a protocol that includes realignment of the instrument and then averaging the aberration maps to reduce the level of uncertainty associated with any single measurement.
Zeri, Fabrizio; De Cusatis, Mario; Lupelli, Luigi; Swann, Peter Graham
To investigate if the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) contact lenses (CL) is affected by the positive power of the CLs. The experimental group comprised 26 subjects, (8 male, 18 female). IOP measurements were undertaken on the subjects' right eyes in random order using a Rebound Tonometer (ICare). The CLs had powers of +2.00D and +6.00D. Measurements were taken over each contact lens and also before and after the CLs had been worn. The IOP measure obtained with both CLs was significantly lower compared to the value without CLs (t test; p<0.001) but no significant difference was found between the two powers of CLs. Rebound tonometry over positive hydrogel CLs leads to a certain degree of IOP underestimation. This result did not change for the two positive lenses used in the experiment, despite their large difference in power and therefore in lens thickness. Optometrists should bear this in mind when measuring IOP with the rebound tonometer over plus power contact lenses. Copyright © 2016 The Authors. Published by Elsevier Espana.. All rights reserved.
Horn, Fraser C; Erickson, Graham B; Karben, Brock; Moore, Benjamin
Athletes who participate in outdoor activities seek products to reduce glare and improve contrast. This study compares performance of low-contrast visual acuity (VA) in bright outdoor conditions between the Maxsight Amber contact lens (CLs) and clear CLs with and without Eye Black grease. Seventeen subjects were fitted with clear CLs, clear lenses with Eye Black grease, Maxsight lenses with Eye Black grease, and Maxsight lenses alone. With each modality, the subject demonstrated low-contrast VA assessed and completed a questionnaire. At the end of testing, subjects completed a questionnaire to survey the performance of each modality. The average low-contrast VA with clear CLs was 20/18.4, which improved to 20/17 with the addition of Eye Black grease (P=0.132). Significant improvement in low-contrast VA was seen with the Maxsight CLs to 20/15.4 (P<0.05), although it was not further improved with the addition of Eye Black grease. The results of the questionnaire showed a preference of the Maxsight CLs throughout the study for low-contrast VA. Although Eye Black grease has its place in sport and some sporting environments, the benefit in contrast acuity is insignificant. The better performance of the amber Maxsight lenses in this study demonstrates a visual performance benefit in bright sunlight.
Weissman, B A; Fatt, I
Edge and boundary effect correction factors have been proposed to modify the oxygen transmissibility and permeability values obtained by polarographic measurement of contact lenses. These two correction factors are opposite in sign: the boundary effect causes oxygen transmissibility and permeability to be underestimated; the edge effect causes the reverse. Two methods are used to define lens thickness values where the two effects should be quantitatively equal and therefore cancel for both rigid gas permeable and hydrogel contact lenses.
Galas, Stephen; Copper, Lenora L
Purpose To evaluate the individual contributions of pigment colorant and packing solution containing polyvinyl pyrrolidone (PVP) on the oxygen permeability (Dk) of a cosmetic printed etafilcon A daily disposable contact lens packaged with PVP. Method The oxygen transport of a contact lens is evaluated through the central optical zone of the lens. Cosmetic printed contact lenses contain pigment colorant in the periphery or mid-periphery of the lens. Therefore, to assess the impact of cosmetic print on oxygen permeability, special lenses need to be produced that contain the colorant within the central optical zone. This technique was used to obtain multiple measurements of nonedge-corrected Dk/t of both the center pigmented lens and its nonpigmented equivalent, using a polarographic measurement described in International Organization for Standardization (ISO) 18369-4:2006(E), and the Dk derived for each measurement is corrected for edge effect. In addition, the edge-corrected Dk values of lenses made from the same monomer batch were measured. The lenses were packaged and autoclaved with and without proprietary technology which embeds PVP in the contact lens during autoclaving. The resulting Dk value of the printed lens material was then used with thickness data to generate true Dk/t profiles for a given lens power. Results The edge-corrected Dk of the printed etafilcon A lens with offset pigment colorant was measured to be 19.7×10−11 (cm2/s) (mL O2/mL·mmHg) at 35°C. This was within ±20% tolerance range as specified in ISO 18369-2:2012(E) for the edge-corrected Dk of the nonpigmented etafilcon A control lens evaluated during the same session, 19.5×10−11 (cm2/s) (mL O2/mL·mmHg). The edge-corrected Dk values of the lenses packaged with PVP (mean 20.1, standard deviation [SD] 0.3) were also within the ±20% tolerance range compared to those packaged without PVP (mean 20.0, SD 0.3). Conclusion The pigment colorant and PVP embedded in the contact lens during
Ascaso, Francisco J; Huerva, Valentín
: The incidence of diabetes mellitus is dramatically increasing in the developed countries. Tight control of blood glucose concentration is crucial to diabetic patients to prevent microvascular complications. Self-monitoring of blood glucose is widely used for controlling blood glucose levels and usually performed by an invasive test using a portable glucometer. Many technologies have been developed over the past decades with the purpose of obtaining a continuous physiological glycemic monitoring. A contact lens is the ideal vehicle for continuous tear glucose monitoring of glucose concentration in tear film. There are several research groups that are working in the development of contact lenses with embedded biosensors for continuously and noninvasively monitoring tear glucose levels. Although numerous aspects must be improved, contact lens technology is one step closer to helping diabetic subjects better manage their condition, and these contact lenses will be able to measure the level of glucose in the wearer's tears and communicate the information to a mobile phone or computer. This article reviews studies on ocular glucose and its monitoring methods as well as the attempts to continuously monitor the concentration of tear glucose by using contact lens-based sensors.
Bonanno, Joseph A.; Clark, Christopher; Pruitt, John; Alvord, Larry
Purpose To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Methods Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Results Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. Conclusions The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea. PMID:19609230
García-Millán, Eva; Quintáns-Carballo, Mónica; Otero-Espinar, Francisco Javier
Drug nanosuspensions (NSs) show a significant potential to improve loading and release properties of the poorly water soluble drug triamcinolone acetonide (TA) from poly(hydroxyethyl methacrylate) (pHEMA) soft contact lenses. In this work, TA NSs were developed by a controlled precipitation method using a fractional factorial Plackett-Burmann design. Poloxamer 407 (PL) and polyvinyl alcohol (PVA) as stabilizing agents were selected. NSs were characterized in terms of their drug content, particle size and morphology. Results indicate that all studied factors, except homogenization speed and sonication, have significant influence on the drug incorporation yield into NSs. Drug nanoparticles showed an interesting size that may be suitable for their incorporation into topical ocular drug delivery systems, as hydrogels. pHEMA hydrogels and daily-wear Hilafilcon B commercial contact lenses (SCLs) were employed to study TA loading capacity and drug release properties using NSs as loading system. Hydrogels have been synthesised by copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methacrylic acid (MA) in accordance with a previous work (García-Millán et al., 2015). Both synthesised hydrogels and SCLs were characterized in terms of their mechanical and physical properties and TA loading and release properties. Selected TA NS was further characterized by studying its physical-chemical stability during the loading process. Results show that the use of TA NSs as loading medium significantly increases drug loading capacity and release of soft contact lenses in comparison with drug saturated solution. Synthesised pHEMA hydrogels and SCLs lenses have good properties as ophthalmic drug delivery systems, but SCLs load higher quantities of drug and release TA in shorter time periods than synthesised pHEMA hydrogel. Copyright © 2017 Elsevier B.V. All rights reserved.
Berntsen, David A.; Merchea, Mohinder M.; Richdale, Kathryn; Mack, Carla J.; Barr, Joseph T.
Purpose To determine the on-eye effect of spherical and toric contact lens design on higher-order aberrations (HOA). Methods Thirty eyes (15 subjects) entered a masked, randomized, cross-over study. Each eye was fitted with the spherical and toric lens of the following brands in random order: Acuvue Advance, Biomedics 55, Frequency 55, and SofLens 66. HOAs were measured using the Zywave II Aberrometer over a 6-mm aperture up to fifth order. A linear model accounting for the fixed effect of lens type and random effects of subject and eye was created. Paired t-tests were completed between lens brands within the spherical and toric lenses and between the spherical and toric lens within each brand. Best-corrected visual acuity (VA) was measured and compared. Results No clinically meaningful differences in total HOAs were found between brands or between the spherical and toric lens within a brand. Positive spherical aberration (SA) was reduced by all spherical and toric lenses compared to wearing no lens by 0.07 to 0.23 μm (p<0.0001). Frequency toric induced the greatest change in SA. The thin-zone design lens (Acuvue Advance for Astigmatism) had a statistically different amount of vertical coma (−0.04 μm) than the three prism-balast toric lenses (0.11 to 0.23 μm; p<0.0001). SofLens toric had the greatest amount of vertical coma, but better VA than Acuvue Advance for Astigmatism and Frequency toric. With the exception of Acuvue Advance for Astigmatism, toric lenses had greater absolute magnitude of vertical coma than their sphere counterparts (all p<0.002). No other significant HOA differences were observed. Conclusions Toric contact lenses with prism-ballast designs demonstrated more vertical coma, but better VA. Positive SA was reduced by spherical and toric contact lenses. The visual quality effect of lens design and material on induced HOAs warrants further investigation. PMID:19156015
Kapoor, Yash; Thomas, Justin C; Tan, Grace; John, Vijay T; Chauhan, Anuj
Eye drops are inefficient means of delivering ophthalmic drugs because of limited bioavailability and these can cause significant side effects due to systemic uptake of the drug. The bioavailability for ophthalmic drugs can be increased significantly by using contact lenses. This study focuses on the development of surfactant-laden poly-hydroxy ethyl methacrylate (p-HEMA) contact lenses that can release Cyclosporine A (CyA) at a controlled rate for extended periods of time. We focus on various Brij surfactants to investigate the effects of chain length and the presence of an unsaturated group on the drug release dynamics and partitioning inside the surfactant domains inside the gel. The gels were imaged by cryogenic scanning electron microscopy (cryo-SEM) to obtain direct evidence of the presence of surfactant aggregates in the gel, and to investigate the detailed microstructure for different surfactants. The images show a distribution of nano pores inside the surfactant-laden hydrogels which we speculate are regions of surfactant aggregates, possibly vesicles that have a high affinity for the hydrophobic drug molecule. The gels are further characterized by studying their mechanical and physical properties such as transparency, surface contact angle and equilibrium water content to determine their suitability as extended wear contact lenses. Results show that Brij surfactant-laden p-HEMA gels provide extended release of CyA, and possess suitable mechanical and optical properties for contact lens applications. The gels are not as effective for extended release of two other hydrophobic ophthalmic drugs, dexamethasone (DMS) and dexamethasone 21 acetate (DMSA) because of insufficient partitioning inside the surfactant aggregates.
Vijay, Ajay Kumar; Willcox, Mark D P
Contact lens cases become contaminated with microbes during use. We wished to compare the adhesion of uncommon bacterial contaminants isolated from lens cases to contact lenses with and without organic soil. Strains of Delftia acidovorans (001), Stenotrophomonas maltophilia (002 and 006), and Achromobacter xylosoxidans (001) isolated from contact lens cases (test strains) and Pseudomonas aeruginosa (Paer1) isolated from eyes at the time of infiltrative response (control strain) were used. Bacteria were grown and resuspended in phosphate-buffered saline (PBS) or 10% organic soil (heat-killed Saccharomyces cerevisiae resuspended in complement inactivated bovine serum). Two silicone hydrogel (senofilcon A and comfilcon A) and one hydrogel lens (etafilcon A) lens materials were used. Bacteria (1.0×10 and 1.0×10 colony-forming units/mL; CFU/mL) adhered to lenses for 24 hr and the numbers of bacteria adherent to each lens type (with and without organic soil) were estimated by culture. All the four test strains adhered in significantly greater numbers to contact lenses after incubation in inoculum prepared with organic soil compared with PBS-D. acidovorans 001 (0.7 log10 CFU; P<0.05), S. maltophilia 002 (1.7 log10 CFU; P<0.05), S. maltophilia 006 (0.9 log10 CFU; P<0.05), and A. xylosoxidans 001 (0.4 log10 CFU; P<0.05). However, the presence of organic soil did not increase adhesion of P. aeruginosa Paer1 (-0.1 log10 CFU; P>0.05). Achromobacter xylosoxidans 001 (P<0.01), D. acidovorans 001 (P<0.01), and S. maltophilia 002 (P<0.01) significantly differed in their adhesion to the three contact lens materials. Bacteria that are commonly found in contact lens cases adhered to contact lenses in relatively high numbers in the presence of organic soil. This might indicate that a similar phenomenon occurs in the presence of tears. This may facilitate their transfer from the lens to the cornea and the production of corneal infiltrates.
Michaud, Langis; Frenette, Benoît
Purpose. This study aimed to evaluate outcomes from the use of a sodium hyaluronate (SH)-based comfort drop, instilled before the insertion of contact lenses, in a population of symptomatic contact lens wearers. Methods. This was a cross-over, open-label, multi-sites study. Subjects were fitted with silicone hydrogel lenses and followed for two months. Before insertion of the lenses, SH drops was instilled in the lens for half of the group. The other half did the same on the second month. Objectives and subjective outcomes were measured and compared before from baseline with the ones collected after usage of SH drops. PMID:24575306
Michaud, Langis; Frenette, Benoît
Purpose. This study aimed to evaluate outcomes from the use of a sodium hyaluronate (SH)-based comfort drop, instilled before the insertion of contact lenses, in a population of symptomatic contact lens wearers. Methods. This was a cross-over, open-label, multi-sites study. Subjects were fitted with silicone hydrogel lenses and followed for two months. Before insertion of the lenses, SH drops was instilled in the lens for half of the group. The other half did the same on the second month. Objectives and subjective outcomes were measured and compared before from baseline with the ones collected after usage of SH drops.
Maulvi, Furqan A; Lakdawala, Dhara H; Shaikh, Anjum A; Desai, Ankita R; Choksi, Harsh H; Vaidya, Rutvi J; Ranch, Ketan M; Koli, Akshay R; Vyas, Bhavin A; Shah, Dinesh O
Glaucoma is commonly treated using eye drops, which is highly inefficient due to rapid clearance (low residence time) from ocular surface. Contact lenses are ideally suited for controlled drug delivery to cornea, but incorporation of any drug loaded particulate system (formulation) affect the optical and physical property of contact lenses. The objective of the present work was to implant timolol maleate (TM) loaded ethyl cellulose nanoparticle-laden ring in hydrogel contact lenses that could provide controlled drug delivery at therapeutic rates without compromising critical lens properties. TM-implant lenses were developed, by dispersing TM encapsulated ethyl cellulose nanoparticles in acrylate hydrogel (fabricated as ring implant) and implanted the same in hydrogel contact lenses (sandwich system). The TM-ethyl cellulose nanoparticles were prepared by double emulsion method at different ratios of TM to ethyl cellulose. The X-ray diffraction studies revealed the transformation of TM to amorphous state. In vitro release kinetic data showed sustained drug release within the therapeutic window for 168h (NP 1:3 batch) with 150μg loading. Cytotoxicity and ocular irritation study demonstrated the safety of TM-implant contact lenses. In vivo pharmacokinetic studies in rabbit tear fluid showed significant increase in mean residence time (MRT) and area under curve (AUC), with TM-implant contact lenses in comparison to eye drop therapy. In vivo pharmacodynamic data in rabbit model showed sustained reduction in intra ocular pressure for 192h. The study demonstrated the promising potential of implantation technology to treat glaucoma using contact lenses, and could serve as a platform for other ocular diseases.
Lin, David Pei-Cheng; Chang, Han-Hsin; Yang, Li-Chien; Huang, Tzu-Ping; Liu, Hsiang-Jui; Chang, Lin-Song; Lin, Chien-Hsun
Purpose Weekly disposable soft contact lenses have been widely used recently, but their shield effects against ultraviolet (UV) irradiation remain to be evaluated. This study investigated the bioprotective effects of several weekly soft contact lenses against UVB irradiation on the corneal surface in a mouse model. Methods Fifty ICR mice were randomly divided into five groups: (1) blank control, (2) exposed to UVB without contact lens protection, (3) exposed to UVB and protected with Vifilcon A contact lenses, (4) exposed to UVB and protected with Etafilcon A contact lenses, and (5) exposed to UVB and protected with HEMA+MA contact lenses. The exposure to UVB irradiation was performed at 0.72 J/cm2/day after anesthesia for a 7-day period, followed by cornea surface assessment for smoothness, opacity, and grading of lissamine green staining. Tissue sections were prepared for hematoxylin and eosin staining and immunohistochemical detection by using antibodies against myeloperoxidase, cytokeratin-5, P63, Ki-67, nuclear factor-kappa B (p65), cyclooxygenase-2, Fas L, and Fas. Results The results showed impaired corneal surface with myeloperoxidase+ polymorphonuclear leukocyte infiltration into the stroma after UVB exposure, in contrast to the intact status of the blank controls. The corneas with Etafilcon A and HEMA+MA contact lenses maintained more cells positive for cytokeratin-5, P63, and Ki-67 compared to those with Vifilcon A or without contact lens protection. Furthermore, less proinflammatory factors, including nuclear factor-kappa (p65), cyclooxygenase-2, Fas L, and Fas, were induced in the corneas protected by Etafilcon A and HEMA+MA. Conclusions This study demonstrated various protective effects of weekly disposable contact lenses against UVB irradiation. The mouse model used in the present study may be used extensively for in vivo assessment of UV shield efficacy. PMID:23734085
Kok, J H; Smulders, F; van Mil, C
Scarring of the cornea often results in an irregular corneal surface, which causes scattering in light perception. Therefore, the impaired visual acuity cannot be adequately corrected by spectacles in most cases. In this study, high oxygen-transmissible aspheric rigid lenses were fitted, with computer assistance, in 26 scarred eyes of 23 consecutive patients. In 15 of 26 eyes (57.7%), a successful fitting with good vision, no complications, and a sufficiently long wearing time was accomplished. The main lens-related complications included fluorescein-staining epithelial defects in five of 26 eyes (19.2%) and epithelial edema in two of 26 eyes (7.7%). Computer-aided fitting was of limited value because keratometer readings were not measurable in 50% of the cases. The results of this study indicate that the application of high oxygen-transmissible aspheric rigid contact lenses may obviate corneal surgery.
Filipecka, Katarzyna; Miedziński, Rafał; Sitarz, Maciej; Filipecki, Jacek; Makowska-Janusik, Małgorzata
The Raman, MIR and UV-vis spectroscopy have been used to characterize Omafilcon A material constructing the one of the Proclear family contact lenses. The Omafilcon A is hydrogel material composed of 2-hydroxyethyl methacrylate (HEMA) and 2-methacryloyloxyethyl phosphorylcholine (PC) polymers crosslinked with ethyleneglycol dimethacrylate (EGDMA). Vibrational and electronic properties of the Omafilcon A material were also investigated by quantum chemical calculations. Experimentally obtained Raman, MIR and optical spectra were compared to the theoretical ones calculated applying RHF and DFT methodology. The quantum chemical calculations were performed for isolated monomers of lenses compounds as well as for their dimers and trimers to elucidate the effect of Omafilcon A polymerization and the role of an individual components.
Filipecka, Katarzyna; Miedziński, Rafał; Sitarz, Maciej; Filipecki, Jacek; Makowska-Janusik, Małgorzata
The Raman, MIR and UV-vis spectroscopy have been used to characterize Omafilcon A material constructing the one of the Proclear family contact lenses. The Omafilcon A is hydrogel material composed of 2-hydroxyethyl methacrylate (HEMA) and 2-methacryloyloxyethyl phosphorylcholine (PC) polymers crosslinked with ethyleneglycol dimethacrylate (EGDMA). Vibrational and electronic properties of the Omafilcon A material were also investigated by quantum chemical calculations. Experimentally obtained Raman, MIR and optical spectra were compared to the theoretical ones calculated applying RHF and DFT methodology. The quantum chemical calculations were performed for isolated monomers of lenses compounds as well as for their dimers and trimers to elucidate the effect of Omafilcon A polymerization and the role of an individual components.
Bettuelli, Michela; Trabattoni, Silvia; Fagnola, Matteo; Tavazzi, Silvia; Introzzi, Laura; Farris, Stefano
The low surface roughness of disposable contact lenses made of a new siloxane-hydrogel loaded with hyaluronic acid is reported, as studied by atomic force microscopy (AFM). Before the wear, the surface is characterized by out-of-plane and sharp structures, with maximum height of about 10 nm. After a wear of 8 h, evidence of two typical morphologies is provided and discussed. One morphology (sharp type) has a similar aspect as the unworn lenses with a slight increase in both the height and the number of the sharp peaks. The other morphology (smooth type) is characterized by troughs and bumpy structures. Wettability and clinical performances are also discussed, the latter deduced by the ocular-surface-disease index (OSDI). The main finding arising from this work is the indication of correlation between the change of the OSDI before and after wear and the lens surface characteristics obtained by AFM.
Porcar, Esteban; Montalt, Juan Carlos; España-Gregori, Enrique; Peris-Martínez, Cristina
To analyse the visual quality achieved by fitting corneo-scleral contact lenses (CScL) in an uncommon case of bilateral keratoconus, high hyperopia and astigmatism. A 45-year-old man presented for eye examination due to the unsatisfactory quality of his vision wearing soft toric contact lenses. He presented high hyperopia and astigmatism with bilateral keratoconus. He was fitted with CScL to correct his irregular astigmatism and ocular aberrations. A diagnostic trial set was used in the fitting process and he was assessed according to standardised fitting methodology. Visual acuity, corneal topography, biometry and ocular aberrations were evaluated. The follow-up period was 1year. The best spectacle-corrected visual acuity was 20/32 with +8.00/-4.50×30° for the right eye (RE) and 20/25 with +7.75/-2.25×120° for the left eye (LE). After CScL fitting, visual acuity was improved to 20/20 and 20/16 for the RE and LE, respectively. The patient wore these contact lenses an average of 13h a day. The total high order aberrations decreased by approximately 79% in the RE (2.37-0.50μm) and 47% in the LE (1.04-0.55μm) after CScL fitting. Visual quality and wearing time were maintained after 1year wearing CScL. In addition, no adverse ocular effects were found during this period. The present case report describes how the patient had CScL fitted successfully for management of keratoconus with high hyperopia and astigmatism. They provided optimal visual quality, along with prolonged use times and no adverse effects to the cornea. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Gispets, Joan; Arjona, Montserrat; Pujol, Jaume; Vilaseca, Meritxell; Cardona, Genís
Purpose A longitudinal prospective, cross-over, double masked study was designed to evaluate task oriented visual satisfaction and wearing success with two types of simultaneous vision multifocal soft contact lenses. Methods Twenty-two presbyopic subjects followed two 14-day trial periods in which they were alternatively and randomly fitted with two types of multifocal lenses. Habitual tasks were described in terms of observation distance, visual demand level and time allocation. Subjects graded visual satisfaction with each pair of lenses and each habitual task at different times during each trial. Overall satisfaction was evaluated after completion of the two trial periods. Wearing success was determined by the percentage of subjects opting to continue multifocal lens wear and by the number of subjects still wearing their lenses six months later. Results Viewing distance and visual demand level were found to influence visual satisfaction (p < 0.001). Visual satisfaction decreased for tasks involving higher visual demands and for near and far viewing distances, rather than for intermediate vision or a combination of near and far vision. A combined effect of lens type and evaluation time was discovered (p = 0.046). Although 78% of subjects decided to continue lens wear, only one subject was wearing them on a daily basis 6 months after the completion of the study. Insufficient quality of vision was reported as the main reason for multifocal contact lens discontinuation. Conclusions A task oriented visual satisfaction evaluation may prove helpful in lens design selection, as well as in predicting wearing success.
Primeau, Brian C.; Greivenkamp, John E.; Sullivan, John J.
The anterior refracting surface of the eye when wearing a contact lens is the thin fluid layer that forms on the surface of the contact lens. Under normal conditions, this fluid layer is less than 10 microns thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens, and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed using a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. The fluid behavior on the contact lens surface is measured, allowing quantitative analysis beyond what typical contact angle or visual inspection methods provide. The interferometer system has measured the formation and break up of fluid layers. Different fluid and contact lens material combinations have been used, and significant fluid layer properties have been observed in some cases. The interferometer is capable of identifying features in the fluid layer less than a micron in depth with a spatial resolution of about ten microns. An area on the contact lens approximately 6 mm wide can be measured with the system. This paper will discuss the interferometer design and analysis methods used. Measurement results of different material and fluid combinations are presented.
Filipecki, Jacek; Kotynia, Katarzyna; Filipecka, Katarzyna
Hydrogel and silicone-hydrogel polymeric materials are widely used in ophthalmology for the manufacture of contact lenses. An important aspect is the investigation of the structure of these materials. This study has been conducted in order to compare the degree of disorder and presence of free volumes in the internal structure of the polymeric soft contact lenses Omafilcon A (hydrogel) and Comfilcon A (silicone-hydrogel). Differences in the occurrence of trapping centers for positrons and free volumes between the types of investigated contact lenses have been demonstrated. Two types of polymeric contact lenses were used as materials: Omafilcon A (hydrogel) and Comfilcon A (silicone-hydrogel). The study was performed using positron annihilation lifetime spectroscopy (PALS). When the results of the measurements has been obtained, a graphical curve has created to describe the relationship of the number of annihilation acts in time. Significant changes were observed between the contact lenses investigated in positron trapping in macropores (based on a two-state model) and the presence of free volumes (based on the Tao-Eldrup model). The use of the positron annihilation two-state model made it possible to demonstrate that a higher positron trapping rate in macropores occurs in the silicone-hydrogel contact lens. Additionally, calculations using the Tao-Eldrup model show the existence of free volumes in both types of materials. The size and fraction of free volumes is much larger in the silicone-hydrogel contact lens.
Da Roza, R.A.; Weaver, C.
The Federal OSHA regulation that prohibits the wearing of contact lenses while using a respirator is being challenged by users. We surveyed 9100 fire fighters around the US and Canada to determine if the wearing of contacts while using a self-contained breathing apparatus (SCBA) had caused any serious problems to warrant this strict regulation. Of the 1405 questionnaires returned, 403 fire fighters do wear contacts with SCBA, despite the regulation. Of these, only six responded that contact-lens related problems had caused them to remove the facepiece in an environment in which the facepiece would normally be worn. In contrast, the safety-related problems caused by eyeglasses in SCBA - which are legal - are proportionately higher. Over half of the supervisors returning the questionnaire admitted that some of their employees wear contacts with SCBA; however, these supervisors knew of only eight cases when contact-lens problems had caused the facepiece to be removed when it should not have been. Our investigation has indicated that these problems were not significantly hazardous. We believe that the use of contacts with a respirator should not be prohibited. 7 refs., 2 figs., 7 tabs.
Primeau, Brian C.; Greivenkamp, John E.
The anterior refracting surface of the eye when wearing a contact lens is the thin fluid layer that forms on the surface of the contact lens. Under normal conditions, this fluid layer is less than 10 μm thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed by use of a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. Quantitative analysis beyond typical contact angle or visual inspection methods is provided. Different fluid and contact lens material combinations have been evaluated, and variations in fluid layer properties have been observed. This paper discusses the interferometer design and analysis methods used. Example measurement results of different contact lens are presented.
González-Méijome, José M; López-Alemany, Antonio; Almeida, José B; Parafita, Manuel A; Refojo, Miguel F
In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 microm2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 microm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane-hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface.
Saviuc, Crina; Dascălu, Luminita; Chifiriuc, Mariana Carmen; Rădulescu, Valeria; Oprea, Eliza; Popa, Marcela; Hristu, Radu; Stanciu, George; Lazăr, Veronica
The aim of present study was to investigate the microbial colonization of worn contact lenses (CLs) and to evaluate the inhibitory effect of pomelo (Citrus maxima) peels essential oil on the biofilm development on unworn CLs. The essential oil was isolated by steam distillation and analyzed by gas chromatography coupled with mass spectrometry, twenty compounds being isolated. The antimicrobial activity of pomelo oil was tested against S. epidermidis and P. aeruginosa strains, known for their ability to develop biofilms on prosthetic devices, by qualitative screening methods and quantitative assay of the minimal inhibitory concentrations (MIC) in order to evaluate the antibiofilm activity. Our study revealed that all worn CLs where 100% colonized by staphylococci and Enterobacteriaceae strains. The pomelo essential oil inhibited the development of bacterial biofilms formed by Gram-positive and Gram-negative microorganisms on soft CLs, its antibiofilm activity being specific and dependent on different physical parameters (contact time and temperature). The architecture of bacterial biofilms developed on soft contact lenses was analyzed using confocal scanning laser microscopy (CSLM).
Kok, J H; Hilbrink, H J; Rosenbrand, R M; Visser, R
This study was performed to investigate the effects of extended-wear of rigid aspherical high gas-permeable contact lenses on the cornea. In the study 32 subjects (62 eyes) were followed over a period of 3 to 24 months. A high gas-permeable contact lens (Dk 92), made of fluoro-silicone-acrylate copolymer, was used. Vision remained constant during the studied period. The corneal thickness decreased significantly (p less than 0.05) during the first six months. Significant changes (p less than 0.05) were found after three months in the corneal curvature, especially in the vertical meridian. No further topographical changes were noted in the period between three and six months of extended-wear. Complications, like acute red eye syndrome and bacterial infections, which may be encountered in soft lens extended-wear, were not noticed. At the end of the study 20 subjects (38 eyes, 61%) were still on extended-wear, 9 subjects (18 eyes, 29%) changed to daily wear and 3 subjects (six eyes, 10%) became unavailable for follow-up. Extended-wear of rigid aspherical high gas-permeable contact lenses may be considered as an acceptable alternative for soft lens extended-wear.
Jones, Lyndon; Powell, Charles H
Contact lens solutions are highly complex mixtures of biocides (preservatives), surfactants, and other agents designed to disinfect, clean, and wet contact lenses. The commercialization of silicone hydrogel (SiHy) lenses has resulted in unique challenges to the manufacturers of contact lens solutions, because the properties of these materials differ markedly from those seen previously with poly-hydroxyethyl methacrylate-based hydrogels. Historically, hydrogel lens uptake and release of low-molecular weight preservatives such as chlorhexidine and thimerosal were known to result in allergic reactions, resulting in corneal irritation, stinging, conjunctival hyperemia, development of corneal infiltrates, palpebral lid changes, and corneal staining. However, little is known about the interaction of modern care systems with modern soft lens materials. Factors to be considered when evaluating the uptake and release of care components include the water content, charge, relative hydrophobicity, surface treatment, and porosity of the lens material, in conjunction with the concentration, charge/molecule, ionicity in the product matrix, molecular weight, and hydrophobicity of the care component in question. These factors control the sorption of the solution components by lenses, resulting in a variety of differences in the amount of the component taken up into the lens material and the amount and rate of subsequent release onto the ocular surface. Because both natural (ocular) and environmental biota become part of the solution-lens system during regimen use of any lens care product, these extraneously introduced substances should also be considered regarding their potential for uptake and either subsequent release onto the ocular surface or functioning as a scaffold for the adhesion of microbes. This article will review current knowledge concerning these interactions and investigate what clinically observable complications may arise from these interactions. It also reviews
Rotman, S; Sandovsky-Losica, Hana; Sionov, E; Segal, Esther
The objective of the study was to evaluate the effect of supplementation of a chitin soluble extract (CSE) to clinically used commercial contact lenses' cleaning/preservation solutions on adherence of Aspergillus niger and Candida albicans to contact lenses. CSE (25 mg ml-1) was added to Solocare or Oxysept. Adherence of A. niger or C. albicans to contact lenses was assessed by exposing lenses to fungi in test solutions and enumeration of fungal colony forming unit. The study included three parts: (i) the disinfecting and adherence-inhibiting effect of Solocare and Oxysept: (ii) the adherence-inhibiting effect of CSE; (iii) the effect of Solocare + CSE or Oxysept + CSE on the fungal adherence to contact lenses. The experiments showed that: (i) Solocare had a significant disinfecting effect on A. niger and C. albicans while that of Oxysept was only minimal. (ii) Neither Solocare nor Oxysept had an inhibitory effect on the fungal adherence. (iii) CSE inhibited significantly the adherence of A. niger and C. albicans. (iv) Addition of CSE to Solocare or Oxysept resulted in almost complete inhibition of adherence Supplementing CSE to lenses' maintenance solutions increases their antifungal potential by adding anti-adherence activity to the disinfecting effect of these solutions, bearing the potential to serve as a prophylactic means.
Maldonado-Codina, Carole; Morgan, Philip B
This study investigated the water contact angles of five commercially available silicone hydrogel contact lenses (Acuvue Advance, Acuvue Oasys, Focus Night & Day, O2 Optix, and PureVision) using sessile drop and captive bubble techniques. The only lens type that showed a significant difference in water contact angle when measured by sessile drop direct from the blister compared with after 48 h of soaking/washing in saline was the Acuvue Advance lens (from 66 degrees to 96 degrees, respectively) (p=0.0002), presumably because of surface active agents within the blister solution. The water contact angle data split the lenses into two distinct groups (p
Sarac, Ozge; Gurdal, Canan; Bostancı-Ceran, Basak; Can, Izzet
The aim of this study was to evaluate tear osmolarity and ocular comfort with two different types of hydrogel daily disposable lenses. The right eyes of 15 first-time contact lens users were included in this prospective study. All eyes wore hilafilcon B silicone hydrogel contact lenses for 8 h (group 1). After 1 week without contact lenses, all eyes wore narafilcon A silicone hydrogel contact lenses for 8 h (group 2). Tear osmolarity measurement was performed before and after 4 and 8 h of each contact lens wear. Ocular comfort was assessed after 4 and 8 h of each contact lens wear. In group 1, the mean baseline, 4- and 8-h tear osmolarity values were 293 ± 10.57, 303.00 ± 10.5 mOsm/L (p = 0.023), and 295.0 ± 1.4 mOsm/L (p > 0.05), respectively. In group 2, the mean baseline, 4- and 8-h tear osmolarity values were 294 ± 13.65, 300.9 ± 11.3 mOsm/L (p = 0.007), and 298.80 ± 7.2 mOsm/L (p > 0.05), respectively. In group 1, the mean comfort score was 7.20 ± 0.45 and 8.60 ± 0.45 at 4 and 8 h, respectively (p = 0.038). In group 2, the mean comfort score significantly decreased from 9.80 ± 0.45 to 7.80 ± 0.84 at 4 h (p = 0.039). Both hydrogel and silicone hydrogel daily disposable contact lenses elevated tear osmolarity during 8 h of contact lens wear. The increase in tear osmolarity with both contact lenses was below the cut-off value for dry eye and was not associated with ocular comfort.
Weissman, B A; Fatt, I
On the eye a contact lens is bathed in tear fluid, which increases its resistance to oxygen flux. For rigid gas-permeable lenses, this effect should be small during open-eye wear because a large amount of oxygen is provided by air-saturated tears that are pumped under the lens. However, under closed-eye conditions this study suggests substantial decrease in overall lens system oxygen transmissibility when lens transmissibility itself is greater than 20 x 10(-9) cm ml O2/s ml mm Hg and when the average thickness of the tear layer is greater than about 20 micron.
Hiraoka, Takahiro; Ishii, Yuko; Okamoto, Fumiki; Oshika, Tetsuro
To investigate the influence of cosmetically tinted soft contact lenses on ocular higher-order aberrations and visual performance, and to analyze the relationship between these parameters after the lens wear. In 44 eyes of 22 subjects, visual acuity, contrast sensitivity under photopic and mesopic conditions, and ocular higher-order aberrations were evaluated before and after wearing the tinted soft contact lenses (1-day Acuvue Colours; Vistakon, Jacksonville, FL). Contrast sensitivity under a photopic condition was determined at 3, 6, 12, and 18 cycles per degree, and the area under the log contrast sensitivity function (AULCSF) was calculated. Mesopic contrast sensitivity with and without glare was assessed. Ocular higher-order aberrations for a 4-mm pupil were measured, and coma-like, spherical-like, and total higher-order aberrations were determined. The tinted contact lens wearing resulted in significant decreases in log contrast sensitivity at all spatial frequencies (P < 0.05) and AULCSF (P < 0.0001), although 100% contrast visual acuity did not change. Log mesopic contrast sensitivity with and without glare was also reduced significantly by the lens wear (P < 0.0001). The contact lens wear significantly increased coma-like, spherical-like, and total higher-order aberrations (P < 0.0001). The induced changes in higher-order aberrations were analyzed in relation to the changes in contrast sensitivity function. Although the changes in coma-like and spherical-like aberrations did not correlate significantly with those in AULCSF (P > 0.05), the changes in total higher-order aberrations showed a significant correlation with those in AULCSF (P < 0.05). On the other hand, there was no significant relationship between the changes in higher-order aberrations and the changes in log mesopic contrast sensitivity with and without glare (P > 0.05). Cosmetically tinted contact lenses increase ocular higher-order aberrations and worsen contrast sensitivity under both
Szczotka-Flynn, Loretta; Lass, Jonathan H; Sethi, Ajay; Debanne, Sara; Benetz, Beth Ann; Albright, Matthew; Gillespie, Beth; Kuo, Jana; Jacobs, Michael R; Rimm, Alfred
This study determined which microbiologic, clinical, demographic, and behavioral factors are associated with corneal infiltrative events (CIEs) during continuous wear of silicone hydrogel (SH) contact lenses. Subjects (n = 205) were fitted with lotrafilcon A lenses for continuous wear and observed for 1 year. The main exposures of interest were corneal staining and bacterial lens contamination. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining CIE free, and Cox proportional hazards regression was used to model the hazard of having a CIE, as a function of key predictor variables. The KM-unadjusted cumulative probability of remaining CIE free was 73.3%. Approximately 53% of subjects had repeated episodes of corneal staining (mild or greater), and 11.3% had repeated episodes of moderate or greater corneal staining. Corneal staining was not associated with the development of a CIE. The frequency of substantial bacterial bioburden on worn lenses at the time of a CIE was 64.7%, compared with only 12.2% during uncomplicated wear. The presence of substantial lens bacterial bioburden was associated with the development of a CIE (adjusted hazards ratio [HR], 8.66; 95% confidence interval [CI], 2.88-26.01). Smoking was also associated with a CIE (adjusted HR, 4.13; 95% CI, 1.27-13.45). Corneal staining is common during continuous wear of SH lenses, but it is not associated with the development of a CIE. Smoking and substantial lens bacterial bioburden pose prominent risks of a CIE. In this study, more than 70% of the total risk of CIE in those with substantial lens bioburden is attributable to this exposure. (ClinicalTrials.gov number, NCT00727402).
Lass, Jonathan H.; Sethi, Ajay; Debanne, Sara; Benetz, Beth Ann; Albright, Matthew; Gillespie, Beth; Kuo, Jana; Jacobs, Michael R.; Rimm, Alfred
Purpose. This study determined which microbiologic, clinical, demographic, and behavioral factors are associated with corneal infiltrative events (CIEs) during continuous wear of silicone hydrogel (SH) contact lenses. Methods. Subjects (n = 205) were fitted with lotrafilcon A lenses for continuous wear and observed for 1 year. The main exposures of interest were corneal staining and bacterial lens contamination. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining CIE free, and Cox proportional hazards regression was used to model the hazard of having a CIE, as a function of key predictor variables. Results. The KM-unadjusted cumulative probability of remaining CIE free was 73.3%. Approximately 53% of subjects had repeated episodes of corneal staining (mild or greater), and 11.3% had repeated episodes of moderate or greater corneal staining. Corneal staining was not associated with the development of a CIE. The frequency of substantial bacterial bioburden on worn lenses at the time of a CIE was 64.7%, compared with only 12.2% during uncomplicated wear. The presence of substantial lens bacterial bioburden was associated with the development of a CIE (adjusted hazards ratio [HR], 8.66; 95% confidence interval [CI], 2.88–26.01). Smoking was also associated with a CIE (adjusted HR, 4.13; 95% CI, 1.27–13.45). Conclusions. Corneal staining is common during continuous wear of SH lenses, but it is not associated with the development of a CIE. Smoking and substantial lens bacterial bioburden pose prominent risks of a CIE. In this study, more than 70% of the total risk of CIE in those with substantial lens bioburden is attributable to this exposure. (ClinicalTrials.gov number, NCT00727402). PMID:20538985
Szczotka-Flynn, Loretta B.; Pearlman, Eric; Ghannoum, Mahmoud
Purpose A contact lens (CL) can act as a vector for microorganisms to adhere to and transfer to the ocular surface. Commensal microorganisms that uneventfully cohabitate on lid margins and conjunctivae and potential pathogens that are found transiently on the ocular surface can inoculate CLs in vivo. In the presence of reduced tissue resistance, these resident microorganisms or transient pathogens can invade and colonize the cornea or conjunctiva to produce inflammation or infection. Methods The literature was reviewed and used to summarize the findings over the last 30 years on the identification, enumeration, and classification of microorganisms adherent to CLs and their accessories during the course of normal wear and to hypothesize the role that these microorganisms play in CL infection and inflammation. Results Lens handling greatly increases the incidence of lens contamination, and the ocular surface has a tremendous ability to destroy organisms. However, even when removed aseptically from the eye, more than half of lenses are found to harbor microorganisms, almost exclusively bacteria. Coagulase-negative Staphylococci are most commonly cultured from worn lenses; however, approximately 10% of lenses harbor Gram-negative and highly pathogenic species, even in asymptomatic subjects. In storage cases, the incidence of positive microbial bioburden is also typically greater than 50%. All types of care solutions can become contaminated, including up to 30% of preserved products. Conclusions The process of CL-related microbial keratitis and inflammation is thought to be preceded by the presence or transfer or both of microorganisms from the lens to the ocular surface. Thus, this detailed understanding of lens-related bioburden is important in the understanding of factors associated with infectious and inflammatory complications. Promising mechanisms to prevent bacterial colonization on lenses and lens cases are forthcoming, which may decrease the incidence of
Niu, Yafei; Sarver, Edwin J.; Stevenson, Scott B.; Marsack, Jason D.; Parker, Katrina E.; Applegate, Raymond A.
Purpose To report the development of a tool designed to dynamically simulate the effect of soft toric contact lens movement on retinal image quality, initial findings on three eyes, and the next steps to be taken to improve the utility of the tool. Methods Three eyes of two subjects wearing soft toric contact lenses were cyclopleged with 1% cyclopentolate and 2.5% phenylephrine. Four hundred wavefront aberration measurements over a 5-mm pupil were recorded during soft contact lens wear at 30 Hz using a complete ophthalmic analysis system aberrometer. Each wavefront error measurement was input into Visual Optics Laboratory (version 7.15, Sarver and Associates, Inc.) to generate a retinal simulation of a high contrast log MAR visual acuity chart. The individual simulations were combined into a single dynamic movie using a custom MatLab PsychToolbox program. Visual acuity was measured for each eye reading the movie with best cycloplegic spectacle correction through a 3-mm artificial pupil to minimize the influence of the eyes’ uncorrected aberrations. Comparison of the simulated acuity was made to values recorded while the subject read unaberrated charts with contact lenses through a 5-mm artificial pupil. Results For one study eye, average acuity was the same as the natural contact lens viewing condition. For the other two study eyes visual acuity of the best simulation was more than one line worse than natural viewing conditions. Conclusions Dynamic simulation of retinal image quality, although not yet perfect, is a promising technique for visually illustrating the optical effects on image quality because of the movements of alignment-sensitive corrections. PMID:18382338
Santodomingo-Rubido, Jacinto; Villa-Collar, César; Gilmartin, Bernard; Gutiérrez-Ortega, Ramón
Purpose Although previous studies suggest that orthokeratology contact lens wear slows eye growth in children with progressing myopia, some limitations in the methodology employed have become evident. Furthermore, the safety of this modality of visual correction has not been assessed. The study “Myopia Control with Orthokeratology Contact Lenses in Spain” (MCOS) is being conducted to compare axial length growth between white European myopic children wearing orthokeratology contact lenses (OK) and wearing distance single-vision spectacles (SV). Additionally, the incidence of adverse events and discontinuations is also recorded. We outline the methodology and baseline data adopted. Methods Subjects aged 6 to 12, with myopia ranging from 0.75 to 4.00 D and astigmatism ≤1.00 D were prospectively allocated OK or SV correction. Measurements of axial length, anterior chamber depth, corneal topography, cycloplegic autorefraction, visual acuity and corneal staining are performed at 6-month intervals. The incidence of adverse events and discontinuations are also recorded. Results Thirty one children were fitted with OK and 31 with SV correction. Eight subjects did not meet the refraction-related inclusion criteria for enrollment. No significant differences were found in baseline mean age and refractive and biometric data betwseen the two groups (P>0.05). No adverse events were found in any of the two groups at baseline. Conclusion To the authors’ knowledge, MCOS is the first prospective clinical trial to assess the safety and efficacy of orthokeratology contact lens wear to slow myopia progression vs. single-vision spectacle wear. The MCOS offers a number of notable features: prospective design; well-matched samples and high-resolution ocular biometry measures, which should collectively elucidate whether orthokeratology contact lens wear is a feasible and safe method for myopia-progression control.
Lee, Sangkyu; Jo, Insu; Kang, Sangmin; Jang, Bongchul; Moon, Joonhee; Park, Jong Bo; Lee, Soochang; Rho, Sichul; Kim, Youngsoo; Hong, Byung Hee
Recently, smart contact lenses with electronic circuits have been proposed for various sensor and display applications where the use of flexible and biologically stable electrode materials is essential. Graphene is an atomically thin carbon material with a two-dimensional hexagonal lattice that shows outstanding electrical and mechanical properties as well as excellent biocompatibility. In addition, graphene is capable of protecting eyes from electromagnectic (EM) waves that may cause eye diseases such as cataracts. Here, we report a graphene-based highly conducting contact lens platform that reduces the exposure to EM waves and dehydration. The sheet resistance of the graphene on the contact lens is as low as 593 Ω/sq (±9.3%), which persists in an wet environment. The EM wave shielding function of the graphene-coated contact lens was tested on egg whites exposed to strong EM waves inside a microwave oven. The results show that the EM energy is absorbed by graphene and dissipated in the form of thermal radiation so that the damage on the egg whites can be minimized. We also demonstrated the enhanced dehydration protection effect of the graphene-coated lens by monitoring the change in water evaporation rate from the vial capped with the contact lens. Thus, we believe that the graphene-coated contact lens would provide a healthcare and bionic platform for wearable technologies in the future.
Nandakumar, Krithika; Evans, Mary Ann; Briand, Karine; Leat, Susan J
In this longitudinal study, a group of school children with Down syndrome (DS) and reduced accommodation were prescribed bifocals and followed to investigate the impact of bifocal spectacles on early literacy and visual perceptual skills. The natural progression of early literacy skills in this population along with the changes with bifocals, described by monthly subtest scores and the time taken to complete literacy and visual perceptual tasks, are reported. Fourteen children with DS, aged eight to 18 years, were followed for five months with single vision lenses; 11 were prescribed bifocals based on their accommodative ability and followed for another five months. A battery of reading and visual perceptual tests was administered before and after prescription of bifocals. Monthly subtests of similar tasks were administered to measure progress. All the visits were videotaped to determine the time taken for the child to complete each task. There was no significant measurable natural progression of early literacy skills in this group of participants on the Word Identification (WI) subtest (Repeated Measures ANOVA, F [4, 24]=1.377, p = 0.271) and Dolch sight words (RMANOVA F [4, 24]= 0.344, p = 0.846). In contrast, once bifocals were prescribed there was significant improvement in the scores of the monthly subtests (p = 0.050, 0.025 and 0.023 for WI, Dolch sight words and numbers, respectively) and the rate of progress in monthly scores improved for WI (p = 0.008). Repeated measures Analysis of Variance showed a significant decrease in the completion times with bifocals for the WI test in the full battery of tests (p = 0.0015). There was significant correlation between the improvement in focus with bifocals and the decrease in completion time for the WI task (p = 0.004). This study demonstrates no significant natural progression over a five-month period in the group of participants with Down syndrome; however, with bifocals, faster and improved performance on some
Tam, Ngai Keung; Pitt, William G; Perez, Krystian X; Handly, Erika; Glenn, Andrew A; Hickey, John W; Larsen, Brian G
The sorption and desorption of radiolabeled dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CH) were measured on 5 types of commercial contact lenses. The lenses were soaked in vitro in an artificial tear fluid for 16h. The effects of borate buffered saline and two commercial multi-purpose lens-care solutions (MPSs) on reducing the lipid (DPPC and CH) sorption and increasing the lipid removal were examined. The results showed that silicone hydrogel (SiHy) lenses accumulated the most lipids, sorbing over an order of magnitude more than polymacon, a conventional hydrogel lens. Pre-soaking the SiHy lenses for 16h in MPSs reduced the DPPC sorption by up to 13% and the CH sorption by up to 11%, compared to controls that were not pre-soaked. However neither these reductions nor those on polymacon were statistically significant (p>0.05). In sorption experiments without presoaking, subsequent exposure to the MPSs removed some DPPC from the lenses (0-3.1% for SiHy lenses and 14-55% for polymacon), but CH removal was 0.0-0.8% for SiHy lenses and 0.6-28% for polymacon lenses. Some of these removals were statistically significant (p<0.05).
White, Charles J; McBride, Matthew K; Pate, Kayla M; Tieppo, Arianna; Byrne, Mark E
Symptoms of contact lenses induced dry eye (CLIDE) are typically treated through application of macromolecular re-wetting agents via eye drops. Therapeutic soft contact lenses can be formulated to alleviate CLIDE symptoms by slowly releasing comfort agent from the lens. In this paper, we present an extended wear silicone hydrogel contact lens with extended, controllable release of 120 kDa hydroxypropyl methylcellulose (HPMC) using a molecular imprinting strategy. A commercial silicone hydrogel lens was tailored to release approximately 1000 μg of HPMC over a period of up to 60 days in a constant manner at a rate of 16 μg/day under physiological flowrates, releasing over the entire range of continuous wear. Release rates could be significantly varied by the imprinting effect and functional monomer to template ratio (M/T) with M/T values 0, 0.2, 2.8, 3.4 corresponding to HPMC release durations of 10, 13, 23, and 53 days, respectively. Lenses had high optical quality and adequate mechanical properties for contact lens use. This work highlights the potential of imprinting in the design and engineering of silicone hydrogel lenses to release macromolecules for the duration of wear, which may lead to decreased CLIDE symptoms and more comfortable contact lenses.
Tarkowski, Witold; Moneta-Wielgoś, Joanna; Młocicki, Daniel
Demodex mites may be a potential etiological factor in the development of various eye and skin disorders. The aim of the study was to investigate the presence of Demodex in the hair follicles of eyelashes and their potential influence on abandoning soft contact lenses which had been previously well tolerated by their users. A group of 62 users of contact lenses (28 with emerging discomfort and 34 without discomfort) were examined. There is a need to check the existence of a relationship between D. folliculorum or/and D. brevis infestation and the emergence of intolerance to the presence of soft contact lenses. The removed lashes were examined under light microscopy, applying standard parasitological methods if demodicosis is suspected. A positive result was assumed if at least one adult stage, larva, protonymph/nymph, or egg of D. folliculorum and/or D. brevis was present. A positive correlation was observed between the presence of Demodex and intolerance to contact lenses by their existing users (p < 0.05), and Demodex sp. infections were observed in 92.86% of patients with intolerance to contact lenses. Our results provide further evidence for the pathogenic role played by the mites in the development of eye diseases.
Tarkowski, Witold; Moneta-Wielgoś, Joanna; Młocicki, Daniel
Demodex mites may be a potential etiological factor in the development of various eye and skin disorders. The aim of the study was to investigate the presence of Demodex in the hair follicles of eyelashes and their potential influence on abandoning soft contact lenses which had been previously well tolerated by their users. A group of 62 users of contact lenses (28 with emerging discomfort and 34 without discomfort) were examined. There is a need to check the existence of a relationship between D. folliculorum or/and D. brevis infestation and the emergence of intolerance to the presence of soft contact lenses. The removed lashes were examined under light microscopy, applying standard parasitological methods if demodicosis is suspected. A positive result was assumed if at least one adult stage, larva, protonymph/nymph, or egg of D. folliculorum and/or D. brevis was present. A positive correlation was observed between the presence of Demodex and intolerance to contact lenses by their existing users (p < 0.05), and Demodex sp. infections were observed in 92.86% of patients with intolerance to contact lenses. Our results provide further evidence for the pathogenic role played by the mites in the development of eye diseases. PMID:26290865
Lopes-Ferreira, Daniela; Ribeiro, Cláudia; Neves, Helena; Faria-Ribeiro, Miguel; Queirós, António; Villa-Collar, César; Jorge, Jorge; González-Méijome, José Manuel
Purpose The purpose of this study was to show the potential of a commercial center-distance multifocal soft contact lens to induce relative peripheral myopic defocus in myopic eyes. Methods Twenty-eight myopic right eyes from 28 patients (mean age: 22.0 ± 2.0 years) were evaluated. The measurements of axial and off-axis refraction were made using a Grand-Seiko WAM-5500 open-field autorefractometer without lens and with multifocal contact lenses (Proclear Multifocal D® Design) of +2.00 D and +3.00 D add power applied randomly. Central mean spherical equivalent refraction was −2.24 ± 1.33 D. Ocular refraction was measured at center and at eccentricities between 35° nasal and 35° temporal (in 5° steps). Results Baseline relative peripheral refractive error (RPRE) as spherical equivalent (M) was −0.69 ± 1.14 D and −0.46 ± 1.38 D at 35° in the nasal and temporal degrees of visual field, respectively. Both add powers increased the relative peripheral myopic defocus up to −0.82 ± 1.23 D (p = 0.002) and −1.42 ± 1.45 D (p < 0.001) at 35° in the nasal field; and −0.87 ± 1.42 D (p = 0.003) and −2.00 ± 1.48 D (p < 0.001) at 35° in the temporal retina with +2.00 D and +3.00 D add lenses, respectively. Differences between +2.00 and +3.00 D add lenses were statistically significant beyond 20° in the nasal visual field and 10° in the temporal visual field. Conclusion It is possible to induce significant changes in the pattern of relative peripheral refraction in the myopic direction with commercially available dominant design multifocal contact lenses. The higher add (+3.00 D) induced an significantly higher effect than the +2.00 D add lens, although an increase of 1 D in add power does not correspond to the same amount of increase in RPRE.
Knappe, S; Stachs, O; Guthoff, R
Wearing orthokeratology contact lenses (OCL, Hecht-see free; Hecht, Germany) overnight can change corneal refraction by up to -4.5 dioptre (dpt) based on corneal adaptation to the double reverse surface of the OCL. This allows a temporary independence on glasses or contact lenses. It is known that the central corneal thickness decreases while the corneal thickness in the periphery probably increases. The aim of this study was to investigate the corneal changes of volunteers wearing OCL with in vivo confocal microscopy. Five young adults (mean 22.8 years, three female, two male) with low to moderate myopia (range -1.75 to -3.5 dpt; sphere equivalent -2.7+/-0.59 dpt) were fitted with OCL of reverse-geometry design in both eyes. Lenses were worn in both eyes overnight and were removed immediately in the morning. The volunteers were examined with in vivo confocal microscopy using a combination of Heidelberg retina tomograph II and the Rostock cornea module before wearing the OCL and after the 1(st), 3(rd), 5(th), 7(th), 13(th), 20(th) and 25(th) nights. The central and mid-peripheral total corneal thickness as well as the epithelial thickness were examined in the morning between 7.30 am and 9.30 am. The central and the mid-peripheral epithelial corneal thickness was reduced significantly (p<0.05) from day 1 to the 13(th) day. This stabilized later until the the examination was concluded. No significant changes (p>0.05) were found in the central or mid-peripheral total corneal thickness after 25 days of wearing the OCL. Wearing OCL leads to a reduction in the central corneal epithelial thickness. Our inability to find an increase in mid-peripheral total and epithelial corneal thickness may be because the expected increase of the mid-peripheral cornea is limited to a defined area, which makes repeated measurements at a particular point difficult.
Opačić, Dalibor; Miljak, Snježana; Ćuruvija-Opačić, Ksenija
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.
Ţălu, Ştefan; StȨpień, Krzysztof; Caglayan, Mustafa Oguzhan
This paper analyses the three-dimensional (3-D) surface morphology of optic surface of unworn contact lenses (CLs) using atomic force microscopy (AFM) and wavelet transform. Refractive powers of all lens samples were 2.50 diopters. Topographic images were acquired in contact mode in air-conditioned medium (35% RH, 23°C). Topographic measurements were taken over a 5 µm × 5 µm area with 512 pixel resolution. Resonance frequency of the tip was 65 kHz. The 3-D surface morphology of CL unworn samples revealed (3-D) micro-textured surfaces that can be analyzed using (AFM) and wavelet transform. AFM and wavelet transform are accurate and sensitive tools that may assist CL manufacturers in developing CLs with optimal surface characteristics.
Weeks, Andrea; Luensmann, Doerte; Boone, Adrienne; Jones, Lyndon; Sheardown, Heather
Model silicone hydrogel contact lenses, comprised of N,N-dimethylacrylamide and methacryloxypropyltris (trimethylsiloxy) silane, were fabricated and hyaluronic acid (HA) was incorporated as an internal wetting agent using a dendrimer-based method. HA and dendrimers were loaded into the silicone hydrogels and cross-linked using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide chemistry. The presence and location of HA in the hydrogels was confirmed using X-ray photoelectron spectroscopy and confocal laser scanning microscopy, respectively. The effects of the presence of HA on the silicone hydrogels on hydrophilicity, swelling behavior, transparency, and lysozyme sorption and denaturation were evaluated. The results showed that HA increased the hydrophilicity and the equilibrium water content of the hydrogels without affecting transparency. HA also significantly decreased the amount of lysozyme sorption (p < 0.002). HA had no effect on lysozyme denaturation in hydrogels containing 0% and 1.7% methacrylic acid (MAA) (by weight) but when the amount of MAA was increased to 5%, the level of lysozyme denaturation was significantly lower compared to control materials. These results suggest that HA has great potential to be used as a wetting agent in silicone hydrogel contact lenses to improve wettability and to decrease lysozyme sorption and denaturation.
Tashakori-Sabzevar, Faezeh; Mohajeri, Seyed Ahmad
Recently, significant advances have been made in order to optimize drug delivery to ocular tissues. The main problems in ocular drug delivery are poor bioavailability and uncontrollable drug delivery of conventional ophthalmic preparations (e.g. eye drops). Hydrogels have been investigated since 1965 as new ocular drug delivery systems. Increase of hydrogel loading capacity, optimization of drug residence time on the ocular surface and biocompatibility with the eye tissue has been the main focus of previous studies. Molecular imprinting technology provided the opportunity to fulfill the above-mentioned objectives. Molecularly imprinted soft contact lenses (SCLs) have high potentials as novel drug delivery systems for the treatment of eye disorders. This technique is used for the preparation of polymers with specific binding sites for a template molecule. Previous studies indicated that molecular imprinting technology could be successfully applied for the preparation of SCLs as ocular drug delivery systems. Previous research, particularly in vivo studies, demonstrated that molecular imprinting is a versatile and effective method in optimizing the drug release behavior and enhancing the loading capacity of SCLs as new ocular drug delivery systems. This review highlights various potentials of molecularly imprinted contact lenses in enhancing the drug-loading capacity and controlling the drug release, compared to other ocular drug delivery systems. We have also studied the effects of contributing factors such as the type of comonomer, template/functional monomer molar ratio, crosslinker concentration in drug-loading capacity, and the release properties of molecularly imprinted hydrogels.
Bergmanson, J P; Ruben, M; Chu, L W
The comparative corneal epithelial effects of rigid gas permeable and soft contact lenses are reported in the present preliminary study using two bush baby monkeys (Galago senegalensis). Both types of lenses produced early cell death among the surface squamous cells while internally the epithelium and its nerve fibers remained normal. Sporadically small abnormal groups of cells involving two to three of the surface layers were observed in both the hard and soft lens wearing corneas. It was concluded that this represented superficial punctate keratitis (SPK). Small superficial intracellular epithelial cysts with membranous contents were infrequently noted in the gas permeable lens wearing cornea and it is suggested here that they were mild forms or precursors of those seen clinically in human corneas. Since the gas permeable lens met the corneal oxygen requirement it is postulated that the traumatic effect of the rigidity of the lens caused the cystic formation to occur. The relative hypoxia induced by the soft contact lens resulted in a mild superficial epithelial edema.
Allinjawi, Kareem; Sharanjeet-Kaur, Sharanjeet-Kaur; Akhir, Saadah Mohamed; Mutalib, Haliza Abdul
Aim: The purpose of this study was to compare the changes in relative peripheral refractive error produced by two different designs of progressive soft contact lenses in myopic schoolchildren. Methods: Twenty-seven myopic schoolchildren age between 13 to 15 years were included in this study. The measurements of central and peripheral refraction were made using a Grand-Seiko WR-5100K open-field autorefractometer without correction (baseline), and two different designs of progressive contact lenses (PCLs) (Multistage from SEED & Proclear from Cooper Vision) with an addition power of +1.50 D. Refractive power was measured at center and at eccentricities between 35º temporal to 35º nasal visual field (in 5º steps). Results: Both PCLs showed a reduction in hyperopic defocus at periphery. However, this reduction was only significant for the Multistage PCL (p= 0.015), (Proclear PCL p= 0.830). Conclusion: Multistage PCLs showed greater reduction in peripheral retinal hyperopic defocus among myopic schoolchildren in comparison to Proclear PCLs. PMID:28163898
Allinjawi, Kareem; Sharanjeet-Kaur, Sharanjeet-Kaur; Akhir, Saadah Mohamed; Mutalib, Haliza Abdul
Aim: The purpose of this study was to compare the changes in relative peripheral refractive error produced by two different designs of progressive soft contact lenses in myopic schoolchildren. Methods: Twenty-seven myopic schoolchildren age between 13 to 15 years were included in this study. The measurements of central and peripheral refraction were made using a Grand-Seiko WR-5100K open-field autorefractometer without correction (baseline), and two different designs of progressive contact lenses (PCLs) (Multistage from SEED & Proclear from Cooper Vision) with an addition power of +1.50 D. Refractive power was measured at center and at eccentricities between 35º temporal to 35º nasal visual field (in 5º steps). Results: Both PCLs showed a reduction in hyperopic defocus at periphery. However, this reduction was only significant for the Multistage PCL (p= 0.015), (Proclear PCL p= 0.830). Conclusion: Multistage PCLs showed greater reduction in peripheral retinal hyperopic defocus among myopic schoolchildren in comparison to Proclear PCLs.
Mohammadi, Saman; Jones, Lyndon; Gorbet, Maud
In this study, we compared, for the first time, the release of a 432 kDa prostaglandin analogue drug, Latanoprost, from commercially available contact lenses using in vitro models with corneal epithelial cells. Conventional polyHEMA-based and silicone hydrogel soft contact lenses were soaked in drug solution ( solution in phosphate buffered saline). The drug release from the contact lens material and its diffusion through three in vitro models was studied. The three in vitro models consisted of a polyethylene terephthalate (PET) membrane without corneal epithelial cells, a PET membrane with a monolayer of human corneal epithelial cells (HCEC), and a PET membrane with stratified HCEC. In the cell-based in vitro corneal epithelium models, a zero order release was obtained with the silicone hydrogel materials (linear for the duration of the experiment) whereby, after 48 hours, between 4 to 6 of latanoprost (an amount well within the range of the prescribed daily dose for glaucoma patients) was released. In the absence of cells, a significantly lower amount of drug, between 0.3 to 0.5 , was released, (). The difference observed in release from the hydrogel lens materials in the presence and absence of cells emphasizes the importance of using an in vitro corneal model that is more representative of the physiological conditions in the eye to more adequately characterize ophthalmic drug delivery materials. Our results demonstrate how in vitro models with corneal epithelial cells may allow better prediction of in vivo release. It also highlights the potential of drug-soaked silicone hydrogel contact lens materials for drug delivery purposes. PMID:25207851
Pinto-Fraga, José; Blázquez Arauzo, Francisco; Urbano Rodríguez, Rubén; González-García, María J
To evaluate the safety and efficacy of a new multipurpose disinfecting solution (MPDS) with a formulation that includes aloe vera on its composition. This is a prospective, randomized, double-masked clinical trial with a crossover design that included seven examinations. Two different MPDSs, Avizor Alvera® (study solution) and All Clean Soft® (control solution), each were used for 1 month. Comfilcon A silicone hydrogel contact lenses were used during the trial. The main outcome variables were corneal staining and deposits on the surfaces of the contact lenses. Other parameters including ocular surface response, contact lens wettability, user satisfaction, and adverse events, were analyzed according to the International Organization for Standardization (ISO) 11980:2010 guidance for clinical investigation. Twenty subjects (10 women, 10 men) (mean age, 27.7±5.6 years; range, 20-41) were included. No differences between both MPDSs were found in the percentage of subjects with corneal staining >0 at day 30 (study: 35%, control: 50%; p=0.46); neither in the percentage of subjects with deposits on the surface of the contact lens >0 at day 30 (study: 26.32%, control: 52.63%; p=0.18). The study MPDS received higher rates in comfort (study: 8.14±1.09, control: 7.94±0.92; p=0.56) and satisfaction at day 30 (study: 8.63±0.91, control: 8.29±0.80; p=0.19), however the scores were not significantly different with the control MPDS. The clinical trial showed that the study MPDS is safe, efficient, and has acceptable physiologic tolerance, according to the ISO 11980:2010 guidance for clinical investigation. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.
Long, Bill; Schweizer, Helmer; Bleshoy, Hans; Zeri, Fabrizio
The purpose of this study was to profile contact lens (CL) experience among patients in eyecare practitioner (ECP) offices and the response to daily wear (DW) of lotrafilcon A silicone hydrogel CLs. Patients at ECP offices were surveyed for their vision correction modality and experience with CLs. Adapted, new, and former CL wearers who were interested in trying CLs were dispensed lotrafilcon A (NIGHT & DAY, CIBA VISION, Duluth, GA) lenses for a 1 month trial of DW. One thousand eight hundred sixty-five surveys were returned with 60% indicating current CL use averaging 6.4 days/week, 13.6 hr/day with 92% satisfied with their current lenses and 58% comfortable all day. Two hundred sixteen patients (59% adapted hydroxyl-ethylmethacrylate or rigid gas permeable CL wearers, 21% new/former, 20% no answer) were enrolled to wear lotrafilcon A CLs. Lens care systems were chosen for new and former wearers by the ECPs from among those approved and available in the countries and were primarily multipurpose systems. Among adapted CL wearers, statistically significant improvements were found within 2 weeks for conjunctival redness (P = 0.023), limbal redness (P< 0.001), corneal neovascularization (P < 0.001), during the day and end-of-day dryness (P = 0.02 for each) and early removal because of dryness (P = 0.02). Seventy-two percent reported comfort all day with lotrafilcon A CLs. New and former wearers at 2 weeks showed increased epithelial microcysts (P = 0.048). New and former wearers at 2 weeks compared with adapted wearers at baseline had less frequent early removal during the day, burning or stinging, uncomfortable lenses, and photophobia while reporting more problems inserting and removing lenses. No adverse events were reported with lotrafilcon A CLs. Adapted CL wearers showed improved clinical signs, subjective symptoms, and comfort when changed to lotrafilcon A for DW. New or former wearers showed few significant changes from baseline in clinical signs and had
Bertozzi, Carolyn R.
Nature has evolved complex and elegant materials well suited to fulfill a myriad of functions. Lubricants, structural scaffolds and protective sheaths can all be found in nature, and these provide a rich source of inspiration for the rational design of materials for biomedical applications. Many biological materials are based in some fashion on hydrogels, the crosslinked polymers that absorb and hold water. Biological hydrogels contribute to processes as diverse as mineral nucleation during bone growth and protection and hydration of the cell surface. The carbohydrate layer that coats all living cells, often referred to as the glycocalyx, has hydrogel-like properties that keep cell surfaces well hydrated, segregated from neighboring cells, and resistant to non-specific protein deposition. With the molecular details of cell surface carbohydrates now in hand, adaptation of these structural motifs to synthetic materials is an appealing strategy for improving biocompatibility. The goal of this collaborative project between Prof. Bertozzi's research group, the Center for Advanced Materials at Lawrence Berkeley National Laboratory and Sunsoft Corporation was the design, synthesis and characterization of novel hydrogel polymers for improved soft contact lens materials. Our efforts were motivated by the urgent need for improved materials that allow extended wear, and essential feature for those whose occupation requires the use of contact lenses rather than traditional spectacles. Our strategy was to transplant the chemical features of cell surface molecules into contact lens materials so that they more closely resemble the tissue in which they reside. Specifically, we integrated carbohydrate molecules similar to those found on cell surfaces, and sulfoxide materials inspired by the properties of the carbohydrates, into hydrogels composed of biocompatible and manufacturable substrates. The new materials were characterized with respect to surface and bulk hydrophilicity, and
Best, Nigel; Drury, Laura; Wolffsohn, James S
to evaluate changes in tear metrics and ocular signs induced by six months of silicone-hydrogel contact lens wear and the difference in baseline characteristics between those who successfully continued in contact lens wear compared to those that did not. Non-invasive Keratograph, Tearscope and fluorescein tear break-up times (TBUTs), tear meniscus height, bulbar and limbal hyperaemia, lid-parallel conjunctival folds (LIPCOF), phenol red thread, fluorescein and lissamine-green staining, and lid wiper epitheliopathy were measured on 60 new contact lens wearers fitted with monthly silicone-hydrogels (average age 36±14 years, 40 females). Symptoms were evaluated by the Ocular Surface Disease Index (OSDI). After six months full time contact lens wear the above metrics were re-measured on those patients still in contact lens wear (n=33). The initial measurements were also compared between the group still wearing lenses after six months and those who had ceased lens wear (n=27). There were significant changes in tear meniscus height (p=0.031), bulbar hyperaemia (p=0.011), fluorescein TBUT (p=0.027), corneal (p=0.007) and conjunctival (p=0.009) staining, LIPCOF (p=0.011) and lid wiper epitheliopathy (p=0.002) after six months of silicone-hydrogel wear. Successful wearers had a higher non-invasive (17.0±8.2s vs 12.0±5.6s; p=0.001) and fluorescein (10.7±6.4s vs 7.5±4.7s; p=0.001) TBUT than drop-outs, although OSDI (cut-off 4.2) was also a strong predictor of success. Silicone-hydrogel lenses induced significant changes in the tear film and ocular surface as well as lid margin staining. Wettability of the ocular surface is the main factor affecting contact lens drop-out. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Thai, Lee Choon; Tomlinson, Alan; Ridder, William H
The purpose of this study was to measure the effect of precontact lens tear film break-up on visual performance. Four asymptomatic soft contact lens wearers had contrast sensitivity measured by a temporal, two-alternative, force choice paradigm combined with a self-paced methods of limits. Stimuli were vertically orientated sine wave gratings (0.5 to 14 cycles per degree [cpd] presented for 16.67 ms. Contrast sensitivity was measured before precontact lens tear break-up by a stimuli presented 2 s after the blink. A post-tear layer break-up measurement taken with the stimuli presented after break-up had been observed by the use of a video camera attached to a Tearscope. Contrast sensitivity was found to be reduced following precontact lens tear film break-up for stimuli of 4, 6, and 10 cpd; the data approached significance at 14 cpd. Further reductions in contrast sensitivity were observed for one subject when measurements were continued for 4 s following break-up. Contrast sensitivity is significantly reduced for middle to high spatial frequencies when the precontact lens tear film dries and breaks up. The combination of observations of visual performance immediately following the blink (from earlier experiments) and measurements following tear film break-up in this experiment allows description of a "vision cycle" for contact lens wearers in the interval between blinks. It is suggested that break-up of the precontact lens tear film could account for the complaints of intermittent blurred vision in some contact lens wearers and may provide a stimulus to blinking in these individuals.
Karlgard, Caroline C. S.; Sarkar, Dilip K.; Jones, Lyndon W.; Moresoli, Christine; Leung, K. T.
The surface composition of hydrogel contact lenses that contain silicon-based monomers, PureVision™ (balafilcon A) and Focus ® Night&Day™ (lotrafilcon A), were investigated by X-ray photoelectron spectroscopy (XPS). Conventional and daily disposable hydrogel lenses based on hydroxyethyl methacrylate (HEMA) were also studied, with the commonly prescribed 1-day Acuvue ® lens (etafilcon A) used as a control. All the lenses were pre-washed and dehydrated by three different methods, including drying in air, drying in nitrogen or freezing with subsequent freeze-drying, before the XPS analysis. The lenses dried in air had more impurities on the surface, and the lenses that were freeze-dried lost transparency, suggesting that drying lenses in nitrogen is the preferred preparation method for XPS analysis. Surface compositions for all lens materials were obtained and this data can be used as a control/base-value for future analysis of the interactions of soft contact lens materials with chemicals such as drugs or tear components.
Severinsky, Boris; Millodot, Michel
Purpose To evaluate the indications and efficacy of high gas permeable scleral contact lenses (GP-SCL). Methods A total database of 97 consecutive patients (140 eyes) fitted with GP-SCL between January 2003 and December 2008, was retrospectively analyzed to determine the benefits of fitting scleral lenses. All lenses were fitted by preformed technique and were non-fenestrated. Patients included keratoconus – 88 eyes (63 %); corneal irregularities after penetrating keratoplasty – 39 eyes (28 %); various ocular surface disorders: Stevens-Johnson syndrome (SJS), graft versus host disease (GVHD) and exposure keratopathy – 6 eyes (4 %); post refractive surgery keratoectasia – 4 eyes (3 %), and high refractive error – 3 eyes (2 %). Results Mean follow up was 27.5 months (range 1–71), mean wearing time in successful wearers group was 12.2 hours per day (range 10–16), mean wearing time in group of wearers who dropped out using GP-SCL, was 5.8 hours (range 3–8). Keratoconus patients achieved median best corrected visual acuity (BCVA) of 20/32, 84 % of patients achieved BCVA of 20/40 or more. The post keratoplasty group achieved median BCVA of 20/25, 92 % of patients achieved BCVA of 20/40 or better. In the other groups, median BCVA was as follows: ocular surface disorders – 20/50, keratoectasia – 20/30, high refractive error – 20/32. Positive fluid-venting was highly associated with successful GP-SCL wearing. Twenty patients (21 %) failed to wear GP-SCL. Conclusions GP-SCL's expand the management of various corneal abnormalities. The main indication for GP-SCL is optical correction of an irregular corneal surface, especially keratoconus and corneal transplant.
Rebeix, V; Sommer, F; Marchin, B; Baude, D; Tran, M D
Spoilage is a primary factor in the biocompatibility of soft contact lenses (SCL) within the lacrimal fluid. Tears are a complex mixture of proteins, lipids, natural surfactants and salts. The spoilation process is due to a contribution of all these components and of the nature of SCL materials themselves. The aim of this study was to set up methods to observe and quantify lacrimal deposits and to select efficient surfactants for preventing protein deposits. The present study was performed on PMMA-NVP SCL. The behaviour of SCL in presence of tears was studied by means of an in vitro artificial tear model consisting of the main tears components and quantified by a colorimetric technique (BCA) performed directly on the lenses. The nature of the deposit was observed directly by atomic force microscopy (AFM) in a liquid medium showing the same adsorption trend noticed in the quantitative results and identifying specific adsorption sites. The assessment of surfactant adsorption was performed using Maron's method, as a mean to evaluate the affinity of surfactant to the surface, while the action of selected surfactants on pre-treated SCL was assessed using the BCA method. Promising results were obtained with these two different methods which can be used easily for the pre-selection of surfactants for further cleaning solution formulation studies.
Compañ, V; López-Alemany, A; Riande, E; Refojo, M F
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact lenses with oxygen transmissibility higher than 100 Dk/t units [1 Dk/t unit=10(-9) [cm(3) O(2) (STp) cm(-2)s(-1)(mmHg)(-1)] posses a large oxygen tension at the lens-cornea interface that substantially reduces the oxygen flux onto the cornea. Lenses whose oxygen transmissibility is lower than 50 Dk/t units allow a rather small oxygen flux onto the cornea under closed eyelids condition that prevent their use for extended wear.
Lira, Madalena; Alves, Carlos; Botelho, Gabriela
In this work, four silicone-hydrogel contact lenses, Purevision® 2 (balafilcon A), Air Optix Aqua™ (lotrafilcon B), Acuvue® Oasys™ (senofilcon A) and Biofinity™ (comfilcon A), and one conventional lens, Acuvue® 2 (etafilcon A), were submitted during 5 weeks at a temperature of 37 °C under an air atmosphere. They were characterized initially and along exposure time in what concerns to the refractive index, water content, transmittance in the ultraviolet-visible region and chemical structure. From the results presented in this work it was possible to observe that in all lens the refractive index increases till 21 days and the water content decreased. At the end of the exposure these parameters are more variable depending on the lens studied. In what concerns to the transmittance in the ultraviolet-visible region it can be concluded that after exposure all lenses present a higher transmittance than initially. From this work it was possible to conclude that there were no significant changes in the wavenumbers where the main functional groups vibrate and in the intensity of the respective bands after 5 weeks of exposure.
Partner, Andrew M; Scott, Robert A H; Shaw, Penny; Coker, William J
Refractive devices used by aviators need to suit the aerospace environment or their failure can have serious implications. A relatively minor visual disability can result in loss of life and aircraft. We surveyed commonly occurring problems with the different types of refractive correction worn by Royal Air Force (RAF) aircrew over the previous 12 mo. We also asked if they had experienced any flight safety incidents (FSI) relating to their refractive correction. A retrospective anonymous questionnaire survey was given to 700 active aircrew occupationally graded as requiring corrective flying spectacles (CFS) or contact lenses (CL) for flying. 63% (443) of the questionnaires were completed. CL were worn by 53% of aircrew; 71% of them used daily disposable CL. CFS were worn by the remaining 47% of aircrew, 14% of whom used multifocal lenses. Of CFS wearers, 83% reported problems including misting, moving, discomfort, and conflict with helmet-mounted devices (HMD). CL-related ocular symptoms were reported in 67% of wearers including cloudy vision, dry eye, photophobia, red eyes, excessive mucus formation, CL movement, itching, and grittiness. No CL-related FSI were reported over the previous 12 mo compared with 5% CFS-related FSI (p < 0.001). The graded performance of CL for vision, comfort, handling, convenience, and overall satisfaction was significantly higher than for CFS. CFS are associated with problems in terms of comfort and safety. CL are well tolerated by aircrew, and deliver improved visual performance.
Weeks, Andrea; Subbaraman, Lakshman N; Jones, Lyndon; Sheardown, Heather
The aim of this study was to determine the influence of hyaluronic acid (HA) on lysozyme sorption in model contact lenses containing varying amounts of methacrylic acid (MAA). One model conventional hydrogel (poly(2-hydroxyethyl methacrylate) (pHEMA)) and two model silicone hydrogels (pHEMA, methacryloxypropyltris(trimethylsiloxy)silane (pHEMA TRIS) and N,N-dimethylacrylamide, TRIS (DMAA TRIS)) lens materials were prepared with and without MAA at two different concentrations (1.7 and 5%). HA, along with dendrimers, was loaded into these model contact lens materials and then cross-linked with 1-ethyl-3-(3-dimethylamino propyl)-carbodiimide (EDC). Equilibrium water content (EWC), advancing water contact angle and lysozyme sorption on these lens materials were investigated. In the HA-containing materials, the presence (P < 0.05) and amount (P < 0.05) of MAA increased the EWC of the materials. For most materials, addition of MAA reduced the advancing contact angles (P < 0.05) and for all the materials, the addition of HA further improved hydrophilicity (P < 0.05). For the non-HA containing hydrogels, the presence (P < 0.05) and amount (P < 0.05) of MAA increased lysozyme sorption. The presence of HA decreased lysozyme sorption for all materials (P < 0.05). MAA appears to work synergistically with HA to increase the EWC in addition to improving the hydrophilicity of model pHEMA-based and silicone hydrogel contact lens materials. Hydrogel materials that contain HA have tremendous potential as hydrophilic, protein-resistant contact lens materials.
Tieppo, Arianna; Pate, Kayla M; Byrne, Mark E
Novel molecularly imprinted, therapeutic contact lenses capable of controlled release of the non-steroidal anti-inflammatory (NSAID) diclofenac sodium were synthesized, exploiting ionic non-covalent interactions. Poly(HEMA-co-DEAEM-co-PEG200DMA) soft contact lenses were prepared (105±5 μm thickness, diameter 15.0±0.2mm, base curve of 8.6±0.2mm) with different monomer to template ratios and dynamic release studies were conducted in artificial lacrimal solution using two different in vitro methods. Under infinite sink conditions, imprinted contact lenses demonstrated concentration dependent release kinetics. Under physiological flow rates, by increasing the M/T ratio from 1 to 10.5, the release rate decreased from 11.72 μg/h to 6.75 μg/h during the first 48 h. The release rate was more constant, moving toward zero-order release. To use these lenses as daily disposable lenses, the first 24h of release was studied and found to be linear with a rate of 17.27, 11.99, and 8.74 μg/h for M/T ratios of 1, 3.5, and 10.5, respectively. Furthermore, the lenses prepared with a M/T ratio of 10.5 released diclofenac at a rate close to the maximum dose delivered by commercial eye drops, making them ideal for use as daily disposable lenses, and potentially leading to better patient benefit with substantially increased efficacy. Copyright © 2012 Elsevier B.V. All rights reserved.
Saini, Arvind; Rapuano, Christopher J; Laibson, Peter R; Cohen, Elisabeth J; Hammersmith, Kristin M
To report the therapeutic practice patterns of silicone hydrogel (SiH) bandage soft contact lenses (BSCL) and the resultant rate of microbial keratitis (MK). A retrospective case series of patients treated with therapeutic BSCLs for ocular surface disease from January 2006 to January 2009 in a tertiary care cornea practice. All patients had a history of ocular surface disease. Seventy-four patients were treated with a therapeutic SiH BSCL (102 intervals of use) for complicated ocular surface disease. Two patients developed infectious corneal infiltrates (2/102, 2.0%) [corrected]. Two of 3 MK episodes were in patients with limbal stem-cell deficiency (2/102, 2.0%). Therapeutic SiH BSCLs were safely used in most patients. However, results suggest that prophylactic antibiotic use did not eliminate the risk for MK with SiH BSCL use in patients with chronic ocular surface disease.
Lara Oya, Ana; Medialdea Hurtado, María Eloisa; Rojo Martín, María Dolores; Aguilera Pérez, Antonia; Alastruey-Izquierdo, Ana; Miranda Casas, Consuelo; Rubio Prats, Marina; Medialdea Marcos, Santiago; Navarro Marí, José María
Fungal keratitis is a severe ocular infection that primarily affects subjects engaged in outdoor activities. Risk factors include allergic conjunctivitis, previous eye surgery, previous treatment with wide-spectrum antimicrobial agents and corticosteroids and using contact lenses. Corneal infection is usually secondary to trauma involving organic material, which is often the only predisposing factor. Early diagnosis based on clinical examination and microbiological investigation (microscopy, cultures and molecular techniques) is crucial to selecting the appropriate antifungal therapy and prevent progression. We report the case of a patient with keratitis due to Beauveria bassiana, an opportunistic and entomopathogenic filamentous fungus that is used as a biological insecticide and which is a rare cause of corneal infection. We review previous cases reports of B. bassiana keratitis published and its main features to compare with our case, a female occasional agriculture worker who had not suffered any trauma involving organic material. The patient received topical and oral antifungal therapy and debridement surgery, with a satisfactory outcome.
Karnowski, Karol; Grulkowski, Ireneusz; Mohan, Nishant; Cox, Ian; Wojtkowski, Maciej
We demonstrate swept source optical coherence tomography (OCT) imaging of contact lenses (CLs) in a wet cell and comprehensive quantitative characterization of CLs from volumetric OCT datasets. The approach is based on a technique developed for lens autopositioning and autoleveling enabled by lateral capillary interactions between the wet cell wall and the lens floating on the liquid surface. The demonstrated OCT imaging has enhanced contrast due to the application of a scattering medium and it improves visualization of both CL interfaces and edges. We also present precise and accurate three-dimensional metrology of soft and rigid CLs based on the OCT data. The accuracy and precision of the extracted lens parameters are compared with the manufacturer's specifications. The presented methodology facilitates industrial inspection methods of the CLs.
To compare the clinical performance of a new polyhexamethylene-biguanide (PHMB)- vs a polyquad-based contact lens care regime with two silicone hydrogel contact lenses. This study was a randomised, controlled and investigator-masked (to the lens regimen) clinical study where the clinical performance of two multipurpose contact lens solutions was compared at a single site. Forty-one existing contact lens wearers were recruited and fitted randomly with either galyfilcon A or lotrafilcon A contact lenses. Subjects wore the same lens type for a period of 2 months but used a different care regime (PHMB- and polyquad-based) in a crossover manner, each for a period of 1 month. The primary outcome measure was the difference in corneal staining. Corneal staining was graded in five different locations: central, superior, inferior, temporal and nasal. Measurements of conjunctival redness, limbal redness, conjunctival staining and papillary conjunctivitis were also carried out throughout the study. Biomicroscopic measures were graded using the Efron grading scales. A variety of symptoms were also measured using a visual analogue scale. There was no statistically significant difference in overall corneal staining between lens types (p = 0.16) or care regimens (p = 0.60). Central corneal staining was significantly greater for the polyquad-based care regimen when compared with the PHMB-based care regimen (p = 0.04). Lotrafilcon A lenses showed greater superior corneal staining (p = 0.0004) and papillary conjunctivitis (p = 0.02), and lower comfort on insertion (p = 0.03) when compared with galyfilcon A lenses regardless of the care regime used. There were no statistically significant differences in the other biomicrosopic signs and symptoms between the lens types and the care regimes. Both care regimes performed in a similar clinical manner and are valid for use with the two silicone hydrogel contact lenses used in this study.
Gifford, Paul; Cannon, Tracey; Lee, Cheryl; Lee, Deborah; Lee, Hai Fang; Swarbrick, Helen A
To investigate differences in ocular aberrations induced by centre-near multifocal soft contact lenses (SCL) relative to single vision SCLs and their effect on contrast sensitivity function (CSF). Ocular aberrometry was measured in 18 cyclopleged subjects (19-24 years) while wearing Ciba Air Optix low (AOlow) and high (AOhigh) add, Bausch & Lomb PureVision low (PVlow) and high (PVhigh) add multifocals, and a Bausch & Lomb PureVision single vision (PVsv) control with the same -3.00 D distance back vertex power. Zernike polynomials were scaled to 4, 5 and 6 mm pupils. CSF was measured at equivalent distances of 6 m, 1 m and 40 cm while fully corrected with spherical trial lenses at 6m. AOlow, AOhigh and PVhigh induced a negative shift in primary spherical aberration (Z12) from PVsv and all multifocal SCLs induced a positive shift in secondary spherical aberration (Z24) (all p<0.01), without significantly increasing coma. Area under the CSF (AUCSF) reduced at 40 cm for all multifocals relative to PVsv (p<0.05), but was not significantly different at 6 m or 1 m. A moderate correlation (r = -0.80, p<0.005) was found between changes in Z12 and AUCSF at 40 cm for AOhigh, with an increase in negative Z12 reducing multifocal-induced loss of CSF. Centre-near multifocal SCLs induced a negative shift in Z12 and a positive shift in Z24. Although CSF was unaffected at 6 m and 1m it was reduced at 40 cm, possibly because changes in Z12 and Z24 were not great enough to induce a significant shift in centre of focus and increase in depth of field. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Mukherjee, Achyut; Ioannides, Antonis; Aslanides, Ioannis
Purpose To evaluate and compare Comfilcon A and Senofilcon A silicone hydrogel contact lenses used as a therapeutic bandage following transepithelial excimer laser photorefractive keratectomy (PRK). Methods Patients undergoing transepithelial PRK for myopia were prospectively recruited. Included patients had a Comfilcon A silicone hydrogel lens inserted in one eye, with a Senofilcon A lens in the contralateral eye. Postoperative assessment of subjective pain, epithelial healing and visual recovery was at day 1, 3 and 7. Contact lens factors including centration, movement and deposits were assessed. Results 48 eyes of 24 patients were included in the study. Mean age was 31 years (SD 11) and mean refractive error −4.5 D (SD 1.8). Mean pain score at day 1 was significantly higher in the Comfilcon group at 4.6 (SD 2.7) vs. 1.5 (SD2.5) in the Senofilcon group (P < 0.005). Mean time to healing was 3.17 days (SD 0.37) in the Comfilcon group, and 3.21 days (SD 0.4) in the Senofilcon group, with no difference in defect size. There was a pronounced central raphe in 1 eye in the Comfilcon group vs. 5 eyes in the Senofilcon group (P = 0.19). Significantly more eyes demonstrated no lens movement in the Senofilcon group (18 vs. 4, P = 0.0001). Conclusion The variation in material characteristics and lens geometry of different silicone hydrogel lenses affects their clinical characteristics in therapeutic roles. Other factors than oxygen permeability may affect pain and epithelial healing, with superior pain relief from the less permeable Senofilcon lens in this study. PMID:25649638
Carracedo, Gonzalo; Villa-Collar, Cesar; Martin-Gil, Alba; Serramito, Maria; Santamaría, Leticia
To compare, in terms of efficacy, the differences between the use of saline solution and a viscous artificial tear to fill the lens during the first month of orthokeratology wear. A pilot, double-masked, crossed, randomized, and prospective study was conducted. In this study, 20 subjects (14 males and 6 females) with a mean age of 16.29±6.22 years (range, 10-26) were fitted with orthokeratology contact lenses. For the study, nonpreserved 0.9% NaCl commercial saline solution (Avizor, Madrid, Spain) and nonpreserved artificial teardrops with 0.3% of hyaluronic acid (Ocudry 0.3%; Avizor, Madrid, Spain) were used. Corneal staining, tear break up time (TBUT), topography, refraction, visual acuity, and subjective comfort and vision with the visual analog scale (score from 0 to 10, being 10 better comfort and vision) were evaluated at 1 day, 1 week, and 1 month of contact lens wear. The corneal staining was statistically greater in the saline group than in the Ocudry group for the first day and during 1 week of wear (P<0.05). Comfort was found to be statistically better, with Ocudry 0.3% than saline solution, being 7.17±1.94 and 6.37±1.63, for the first day, and 8.78±0.43 and 8.15±0.62 for the day 28, respectively (P<0.05). However, no differences were found for subjective vision scores, TBUT, spherical equivalent, best-corrected visual acuity and uncorrected visual acuity, and mean keratometry between groups for any visit (P>0.05). Viscous artificial tears improve the subjective comfort of patients and reduce the corneal staining, compared with saline solution during the orthokeratology lenses fitting process. However, no differences between solutions for the treatment efficacy, in vision and corneal topography, were found.
Walsh, James E; Bergmanson, Jan P G
The human eye is exposed to toxic ultraviolet radiation (UVR) from sunlight and artificial sources. The UVR-induced damage occurs in ocular tissues from the corneal surface to the retina. Although the cornea and crystalline lens provide inherent UVR protection, the anterior ocular surface and the limbus, which contains stem cells, receive toxic levels of UVR from relatively short solar exposures. Shading headwear and some UVR-blocking sunglasses are designed to reduce direct solar exposure but may not protect the eye from diffuse ambient and surface reflected light. If the squint mechanism is reduced because of the reduction of visible light, the ocular surface is then exposed to ambient and reflected UVR. In addition, laterally incident radiation that is focused across the cornea onto the limbus, a phenomenon known as peripheral light focusing, can increase the dose at the nasal limbus by a factor of 20. The UVR-blocking contact lenses that cover the limbus provide protection from all sources of ocularly incident UVR. Although directly relating solar UVR dose to ocular damage is epidemiologically challenging, irradiation of ocular cell cultures can estimate the toxic effects of UVR exposure. The use of UVR-blocking contact lenses greatly increases the time the wearer can be exposed to solar UVR before a toxic ocular dose is reached. There is a need for the development of a scientifically rigorous, clinically applicable ocular protection factor metric, based not only on the transmittance of eyewear but on the protection afforded from the total UVR field and the length of that exposure.
Lorentz, Holly; Jones, Lyndon
The tear film is a complex fluid that is precisely maintained and which is essential to the health of the ocular surface. One of the major components of the tear film is lipid, which is produced by the meibomian glands and serves many important functions on the ocular surface. It is estimated that there are more than 45 individual lipids within the tear film, which vary greatly in their structure and properties. The composition of the lipid within the tear film has an enormous influence on the stability of the tear film, with a subsequent impact on the occurrence of dry eye and the ultimate success of contact lens wear. The purpose of this review article is to describe the composition of the tear film lipids and their interaction with contact lens materials, with a particular emphasis on how the chemistry of novel silicone hydrogel materials has resulted in clinicians needing to understand the deposition of lipids onto contact lenses and how they may best manage this complication.
Yu, Qing; Wu, Jiang-Xiu; Zhang, He-Ning; Ye, Sheng; Dong, Shi-Qi; Zhang, Chen-Hao
AIM To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. METHODS The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. RESULTS Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows: root mean square (RMS) (pre)=(1.438±0.328)µm, RMS (30 minutes)=(1.076±0.355)µm, RMS (1 day)=(1.362±0.402)µm, RMS (3 days)=(1.373±0.398)µm, RMS (7 days)=(1.387±0.415)µm, and RMS (14 days)=(1.430±0.423)µm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2nd- and 3rd-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4th-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. CONCLUSION The use RGP contact lenses greatly reduced total aberration of
Varikooty, Jalaiah; Keir, Nancy; Woods, Craig A; Fonn, Desmond
To determine whether the refractive index (RI) of a soft contact lens can be evaluated using refractometry while the lens remains on the eye and to compare this with more traditional ex vivo RI measurements. A slitlamp apparatus was modified to incorporate a customized Atago hand refractometer. With a double-masked study design, nine adapted symptomatic soft contact lens wearers wore a contact lens in each eye (lotrafilcon B and etafilcon A) in a randomized order. In vivo RI was determined from the relative Brix scale measurements immediately after lens insertion and after 1 and 10 hr of lens wear. Ex vivo refractometry was performed after 10 hr of lens wear for comparison. Means +/- standard errors of the means are reported. In vivo RI values at baseline were 1.422 +/- 0.0004 (lotrafilcon B) and 1.405 +/- 0.0021 (etafilcon A); after 1 hr of lens wear, values were 1.423 +/- 0.0006 and 1.408 +/- 0.0007, respectively; and after 10 hr of lens wear, values were 1.424 +/- 0.0004 and 1.411 +/- 0.0010, respectively. Ex vivo RI values at the end of the 10 hr wearing period were 1.424 +/- 0.0003 (lotrafilcon B) and 1.412 +/- 0.0017 (etafilcon A). The change in in vivo RI across the day was statistically significant for the etafilcon A lens (repeated-measures analysis of variance, P<0.01) but not for the lotrafilcon B lens (P>0.05). This novel adaptation of refractometry was able to measure the RI of soft contact lenses during wear (without lens removal). End of day RI measurements using in vivo and ex vivo refractometry were comparable with each other. Future work is required to determine whether this in vivo method can improve our understanding of the relationships between soft contact lens RI, hydration, on-eye lens performance, and symptomology.
Furlan, Walter D; Ferrando, Vicente; Monsoriu, Juan A; Zagrajek, Przemysław; Czerwińska, Elżbieta; Szustakowski, Mieczysław
A 3D printer was used to realize custom-made diffractive THz lenses. After testing several materials, phase binary lenses with periodic and aperiodic radial profiles were designed and constructed in polyamide material to work at 0.625 THz. The nonconventional focusing properties of such lenses were assessed by computing and measuring their axial point spread function (PSF). Our results demonstrate that inexpensive 3D printed THz diffractive lenses can be reliably used in focusing and imaging THz systems. Diffractive THz lenses with unprecedented features, such as extended depth of focus or bifocalization, have been demonstrated.
Bakaraju, Ravi C; Ehrmann, Klaus; Ho, Arthur
To compare the computed optical performance of prototype lenses designed using deliberate manipulation of higher-order spherical aberrations to extend depth-of-focus (EDOF) with two commercial multifocals. Emmetropic, presbyopic, schematic eyes were coupled with prototype EDOF and commercial multifocal lenses (Acuvue Oasys for presbyopia, AOP, Johnson & Johnson & Air Optix Aqua multifocal, AOMF, Alcon). For each test configuration, the through-focus retinal image quality (TFRIQ) values were computed over 21 vergences, ranging from -0.50 to 2.00D, in 0.125D steps. Analysis was performed considering eyes with three different inherent aberration profiles: five different pupils and five different lens decentration levels. Except the LOW design, the AOP lenses offered 'bifocal' like TFRIQ performance. Lens performance was relatively independent to pupil and aberrations but not centration. Contrastingly, AOMF demonstrated distance centric performance, most dominant in LOW followed by MED and HIGH designs. AOMF lenses were the most sensitive to pupil, aberrations and centration. The prototypes demonstrated a 'lift-off' in the TFRIQ performance, particularly at intermediate and near, without trading performance at distance. When compared with AOP and AOMF, EDOF lenses demonstrated reduced sensitivity to pupil, aberrations and centration. With the through focus retinal image quality as the gauge of optical performance, we demonstrated that the prototype EDOF designs were less susceptible to variations in pupil, inherent ocular aberrations and decentration, compared to the commercial designs. To ascertain whether these incremental improvements translate to a clinically palpable outcome requires investigation through human trials. Copyright © 2017 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.
Kluka, D A; Love, P A
Contrast sensitivity (CS) has recently emerged as an important predictor of visual performance. Few studies, however, have been published involving CS and its role in vision for sport. The purpose of this investigation was to determine if significant differences occurred in CS between female professional and collegiate tennis players who wore daily-wear soft contact lenses (N = 10) and those players who wore no corrective lenses (N = 10) in competition as measured by the Stereo Optical Optec 2000 Vision Tester. Subjects were between the ages of 18 and 37 years. Mean ages were 21.76 (+/- 4.018) and 25.40 (+/- 5.379) years for those wearing lenses and those not, respectively. Each subject was preliminarily screened for SVA-distance, lateral/vertical phorias, stereopsis, and color perception. All subjects were within accepted limits. CS was assessed at 1.5, 3, 6, 12, and 18 cycles per degree (cpd). Each subject was assessed monocularly; eye initially assessed was determined randomly. A 2 x 2 factorial analysis of variance (alpha = .05) was used to analyze data. No significant differences were found between eyes. Significant differences were found at 3, 6, 12, and 18 cpd. It may be concluded that those female professional and collegiate tennis players wearing no corrective lenses were significantly higher in CS at intermittent and high spatial frequencies than those who wore daily-wear soft contact lenses in competition.
Schultz, C L; Pezzutti, M R; Silor, D; White, R
S. marcescens 8100 and P. aeruginosa 15442 were used to study bacterial adhesion to hydrogel contact lenses which had not been worn. Bacterial removal from unworn lens materials was assessed with a calibrated vortex device modified with a digital rpm readout and fitted with a test tube attachment (MVD). The MVD, which relies on a whirlpool-like force to remove the bacteria, showed that bacteria adhered to the same degree to etafilcon A, vifilcon A and polymacon lenses under standardized conditions. Tracking the isoenzyme patterns of these bacterial species over time showed instability of S. marcescens upon repeated passage. This instability was not evident with P. aeruginosa. Bacterial adhesion of P. aeruginosa 15442, to human worn and unworn etafilcon A materials was determined with a Modified Robbins Device. The MRD was closed off at both ends stopping medium and bacterial movement after 1 h of fluid flow over the lens surface. The results show that immediately following this 1-h period more bacteria adhere to unworn contact lenses than to worn lenses. However, bacterial counts were equivalent on worn and unworn lenses following 5 h of static incubation.
Swinger, C A
The limited experience with LRK precludes a valid comparison with IOLs and extended-wear contact lenses. Only observations, unsupported by valid statistical analysis, are possible. Some of these observations follow. Technically, LRK is very difficult. In their present form, the classic Barraquer procedures could never be used widely. However, if lenticle banks were to supply preground lenticles, the level of difficulty of LRK procedures would be comparable to IOL implantation. The magnitude of refractive correction possible with LRK compares favorably with that of contact lenses and IOLs. However, the accuracy of achieving a given correction is lower with LRK. Unlike contact lenses or IOLs, LRK induces both regular and irregular astigmatism. The latter accounts, in part, for the delayed visual result with LRK. The percentage of patients with 20/40 or better vision following LRK compares favorably with the percentages for contact lenses or IOLs, whereas the percentage of patients with 20/25 or better vision does not. This is true for at least 1 year following surgery. Compared to extended-wear contact lenses, IOLs and LRK typically require less commitment, fewer postoperative visits, and less expenditure by the patient, in terms of time and money, to achieve full-time correction. Although LRK is associated with a number of postoperative complications, none are known to be intraocular, and there have been no known reports of permanent severe visual loss. In contrast, the patient with an extended-wear contact lens or IOL is permanently at risk to develop sight-threatening complications. This is not the case with LRK, which has no known complications after the early postoperative period. Application of the IOL or extended-wear contact lens to the neonate or pediatric patient is associated with increased risk and difficulty. This may not be true with LRK, especially epikeratophakia. The major advantages of LRK appear to be permanent optical correction without the threat
Scholtz, Sibylle K; Auffarth, Gerd U
Alhazen, ibn al-Haytham, (965 Basra - c. 1040 in Cairo) was a Muslim polymath who made significant contributions to the principles of optics, being the first to recognize the optical effect by transparent objects in the 11th century. His insights led to a fundamental revolution, enabling older presbyopic persons to read again. Today many more options are available to help visually impaired people correct their sight defects. This article will give an historical overview of the sight aids which are available today and will describe the very first beginnings of the development of the "reading stone" or "glasses". Further, it will also give a chronological overview of more modern techniques, e.g., intraocular lenses, contact lenses and the options of refractive surgery.
Sankaridurg, Padmaja R.; Sharma, Savitri; Willcox, Mark; Naduvilath, Thomas J.; Sweeney, Deborah F.; Holden, Brien A.; Rao, Gullapalli N.
Microorganisms, especially gram-negative bacteria, are considered to play a role in the etiology of certain corneal infiltrative events (CIEs) observed during soft contact lens wear. This study explored the possibility of microbial colonization of soft contact lenses as a risk factor leading to CIEs. In a clinical trial conducted from March 1993 to January 1996, 330 subjects wore disposable soft contact lenses on a 6-night extended-wear and disposal schedule. During this period, 4,321 lenses (118 during CIEs; 4,203 during asymptomatic lens wear) were recovered aseptically and analyzed for microbial colonization. A greater percentage of lenses were free from microbial colonization during asymptomatic wear than during CIEs (42 versus 23%; P < 0.0001). The incidence of gram-positive bacteria, gram-negative bacteria and fungi was greater during CIEs than during asymptomatic lens wear (P < 0.05). During asymptomatic lens wear, gram-positive bacteria were isolated most frequently and were usually normal external ocular microbiota. Of the gram-positive bacteria, the incidence of Streptococcus pneumoniae was greater during CIE than during asymptomatic wear (7.6 versus 0.6%; P < 0.0001). While gram-negative bacteria were seen in few cases during asymptomatic wear, their incidence during CIE in comparison to asymptomatic wear was substantial and significant (23.7 versus 3.8%; P < 0.0001). Also, the level of colonization was high. Of CIEs, events of microbial keratitis, contact lens acute red eye, and asymptomatic infiltrative keratitis were associated with lens colonization with gram-negative bacteria or S. pneumoniae. Colonization of soft contact lenses with pathogenic bacteria, especially gram-negative bacteria and S. pneumoniae, appears to be a significant risk factor leading to CIE. PMID:11101574
Sankaridurg, P R; Sharma, S; Willcox, M; Naduvilath, T J; Sweeney, D F; Holden, B A; Rao, G N
Microorganisms, especially gram-negative bacteria, are considered to play a role in the etiology of certain corneal infiltrative events (CIEs) observed during soft contact lens wear. This study explored the possibility of microbial colonization of soft contact lenses as a risk factor leading to CIEs. In a clinical trial conducted from March 1993 to January 1996, 330 subjects wore disposable soft contact lenses on a 6-night extended-wear and disposal schedule. During this period, 4,321 lenses (118 during CIEs; 4,203 during asymptomatic lens wear) were recovered aseptically and analyzed for microbial colonization. A greater percentage of lenses were free from microbial colonization during asymptomatic wear than during CIEs (42 versus 23%; P < 0.0001). The incidence of gram-positive bacteria, gram-negative bacteria and fungi was greater during CIEs than during asymptomatic lens wear (P < 0.05). During asymptomatic lens wear, gram-positive bacteria were isolated most frequently and were usually normal external ocular microbiota. Of the gram-positive bacteria, the incidence of Streptococcus pneumoniae was greater during CIE than during asymptomatic wear (7.6 versus 0.6%; P < 0. 0001). While gram-negative bacteria were seen in few cases during asymptomatic wear, their incidence during CIE in comparison to asymptomatic wear was substantial and significant (23.7 versus 3.8%; P < 0.0001). Also, the level of colonization was high. Of CIEs, events of microbial keratitis, contact lens acute red eye, and asymptomatic infiltrative keratitis were associated with lens colonization with gram-negative bacteria or S. pneumoniae. Colonization of soft contact lenses with pathogenic bacteria, especially gram-negative bacteria and S. pneumoniae, appears to be a significant risk factor leading to CIE.
dos Santos, Jose-Fernando Rosa; Alvarez-Lorenzo, Carmen; Silva, Maite; Balsa, Luis; Couceiro, Jose; Torres-Labandeira, Juan-Jose; Concheiro, Angel
The aim of this work was to develop acrylic hydrogels with high proportions of cyclodextrins maintaining the mechanical properties and the biocompatibility of the starting hydrogels, but notably improving their ability to load drugs and to control their release rate. Poly(hydroxyethylmethacrylate) hydrogels were prepared by copolymerization with glycidyl methacrylate (GMA) at various proportions and then beta-cyclodextrin (betaCD) was grafted to the network by reaction with the glycidyl groups under mild conditions. This led to networks in which the betaCDs form no part of the structural chains but they are hanging on 2-3 ether bonds through the hydroxyl groups. The pendant betaCDs did not modify the light transmittance, glass transition temperature, swelling degree, viscoelasticity, oxygen permeability, or surface contact angle of the hydrogels, but decreased their friction coefficient by 50% and improved diclofenac loading by 1300% and enhanced drug affinity 15-fold. The hydrogels were able to prevent drug leakage to a common conservation liquid for soft contact lenses (SCLs) and to sustain drug delivery in lacrimal fluid for two weeks. To summarize, the hydrogels with pendant betaCDs are particularly useful for the development of cytocompatible medicated implants or biomedical devices, such as drug-loaded SCLs.
Cerretani, Colin; Peng, Cheng-Chun; Chauhan, A; Radke, C J
In addition to improving oxygen permeability, modern silicone-hydrogel (SiHy) soft contact lenses (SCLs) exceed a limiting diffusive ion permeability to aqueous sodium chloride. Below the ion-permeability threshold, siloxane-based SCLs are prone to bind against the corneal epithelium. Salt permeability is argued to reflect indirectly water hydraulic permeability. However, no quantitative explanation is available to date for a threshold salt permeability. We hypothesize that molecular salt diffusion through a SCL supports the postlens tear film (PoLTF) by enhancing water flow into the PoLTF from the cornea. Higher salt concentrations in the PoLTF raise the osmotic pressure there relative to that in the cornea increasing osmotic water withdrawal from the cornea. The proposed osmotic-withdrawal mechanism successfully predicts a self-consistent threshold lens salt permeability when thin-film attractive binding forces are introduced. For the first time, we present a quantitative picture for the possible origin of a threshold salt permeability in SCL manufacture. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Legras, Richard; Benard, Yohann; Rouger, Hélène
We measured high-contrast visual acuity (VA) and 12c/deg contrast sensitivity (CS) through-focus functions (TFF) of four eyes of four cyclopleged subjects in three conditions: naked eye, with a center-distance and center-near Proclear(R) multifocal addition 2D contact lens. In all conditions, an adaptive optics system statically compensated the astigmatism of the subject's eye alone. Multifocal contact lenses enlarged the width of the curve of through-focus visual performance but reduced the peak performance. We investigated the ability of image quality metrics based on wave-aberration measurements to predict VA and CS TFF. CS(12) metric through-focus and measured through-focus contrast sensitivities were well correlated (r(2)=0.74). Even if visual acuity metrics were often poorer than measured ones, the shapes of the measured through-focus curves and rMTFa(5-15) through-focus were quite comparable (r(2)=0.67). Copyright 2010 Elsevier Ltd. All rights reserved.
Pimenta, A F R; Ascenso, J; Fernandes, J C S; Colaço, R; Serro, A P; Saramago, B
Optimization of drug delivery from drug loaded contact lenses assumes understanding the drug transport mechanisms through hydrogels which relies on the knowledge of drug partition and diffusion coefficients. We chose, as model systems, two materials used in contact lens, a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone based hydrogel, and three drugs with different sizes and charges: chlorhexidine, levofloxacin and diclofenac. Equilibrium partition coefficients were determined at different ionic strength and pH, using water (pH 5.6) and PBS (pH 7.4). The measured partition coefficients were related with the polymer volume fraction in the hydrogel, through the introduction of an enhancement factor following the approach developed by the group of C. J. Radke (Kotsmar et al., 2012; Liu et al., 2013). This factor may be decomposed in the product of three other factors EHS, Eel and Ead which account for, respectively, hard-sphere size exclusion, electrostatic interactions, and specific solute adsorption. While EHS and Eel are close to 1, Ead>1 in all cases suggesting strong specific interactions between the drugs and the hydrogels. Adsorption was maximal for chlorhexidine on the silicone based hydrogel, in water, due to strong hydrogen bonding. The effective diffusion coefficients, De, were determined from the drug release profiles. Estimations of diffusion coefficients of the non-adsorbed solutes D=De×Ead allowed comparison with theories for solute diffusion in the absence of specific interaction with the polymeric membrane.
Keir, Nancy; Simpson, Trefford; Fonn, Desmond
Purpose To compare the short-term visual and optical performance of silicone hydrogel contact lenses for myopia ≥ −3.00D. Methods This was a short-term, non-dispense, double-masked, randomized study investigating Night&Day (ND), PureVision (PV), O2 Optix (O2), Biofinity (BF), Acuvue Advance (AA) and Acuvue OASYS for myopia ≥ −3.00D. Testing was conducted under scotopic conditions. Measures (one eye only) included: high- and low-contrast visual acuity (HCVA/LCVA), contrast sensitivity, subjective clarity of vision ratings (0-100 scale using reference images, with test image representing grade 50) and ocular aberrations (up to the 4th order, analyzed across individual scotopic pupil sizes). Results Three males and 27 females participated, with a mean (± SD) age of 24.9 ± 7.7 yrs (range 19 to 53 yrs), sphere of −5.30 ± 1.73D (range −3.00 to −10.75D) and cylinder −0.36 ± 0.23D (range 0 to −0.75D). Mean (± SEM) logMAR HCVA ranged from 0.06 (PV) to 0.10 (AA) (± 0.02), LCVA from 0.33 (BF) to 0.40 (AA) (± 0.02) and contrast sensitivity from 2.33 (BF) to 2.53 (ND) (± 0.15) (differences not statistically significant; all p > 0.05). Subjective ratings for the test image ranged from 59 (PV) to 64 (ND) (± 4) and 56 (AA) to 65 (ND) (± 4), for monochromatic and polychromatic reference images, respectively (all p > 0.05). There was a statistically significant impact on ocular aberrations with all study lenses compared to no lens. Between-lens differences were statistically significant for defocus (Z02), horizontal coma (Z 13) and spherical aberration (Z04). Conclusions Despite some differences in ocular aberrations, there were no significant differences in HCVA, LCVA, contrast sensitivity or subjective ratings across lenses.
Scheuer, Catherine A; Rah, Marjorie J; Reindel, William T
Purpose This study was conducted to determine 1) the concentration of hyaluronan (HA) in the tear films of contact lens (CL) wearers versus non-CL wearers and 2) whether HA sorbed from Biotrue, an HA-containing multipurpose solution (MPS), onto senofilcon A lenses affects the concentration of HA in tears after 2 hours of wear. Patients and methods Tears of habitual CL wearers and non-CL wearers were collected on Schirmer strips at baseline and after 2 hours of wear of senofilcon A CLs that had first been either rinsed with Sensitive Eyes Saline or soaked in Biotrue MPS for 14 hours. HA concentrations were measured by enzyme-linked immunosorbent assay (ELISA) and adjusted for sample volumes. Results No difference in baseline concentrations of HA in tears was found between CL wearers and non-CL wearers (P=0.07), nor between males and females (P=0.06). However, age was significantly negatively associated with HA concentration (P<0.01), and mostly, CL wear contributed to a significant association (P<0.01). Among saline-rinsed CL wearers, no change in HA concentration in tears was observed after 2 hours of wear (P=0.38). By contrast, a significant increase in HA concentration was observed in the tears from eyes that had worn CLs soaked in Biotrue MPS when compared to baseline (P=0.01) or to saline-rinsed control (P=0.03). Conclusion 1) In this study population, no difference in baseline concentration of HA was observed between CL wearers and non-CL wearers, and 2) after 2 hours of wear of senofilcon A lenses that were soaked in Biotrue MPS, HA concentrations in the tear films of CL wearers increased. PMID:27784983
Suzaki, Asaki; Maeda, Naoyuki; Fuchihata, Mutsumi; Koh, Shizuka; Nishida, Kohji; Fujikado, Takashi
To evaluate the visual performance and optical quality of a standardized asymmetric soft contact lens (SCL) used for correction of higher-order aberrations (HOAs) in eyes with keratoconus. We included 30 eyes (26 patients) with keratoconus (average K: 45.7 ± 2.3 diopters [D]). The patients were subjected to corneal tomography, aberrometry, measurements of manifest refraction and visual acuity (VA), and visual analog scale (VAS) assessments. The study lenses were made using a molding method and consisted of six standardized types, in which an asymmetric power distribution of approximately 2 to 12 D (2-D step) was used to correct HOAs. The lens type suitable for each eye was selected based on the corneal tomography and aberrometry data. The on-eye performance of the lens was evaluated using aberrometry (4-mm pupil), over refraction, VA, and VAS. The standardized asymmetric SCL improved the best spectacle-corrected VA from -0.07 ± 0.09 to -0.11 ± 0.08 logMAR (P < 0.05) and the mean VAS score from 66.2 ± 21.8 to 75.4 ± 20.5 (P < 0.05). Vertical coma decreased significantly (-0.50 ± 0.36 μm without SCL; -0.36 ± 0.34 μm with SCL; P < 0.01). In subgroup analysis, subjects in the high VAS group (score ≥ 75) accounted for 70% of all subjects, and this was the group in which the vertical coma decreased significantly from the level without the lens. A standardized asymmetric SCL can reduce HOAs and improve vision quality when compared with spectacles in patients with keratoconus who wear rigid gas-permeable lenses.
Phan, Chau-Minh; Bajgrowicz, Magdalena; McCanna, David J; Subbaraman, Lakshman N; Jones, Lyndon
To evaluate the effects of two commercial silicone hydrogel contact lenses (CLs) soaked with natamycin (NA) or fluconazole (FL) on the growth of Candida albicans in an in vitro eye model. Three-D printed molds were used as a cast for making eye-shaped models comprising potato dextrose agar. Senofilcon A (SA) and lotrafilcon B (LB) CLs were incubated with either 2 mL of NA or FL at a concentration of 1 mg/mL for 24 hr. To simulate a fungal infection, the eye models were coated with C. albicans. The drug-soaked lenses were placed on top of the eye models. Seven experimental conditions were examined: (1) NA-SA, (2) NA-LB, (3) FL-SA, (4) FL-LB, (5) SA, (6) LB, and (7) control-no lens. At specified time points (t=1, 8, 16, 24, 48 hr), the agar eyes from each experimental condition were removed from the incubator and photographed. The yeast cells from the 24 and 48 hr time point were also analyzed using light microscopy. At 24 and 48 hr, there was considerable growth observed for all conditions except for the NA-SA and NA-LB conditions. When observed under the microscope at 24 and 48 hr, the morphology of the yeast cells in the FL-SA and SA condition were similar to that of the control (oval shaped). There was limited hyphae growth observed for LB and significant visible hyphae growth for the NA-LB group. For NA-SA, NA-LB, and FL-LB groups, the cells were significantly smaller compared with the control. For NA-SA and NA-LB, there was limited growth of C. albicans observed on the eye models even after 48 hr. Under the microscope, the cell morphology differ noticeably between each testing condition, and is dependent on drug-lens combinations.
Chao, Cecilia; Golebiowski, Blanka; Stapleton, Fiona; Richdale, Kathryn
This study investigated changes in selected tear cytokine concentrations (IL-1β, IL-1Ra, IL-6, IL-10, IL-12 (p70), and TNF-α) after a 1-week washout from soft contact lens wear (CLW), and the repeatability of cytokine measurements using custom multiplex assays. A total of 10 subjects completed this 6-visit (immediately following contact lens removal, and after 1, 2, 3, 4, and 7 [±1] days without CLW) pilot study. Approximately 20 to 30 μL of pooled basal tears were collected from both eyes at each visit. Two custom multiplex assays were used by two operators to quantify the concentration of tear cytokines. Tear samples from subjects 1 to 6 were analyzed using the first kit by operator 1. Tear samples from subject 7 to 10 plus additional tear samples from subjects 1 to 5, which were used to determine the between-kit per operator repeatability, were analyzed using the second kit by operator 2. Linear mixed models were used to determine changes in tear cytokine concentrations over time. Between-kit per operator and within-kit per operator repeatabilities were assessed using the Bland and Altman analysis. There were no significant changes in tear cytokine concentrations over a 1-week washout of CLW. More than 99% of the tear samples had detectable levels of cytokines using custom multiplex assays. Within-kit per operator repeatability was good, but between-kit per operator repeatability was poor; likely due to protein degradation, differences in operator experience, and operating procedures. A washout period may not be necessary when evaluating changes in tear cytokines with new contact lenses or lens care products. A well-trained operator using standardized operating procedures can produce repeatable measurements using custom multiplex assays.
Srinivasan, Sruthi; Otchere, Heinz; Yu, Mili; Yang, Jeffery; Luensmann, Doerte; Jones, Lyndon
This study evaluated the impact of various cosmetics on the surface properties of silicone hydrogel (SiHy) contact lens materials. In this in vitro experiment, 7 SiHy contact lens materials were coated with 1 of 9 cosmetics, including common hand creams (3), eye makeup removers (3), and mascaras (3). Dark-field microscopy images were taken to determine pixel brightness (PB) after cosmetic exposure, which describes the visible surface deposition (n=6 for each lens type), with a higher PB indicating increased deposition. The sessile drop technique was used to determine the advancing contact angle (CA). Measurements were repeated for both methods after a single peroxide-based cleaning cycle. Pixel brightness was significantly higher for mascara-coated lenses compared with the other cosmetic products (P<0.01). The peroxide-based lens care solution removed most deposits from the nonwaterproof mascara for 4 lens types, whereas deposits remained relatively unchanged for 1 waterproof mascara (P>0.05). Hand creams and makeup remover had minimal impact on PB. Changes in CA measurements after cosmetic application were highly lens dependent. Hand creams caused primarily a decrease in CA for 5 of the 7 lens types, whereas 1 of the waterproof mascaras caused a significant increase of 30 to 50° for 3 lens types. Some mascara-lens combinations resulted in increased CA and PB, which could have an impact on in vivo lens performance. Nonwaterproof mascara was mostly removed after a cleaning cycle. Further research is needed to understand the clinical implications for SiHy lens wearers using cosmetics.
Ramdas, Wishal D; Vervaet, Charles J W C
To investigate the rate of progression of keratoconus in patients wearing pancorneal toric edge rigid gas-permeable contact lenses (pancorneal RGP-CL) compared to non-pancorneal RGP-CL. We also evaluated alterations in anterior chamber parameters with the progression of keratoconus and investigated the location of the cone in eyes with keratoconus. The current study was a retrospective study including patients with clinically evident keratoconus from the outpatient clinic from the Department of Ophthalmology of the Erasmus Medical Center, Rotterdam, the Netherlands. Medical history and contact lens characteristics were documented. All participants underwent ophthalmic examination including corneal topography. Corneal topography was repeated at one of the consecutive visits of the patient. Patients were divided into two groups: those wearing pancorneal RGP-CL and those wearing other contact lens types. As a measure of progression of keratoconus differences in corneal topography parameters between both groups were compared. A total of 82 patients were included of which 42 had follow-up (mean 17.8 months) data. We found a significant difference in progression between eyes fitted with and without pancorneal RGP-CL (K-flat: p=0.09, K-steep: p=0.02, K-mean: p=0.02, and K-minimum: p=0.04). Compared with eyes fitted without pancorneal RGP-CL no significant difference in K-values was found for eyes fitted with pancorneal RGP-CL during follow-up. Furthermore, a significant decrease in anterior chamber volume (p<0.001) and corneal volume (p=0.008) was found during follow-up. In 86.6% the location of the cone was located infero-temporal. Pancorneal RGP-CL have a better effect on stabilizing progression of keratoconus than non-pancorneal RGP-CL. The finding of an infero-temporal location of the cone in keratoconic corneas may improve results of contact lens fitting and surgical management. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights
Abbey, Ashkan M.; Gregori, Ninel Z.; Surapaneni, Krishna; Miller, Darlene
Purpose While manufacturers recommend cleaning ophthalmic lenses with detergent and water and then a specific disinfectant, disinfectants are rarely used in ophthalmic practices. The aim of this pilot study was to evaluate the efficacy of detergent and water versus bleach, a recommended disinfectant, to eliminate common ocular bacteria and viruses from ophthalmic lenses. Methods Three bacterial strains (Staphylococcus epidermidis, Corynebacterium straitum, and methicillin-resistant Staphylococcus aureus (MRSA) and two viral strains (adenovirus and herpes simplex virus (HSV) type-1) were individually inoculated to 20 gonioscopy and laser lenses. Lenses were washed with detergent and water and then disinfected with 10% bleach. All lenses were cultured after inoculation, after detergent and water, and after the bleach. Bacterial cultures in thioglycollate broth were observed for 3 weeks and viral cultures for 2 weeks. The presence of viruses was also detected by multiplex polymerase chain reaction (PCR). Results All 20 lenses inoculated with Staphylococcus epidermidis, Corynebacterium straitum, adenovirus, and HSV-1 showed growth after inoculation, but no growth after detergent/water and after the bleach. All lenses showed positive HSV and adenovirus PCR after inoculation and negative PCR after detergent/water and after bleach. All MRSA contaminated lenses showed growth after inoculation and no growth after detergent and water. However, one lens showed positive growth after bleach. Conclusions Cleaning with detergent and water appeared to effectively eliminate bacteria and viruses from the surface of contaminated ophthalmic lenses. Further studies are warranted to design practical disinfection protocols that minimize lens damage. PMID:24747806
Cho, P; Ng, V
Dryness due to contact lens wear and poor wetting of contact lenses among contact lens wearers is a common observation and contact lens manufacturers have introduced new, better quality soft lens materials that are claimed to be more deposit resistant, and/or dehydration resistant. The purpose of this study was to evaluate and compare the clinical performance of Hydron ActiSoft 60 section sign, made of a new material (HyGMAtrade mark) which is claimed to be dehydration resistant with excellent wettability, with ActiFresh 400, made of conventional non-ionic hydrogel material. The experiment was conducted as a double-masked, randomised, cross-over study. Clinical assessment included pre-lens non-invasive tear break up time (PL-NITBUT), logMar visual acuity and contrast sensitivity (CS). Corneal staining, if any, was recorded at each visit. Subjective ratings in regard to dryness, grittiness, lens awareness, vision, comfort, handling (removal), handling (cleaning) and the overall preference of each lens type were obtained at the end of 3 (Phase A) and 6 months' (Phase B) wear. Twenty-eight subjects successfully completed the study. In Phase A, no significant differences were found in both baseline PL-NITBUT and PL-NITBUT after wearing the same lenses for 1 month between the two lens types. In phase B, baseline PL-NITBUT for ActiFresh 400 was significantly shorter than that for ActiSoft 60. However, after 1 month of wear, the difference in PL-NITBUT between the two lens types was no longer significant. PL-NITBUT was significantly reduced after 1 month's wear for both ActiSoft 60 and Actifresh 400, and in both Phase A and Phase B. The two lens types provided comparable logMAR visual acuity, and there was no significant differences in CS (Pelli Robson) between spectacle lens correction (equivalent spheres) and either lens type. The incidence of corneal epithelial staining was significantly higher and more severe with ActiFresh 400 than with ActiSoft 60, both in Phase A
Chowhan, M A; Asgharian, B; Fontana, F
The comfort of rigid gas-permeable contact lenses is influenced by multiple factors, including the composition of lens material and the presence of surface deposits and/or cleaning solution residues on the lens, as well as the direct effect of lens care solutions on the lens and eye. This study was designed to examine the comparative properties of several soaking solutions with respect to wettability, viscosity, and substantivity, which are essential to maintaining patient comfort. Solutions included in this trial were: OPTI-SOAK Conditioning Solution, Boston Advance Conditioning Solution, Boston Advance Conditioning Solution, Boston Conditioning Solution, Barnes-Hind Wetting and Soaking Solution, Duracare Conditioning, and Total Cleaning, Wetting & Soaking Solution. Wettability, as indicated by mean wetting angle, was determined and OPTI-SOAK Conditioning Solution, followed by Boston Advance and Boston Conditioning solutions, respectively, yielded superior results. For viscosity, OPTI-SOAK Conditioning Solution again provided the most favorable (highest) viscosity, followed by Boston Conditioning and Barnes-Hind solutions. With regard to substantivity, a measure of sustained wettability, Boston Conditioning Solution achieved the highest measurement, followed by OPTI-SOAK and Boston Advance solutions. On the basis of this in vitro evaluation, OPTI-SOAK Conditioning Solution provided the highest potential for patient comfort based on a combination of wettability, viscosity, and substantivity.
Abadías, Clara; Serés, Carme; Torrent-Burgués, Juan
The objective of this work is to apply Atomic Force Microscopy in Peak Force mode to obtain topographic characteristics (mean roughness, root-mean-square roughness, skewness and kurtosis) and mechanical characteristics (adhesion, elastic modulus) of Siloxane-Hydrogel Soft Contact Lenses (CLs) of two different materials, Lotrafilcon B of Air Optix (AO) and Asmofilcon A of PremiO (P), after use (worn CLs). Thus, the results obtained with both materials will be compared, as well as the changes produced by the wear at a nanoscopic level. The results show significant changes in the topographic and mechanical characteristics of the CLs, at a nanoscopic level, due to wear. The AO CL show values of the topographic parameters lower than those of the P CL after wear, which correlates with a better comfort qualification given to the former by the wearers. A significant correlation has also been obtained between the adhesion values found after the use of the CLs with tear quality tests, both break-up-time and Schirmer.
Torrent-Burgués, J; Sanz, F
Contact lenses (CLs) are of common use and the biocompatibility, topography and mechanical properties of the used materials are of major importance. The objective of this contribution is to apply the AFM in mode Peak Force to obtain surface topography and mechanical characteristics of un-worn CLs of different materials. One material of hydrogel, two of siloxane-hydrogel and one of rigid gas-permeable were used in the study. The results obtained with different materials have been compared, at a nanoscopic level, and the conclusions are diverse. There is no significant influence of the two environments used to measure the characteristics of the CLs, either water or saline solution. The pHEMA hydrogel CL (Polymacon of Soflens) shows the highest values of roughness, adhesion and elastic modulus. The siloxane-hydrogel CL named Asmofilcon A of PremiO presents the lowest values of mean roughness (Ra), root-mean-square roughness (RMS or Rq), adhesion (Adh) and elastic modulus (Ym), meanwhile the siloxane-hydrogel CL named Lotrafilcon B of Air Optix presents the lowest value of skewness (Rsk) and the rigid gas-permeable CL, named RXD, presents the lowest values of kurtosis (Rku) and maximum roughness (Rmax).
Paradiso, P; Colaço, R; Mata, J L G; Krastev, R; Saramago, B; Serro, A P
In this article, liposome-based coatings aiming to control drug release from therapeutic soft contact lenses (SCLs) materials are analyzed. A PHEMA based hydrogel material loaded with levofloxacin is used as model system for this research. The coatings are formed by polyelectrolyte layers containing liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC + cholesterol (DMPC + CHOL). The effect of friction and temperature on the drug release is investigated. The aim of the friction tests is to simulate the blinking of the eyelid in order to verify if the SCLs materials coated with liposomes are able to keep their properties, in particular the drug release ability. It was observed that under the study conditions, friction did not affect significantly the drug release from the liposome coated PHEMA material. In contrast, increasing the temperature of release leads to an increase of the drug diffusion rate through the hydrogel. This phenomenon is recorded both in the control and in the coated samples. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1799-1807, 2017. © 2016 Wiley Periodicals, Inc.
Björkblom, Benny; Eidet, Jon R; Utheim, Tor P; Ulltveit-Moe, Harald F; Raeder, Sten
Cultured autologous oral mucosal epithelial cells (OMECs) have proven useful in the treatment of ocular surface disorders. This study is the first to investigate the potential of expanding OMEC in a xenobiotic- and serum-free medium using therapeutic contact lenses (CLs) as a substrate and carrier. Porcine OMEC were seeded on laminin-coated lotrafilcon A therapeutic CLs with the density of 8 × 10(4) cells/lens and cultured in a defined serum and xenobiotic-free medium. Confocal immunofluorescence microscopy was used to analyze the following: (1) cellular morphology by using rhodamine-phalloidin staining of F-actin, (2) phenotype by applying antibodies against the progenitor cell marker p63 and the putative stem cell marker ABCG2 and (3) cell viability by using propidium iodide and Hoechst 33342 dual staining. Porcine OMEC attached well to the CLs, and cell-to-cell contacts were evident. After three days in culture, the OMEC displayed a confluent monolayer with uniform cobblestone morphology, whereas stratified cultures with 2-3 layers were formed after six days. No significant difference in expression of p63 was observed after three-day culture (79.4 ± 14.8%) compared with six-day culture (60.3 ± 18.9%). ABCG2 expression in the basal cell layer was 6.3 ± 1.0% and 4.8 ± 1.8% after three- and six-day culture, respectively. The basal layer viability of cultured OMECs was 99.3 ± 0.2% and 82.8 ± 1.1% after three and six days culture, respectively. The use of therapeutic CLs has potential as a substrate and carrier for OMEC cultured in a xenobiotic- and serum-free culture system.
Zheng, Bin; Shen, Lijun; Walker, Maria K; Zhang, Zongduan; Zheng, Jingwei; She, Xiangjun; Zhou, Jing; Xu, Zhaoxia; Chen, Yan
To evaluate the clinical value of rigid gas permeable contact lenses (RGPCLs) in patients with traumatic corneal scarring and address implications of primary corneal repair. Eighteen subjects with a history of corneal laceration were fit with RGPCLs. Scar locations were divided into two zones; each patient was examined using Pentacam. Entering data included uncorrected visual acuity (UCVA), spectacle-corrected visual acuity (SVA), time between injury and RGPCL fitting, location and size of scar, and amount of corneal astigmatism. Follow-up data included RGPCL visual acuity (RGPCLVA), RGPCL-related complications, and dropout characteristics. Visual acuity values were converted to logMAR for analysis. No serious complications occurred. The average time between suture removal and RGPCL fitting was 5.7±5.5 months. Average corneal astigmatism was -3.44±2.09 diopters. One subject had developed corneal ectasia. RGPCLVA was more than 0.1 in three subjects: one experienced primary corneal repair complications, and two subjects (<10 years) developed amblyopia. In both zones, the difference in RGPCLVA outcome between zone I and zone II was not statistically significant (F=0.060, P=0.809). The difference between SVA in zones I and II was found to be statistically significant (F=6.131, P=0.026), as were the differences between SVA and RGPCLVA (F=8.598, P=0.010). The scar size had no significant influence on RGPCLVA, SVA, or UCVA. Four participants (22.2%) were successfully fit. Dropout characteristics included ocular discomfort, inconvenience, parental apprehension, and low motivation. Rigid gas permeable contact lens is an ideal method for evaluating visual potential in patients with traumatic corneal astigmatism. Pentacam examinations of those patients with poor RGPCLVA can help an ophthalmologist find and understand existing problems in suture techniques.
Mousavi, Maryam; Jesus, Danilo A; Garaszczuk, Izabela K; Szczesna-Iskander, Dorota H; Iskander, D Robert
To evaluate the clinical value of non-invasive keratograph tear film breakup time (NIKBUT) in the assessment of pre-corneal and pre-lens tear film quality for prescribing contact lenses (CLs). Forty-six subjects aged 25.5±4.3 (mean±standard deviation) years were recruited. Visual acuity (VA), anterior eye health checks and NIKBUT were evaluated. On the following day, subjects were fitted with a daily Silicon Hydrogel (SiHy) CL in one eye and a Hydrogel (Hy) CL in the other. After four hours one material for both eyes was chosen based on a qualitative analysis which included VA, CL fitting and comfort. Information about the first and the mean NIKBUT was then contrasted against the prescription decision. Thirty-four subjects were fitted with SiHy and twelve with Hy CL. No statistically significant differences were found for both NIKBUT parameters between left and right eye at baseline (p=0.38 and p=0.50, respectively) and post four hours of CL wear (p=0.61 and p=0.06). The chosen lens did not always correspond to longer NIKBUT. In 39.1% and 34.8% of cases (i.e., 18 and 16 out of 46), there was a match between prescription decision and the first and the mean NIKBUT results, respectively. Although there is no evidence whether tear film surface quality measurement has a superior diagnostic values compared to other traditional clinical measures used in practice, NIKBUT measurements have provided additional information that could be of interest during CL fit. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Osuagwu, Uchechukwu L; Ogbuehi, Kelechi C
To assess the transmittance, in the 200-700nm electromagnetic radiation spectrum, by popularly used tinted soft contact lenses (CLs). The spectra transmittances of ultraviolet (UV)-blocking (I Day Acuvue Define, Freshlook ONE DAY) and non-UV-blocking (Durasoft 3, Tutti, and NeoCosmo) tinted soft CLs were tested. The transmittance of each lens, including nine different colors of Freshlook CL was recorded on spectrophotometer, and the data used to also calculate a UV protection factor (PF) for each lens brand tested, with a higher value indicating a higher level of protection. The UV-blocking CLs significantly reduced UVC, UVB & UVA transmission and thereby meet the American National Standards Institution standard for class 2 UV blockers: a maximum of 30% transmittance of UVA and 5% transmittance of UVB wavelengths. In contrast, the Durasoft 3, Tutti, and NeoCosmo CLs demonstrated negligible UV-blockage. The Acuvue Define CL offered the greatest protection from UVC (PF=69) and UVB (PF=55), but with only 35% luminous transmittance, while the Freshlook CL (especially gemstone green) offered the best protection from UVA (PF=24) and showed about 55% translucency. Overall, the UV-blocking CLs performed equally well across the UV spectrum. Different colors of Freshlook CL transmitted statistically and clinically significantly different amounts of visible light but similar amounts of UVR. Freshlook and Acuvue Define CLs which are designated as UV-blockers significantly reduced UVR transmission to safe levels whereas Tutti, NeoCosmo and Durasoft 3 did not. Transmission within the Freshlook CL family was more dependent on color in the visible light spectrum, but not in the UV-spectrum, where the gemstone green performing best among the tested colors. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Sultan, Pinar; Dogan, Cezmi; Iskeleli, Guzin
The purpose of this study was to investigate the efficacy and safety of the Toris K silicone hydrogel contact lens (SwissLens; Prilly, Switzerland) in keratoconus patients. A database with information on 50 keratoconus patients (64 eyes) fitted with Toris K soft contact lenses over a 2-year period was retrospectively reviewed. Demographic data, prefitting refraction, the reason for choosing the Toris K soft contact lens, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best-corrected visual acuity with a rigid gas permeable lens (BCVA RGP), best-corrected visual acuity with the Toris K lens (BCVA Toris K), and complications were evaluated. The mean age ± standard deviation at the time of fitting was 27.92 ± 9.86 years. The mean spherical refractive power was -4.62 ± 6.53 dioptres, and the mean cylinder was -3.78 ± 2.43 dioptres. The most common reason for using Toris K soft contact lenses was an inability to fit the patient with a RGP contact lens. There was a statistically significant difference between UCVA and BCVA Toris K (p = 0.0001), as well as between BSCVA and BCVA Toris K (p = 0.0001). However, there was no statistically significant difference between BCVA Toris K and BCVA RGP (p = 0.20). Superficial punctate keratitis and giant papillary conjunctivitis were the most common complications. The Toris K contact lens is a viable alternative for the optical management of all grades of keratoconus. The Toris K soft contact lens is a promising alternative for the visual rehabilitation of keratoconus patients who cannot tolerate RGP lenses or achieve a good fit.
Engle, Andrew T; Laurent, John M; Schallhorn, Steven C; Toman, Steven D; Newacheck, James S; Tanzer, David J; Tidwell, James L
To compare the efficacy of 2 types of bandage contact lenses (BCLs) after photorefractive keratectomy (PRK). Navy Refractive Surgery Center, Naval Medical Center San Diego, San Diego, California, USA. In this prospective study, 100 patients received PRK in both eyes. Each patient received a BCL composed of etafilcon A (Acuvue [ACV], Vistakon Inc.) (14.0 diameter, 8.4/8.8 base curve) in 1 eye and lotrafilcon A (Focus Night & Day [N&D], Ciba Vision) (13.8 diameter, 8.4/8.6 base curve) in the fellow eye. The patient was masked to the lens type in each eye. The postoperative medication regimen was the same with both lenses. The epithelial defect size and subjective level of discomfort were measured at surgery and daily after surgery until both eyes had reepithelialized and the lenses were removed. The mean epithelial defect size at surgery was similar with both BCLs (ACV 57.07 mm(2) and N&D 57.53 mm(2); P=.422). On postoperative days 1 and 2, the mean defect size was significantly smaller in eyes with the N&D lens (day 1, ACV 21.53 and N&D 18.74; day 2, ACV 3.62 and N&D 2.12) (paired t test, P<.001). On day 1, no eye had completely reepithelialized; on day 2, 20 eyes with N&D lenses and 13 eyes with ACV lenses had. On day 3, 70 eyes with N&D lenses and 66 eyes with ACV lenses had reepithelialized. The mean discomfort index was significantly higher in the eyes with ACV lenses on days 1 and 2 (paired t test, P<.001 and P<.002, respectively). Topical nonpreserved tetracaine was used significantly more often in eyes with ACV lenses on days 1, 2, and 3 (paired t test, P<.001, P<.008, P<.003, respectively). No correlation between the use of tetracaine in the first 24 hours and the rate of reepithelialization was noted (R(2)=0.0025 for ACV and R(2)=0.0003 for N&D). The lotrafilcon A lens resulted in significantly faster corneal reepithelialization and reduced patient discomfort in most patients during the first 48 hours after PRK.
Braga, Mara E M; Costa, Viviana P; Pereira, Mário J T; Fiadeiro, Paulo T; Gomes, Ana Paula A R; Duarte, Catarina M M; de Sousa, Hermínio C
In this work we employed a supercritical solvent impregnation (SSI) process using a scCO(2)+EtOH (5% molar) solvent mixture to impregnate acetazolamide (ACZ) into commercially available silicone-based soft contact lenses (Balafilcon A, Pure Vision, Bausch & Lomb). Contact lenses (SCLs) drug-loading was studied at 40°C and 50°C, and from 15 MPa up to 20 MPa, and using low depressurization rates in order to avoid any harm to SCLs. The effect of impregnation processing time on the loaded ACZ amounts was also studied (1, 2 and 3h). In vitro drug release kinetics studies were performed and the released ACZ was quantified spectrophotometrically. Several analytical techniques were employed in order to characterize the processed and non-processed SCLs in terms of some of their important functional properties. Obtained results demonstrated that ACZ-loaded therapeutic Balafilcon A SCLs can be successfully prepared using the employed SSI process. Furthermore, it was possible to control ACZ loaded amounts and, consequently, to adjust the final ACZ release levels into the desired therapeutic limits, just by changing the employed operational conditions (P, T, processing time and depressurization rate) and without change some of their most important thermomechanical, surface/wettability and optical properties. Obtained soft contact lenses can be potentially employed as combined biomedical devices for simultaneous therapeutic and correction of refractive deficiencies purposes.
Paradiso, Patrizia; Chu, Virginia; Santos, Luís; Serro, Ana Paula; Colaço, Rogério; Saramago, Benilde
Although the plasma technology has long been applied to treat contact lenses, the effect of this treatment on the performance of drug-loaded contact lenses is still unclear. The objective of this work is to study the effect of nitrogen plasma treatment on two drug-loaded polymeric formulations which previously demonstrated to be suitable for therapeutic contact lenses: a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel loaded with levofloxacin and a silicone-based hydrogel loaded with chlorhexidine. Modifications of the surface and the optical properties, and alterations in the drug release profiles and possible losses of the antimicrobial activities of the drugs induced by the plasma treatment were assessed. The results showed that, depending on the system and on the processing conditions, the plasma treatment may be beneficial for increasing wettability and refractive index, without degrading the lens surface. From the point of view of drug delivery, plasma irradiation at moderate power (200 W) decreased the initial release rate and the amount of released drug, maintaining the drug activity. For lower (100 W) and higher powers (300 W), almost no effect was detected because the treatment was, respectively, too soft and too aggressive for the lens materials.
B. O., Ajayi; F.E., Kio; F.D., Otajevwo
Fifty conjunctival swab samples collected from ELISA confirmed HIV/AIDS seropositive patients who were referred to the HIV/AIDS laboratories of the University of Benin Teaching Hospital and Central Hospital both based in Benin City, Nigeria were aseptically cultured on appropriate media by standard methods. The resulting isolates/strains, after identification by standard methods, were tested for their ability to adhere to two hydrophobic non-ionic daily wear silicone hydrogel soft contact lenses (i.e. lotrafilcon B, WC 33% and polymacon, WC 38%) as well as to two hydrophilic ionic conventional extended wear silicone hydrogel soft contact lenses (i.e. methafilcon A, WC 55% and omafilcon A, WC 60%) by the adhesiveness/slime production modified vortex/Robin device method. Evidence of adhesiveness/slime production was indicated by presence of a visible stained film lining the surface of the contact lens which was measured and recorded as strong or weak according to the density of the adhered bacterial film. Fourteen (28.0%) Staphylococcus aureus strains and 10 (20.0%) Pseudomonas aeruginosa strains were obtained among other organisms. Staphylococcus aureus strains adhered in decreasing order to lotrafilcon B (55.4 ± 4.7), polymacon (46.4 ± 8.4), methfilcon A (46.4 ± 8.4) and omafilcon A (25.0 ± 6.4) with no significant difference in adhesive strengths of individual strains (P > 0.05). Pseudomonas aeruginosa strains also recorded decreasing adhesive strengths to lotrafilcon B (37.5 ± 8.2), polymacon (28.6 ± 6.3), methafilcon A (26.8 ± 5.5) and omafilcon A (23.2 ± 5.5) also with no significant difference in adhesive strengths of individual strains (P > 0.05). Attachment strengths of Staph. aureus strains to all four contact lenses were higher than those of Pseudomonas aeruginosa strains. Both organisms adhered most to hydrophobic lotrafilcon B and least to hydrophilic omafilcon A. This invitro adhesion studies revealed that daily wear silicone hydrogel low water
Abbey, Ashkan M; Gregori, Ninel Z; Surapaneni, Krishna; Miller, Darlene
Although manufacturers recommend cleaning ophthalmic lenses with detergent and water and then with a specific disinfectant, disinfectants are rarely used in ophthalmic practices. The aim of this pilot study was to evaluate the efficacy of detergent and water versus that of bleach, a recommended disinfectant, to eliminate common ocular bacteria and viruses from ophthalmic lenses. Three bacterial strains (Staphylococcus epidermidis, Corynebacterium straitum, and methicillin-resistant Staphylococcus aureus and 2 viral strains (adenovirus and herpes simplex virus [HSV] type-1) were individually inoculated onto 20 gonioscopy and laser lenses. The lenses were washed with detergent and water and then disinfected with 10% bleach. All the lenses were cultured after inoculation, after washing with detergent and water, and after disinfecting with the bleach. Bacterial cultures in thioglycollate broth were observed for 3 weeks, and viral cultures were observed for 2 weeks. The presence of viruses was also detected by multiplex polymerase chain reaction (PCR). All 20 lenses inoculated with S. epidermidis, C. straitum, adenovirus, and HSV-1 showed growth after inoculation but no growth after washing with detergent/water and after disinfecting with the bleach. All lenses showed positive HSV and adenovirus PCR results after inoculation and negative PCR results after washing with detergent/water and after disinfecting with bleach. All methicillin-resistant S. aureus-contaminated lenses showed growth after inoculation and no growth after washing with detergent and water. However, 1 lens showed positive growth after disinfecting with bleach. Cleaning with detergent and water seemed to effectively eliminate bacteria and viruses from the surface of contaminated ophthalmic lenses. Further studies are warranted to design practical disinfection protocols that minimize lens damage.
Sheedy, J E; Buri, M; Bailey, I L; Azus, J; Borish, I M
The optical characteristics of the major progressive addition lenses were measured using an automated lensometer with a specially designed lens holder to simulate eye rotation. Measurements were made every 3 degrees (about 1.5 mm) and graphs of isospherical equivalent lines and isocylinder lines were developed. Generally the near zone of these lenses is narrower and lower than in bifocal or trifocal lenses. Distinct differences exist between the various progressive lenses. The width of the near zone, rate of power progression, amount of unwanted cylinder (level with the distance center), and clarity of the distance zone are compared for the various lenses. The optical measurements demonstrate an apparent trade-off between the size of the cylinder-free area of the lens and the amount of the cylinder.
Ruiz-Alcocer, Javier; Madrid-Costa, David; Radhakrishnan, Hema; Ferrer-Blasco, Teresa; Montés-Micó, Robert
The aim of this study was to evaluate ocular aberration changes through different simultaneous vision multifocal contact lenses (CLs). Eighteen young-adult subjects with a mean age of 29.8±2.11 years took part. Changes in accommodative response, spherical aberration (C(4)(0)), horizontal coma (C(3)(1)), vertical coma (C(3)(-1)), and root mean square (RMS) of higher-order aberrations (HOAs, third to sixth orders) were evaluated. Measurements were obtained with a distance-single vision CL and 2 aspheric multifocal CLs of simultaneous focus center-near design (PureVision Low Add and PureVision High Add) for 2 accommodative stimuli (-2.50 and -4.00 D). All measurements were performed monocularly with a Hartmann-Shack aberrometer (IRX-3; Imagine Eyes, Orsay, France). No statistically significant differences were found in accommodative responses to -2.50- and -4.00-D stimuli between the single vision CL and the 2 multifocal CLs. Spherical aberration was found to decrease and become more negative with accommodation for both stimuli with all three CLs. Horizontal coma decreased significantly with accommodation (-2.5- and -4.00-D stimuli) for the distance-single vision CLs (P=0.002 and P=0.003). No differences were found in vertical coma Zernike coefficients. The RMS of HOAs was found to decrease only with the single vision CLs for both stimuli (P<0.01). Data obtained in this study suggest that in young subjects, the multifocal CLs studied do not induce large changes in accommodative response compared with the distance-single vision CLs. Spherical aberration reduced significantly with accommodation.
Compañ, Vicente; Oliveira, Cristina; Aguilella-Arzo, Marcel; Mollá, Sergio; Peixoto-de-Matos, Sofia C; González-Méijome, José M
We defined the theoretical oxygen tension behind modern scleral contact lenses (CLs) made of different rigid gas permeable (RGP) materials, assuming different thickness of the tear layer behind the lens. A second goal was to show clinically the effect of the postlens tear film on corneal swelling. We simulated the partial pressure of oxygen across the cornea behind scleral CLs made of different lens materials (oxygen permeability Dk, 75-200 barrer) and different thickness (Tav, 100-300 μm). Postlens tear film thicknesses (Tpost-tear) ranging from 150 to 350 μm were considered. Eight healthy subjects were fitted randomly with a scleral lens with a thin and a thick postlens tear layer in two different sessions for a period of 3 hours under open-eye conditions. The CLs with less than 125 barrer of Dk and a thickness over 200 μm depleted the oxygen availability at the lens-cornea interface below 55 mm Hg for a postlens tear film of 150 μm. For a postlens tear film thickness of 350 μm, no combination of material or lens thickness will meet the criteria of 55 mm Hg. Our clinical measures of corneal edema showed that this was significantly higher (P < 0.001, Wilcoxon signed ranks test) with the thicker compared to the thinner Tpost-tear (mean ± SD, 1.66 ± 1.12 vs. 4.27 ± 1.19%). Scleral RGP CLs must be comprised of at least 125 barrer of oxygen permeability and up to 200 μm thick to avoid hypoxic effects even under open eye conditions. Postlens tear film layer should be below 150 μm to avoid clinically significant edema. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.
Gomes, Thiago dos Santos; Magnet, Angela; Izquierdo, Fernando; Vaccaro, Lucianna; Redondo, Fernando; Bueno, Sara; Sánchez, Maria Luisa; Angulo, Santiago; Fenoy, Soledad; Hurtado, Carolina; del Aguila, Carmen
Purpose Acanthamoeba keratitis (AK) is a painful and potentially blinding corneal infection caused by Acanthamoeba spp. In Madrid, environmental studies have demonstrated a high presence of these free-living amoebae in tap water. Since most of AK cases occur in contact lenses (CL) wearers with inadequate hygiene habits, the presence of Acanthamoeba in discarded CL has been studied and compared with other common etiological agents of keratitis, such as Pseudomonas aeruginosa and Staphylococcus aureus. Methods One hundred and seventy-seven healthy individuals from Madrid contributed their discarded CL and answered a questionnaire on hygiene habits. DNA was extracted from the CL solution and analyzed by real-time PCR for Acanthamoeba, Pseudomonas aeruginosa and Staphylococcus aureus. These CL and their solutions were also cultured on non-nutrient agar to isolate Acanthamoeba. Results Among the 177 samples, Acanthamoeba DNA was detected in 87 (49.2%), P. aeruginosa DNA in 14 (7.9%) and S. aureus DNA in 19 (10.7%). Cultivable amoebae, however, were observed in only one sample (0.6%). This isolate was genotyped as T4. The habits reported by this CL owner included some recognized risk factors for AK, but in this study only the practice of “not cleaning the CL case” presented some statistical significant association with Acanthamoeba DNA presence. Detection of the investigated bacterial DNA did not demonstrate statistical significant association with the studied practices, but the presence of P. aeruginosa revealed a possible inhibition of Acanthamoeba in these samples. Conclusions The PCR results suggest a high presence of Acanthamoeba spp. in healthy CL wearers from Madrid, but we can assume that CL solutions are properly disinfecting the CL since only 1.1% of the positive PCR samples correspond to viable amoebae and, after four years, only one participant reported stronger ocular problems. Nevertheless, more studies are necessary to corroborate this hypothesis. PMID
Artigas, José M; Navea, Amparo; García-Domene, M Carmen; Gené, Andrés; Artigas, Cristina
To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)). The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer. Five of the nine soft CLs analysed state that they incorporate UV filters, but the other four do not specify anything in this regard. The spectral transmission of all the CLs studied is excellent in the visible region. The CLs with UV filters filter out this radiation more or less effectively. Xe lamps emit a part in the UV region. Incandescent, fluorescent and white LEDs do not emit at all in the UV. Incorporating UV filters is important when the illumination is from a Xe lamp since this light source emits in the UV region. This, however, does not occur with incandescent and fluorescent lamps or white LEDs. The CLs that do incorporate UV filters meet all the standard requirements that the U.S. FDA (Food and Drug Administration) has for UV-blocking CLs Class II (OcularScience, CooperVision and Neolens), and AcuvueMoist and HydronActifresh400 even comply with the stricter Class I. The CLs without UV filters let UVA, UVB and even some UVC through. Copyright © 2015. Published by Elsevier Ltd.
Inamoto, Yoshihiro; Sun, Yi-Chen; Flowers, Mary E. D.; Carpenter, Paul A.; Martin, Paul J.; Li, Peng; Wang, Ruikang; Chai, Xiaoyu; Storer, Barry E.; Shen, Tueng T.; Lee, Stephanie J.
To examine safety and efficacy of bandage soft contact lenses (BSCLs) for ocular chronic graft-versus host disease (GVHD), we conducted a phase II clinical trial. Extended-wear BSCLs were applied under daily topical antibiotics prophylaxis. Patients completed standardized symptom questionnaires at enrollment and at 2 weeks, 4 weeks and 3 months afterwards. Ophthalmologic assessment was performed at enrollment, at 2 weeks and afterwards as medically needed. Assessments at follow-up were compared with baseline by paired t-test. Nineteen patients with ocular GVHD who remained symptomatic despite conventional treatments were studied. The mean Lee eye subscale score was 75.4 at enrollment, and improved significantly to 63.2 at 2 weeks (p=0.01), to 61.8 at 4 weeks (p=0.005) and to 56.3 at 3 months (p=0.02). The ocular surface disease index score and 11-point eye symptom ratings also improved significantly. According to the Lee eye subscale, clinically meaningful improvement was observed in 9 patients (47%) at 2 weeks, in 11 (58%) at 4 weeks and in 9 (47%) at 3 months. Visual acuity improved significantly at 2 weeks compared with enrollment values. Based on slit lamp exam at 2 weeks, punctate epithelial erosions improved in 58% of the patients, showed stability in 16% and worsened in 5%. No corneal ulceration or ocular infection occurred. BSCLs are a widely available, safe and effective treatment option that improves manifestations of ocular graft-versus host disease in approximately 50% of patients. This study was registered at www.clinicaltrials.gov as NCT01616056. PMID:26189353
Luensmann, Doerte; Yu, Mili; Yang, Jeffery; Srinivasan, Sruthi; Jones, Lyndon
To evaluate the impact of cosmetics on silicone hydrogel (SiHy) contact lens shape, lens power, and optical performance. In this in vitro experiment, 7 SiHy materials were coated with 9 marketed brands of cosmetics, including hand creams (HCs) (3), eye makeup removers (MRs) (3), and mascaras (3). Diameter, sagittal depth, and base curve were determined using the Chiltern (Optimec Limited), whereas lens power and optical performance were assessed using the Contest Plus (Rotlex). Six replicates were used for each lens and cosmetic combination. Measurements were repeated after a cleaning cycle using a one-step hydrogen peroxide solution. Makeup removers had the greatest impact on diameter, sagittal depth, and base curve, resulting in changes of up to 0.5, 0.15, and 0.77 mm, respectively. The HCs and mascaras had little impact on these parameters; however, differences were observed between lens types. Optical performance was reduced with all mascaras, and a decrease of greater than 2 units on a 0 to 10 scale (10=uniform power distribution) was seen for 5 lens types exposed to waterproof mascara (P<0.01). Most HCs and MRs had minimal impact on image quality. Lens power did not change with any of the cosmetics (± 0.25 diopter; P>0.05). Lens cleaning resulted in some recovery of the lens parameters, and efficiency varied between cosmetics. Some eye MRs and waterproof mascaras changed the shape and optical performance of some SiHy lenses. Further research is needed to understand the clinical implications for SiHy lens wearers using cosmetics.
Madrid-Costa, David; Ruiz-Alcocer, Javier; Radhakrishnan, Hema; Ferrer-Blasco, Teresa; Montés-Micó, Robert
To evaluate induced changes in pupil and accommodative response for different accommodative stimuli with three different multifocal contact lenses (CLs). Accommodative and pupil responses with three aspheric multifocal CLs of simultaneous focus center near (PureVision Low Add, PureVision High Add and Focus Progressives) for two accommodative stimuli of -2.5 and -4.00 D were recorded in 10 young subjects. Accommodative response, peak velocity, and time constant of accommodation and pupil constriction were assessed. The measurements were evaluated in all the participants with distance-single vision CLs and with the three multifocal CLs. The monocular measurements were performed in a random sequence for each participant. All parameters were measured with a Hartmann-Shack aberrometer (IRX-3; Imagine Eyes, Orsay, France). Differences were not found in accommodation response for both accommodative stimuli studied between the single vision lens and the three different multifocal CLs (p > 0.05 for both stimuli). For the 2.5 D stimulus, significant differences were not found in peak velocity and time constant between the single vision lens and the three different multifocal CLs (p > 0.05 for all situations); in amplitude of pupil constriction, differences were only found for the situation with PureVision High Add, where the value was lower than the single vision lens (p = 0.015). For the 4.00 D stimulus, differences with single vision lens in peak of velocity and time constant were only found with PureVision Low Add, where the peak velocity value was higher and the time constant was lower (p = 0.024 and p = 0.032 for peak of velocity and time constant, respectively); for amplitude of pupil constriction differences were not found (p > 0.05). Data obtained in this pilot study suggest that in young observers, the multifocal CLs studied do not induce large changes in accommodative system compared with the single vision lens.
El Ameen, A; Majzoub, S; Pisella, P-J
Starting at 40 years of age, prespyopia affects a quarter of the world population. Many techniques of presbyopia surgery have emerged in recent years. The purpose of this study was to compare monovision and multifocality and to identify clinical and electrophysiological predictive markers of visual comfort for each correction available in clinical practice. Ten presbyopic patients participated in this study. Patients received monovision and multifocal correction using contact lenses for three weeks each in a random order. A clinical evaluation (visual acuity, TNO test, binocular contrast sensitivity and quality of vision questionnaires) and an electrophysiological evaluation (monocular and binocular pattern VEP with multiple spatial frequencies: 60, 30 and 15') were performed before and after each correction modality. The P100 was significantly wider and slightly earlier after binocular compared to monocular stimulation at T0. The TNO stereopsis score decreased significantly after correction. No other significant differences, either on clinical or electrophysiological criteria, were found between the two modes of correction. Several significant correlations were found between the stereoacuity difference depending upon correction and evoked potentials by binocular pattern at T0. The larger the stereoacuity difference (better stereoacuity with multifocal compensation), the longer the latency of the P100 using 60' checks (R=0.82; P=0.004) and the greater the amplitude of the N75 using 30' (R=0.652; P=0.04). Our study found no differences between the 2 types of correction, but it highlights a benefit of VEP used in current practice and measurement of the P100 wave, the best indicator of stereopsis and the most consistent, to predict visual comfort after compensation presbyopia.
Lafay-Cousin, Lucie . E-mail: email@example.com; Millar, Barbara-Ann; Mabbott, Donald; Spiegler, Brenda; Drake, Jim; Bartels, Ute; Huang, Annie; Bouffet, Eric
Purpose: To report the incidence, characteristics, treatment, and outcomes of bifocal germinomas treated with chemotherapy followed by focal radiation. Methods and Materials: This was a retrospective review. Inclusion criteria included radiologic diagnosis of bifocal germinoma involving the pineal and neurohypophyseal region, no evidence of dissemination on spinal MRI, negative results from cerebrospinal fluid cytologic evaluation, and negative tumor markers. Results: Between 1995 and 2004, 6 patients (5 male, 1 female; median age, 12.8 years) fulfilled the inclusion criteria. All had symptoms of diabetes insipidus at presentation. On MRI, 4 patients had a pineal and suprasellar mass, and 2 had a pineal mass associated with abnormal neurohypophyseal enhancement. All patients received chemotherapy followed by limited-field radiation and achieved complete remission after chemotherapy. The radiation field involved the whole ventricular system (range, 2,400-4,000 cGy) with or without a boost to the primary lesions. All patients remain in complete remission at a median follow-up of 48.1 months (range, 9-73.4 months). Conclusions: This experience suggests that bifocal germinoma can be considered a locoregional rather than a metastatic disease. Chemotherapy and focal radiotherapy might be sufficient to provide excellent outcomes. Staging refinement with new diagnostic tools will likely increase the incidence of the entity.
Beattie, Tara K; Tomlinson, Alan; McFadyen, Angus K; Seal, David V; Grimason, Anthony M
To establish if silicone hydrogel (S-H) contact lenses could be a risk factor for Acanthamoeba infection by facilitating the attachment of trophozoites to their surface and transfer to the cornea and to determine the effect Acanthamoeba culture technique, patient wear, and Pseudomonas biofilm coating have on attachment to the S-H lens. Experimental material study. Attachment to a S-H lens was compared with that of a conventional hydrogel control lens. Sixteen replicates were carried out for both lens types under each test condition. Unworn S-H (PureVision; Bausch & Lomb, Kingston-Upon-Thames UK) and conventional hydrogel (Acuvue; Vistakon, Johnson & Johnson, Jacksonville, FL USA) lens quarters were incubated for 90 minutes in suspensions of liquid or plate-cultured Acanthamoeba castellanii trophozoites. Unworn, worn, and Pseudomonas biofilm coated S-H and hydrogel quarters were incubated for 90 minutes with plate-cultured trophozoites. Trophozoites attached to one surface of each lens quarter were counted by direct light microscopy. Logarithmic transformation of data allowed the use of a parametric analysis of variance. Lens polymer had a significant effect on attachment (P < 0.001), with higher numbers of trophozoites attaching to the S-H lens. Culture technique also had a significant effect on attachment (P = 0.013), with higher numbers of liquid-cultured organisms attaching to both lens types. A significant increase in attachment was demonstrated with worn and Pseudomonas biofilm-coated hydrogel lenses (P < 0.001); however, this difference was not seen with the S-H lens. Acanthamoebal attachment to the S-H lenses was significantly greater than to the conventional hydrogel. Liquid-cultured trophozoites demonstrated a higher affinity for the lenses tested. Wear and bacterial biofilm coating had no effect on attachment to S-H lenses. The increased attachment found with the S-H lens may be an inherent characteristic of the polymer or a side effect of the surface
Afzha, Rooh; Chatterjee, Anirban; Subbaiah, Shobha Krishna; Pradeep, Avani Rangaraju
Background: Ultrasonic scaler is a preferential treatment modality among the clinicians. However, the aerosol/splatter generated is a concern for patients and practitioners. Therefore, the purpose of this study was to evaluate contamination of contact lenses of the dentist after scaling and root planing using ultrasonic scalers with and without protective eyewear. Materials and Methods: Thirty patients were randomly selected for scaling and root planing and divided into 2 groups of 15 each. Group A – dentist wearing contact lenses and protective eyewear. Group B - dentist wearing only contact lenses. After scaling and root planing using ultrasonic scalers, the lenses were subjected to culture and 16S rRNA (16S ribosomal RNA) gene sequencing. Results: In Group A – 15 out of thirty samples were contaminated, in Group B – all the thirty samples were contaminated. Most of the samples showed Gram-positive bacteria and 5 samples were contaminated with fungi. 16S rRNA gene sequencing of forty contaminated samples showed that 31 were contaminated with Streptococcus mutans and 9 with Staphylococcus aureus. Conclusion: Keeping in mind the limitation of the study for the absence of negative control, we would like to conclude that dental practitioners should better avoid contact lenses in a dental setup because of the risk of contamination of the contact lenses from the various dental procedures which can produce aerosol/splatter and if worn, it is recommended to wear protective eyewear. PMID:27563200
Ahn, Jeong-Taek; Jeong, Man-Bok; Park, Young-Woo; Kim, Se-Eun; Ahn, Jae-Sang; Lee, Yes-Ran; Lee, Eui-Ri; Seo, Kangmoon
To compare and evaluate the accuracy of intraocular pressure (IOP) measured through a therapeutic contact lens, using applanation (TonoPen XL(®)) and rebound (TonoVet(®)) tonometers in enucleated dog eyes. A total of 30 enucleated eyes from 15 beagle dogs. To measure accurate IOP, the anterior chamber of each enucleated eye was cannulated with two 26-gauge needles and two polyethylene tubes were connected vertically to an adjustable reservoir bag of normal saline and a pressure transducer. IOP was measured by the TonoPen XL(®) followed by the TonoVet(®) without a contact lens. After a contact lens was applied to the cornea, IOP was re-measured in the same order. Three consecutive IOP measurements were performed using both tonometers. Without the contact lens, the IOP values obtained by both tonometers correlated well according to the regression analysis (TonoVet(®): γ(2) = 0.98, TonoPen XL(®): γ(2) = 0.97, P < 0.001). The TonoPen XL(®) consistently underestimated values as transducer IOP increased; however, IOP values measured with the TonoPen XL(®) were in close agreement and were less variable than those determined with the TonoVet(®) when a contact lens was applied to the cornea. Bland-Altman analysis was used to determine the lower and upper limits of agreement (TonoVet(®): -29.7 and +21.1 mmHg, TonoPen XL(®): -3.9 and +3.6 mmHg) between the two devices. This study suggests that the TonoPen XL(®) is a useful tonometer for dogs wearing therapeutic contact lenses, and importantly, contact lenses would not need to be removed prior to IOP measurement. © 2012 American College of Veterinary Ophthalmologists.
Background The contaminated contact lens provides Pseudomonas aeruginosa an ideal site for attachment and biofilm production. Continuous contact of the eye to the biofilm-infested lens can lead to serious ocular diseases, such as keratitis (corneal ulcers). The biofilms also prevent effective penetration of the antibiotics, which increase the chances of antibiotic resistance. Methods For this study, 22 Pseudomonas aeruginosa isolates were obtained from 36 contact lenses and 14 contact lens protective fluid samples. These isolates were tested against eight commonly used antibiotics using Kirby-Bauer disk diffusion method. The biofilm forming potential of these isolates was also evaluated using various qualitative and quantitative techniques. Finally, a relationship between biofilm formation and antibiotic resistance was also examined. Results The isolates of Pseudomonas aeruginosa tested were found resistant to most of the antibiotics tested. Qualitative and quantitative biofilm analysis revealed that most of the isolates exhibited strong biofilm production. The biofilm production was significantly higher in isolates that were multi-drug resistant (p < 0.0001). Conclusion Our study indicates that multi-drug resistant, biofilm forming Pseudomonas aeruginosa isolates are mainly involved in contact lens associated infections. This appears to be the first report from Pakistan, which analyzes both antibiotic resistance profile and biofilm forming potential of Pseudomonas aeruginosa isolates from contact lens of the patients with contact lens associated infections. PMID:24134792
Hart, D E; Plociniak, M P; Grimes, G W
Historically, biochemical studies of the interaction between tears and hydrogel contact lenses have not been coordinated with the study of the morphological ultrastructure of the phenomena. Moreover, terms that have distinct and different meanings--pellicle, coating, deposit, and biofilm--have been used interchangeably and often incorrectly when applied within the context of the general field of contact lens biotechnology to describe the tear-polymer interaction. We describe our elucidation of morphological and elemental characteristics of the normal pellicle that forms on the lens surface and urge standard use of the word "pellicle" to specify this entity. Fourteen worn hydrogel lenses (8 Group 1 and 6 Group 4 lenses according to the FDA classification) were rinsed, quartered, and fixed or dried, depending on the analysis to be performed. Scanning electron microscopy (SEM) was used to examine the morphology of the pellicle and quantify its thickness. X-ray analysis was used to detect elements associated with the anterior, central, and posterior portions of the lenses and their relative distribution. A distinctive morphological pellicle ranging from 0.1 to 8.6 microns was present on 12 of the 14 lenses. The pellicle was thicker on the Group 4 lenses than on the Group 1 lenses (P < 0.003). However, the pellicle on Group 1 lenses became thicker with increasing lens age (P < 0.02), but not as thick as on Group 4 lenses. Morphologically distinct lipid or jelly bump deposits were observed at the surface of both lenses from a single patient wearing 2 week old Group 4 lenses. Eleven lenses had sulfur-bearing tear components on the anterior zone. Sulfur was deposited within the matrix of nine lenses. The sulfur containing moieties were more prevalent on Group 4 lenses (P < 0.002). More sulfur was assayed on older lenses (P < 0.004). The anterior lens zone had more sulfur-bearing tear components than did the posterior or center zones (P < 0.05). The physiologically normal
Zhang, Wenji; Zu, Dongni; Chen, Jianting; Peng, Junjie; Liu, Yun; Zhang, Hefeng; Li, Sanming; Pan, Weisan
Postcataract endophthalmitis treatment through eye drops is of low corneal bioavailability and short residence time. The dominant NSAIDs therapy also suffers from severe ocular irritancy and low patients compliance. This study dispersed bovine serum albumin (BSA) coated meloxicam (MX) nanocrystals encapsulating nanoaggregates (BSA-MX-NA) in contact lenses to reduce drug ocular irritancy and increased drug release duration. The BSA-MX-NA (∼100 nm) were prepared using acid-base neutralization in aqueous solutions and were dispersed in poly(hydroxylethyl methacrylate) gels, which are common contact lens materials. Drug release studies showed that the gels released the drug for about 5 days. The proposed drug transport mechanism is a diffusion process which can be described by the Ritger-Peppas model with the diffusional exponent n of 0.4768. The drug release can be affected by the gel thickness and the cross-linking degree. A 400 micro thick gels with 100 μL cross-linker TEGDMA leads to an adequate meloxicam release for therapeutic application. The ocular irritation studies showed that BSA-MX-NA loaded p-HEMA gels are significantly less irritating to the ocular tissues as compared to marketed MX solutions. The developed contact lenses loaded with BSA-MX-NA could be very useful for extended delivery in postcataract endophthalmitis treatment. Copyright © 2014 Elsevier B.V. All rights reserved.
Ali, Maryam; Horikawa, Shin; Venkatesh, Siddarth; Saha, Jishnu; Hong, Jong Wook; Byrne, Mark E
Zero-order or concentration independent release kinetics are highly desirable from drug delivery devices. In this paper we demonstrate experimentally, for the first time, zero-order release of a small molecular weight therapeutic, ketotifen fumarate (MW=425), from molecularly imprinted hydrogels used as therapeutic contact lenses. We performed dynamic, in vitro drug release studies from imprinted hydrogel contact lenses within a novel microfluidic device that simulates the volumetric flow rates, tear volume and tear composition of the eye. Imprinted gels with multiple functional monomers and complexation points to the drug demonstrated a significantly delayed release of drug compared to less functionalized systems. There were no statistical differences in experimentally determined equilibrium swollen polymer volume fractions, which correlate with molecular weight between crosslinks and mesh size of the gel. Under infinite sink conditions, imprinted contact lenses demonstrated Fickian (concentration dependent) release kinetics with diffusion coefficients ranging from 4.04 x 10(-9) to 5.57 x 10(-10) cm(2)/s. The highest functionalized gel exhibited a diffusion coefficient averaging ten times smaller than less functionalized gels and released drug for over 5 days with 3 distinct rates of release. Under physiological volumetric flow rates, the release rate was constant for a duration of 3.5 days delivering a therapeutically relevant dosage and was fit to a power law model indicating zero-order release characteristics with n=0.981+/-0.006 (r(2)=0.997). This work demonstrates the potential of micro/nanofluidic devices to determine physiological release rates and stresses the importance of matching local conditions to adequately characterize drug delivery devices. It also demonstrates the enormous potential for molecular imprinting to further tailor therapeutic release kinetics via the imprinting process.
Maulvi, Furqan A; Shaikh, Anjum A; Lakdawala, Dhara H; Desai, Ankita R; Pandya, Mihir M; Singhania, Sulabh S; Vaidya, Rutvi J; Ranch, Ketan M; Vyas, Bhavin A; Shah, Dinesh O
Contact lenses are widely used for ophthalmic drug delivery, but incorporation of drug or formulation in the contact lenses affects its optical and physical property. In the present study, we have designed a novel hyaluronic acid (HA)-laden ring implant contact lenses (modified cast moulding method), to circumvent the changes in critical lens property. The objective was to improve the ocular residence time of HA, by providing sustained ocular HA delivery through implant contact lenses for the treatment of dry eye syndrome. Optimization of HA-implant was carried out using 3(2) factorial design by tailoring the amount of cross linker and thickness of implant, to achieve sustained HA release with constraint on effective ion diffusivity. The in vivo pharmacokinetic study in rabbit tear fluid showed sustained HA release up to 15days, by fabricating implant (80μgHA loading) with 78.4μm thickness (total thickness of lens=100μm) using 0.925% of cross linker, with effective ion diffusivity>1.5×10(-6)mm(2)/min. In vivo efficacy study in benzalkonium chloride induced dry eye syndrome rabbits showed faster healing with implant contact lenses in comparison to positive control group. The study demonstrated the promising potential of implantation technology to deliver hyaluronic acid without compromising optical and physical properties of contact lens.
Cowell, B A; Willcox, M D; Schneider, R P
Adhesion of bacteria to hydrogel lenses is thought to be an initial step of ocular colonization allowing evasion of normal host defences. The salt concentration of media is an important parameter controlling microbial adhesion. Salinity varies from 0.97% NaCl equivalents in the open eye to 0.89% in the closed eye state. In this study, the effect of sodium chloride in the concentration range of 0.8-1.0% (w/v) NaCl on adhesion of ocular bacteria to soft contact lenses was investigated using a static adhesion assay. Pseudomonas aeruginosa was found to adhere to lenses in significantly greater amounts than Serratia marcescens, Flavobacterium meningosepticum, Stenotrophomonas maltophilia and Staphylococcus intermedius. Increasing NaCl from 0.8% to 1.0% (w/v) increased adhesion of all bacteria tested. This adhesion was strong since the organisms could not be removed by washing in low ionic buffer. Adhesion of these organisms did not correlate with their cell surface properties as determined by bacterial adhesion to hydrocarbons (BATH) and retention on sepharose columns.
Calatayud, Arnau; Ferrando, Vicente; Remón, Laura; Furlan, Walter D; Monsoriu, Juan A
Optical vortex beams, generated by Diffractive Optical Elements (DOEs), are capable of creating optical traps and other multi-functional micromanipulators for very specific tasks in the microscopic scale. Using the Fibonacci sequence, we have discovered a new family of DOEs that inherently behave as bifocal vortex lenses, and where the ratio of the two focal distances approaches the golden mean. The disctintive optical properties of these Fibonacci vortex lenses are experimentally demonstrated. We believe that the versatility and potential scalability of these lenses may allow for new applications in micro and nanophotonics.
Alfonso, José F; Fernández-Vega, Luis; Baamonde, M Begoña
To assess the efficacy and safety of implanting a bifocal diffractive intraocular lens (IOL) using the piggyback technique to provide pseudoaccommodation. Instituto Oftalmológico Fernández-Vega, Oviedo, Spain. This prospective noncomparative case series included 6 pseudophakic emmetropic patients who had a monofocal IOL implanted in the capsular bag. All eyes had secondary piggyback Acri. Twin bifocal diffractive IOL (Acri.Tec) implantation in the ciliary sulcus to provide pseudoaccommodation. Contralateral implantation of 1 Acri. Twin near-weighted 733D IOL in the nondominant eye and 1 Acri. Twin distance-weighted 737D IOL in the dominant eye was performed. Monocular and binocular best distance-corrected visual acuity and distance-corrected near visual acuity were evaluated 6 months after surgery. The mean binocular best distance-corrected visual acuity and distance-corrected near visual acuity were -0.080 +/- 0.056 logMAR and -0.016 +/- 0.037 logMAR, respectively. There were no statistically significant differences in binocular best distance-corrected acuity after the piggyback IOL implantation (P>.01). The differences between monocular and binocular visual acuity were the result of the distance- and near-weighted light distribution of the Acri. Twin IOLs. All IOLs were well centered with no tilt. Two eyes had pupillary capture of the optic. The Acri. Twin bifocal diffractive IOL implanted in the ciliary sulcus using the piggyback technique provided pseudoaccommodation in emmetropic pseudophakic eyes. Binocular implantation of these IOLs should be performed considering the differences in light distribution of the distance-weighted IOL and the near-weighted IOL models.
blepharitis and coated lenses. 1...- Suspension and attrition In accordance with accepted clinical practice and the terms of the approved research protocol...conjunctivitis 6 0 Neovascularization (>2mm) 3 3 Decreased visual acuity (>7 days duration) 2 0 Blepharitis 1 0 Corneal staining 1 0 Corneal stromal infiltrates 0...Phlyetenule-- -- --- - - Corneal stromal infilt -- ---------- Blepharitis -- --- -- - -- - - Corneal ulcer-- ----- -- 1691 % V SS -U Si’..~ 4
Monti, Patrizia; Simoni, Rosa
The role played by water in the molecular structure and properties of commercial soft contact lenses (hydrogels) based on poly 2-hydroxyethyl methacrylate (PHEMA) or poly vinylpyrrolidone (PVP) was investigated by means of vibrational spectroscopy and thermal analyses. The results of this study show that the materials having the greatest water percentage have elastic properties closer to those of the ocular tissues with which they come into contact. Water interacts by hydrogen bonding with the hydrophilic groups present in the polymers, and the strength of this interaction depends on the type of hydrophilic group involved. Moreover, in the case of PVP materials, water also modifies the conformation of the hydrophobic groups. The arrangement of surface water molecules can explain the different adhesion capability of Staphilococcus aureus on this type of lens depending on the water content. In connection with this, a simple model is presented. The water molecules present in the hydrogel structures completely exchange with those of the biological environment. A quantitative analytical method for evaluating the amount of water in commercial lenses by means of Raman spectroscopy is reported.
Holden, B A; Sweeney, D F; La Hood, D; Kenyon, E
The edema response over a 24-hour sleep/wake cycle of ten subjects wearing a rigid gas-permeable (RGP) lens in one eye and a hydrogel lens in the other was evaluated. Lenses that result in equivalent amounts of overnight edema were selected. There was no significant difference in the rates of deswelling during the initial hour. However, at three and five hours after eye opening, the amount of residual edema was greater in the eye wearing the hydrogel lens. We suggest that when an RGP lens provides the same closed-eye level of oxygen as a hydrogel lens, the greater tear exchange of the RGP lens will result in a greater open-eye oxygen supply, leading to less daytime edema. This suggests that the more complete deswelling we observed with RGP lenses can be attributed to a lower stimulus to open-eye swelling. Biomicroscopy, subjective vision, and patient comfort were also rated on waking and ten hours after eye opening. On eye opening there was significantly more back-surface debris (P = 0.01) with the RGP lenses. Patients wearing RGPs rated comfort as poorer and vision as better but only the latter attained statistical significance.
Dominguez-Godinez, Carmen Olalla; Martin-Gil, Alba; Carracedo, Gonzalo; Guzman-Aranguez, Ana; González-Méijome, José Manuel; Pintor, Jesús
Purpose To evaluate the possible use of soft contact lenses (CL) to improve the secretagogue role of diadenosine tetraphosphate (Ap4A) promoting tear secretion. Methods Two conventional hydrogel CL (Omafilcon A and Ocufilcon D) and two silicone hydrogel (SiH) CL (Comfilcon A and Balafilcon A) were used. Ap4A was loaded into the lenses by soaking in a 1 mM Ap4A solution during 12 h. In vitro experiments were performed by placing the lenses in multi-wells during 2 h containing 1 ml of ultrapure water. 100 μl aliquots were taken at time zero and every minute for the first 10 min, and then every 15 min. In vivo experiments were performed in New Zealand rabbits and both the dinucleotide release from SiH and tear secretion were measured by means of Schirmer strips and high-pressure liquid chromatography (HPLC) analysis. Results Ap4A in vitro release experiments in hydrogel CL presented a release time 50 (RT50) of 3.9 ± 0.2 min and 3.1 ± 0.1 min for the non-ionic and the ionic CL, respectively. SiH CL released also Ap4A with RT50 values of 5.1 ± 0.1 min for the non-ionic and 2.7 ± 0.1 min for the ionic CL. In vivo experiments with SiH CL showed RT50 values of 9.3 ± 0.2 min and 8.5 ± 0.2 min for the non-ionic and the ionic respectively. The non-ionic lens Ap4A release was able to induce tear secretion above baseline tear levels for almost 360 min. Conclusion The delivery of Ap4A is slower and the effect lasts longer with non-ionic lenses than ionic lenses.
Pescosolido, Nicola; Casciani, Lorena
In this paper, the chemical-physical interactions between two commercially available ophthalmic solutions and hydrogel contact lenses classified according to the four Food and Drug Administration groups were studied by measuring transversal relaxation times (T(2)) of water molecules by low-field nuclear magnetic resonance techniques. The aim was to evaluate possible modifications to the contact lens structure, with particular emphasis on their hydration mechanism. No significant variations in the T(2) values were observed when the T(2) values of the first component of samples swollen with saline solution as the reference were compared with samples of the same set of lenses swollen in the two commercially available ophthalmic solutions. We can, therefore, assume that the hydration characteristics remained unchanged in all the samples studied, and that the experimental ophthalmic solutions ensured an adequate hydration of the sample hydrogel contact lenses without any negative effects on the structure of their polymer chains.
Bietti, G B; De Caro, G; Giraldi, J P; Romani, E
Research has been performed, both experimentally and clinically, to establish the value of the association of soft contact lenses and some types of eye drops. The use of soft contact lenses with eye drops may be useful in some special cases: a) more prolonged and more sustained effect compared with the usual way of administration of eye drops (especially antiglaucomatous substances, antimetabolites, mydriatics); b) possibility of reducing the concentration to avoid local discomfort or systemic side-effects, without loss of their effectiveness on the eye conditions to be treated. The combined use of soft lenses (12.5-15 mm in diameter) with eye drops may be obtained either by presoaking the lens in the liquid or by regular instillation of eye drops after insertion of the lens; the two techniques may of course be associated. In the present research the advantages of utilizing hydrophylic lenses with osmotically active substances, to obtain a better and more protracted dehydration of the cornea, were first examined, in vitro and in vivo. The following substances were tested: 10% propylenglycol, 10% glycerol, 10% glucose and 5% natrium chloride. The clearing effect of the different types of treatment was evaluated in 45 patients with edematous bullous keratopathy with an instrument which measured the infrared light emitted by an optic fiber and reflected by the cornea. The effects were more marked for the epithelial than for the stromal oedema. Another group of investigations was performed with two polypeptides with high molecular weight: Eledoisin, extracted from a mediterranean octopus, Eledone moschata, and Physalaemin, extracted from the skin of a south american batrachian, Physalaemus fuscomaculatus, both of these stimulate the lacrimal secretion and were previously successfully employed topically by the authors against keratoconjunctivitis sicca. The increase of the amount of fluid was however short-lived. Eledoisin at a concentration of 200 mug/ml, was examined
Bakaraju, Ravi C; Ehrmann, Klaus; Falk, Darrin; Ho, Arthur; Papas, Eric
A bench-top physical model eye that closely replicates both anatomical and optical properties of an average human eye was designed and constructed. The cornea was sourced from a flouro-polymer with refractive index (RI) of 1.376 and crystalline lenses were made of Boston RGP polymers, EO and Equalens II, with an equivalent RI of 1.429 and 1.423 respectively. These materials served to make crystalline lens components of different age groups and accommodative states. De-Ionized water, with RI of 1.334 represented both aqueous and vitreous humor. The complementary metal-oxide sensor of a PixelLink digital camera with a resolution of 5MP and a 2.2 microm pixel pitch, hosted on a motor-base, served as the 'acting' retina. The translation and rotary functions of the motor-base facilitated the simulation of different states of ametropia and assessment of peripheral visual function, respectively. We validated one of its configurations to suit normal viewing conditions and results from the on and off-axis optical quality measurements are presented. As a demonstration of potential practical uses, several corrective soft contact lenses were placed on the model eye and their optical performance evaluated.
Korogiannaki, Myrto; Zhang, Jianfeng; Sheardown, Heather
Discontinuation of contact lens wear as a result of ocular dryness and discomfort is extremely common; as many as 26% of contact lens wearers discontinue use within the first year. While patients are generally satisfied with conventional hydrogel lenses, improving on-eye comfort continues to remain a goal. Surface modification with a biomimetic, ocular friendly hydrophilic layer of a wetting agent is hypothesized to improve the interfacial interactions of the contact lens with the ocular surface. In this work, the synthesis and characterization of poly(2-hydroxyethyl methacrylate) surfaces grafted with a hydrophilic layer of hyaluronic acid are described. The immobilization reaction involved the covalent attachment of thiolated hyaluronic acid (20 kDa) on acrylated poly(2-hydroxyethyl methacrylate) via nucleophile-initiated Michael addition thiol-ene "click" chemistry. The surface chemistry of the modified surfaces was analyzed by Fourier transform infrared spectroscopy-attenuated total reflectance and X-ray photoelectron spectroscopy. The appearance of N (1s) and S (2p) peaks on the low resolution X-ray photoelectron spectroscopy spectra confirmed successful immobilization of hyaluronic acid. Grafting hyaluronic acid to the poly(2-hydroxyethyl methacrylate) surfaces decreased the contact angle, the dehydration rate, and the amount of nonspecific sorption of lysozyme and albumin in comparison to pristine hydrogel materials, suggesting the development of more wettable surfaces with improved water-retentive and antifouling properties, while maintaining optical transparency (>92%). In vitro testing also showed excellent viability of human corneal epithelial cells with the hyaluronic acid-grafted poly(2-hydroxyethyl methacrylate) surfaces. Hence, surface modification with hyaluronic acid via thiol-ene "click" chemistry could be useful in improving contact lens surface properties, potentially alleviating symptoms of contact lens related dryness and discomfort during
Cherepnin, A I; Smoliakova, G P; Sorokin, E L
The surface lachrymal-fluid (LF) tension was investigated by teardrop dissection in 115 patients with myopia before they were prescribed soft contact lenses (SCL). Such tension was found to be of clinical importance for the development of SCL adaptation disorders. A longer adaptation period in patients with myopia was associated with a low surface LF tension. A high surface LF tension concurrent with the teardrop dissection mode of the destruction type was typical of the pathological nature of SCL adaptation (12.1% of patients). The obtained data are needed to detect timely the risk of dysadaptation disorders and corneal complications before SCL prescription for the purpose of undertaking the pathogenetically substantiated medication to prevent such complications.
Alexandrov, Sergey A; Zvyagin, Andrei V; Silva, K K M B Dilusha; Sampson, David D
We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.
Guthrie, Sarah E; Jones, Lyndon; Blackie, Caroline A; Korb, Donald R
The purpose of this study was to determine the clinical impact of using SYSTANE BALANCE Lubricant Eye Drops (Alcon, Fort Worth, TX), an oil-in-water emulsion, as a rewetting eye drop in symptomatic contact lens wearers. Subjects who had previously experienced contact lens discomfort (CLD), with a mean lens wearing history of 18.6±12.8 years, were randomly assigned to use a Test (SYSTANE BALANCE Lubricant Eye Drops; n=76) or control (habitual nonlipid contact lens rewetting eye drop; n=30) drop over their contact lenses within 5 min of lens insertion and then subsequently at 2 hr intervals up to a maximum of 4 drops per eye daily for a 1-month period. Assessments of subjective comfort, comfortable wearing time, lid wiper epitheliopathy (LWE), and corneal staining were conducted at baseline and after 1 month, after 6 hr of lens wear. Comfort, wearing time, LWE, and corneal staining all showed statistically significant improvements in the test group using SYSTANE BALANCE Lubricant Eye Drops at the 1-month visit compared with baseline data (all P<0.01) and compared with the control group at the 1-month visit (P<0.01, P=0.01, P<0.01, and P=0.03, respectively). The use of SYSTANE BALANCE Lubricant Eye Drops as a rewetting drop in a group of wearers who experienced symptoms of CLD improved subjective comfort scores, increased comfortable wearing time, and reduced signs of LWE and corneal staining, when compared with the use of non-lipid-containing contact lens rewetting eye drops.
Voitenko, Igor; Storm, Ronald; Westfall, Raymond; Rogers, Stanley
An optical system consisting of an aqueous electrolyte resting on a polymer/gold/indium-tin-oxide (ITO) layer deposited onto a glass substrate is analyzed to acquire contact angle - focal distance data as a function of applied voltage. The shape factor of a liquid lens and its dependence on the perimeter of contact line and contact angle was analyzed in the presence of an electrical field applied between the electrolyte and planar electrode system. The contact angle of a liquid on a thin, transparent film of gold (20 nm thick) - on ITO under electrolyte solution could be varied from 110 +/- 3° when the gold was held at -2.4 V to 41 +/- 3° without voltage. The behavior of a water-based electrolyte and water-soluble polymer blend and its influence on the shape of contact line and profile of the lens were investigated by employing a holographic setup at wavelengths of 632.8 and 543.5 nm. Optical micrographs showing the profile of the lens, aberration-less aperture, deformation of contact line, and shape of the liquid lens, respectively, were analyzed in reflection and transmission. Both the advancing and receding contact angles were measured directly from digitized images of the profile of the lens. The dynamic range of linear beam steering and dependence of the focal length of the liquid lens on the applied voltage are discussed.
Svitova, Tatyana F.; Lin, Meng C.
Purpose To explore interfacial behaviors and effect of temperature and dilatation on dynamic properties of multilayered human tear lipids extracted from silicone hydrogel (SiH) lenses worn by asymptomatic Asian and Caucasian subjects. Methods Interfacial properties of lipids extracted from Focus® N&D lenses worn by 14 subjects continuously for 1 month were studied. The lipids were deposited on an air bubble immersed in a model tear electrolytes (MTE) solution to form 100 ± 20 nm-thick films. Surface pressure was recorded during slow expansion/contraction cycles to evaluate compressibility and hysteresis of lipid films. Films were also subjected to fast step-strain dilatations at temperatures 22°–45° C for their visco-elastic properties assessment. Results Iso-cycles for Asian and Caucasian lipids were similar at low surface pressures, but had distinctly different compressibility and hysteresis at dynamic pressures exceeding 30 mN/m. Rheological parameters of reconstituted lipids were also dissimilar between Asian and Caucasian. The elastic modulusE∞ for Caucasian lipids was 1.5 times higher than that for Asian lipids, whereas relaxation time (t) was on average 1.3 times higher for Asian. No significant changes were observed in rheological properties of both Asian and Caucasian lipids when temperature increased from 22.0° to 36.5° C. However, for Caucasian lipids, E∞ reduced considerably at temperatures above 42.0° C, while t remained unchanged. For Asian lipids, both E∞ and t started to decline as temperature increased to 38° C and higher. Conclusions Higher elastic modulus of Caucasian lipids and elasticity threshold at certain deformations indicate stronger structure and intermolecular interactions as compared with more viscous Asian lipids. The differences in interfacial behaviors between Asian and Caucasian lipids may be associated with the differences in their chemical compositions. PMID:24270592
Chen, Sarah P.; Massaro-Giordano, Giacomina; Pistilli, Maxwell; Schreiber, Courtney A.; Bunya, Vatinee Y.
Purpose To examine the relationship between oral contraceptive pill (OCP) use, contact lens wear, and dry eye signs and symptoms in healthy young females. Methods Fifty-two women using OCPs and forty-five women not using any form of hormonal contraception were enrolled. Medical, menstrual, and contact lens histories were obtained and dry eye symptoms were assessed using the Ocular Surface Disease Index (OSDI) and Symptom Assessment iN Dry Eye (SANDE) questionnaires. Tear osmolarity testing was performed using the TearLab™ Osmolarity System. Results Mean age of all subjects was 26.0 ± 3.7 years. There were no significant differences in any of the measurements between the follicular and luteal phases. While SANDE scores were significantly higher in subjects with OCP and recent contact lens use (p<0.01), there were no significant differences in OSDI and tear osmolarity amongst the same subject groups. Subjects who reported both OCP and recent contact lens use had significantly higher OSDI and SANDE scores (p=0.015 and p<0.001, respectively). Conclusions There were no differences between the phases of the menstrual cycle. Tear osmolarity was not affected by OCP or contact lens use in young females. However, the combination of OCP use and contact lens wear may increase the severity of dry eye symptoms. PMID:23086364
Castillo, E J; Koenig, J L; Anderson, J M
Tear protein and gamma-globulin mixtures were adsorbed on soft contact lenses of different chemical composition, surface quality and water content. The adsorption process was followed by Fourier transform infrared-attenuated total reflectance spectroscopy (ATR-FTIR). It was found that gamma-globulin underwent a conformational and orientational change after its adsorption and the extent of structural change appeared to be proportional to the binding strength of the protein with the hydrogel surface. Electrostatic interactions play a major role in the protein adsorption on lenses containing methacrylic acid. Lysozyme is selectively adsorbed on all of the high water content hydrogels and mucin is the major protein component for the pure PHEMA type of lenses. Studies on in vivo spoiled PHEMA and PVP/MMA lenses indicate that lysozyme is the major adsorbed deposit. Papain cleaning of in vivo spoiled lenses shows that although a portion of the deposits is desorbed, the enzyme itself becomes irreversibly adsorbed to the contact lens which may cause harmful effects to the eye.
Bendavid, Itai; Avisar, Inbal; Serov Volach, Irena; Sternfeld, Amir; Dan Brazis, Idit; Umar, Lewaa; Yassur, Yiftach; Singer, Pierre; Cohen, Jonathan David
To compare the effectiveness of bandage contact lenses and punctal plugs with ocular lubricants in preventing corneal damage in mechanically ventilated and sedated critically ill patients. Single-center, prospective, randomized, pilot study. Sixteen-bed, general ICU at a tertiary academic medical center. Adults admitted to the ICU and anticipated to require mechanical ventilation and continuous sedation for greater than or equal to 4 days. Patients were randomized to receive eye care with ocular lubricants (n = 38), bandage contact lenses (n = 33), or punctal plugs (n = 33). The bandage contact lenses were changed every 4 days, whereas the punctal plugs remained in situ for the entire study. The primary endpoint was the presence or absence of corneal damage as assessed by the grade of keratopathy. Patients were examined by an ophthalmologist blinded to the study group every 4 days and at the time of withdrawal from the study, due to cessation of sedation, discharge from the ICU, or death. The mean duration of the study was 8.6 ± 6.2 days. The grade of keratopathy in the ocular lubricant group increased significantly in both eyes (p = 0.01 for both eyes) while no worsening was noted in either the lens or punctal plugs groups. In a post hoc analysis of patients with an initially abnormal ophthalmic examination, significant healing of keratopathy was noted in the lens group (p = 0.02 and 0.018 for left and right eyes, respectively) and in the right eye of the plugs group (p = 0.005); no improvement was noted in the ocular lubricant group. Compared with ocular lubrication, bandage contact lenses and punctal plugs were more effective in limiting keratopathy, and their use, particularly of bandage contact lenses, was associated with significant healing of existing lesions.
Salopek-Rabatić, Jasminka; Pavan, Josip; Kastelan, Snjezana; Rabatić, Leon
Anisometropy as a first step on a way forward future amblyopic child, can be prevent and treat if this condition is recognased on time. Second step is wisdom, right contact lens fit on bothes eyes. As follow, some ortoptic-pleoptic procedures depending on (objective, subjective squinting angle, state of fusion, visus on bothes eyes and separatly each eay and condition of nervus opticus (VEP), normal or absent retinal corespondence, are recomended. There is no limit how old a child is, but best choice and best compliance is age between five and twelve. Contact lens materiales, different fit procedures, right diagnosys and tips all about are discussed.
Ho, C P; Yasuda, H
Silicone rubber has great advantages as a contact lens material because of its very high oxygen permeability, softness, and excellent mechanical strength and durability. Practical application is hampered by inherent characteristics of elastomers, i.e., high tackiness and highly hydrophobic surface properties. By applying a thin layer, e.g., 5 nm, of plasma polymer of methane, it was found that all these disadvantages can be eliminated without sacrificing high oxygen permeation rate, e.g., less than 15% reduction. Optimization of operational parameters to achieve this task has been investigated. It was also found that under optimum conditions the coating withstood severe and repeated flexing of the contact lens.
Taher, Eman E; Méabed, Eman M H; Abdallah, Islam; Abdel Wahed, Wafaa Y
Acanthamoeba keratitis (AK) is a severe corneal infection that may occur as a serious outcome of improper use of contact lenses (CL). The study aimed to diagnose AK in soft CL users presenting with infectious keratitis, and to identify the prevalent genotypes isolated from different cases. Another aim was to determine the CL hygiene-related risk behaviors, and to explore the risk of water exposure for developing AK. A cross sectional study was performed. A questionnaire was carried out including 260 clinically diagnosed cases as infectious keratitis (170 females and 90 males); all of them were soft CL users for the suspected risk factors. Corneal scrapes from the affected eyes were cultured to diagnose bacterial and AK. PCR was performed and the amplified products were sequenced and compared with GenBank data. The parasite was positively amplified from 32 samples (12.3%). Acanthamoeba T4 genotype was identified in 27/32 (84.4%) of isolates. Other detected genotypes belonged to T5 and T3 genotypes at rates of 9.4%, and 6.25%, respectively. The most important risk factors associated with development of AK were female sex, sleeping while wearing CL, and exposure to water resources through different practices. These practices included rinsing the CL case in tap water, swimming and/or showering while wearing CL, using multipurpose solution for cleaning the lenses, using water from over-building tanks. Rubbing the eyes due to discomfort when applying CL was an additional important risk factor associated with AK. The protective factor was regular hand washing before using CL. CL users were more exposed to AK and should gain enough health education regarding proper lens hygiene and dangers of tap water exposure. Copyright © 2017. Published by Elsevier Ltd.
García-Millán, Eva; Koprivnik, Sandra; Otero-Espinar, Francisco Javier
This paper proposes an approach to improve drug loading capacity and release properties of poly(2-hydroxyethyl methacrylate) (p(HEMA)) soft contact lenses based on the optimization of the hydrogel composition and microstructural modifications using water during the polymerization process. P(HEMA) based soft contact lenses were prepared by thermal or photopolymerization of 2-hydroxyethyl methacrylate (HEMA) solutions containing ethylene glycol di-methacrylate as crosslinker and different proportions of N-vinyl-2-pyrrolidone (NVP) or methacrylic acid (MA) as co-monomers. Transmittance, water uptake, swelling, microstructure, drug absorption isotherms and in vitro release were characterized using triamcinolone acetonide (TA) as model drug. Best drug loading ratios were obtained with lenses containing the highest amount (200 mM) of MA. Incorporation of 40% V/V of water during the polymerization increases the hydrogel porosity giving a better drug loading capacity. In vitro TA release kinetics shows that MA hydrogels released the drug significantly faster than NVP-hydrogels. Drug release was found to be diffusion controlled and kinetics was shown to be reproducible after consecutive drug loading/release processes. Results of p(HEMA) based soft contact lenses copolymerized with ethylene glycol dimethacrylate (EGDMA) and different co-monomers could be a good alternative to optimize the loading and ocular drug delivery of this corticosteroid drug.
have been thought to be associated with immune complex formation (Mondino, 1988). The inflammation-stimulating antigen may be exogenous, as in Staph ... aureus exotoxin induced infiltrates. The antigen also may be endogenous, as in Mooren’s ulcer. Either mechanism cf action could contribute to contact
Piñero, David P; Carracedo, Gonzalo; Ruiz-Fortes, Pedro; Pérez-Cambrodí, Rafael J
The aim was to evaluate the visual performance achieved with a new multifocal hybrid contact lens and to compare it with that obtained with two other currently available multifocal soft contact lenses. This pilot prospective comparative study comprised a total of 16 presbyopic eyes of eight patients ranging in age from 43 to 58 years. All patients were fitted with three different models of multifocal contact lens: Duette multifocal (SynergEyes), Air Optix AQUA multifocal (Alcon) and Biofinity multifocal (CooperVision). Fittings were performed randomly in each patient according to a random number sequence, with a wash-out period between fittings of seven days. At two weeks post-fitting, visual, photopic contrast sensitivity and ocular aberrometry were evaluated. No statistically significant differences were found in distance and near visual acuity achieved with the three different types of multifocal contact lens (p ≥ 0.05). Likewise, no significant differences between lenses were found in the monocular and binocular defocus curve (p ≥ 0.10). Concerning contrast sensitivity, better monocular contrast sensitivities for 6, 12 and 18 cycles per degree were found with the Duette and Air Optix multifocal compared to Biofinity (p = 0.02). Binocularly, differences between lenses were not significant (p ≥ 0.27). Furthermore, trefoil aberration was significantly higher with Biofinity multifocal (p < 0.01) and Air Optix (p = 0.01) multifocal compared to Duette. The Duette multifocal hybrid contact lens seems to provide similar visual quality outcomes in presbyopic patients with low corneal astigmatism, when compared with other soft multifocal contact lenses. This preliminary result should be confirmed in studies with larger samples. © 2015 The Authors. Clinical and Experimental Optometry © 2015 Optometry Australia.
Timucin, Ozgur Bulent; Karadag, Mehmet Fatih; Cinal, Adnan; Asker, Muntecep; Asker, Selvi; Timucin, Damla
To assess the corneal endothelial cell density (ECD) in keratoconus patients with no history of contact lens use. Yuzuncu Yil University, School of Medicine and Van Training and Research Hospital, Department of Ophthalmology, Van, Turkey. Cross-sectional controlled study. The eyes of 65 patients with the diagnosis of keratoconus with no history of contact lens wear and the eyes of 40 healthy controls were prospectively examined using the Heidelberg Retinal Tomography Rostock Cornea Module (HRT3/RCM). The average ECD from the two groups were then compared. Of the cases with keratoconus, 44 (67.7%) were men and 21 (32.3%) were women. The mean age was 20.9±6.8 (range=10-41) years. Of the controls, 28 (70%) were men and 12 (30%) were women. The mean age was 23.9±5.8 (range=14-35) years. Of the 65 eyes with keratoconus, 19 (29.2%) had mild keratoconus, 21 (32.3%) had moderate keratoconus, and 25 (38.5%) had severe keratoconus. The mean ECD was 2731.6±303.2 cells/mm2 in cases with keratoconus and 2664.9±319.5 cells/mm2 in controls. There was no difference between the densities (unpaired t-test, P=0.4). No significant relationships were found between the ECD data and central corneal thickness or steepest keratometric. Endothelial cell density was unaltered in keratoconic patients without a history of contact lens use when compared with healthy controls. Change in ECD is independent from the central corneal thickness and the stage of keratoconus. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Baguet, J; Sommer, F; Duc, T M
Soft contact lens (SCL) surfaces were imaged with atomic force microscopy (AFM). High-resolution images of unworn SCL were obtained under nearly physiological medium. We present images of surfaces of collagen bandage lens under dry or aqueous conditions and of SCL of different water content and fabrication processes. Roughness parameters were determined. AFM studies of surfaces of SCL are expected to provide useful information on the hydrogel surfaces.
Asharlous, Amir; Mirzajani, Ali; Jafarzadehpur, Ebrahim; KhabazKhoob, Mehdi; Ostadimoghaddam, Hadi
To investigate the effect of a lubricating drop on optical quality, tear film stability, and subjective symptoms in individuals wearing silicone hydrogel contact lens. In this one-day, prospective single-center clinical study, Pre-lens Tear Deformation Time (PL-TDT), Root-Mean-Square (RMS) of Low Order Aberrations (LOA) and High Order Aberrations (HOA), individual twelve Zernike coefficients, and subjective symptoms were assessed in 43 volunteers (mean age 19.58 ± 1.63, 86 eyes) at 6 h after inserting the contact lens and then at 60 min after instilling a lubricating drop (Comfort drops, Avizor, Madrid-Spain). PL-TDT, LOA-RMS, and HOA-RMS values measured before drop instillation were not significantly different with those measured after drop. None of the Zernike coefficients were significantly different after instilling lubricating drop. Statistically significant decrement in both frequency and severity values in blurry vision, dryness, discomfort, burning, itching, foreign body sensation, excessive blinking, and lacrimation were seen after drop instillation (all P < 0.05). Our results showed that although the lubricating drop did not improve the tear film stability and optical quality in the silicone hydrogel contact lens wearers, subjects experienced a subjective improvement.
Yun, Jun-Won; Hailian, Quan; Na, Yirang; Kang, Byeong-Cheol; Yoon, Jung-Hee; Cho, Eun-Young; Lee, Miri; Kim, Da-Eun; Bae, SeungJin; Seok, Seung Hyeok; Lim, Kyung-Min
In an effort to explore the use of alternative methods to animal testing for the evaluation of the ocular irritancy of medical devices, we evaluated representative contact lenses with the bovine corneal opacity and permeability test (BCOP) and an in vitro eye irritation test using the three-dimensionally-reconstructed human corneal epithelium (RhCE) models, EpiOcular™ and MCTT HCE™. In addition, we compared the obtained results with the ISO standard in vivo rabbit eye irritation test (ISO10993-10). Along with the positive controls (benzalkonium chloride, BAK, 0.02, 0.2, and 1%), the extracts of 4 representative contact lenses (soft, disposable, hard, and colored lenses) and 2 reference lenses (dye-eluting and BAK-coated lenses) were tested. All the lenses, except for the BAK-coated lens, were determined non-irritants in all test methods, while the positive controls yielded relevant results. More importantly, BCOP, EpiOcular™, and MCTT HCE™ yielded a consistent decision for all the tested samples, with the exception of 0.2% BAK in BCOP, for which no prediction could be made. Overall, all the in vitro tests correlated well with the in vivo rabbit eye irritation test, and furthermore, the combination of in vitro tests as a tiered testing strategy was able to produce results similar to those seen in vivo. These observations suggest that such methods can be used as alternative assays to replace the conventional in vivo test method in the evaluation of the ocular irritancy of ophthalmic medical devices, although further study is necessary. Copyright © 2016. Published by Elsevier Ltd.
Chalmers, Robin L; Wagner, Heidi; Kinoshita, Beth; Sorbara, Luigina; Mitchell, G Lynn; Lam, Dawn; Richdale, Kathryn; Zimmerman, Aaron
To compare the habits of United States (US) soft contact lens (SCL) wearers who bought SCLs from their eye care practitioner (ECP), on the internet/telephone, or at retail (not where they were examined) to test the effect of proximity to the prescriber on SCL wear and care practices. Adult SCL wearers completed an adapted Contact Lens Risk Survey (CLRS) online that queried items related to risk factors for SCL-related complications. Responses from subjects who purchased at the ECP, via the internet/telephone, or at a retail store were compared (Chi-Square). Purchase sources were: ECP 646 (67%, 44±12 yrs, 17% male), Retail 104 (11%, 45±13 yrs, 28% male), and Internet/telephone 218 (23%, 45±12 yrs, 18% male); age (p=0.51), gender (p=0.021). Internet purchasers had fewer annual eye exams (79% ECP, 83% retail, 66% internet/telephone, p=0.007), purchased more hydrogel SCLs (34% ECP, 29% retail, 45% internet/telephone, p=0.0034), and paid for SCLs with insurance less often (39% ECP, 29% retail, 19% internet/telephone, p<0.0001). Other behaviors were similar across groups (p>0.05). In this sample, the purchase location of SCL wearers had limited impact on known risk factors for SCL-related complications. Internet purchasers reported less frequent eye exams and were more likely to be wearing hydrogel SCLs. Closer access to the ECP through in-office SCL purchase did not improve SCL habits or reduce the prevalence of risk behaviors. Copyright © 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Kopf, Miriam; Yi, Fan; Robert Iskander, D.; Collins, Michael J.; Shaw, Alyra J.; Straker, Benjamin
Purpose To investigate changes in tear film surface quality after commencing soft contact lens wear. Methods Tear film surface quality (TSQ) was assessed during the interblink period using dynamic videokeratoscopy at 25 Hz. A quantitative value of TSQ is derived for each raw Placido ring image. Eleven young subjects with normal tear characteristics participated in the study. Dynamic videokeratoscopy was taken three times per day; in the morning, at lunchtime, and in the afternoon. This was done on two baseline days (bare eye) and on the first and seventh days of lens wear for a conventional hydrogel lens and following a week of no lens wear, for a further week of silicone hydrogel lens wear. Additionally clinical tests to assess TSQ were conducted and subjects were also asked to rate the subjective dryness of their eyes. Results All lens wear measurements showed a significant worsening of TSQ compared to bare eye measurements (repeated measures ANOVA, P<0.01). A significant diurnal change was found on the first day of silicone hydrogel contact lens wear, where TSQ improved during the day (P=0.045). However, no diurnal changes were found in TSQ for the other lens wearing days or for the bare eye condition (P>0.05). The subjective rating of dryness correlated with TSQ values (Pearson's r=0.62, P<0.05) for the bare eye condition, but not during contact lens wear. TSQ derived from the right and left bare eyes of the same individuals showed a significant correlation (Pearson's r=0.61, P<0.05). Conclusions The measurement of TSQ using dynamic videokeratoscopy differentiates between bare eye and lens wearing conditions. It also shows a small systematic improvement in tear surface quality during the first day of silicone hydrogel lens wear and a significant association with subjective dryness for the bare eye condition.
Chalmers, Robin; Long, Bill; Dillehay, Sally; Begley, Carolyn
To determine dryness symptoms attributable to hydrogel contact lens (HCL) wear by comparing symptoms from age-matched HCL wearers and non-wearers in a cross-sectional study, and to compare that difference to the change in proportion of subjects reporting frequent dryness among HCL wearers after refitting with lotrafilcon A or B silicone hydrogels (SHCLs). Prevalence of frequent dryness symptoms was compared between HCL and non-wearers from a cross-sectional, historical dataset of Dry Eye/Contact Lens Dry Eye Questionnaires using an age-matched subset of 259 HCL and 246 non-wearers. Prospective change in prevalence of frequent dryness from non-randomized studies (n = 1036), in which daily wear (DW) HCL wearers were refit with lotrafilcon A or B SHCLs, was then compared to the cross-sectional difference between HCL wearers and non-wearers. In the Dry Eye/Contact Lens Dry Eye Questionnaires dataset, 47% fewer non-wearers reported frequent dryness than HCL wearers (p = 0.0001). In the lotrafilcon A DW refitting trials, frequent dryness was reported by 67 and 62% fewer subjects for during the day (DD) and end of the day (EOD) dryness (p = 0.0001, both) after refitting. In continuous wear lotrafilcon A trials, there were 63 and 41% reductions in the proportion reporting frequent DD and EOD dryness (p = 0.014 and p = 0.02). Refitting to DW lotrafilcon B yielded a 48 and 46% reduction in the number of subjects reporting frequent DD and EOD dryness (p < 0.0001, both). After refitting DW HCL wearers with either lotrafilcon A or B SHCLs, the proportion of symptomatic wearers was approximately half; an amount similar to the difference in proportion between HCL and non-wearers. This raises the possibility that refitting HCL wearers with SHCLs eliminates the component of dryness that is induced by HCL wear. Further research with more robust experimental design is recommended to test this hypothesis.
Nasr, Farzaneh Hashemi; Khoee, Sepideh; Dehghan, Mohammad Mehdi; Chaleshtori, Sirous Sadeghian; Shafiee, Abbas
To improve the efficiency of topical ocular drug administration, we focused on development of a nanoparticles loaded contact lens to deliver the hydrophobic drug over a prolonged period of time. The cross-linked nanoparticles based on PCL (poly ε-caprolactone), 2-hydroxy ethyl methacrylate (HEMA), and poly ethylene glycol diacrylate (PEG-DA) were prepared by surfactant-free miniemulsion polymerization. The lens material was prepared through photopolymerization of HEMA and N-vinylpyrrolidone (NVP) using PEG-DA as the cross-linker. Effects of nanoparticles loading on critical contact lens properties such as transparency, water content, modulus and ion and oxygen permeabilities were studied. Nanoparticles and hydrogel showed high viability, indicating the absence of cytotoxicity and stimulatory effect. Drug release studies revealed that the hydrogel embedded with nanoparticles released the drug for a period of 12 days. The results of this study provide evidence that nanoparticles loaded hydrogels could be used for extended delivery of loteprednol etabonate and perhaps other drugs.
Qu, Wenwen; Hooymans, Johanna M M; Qiu, Jun; de-Bont, Nik; Gelling, Onko-Jan; van der Mei, Henny C; Busscher, Henk J
Surface properties of lens cases are determinant for their cleanability and for microbial transmission from lens cases to contact lenses (CLs). PEG-polymer-brush-coatings are known to decrease microbial adhesion more than other surface-coatings. Here, we applied a robust, silica nanoparticles-based brush-coating to polypropylene cases to evaluate their ease of cleaning and probability of bacterial transmission to CLs. Adhesion forces of nine bacterial strains (Pseudomonas, Staphylococci, and Serratia) to rigid CLs, polypropylene, and silica nanoparticles-based brush-coated polypropylene were measured using atomic-force-microscopy and subjected to Weibull analyses to yield bacterial transmission probabilities. Biofilms of each strain were grown in coated and uncoated cases and rinsed with a NaCl or antimicrobial lens care solution. Residual, viable organisms were quantified. Bacterial adhesion forces of all strains were significantly, up to tenfold smaller on brush-coated than on uncoated polypropylene. This yielded, higher transmission probabilities to a CL, but mild-rinsing yielded 10-100 fold higher removal of bacteria from brush-coated than from polypropylene cases. Moreover, due to weak adhesion forces, bacteria on brush-coated cases were two-to-three fold more susceptible to an antimicrobial lens care solution than on polypropylene cases. Therewith, the design of lens case surfaces is a compromise between ease of cleaning and transmission probability to CLs.
Riley, Colleen; Young, Graeme; Chalmers, Robin
Many soft contact lens wearers have symptoms or signs that compromise successful lens wear. This study estimated the prevalence of problems in current wearers of soft contact lenses and tested the effect of refitting patients with senofilcon A silicone hydrogel lenses (ACUVUE Oasys). Prevalence was estimated from 1,092 current lens wearers for frequent or constant discomfort or dryness, at least 2 hours of uncomfortable wear, at least grade 2 limbal or bulbar hyperemia (0-4), or at least grade 3 corneal staining (0-15). In the second part of the study, 112 of the 564 wearers classified as problem patients were refitted with senofilcon A lenses and reassessed 2 weeks later. Fifty-two percent (564 of 1,092) had some qualifying criteria, with dryness reported by 23%, discomfort by 13%, and at least 2 hours of uncomfortable wear by 27%. Six percent of subjects had qualifying limbal hyperemia; 10% had bulbar hyperemia; and 12% had corneal staining. After refitting 112 problem patients, 75% had less dryness; 88% had better comfort (P<0.0001 each); and 76% had fewer uncomfortable hours of wear (P=0.004). Although the average wearing time was unchanged, comfortable wearing time increased significantly (10.4 to 11.6 hours) (P=0.004). All (35 of 35) eyes with qualifying limbal hyperemia before the refit also improved (P<0.0001), as did 80% (40 of 50) of those with bulbar hyperemia (P<0.0001) and 76% (26 of 34) of those with corneal staining (P=0.005). Most soft lens wearers encounter clinically significant signs or symptoms with their current contact lenses. Refitting with new-generation silicone hydrogel lenses (senofilcon A) can alleviate some of these common problems.
Rathi, Varsha M; Mandathara, Preeji S; Dumpati, Srikanth
Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL. PMID:23925325
Arines, Justo; Gargallo, Ana
The training in the use of the slit lamp has always been difficult for students of the degree in Optics and Optometry. Instruments with associated cameras helps a lot in this task, they allow teachers to observe and control if the students evaluate the eye health appropriately, correct use errors and show them how to do it with a visual demonstration. However, these devices are more expensive than those that do not have an integrated camera connected to a display unit. With the aim to improve students' skills in the management of slit lamp, we have adapted USB HD webcams (Microsoft Lifecam HD-5000) to the objectives of the slit lamps available in our contact lenses laboratory room. The webcams are connected to a PC running Linux Ubuntu 11.0; therefore that is a low-cost device. Our experience shows that single method has several advantages. It allows us to take pictures with a good quality of different conditions of the eye health; we can record videos of eye evaluation and make demonstrations of the instrument. Besides it increases the interactions between students because they could see what their colleagues are doing and take conscious of the mistakes, helping and correcting each others. It is a useful tool in the practical exam too. We think that the method supports the training in optometry practice and increase the students' confidence without a huge outlay.
Diec, Jennie; Naduvilath, Thomas; Tilia, Daniel; Papas, Eric B; Lazon de la Jara, Percy
To describe a ranked symptoms scale (RSS) discriminating subjective responses in contact lens (CL) wear in various situations. Forty experienced clinical trial participants were interviewed for their perceptions of ocular comfort scales, resulting in a numerical RSS. For further evaluation, 20 CL wearers enrolled into a prospective, randomised, crossover trial. Two silicone-hydrogel CLs and a lens care solution (LCS) [Combinations A & B] were selected based on prior performance identifying best/worst combinations for end-of-day comfort. The RSS and a numerical rating scale (NRS) were administered at two time-points (insertion/removal) on alternating days for 6 days. Both NRS and RSS showed acceptable internal consistency for comfort, vision and handling (Cronbach alpha=0.71 for both scales) and similar repeatability for comfort and handling (coefficients-of-repeatability within 0.1 and 0.2 units, respectively, for each scale). The NRS and RSS discriminated differences between combinations for comfort (p≤0.031) and vision (p≤0.026) at both time-points. Additionally, the RSS showed lens/edge awareness influenced discomfort the most, ranking higher at insertion (p=0.038) and higher for Combination-B at both time-points (p≤0.002). Symptoms of dryness and tired eyes increased for both combinations at removal (p<0.02). The RSS also showed haziness and blurred distance vision influenced vision dissatisfaction with Combination-B at lens removal (p≤0.038) while eye strain/headache increased for both combinations by time of removal (p≤0.013). The RSS is able to discriminate subjective responses between combinations and time-of-day. The RSS's ability to rank symptoms may be a useful tool in understanding perceptions of discomfort or dissatisfaction with CL wear. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
O'Brien, C; Charman, W N
After a preliminary investigation of the effects of tool feed rate and spindle speed on the surface roughness of unhydrated, lathe-cut polymacon surfaces, a laboratory and clinical comparison was made between lenses with identical parameters except that the lathe-cut posterior surface was left unpolished in the "test" lenses and was polished in the "control" lenses. The lenses had moulded anterior surfaces. Laboratory comparisons included surface roughness, lens power and its uniformity across the surface. Double-blind clinical trials over 4-hour (27 subjects) and 1-month (10 subjects) periods, involved one eye of each subject wearing a "test" lens and the other, a "control" lens. No clinically significant differences were found between the results for the test and control lenses. It is concluded that today's lathing technology makes a final polishing stage unnecessary.
Chen, Qi; Tao, Aizhu; Shen, Meixiao; Jiao, Shuliang; Lu, Fan
Purpose. To determine the dynamic pre- and postlens tear film (PLTF and PoLTF) thicknesses by using optical coherence tomography (OCT). Methods. Ultrahigh-resolution OCT was used to image the tear film of 22 subjects before and after contact lens wear. A soft lens with 1 drop of artificial tears on its concave surface was inserted onto one randomly selected eye. OCT images were taken before insertion, immediately afterward, and every 2 minutes for 10 minutes. For the contralateral eye, the lens inserted was not prewetted on the concave surface. OCT images were taken before insertion, immediately afterward, and at 3 minutes. Then another drop was instilled, and images were taken immediately afterward and every 2 minutes for 10 minutes. Images were processed by custom software to yield tear film thickness. Results. The thickness of precorneal tear film (PCTF) was 1.9 ± 0.9 μm. The PoLTF was visualized clearly in all cases immediately after lens insertion, with 1 drop on the lens concave surface. Through the first 6 minutes after insertion, the PoLTF was greater than the PCTF. The PLTF (n = 12) and PoLTF (n = 9) were visualized immediately after lens insertion. After 3 minutes, the PLTF in most subjects and PoLTF in all subjects were invisible. The thickness of the PLTF increased after the instillation of artificial tears, whereas the PoLTF did not at any checkpoint for 10 minutes. Conclusions. Ultrahigh-resolution OCT is a promising tool for measuring the tear film. The PoLTF did not increase after instillation of artificial tears. PMID:19933178
Miñones Conde, M; Conde, O; Trillo, J M; Miñones, J
Mixed monolayers of poly(methyl methacrylate) (PMMA), the main component of hard contact lenses, and dipalmitoyl phosphatidyl choline (DPPC), a characteristic phospholipidic constituent of ocular tear films, were selected as an in vitro model in order to observe the behavior of contact lenses on the eye. Using Langmuir monolayer and Brewster angle microscopy (BAM) techniques, the interaction between both components was analyzed from the data of surface pressure-area isotherms, compressional modulus-surface pressure, and relative film thickness versus time elapsed from the beginning of compression, together with BAM images. Regardless of the surface pressure at which the molecular/monomer areas (A(m)) were recorded, the A(m) mole fractions of PMMA (X(PMMA)) plots show that the experimental results match the theoretical values calculated from additivity rule A(m) = X(PMMA)A(PMMA) + X(DPPC)A(DPPC). The application of the Crisp phase rule to the phase diagram of the PMMA-DPPC system can explain the existence of a mixed monolayer made up of miscible components with ideal behavior at surface pressures below 25 mN/m. However, at very high surface pressures, when collapse is reached (at 60 mN/m), the single collapsed components are segregated into two independent phases. These results allows us to argue that PMMA hard contact lenses in the eye do not alter the structural characteristics of the phospholipid (DPPC) in tears.
Topakova, Anastassia A.; Salmin, Vladimir V.; Gar'kavenko, Victor V.; Levchenko, Julia S.; Lazarenko, Victor I.
Fluorimetry of eye is a perspective technique for research and diagnostics in ophthalmology. It is connected to the structural and functional characteristics of eye that is, actually, the optical system allowing transferring the radiation both for excitation and for registration of fluorescence in different eye's compartments: cornea, lens, vitreous body, and fundus of the eye. At present, different models of ophthalmologic fluorophotometers for the analysis of eye fluorescence as well as more advanced models - scanning fluorophotometers - are offered. Assessment of corneal status in persons wearing contact lenses or in patients with pathological changes (i.e. diabetes mellitus) would give us an opportunity to identify the initial manifestations of corneal pathology at the pre-symptomatic phase. In this paper, we present data on the compact spectrofluorimeter with UV LEDs-induced excitation as well as the method for assessing hypoxic alterations in the eye limb zone caused by contact lenses wearing. We demonstrate dependence of autofluorescence spectra on the contact lenses types and duration of their permanent wearing.
Severinsky, Boris; Wajnsztajn, Denise; Frucht-Pery, Joseph
The aim was to the evaluate performance of a novel silicone hydrogel mini-scleral contact lens (SHmS) for optical correction of keratoconus in the early stages after the corneal collagen cross-linking procedure (CXL). We retrospectively analysed the visual acuity improvement and corneal adaptation in the first 10 eyes of nine patients fitted with SHmS lenses one to 3.5 months after corneal collagen cross-linking. The lenses were designed to rest over the patients' sclera and peri-limbal cornea and vault the central cornea with minimal support over it. Visual acuities with manifest refraction and contact lenses, refractive and topographical values (Kmin and Kmax) were evaluated on lens dispensing and after six month of lens wearing. Ocular physiological responses were evaluated using the Institute of Eye Research (IER) grading scales. SHmS fitting was performed 2.1 ± 0.97 (SD) months after collagen cross-linking. Mean follow up was 10.9 ± 4.41 months (range six to 18 months). Mean decimal visual acuity with SHmS was 0.66 ± 0.22 (approximately 6/9 Snellen fraction, range 0.3 to 0.1) or 0.75 ± 0.14 (approximately 6/8.1, range 0.5 to 1.0), when omitting two amblyopic eyes. Nine (90 per cent) eyes were successfully fitted, that is, able to wear the lenses for 10 hours per day or longer. Mean wearing time was 11.7 hours (range six to 14) per day. No corneal neovascularisation or papillary reaction was found in all fitted eyes. SHmS contact lenses provide successful visual rehabilitation shortly after corneal collagen cross-linking. This new soft contact lens design with scleral fixation and minimal apical touch was demonstrated to be safe shortly after collagen cross-linking, as the avoidance of contact with the treated zone minimises contact lens influence on corneal recovery. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.
Imamura, Yoshifumi; Chandra, Jyotsna; Mukherjee, Pranab K.; Lattif, Ali Abdul; Szczotka-Flynn, Loretta B.; Pearlman, Eric; Lass, Jonathan H.; O'Donnell, Kerry; Ghannoum, Mahmoud A.
Fungal keratitis is commonly caused by Fusarium species and less commonly by Candida species. Recent outbreaks of Fusarium keratitis were associated with contact lens wear and with ReNu with MoistureLoc contact lens care solution, and biofilm formation on contact lens/lens cases was proposed to play a role in this outbreak. However, no in vitro model for contact lens-associated fungal biofilm has been developed. In this study, we developed and characterized in vitro models of biofilm formation on various soft contact lenses using three species of Fusarium and Candida albicans. The contact lenses tested were etafilcon A, galyfilcon A, lotrafilcon A, balafilcon A, alphafilcon A, and polymacon. Our results showed that clinical isolates of Fusarium and C. albicans formed biofilms on all types of lenses tested and that the biofilm architecture varied with the lens type. Moreover, differences in hyphal content and architecture were found between the biofilms formed by these fungi. We also found that two recently isolated keratitis-associated fusaria formed robust biofilms, while the reference ATCC 36031 strain (recommended by the International Organization for Standardization guidelines for testing of disinfectants) failed to form biofilm. Furthermore, using the developed in vitro biofilm model, we showed that phylogenetically diverse planktonic fusaria and Candida were susceptible to MoistureLoc and MultiPlus. However, Fusarium biofilms exhibited reduced susceptibility against these solutions in a species- and time-dependent manner. This in vitro model should provide a better understanding of the biology and pathogenesis of lens-related fungal keratitis. PMID:17999966
Brennan, Noel A; Coles, M L Chantal; Comstock, Timothy L; Levy, Brian
To evaluate silicone-hydrogel balafilcon A (PureVision, Bausch & Lomb Inc., Rochester, NY) contact lenses worn on a 30-day continuous wear basis when compared with a traditional hydrogel (Acuvue, Vistakon, Johnson and Johnson Vision Products, Inc., Jacksonville, FL) worn on a 7-day extended wear schedule. Prospective, comparative, paired-eye, interventional, multicenter clinical trial. Two hundred twelve ametropes with no significant ocular pathology. Subjects with normal ocular health who conformed to a set of standard criteria were monitored at seven different sites around the globe. Subjects wore both study lenses simultaneously, one on each eye. Lenses were assigned to right and left eyes according to a randomized schedule. The silicone hydrogel was removed and replaced every month and the traditional hydrogel was removed every 7 days and replaced at 14-day intervals. Subjects were followed for up to 1 year with discontinuation on indication divided between lens-related causes, unrelated factors, and loss to follow-up. Discontinuations, symptoms, vision, lens fit, lens surface assessment, slit-lamp assessment, and patient preferences. One hundred twenty three subjects completed the 12-month wearing period. There were no vision-threatening events with either lens type. The silicone-hydrogel lenses showed statistically superior performance in physiologic terms with regard to epithelial microcysts, striae, corneal staining, limbal injection, and bulbar injection. Inflammatory reactions, such as corneal infiltrates and tarsal conjunctival abnormalities occurred at similar rates between the lens types. Visible deposition and postlens debris with associated transient corneal indentation were significantly lower with the traditional hydrogel material at specific time points in the study. Visual acuity was comparable with the two lens types. Subjects rated the silicone-hydrogel material as preferable on subjective scales of dryness, comfort, and lens handling. Overall
Brown, Karl David; Low, Suet; Mariappan, Indumathi; Abberton, Keren Maree; Short, Robert; Zhang, Hong; Maddileti, Savitri; Sangwan, Virender; Steele, David; Daniell, Mark
Extensive damage to the limbal region of the cornea leads to a severe form of corneal blindness termed as limbal stem cell deficiency (LSCD). Whereas most cases of corneal opacity can be treated with full thickness corneal transplants, LSCD requires stem cell transplantation for successful ocular surface reconstruction. Current treatments for LSCD using limbal stem cell transplantation involve the use of murine NIH 3T3 cells and human amniotic membranes as culture substrates, which pose the threat of transmission of animal-derived pathogens and donor tissue-derived cryptic infections. In this study, we aimed to produce surface modified therapeutic contact lenses for the culture and delivery of corneal epithelial cells for the treatment of LSCD. This approach avoids the possibility of suture-related complications and is completely synthetic. We used plasma polymerization to deposit acid functional groups onto the lenses at various concentrations. Each surface was tested for its suitability to promote corneal epithelial cell adhesion, proliferation, retention of stem cells, and differentiation and found that acid-based chemistries promoted better cell adhesion and proliferation. We also found that the lenses coated with a higher percentage of acid functional groups resulted in a higher number of cells transferred onto the corneal wound bed in rabbit models of LSCD. Immunohistochemistry of the recipient cornea confirmed the presence of autologous, transplanted 5-bromo-2'-deoxyuridine (BrdU)-labeled cells. Hematoxylin staining has also revealed the presence of a stratified epithelium at 26 days post-transplantation. This study provides the first evidence for in vivo transfer and survival of cells transplanted from a contact lens to the wounded corneal surface. It also proposes the possibility of using plasma polymer-coated contact lenses with high acid functional groups as substrates for the culture and transfer of limbal cells in the treatment of LSCD.
Brown, Karl David; Low, Suet; Mariappan, Indumathi; Abberton, Keren Maree; Short, Robert; Zhang, Hong; Maddileti, Savitri; Sangwan, Virender; Steele, David
Extensive damage to the limbal region of the cornea leads to a severe form of corneal blindness termed as limbal stem cell deficiency (LSCD). Whereas most cases of corneal opacity can be treated with full thickness corneal transplants, LSCD requires stem cell transplantation for successful ocular surface reconstruction. Current treatments for LSCD using limbal stem cell transplantation involve the use of murine NIH 3T3 cells and human amniotic membranes as culture substrates, which pose the threat of transmission of animal-derived pathogens and donor tissue-derived cryptic infections. In this study, we aimed to produce surface modified therapeutic contact lenses for the culture and delivery of corneal epithelial cells for the treatment of LSCD. This approach avoids the possibility of suture-related complications and is completely synthetic. We used plasma polymerization to deposit acid functional groups onto the lenses at various concentrations. Each surface was tested for its suitability to promote corneal epithelial cell adhesion, proliferation, retention of stem cells, and differentiation and found that acid-based chemistries promoted better cell adhesion and proliferation. We also found that the lenses coated with a higher percentage of acid functional groups resulted in a higher number of cells transferred onto the corneal wound bed in rabbit models of LSCD. Immunohistochemistry of the recipient cornea confirmed the presence of autologous, transplanted 5-bromo-2′-deoxyuridine (BrdU)-labeled cells. Hematoxylin staining has also revealed the presence of a stratified epithelium at 26 days post-transplantation. This study provides the first evidence for in vivo transfer and survival of cells transplanted from a contact lens to the wounded corneal surface. It also proposes the possibility of using plasma polymer-coated contact lenses with high acid functional groups as substrates for the culture and transfer of limbal cells in the treatment of LSCD. PMID:24328453
Stapleton, F.; Kasses, S.; Bolis, S.; Keay, L.
BACKGROUND/AIMS—Current contact lenses (CLs) when worn on an extended wear basis cause corneal epithelial alterations. The aim of this study was to evaluate changes in corneal epithelial cell morphology and physiology following short term (3 months) wear of highly oxygen permeable CLs and to compare this with disposable CLs. METHODS—Subjects were wearers of highly oxygen permeable CLs (n=11, wearing CLs on a 30 night schedule), disposable CL users (n=6, wearing CLs on a 6 night schedule), and non-CL wearers (n=20). Mean CL wear experience was 3 months. Epithelial cells were harvested using corneal cytology and were stained using acridine orange and ethidium bromide. Epithelial cell size and viability were determined. RESULTS—The majority of epithelial cells recovered were non-viable (71%), and the mean longest cell diameter was 38 (SD 8) µm. Disposable CLs caused an increase in cell size (42 (7) µm) compared with both non-wear (39 (7) µm, p=0.01) and wear of highly oxygen permeable CLs (37 (10) µm, p=0.0049). There was no difference in cell viability between groups. CONCLUSIONS—Extended wear of disposable CLs caused an 8% increase in cell diameter in harvested corneal epithelial cells following 3 months of CL wear. Cells harvested following 3 months' wear of highly oxygen permeable CLs were indistinguishable from those recovered from non-CL wearers. PMID:11159475
Nielsen, Kim; Vorum, Henrik; Ehlers, Niels; Aagaard, Nicolaj; Hjortdal, Jesper; Honoré, Bent
Tear film proteins adhere to the surface of contact lenses (CLs). While the proteins in the tears have been extensively studied with various proteomic techniques, adhered proteins to CLs are less studied. In this pilot study, we have separated proteins with 2D gel electrophoresis prior to the conventional mass spectrometry (MS) in order to analyse the deposited proteins on hydrogel CLs from myopic patients. pHEMA and PVA hydrogel CLs worn by 3 patients for different time lengths were analysed. After wear, the CLs were frozen at -20°C. Proteins were extracted in lysis buffer, separated on 12% polyacrylamide gels and silver-stained. Protein spots were excised and identified with liquid chromatography - tandem MS. Deposited proteins were extracted with a yield of 26-66 μg and separated by 2D gel electrophoresis. The silver-stained gels showed similar protein patterns independent of the patient, hydrogel type and wear time. Seventy-two spots were analysed with MS, representing at least 12 different tear film proteins or protein fragments. Deposited tear film proteins from a single set of CLs worn for 1 day can successfully be analysed first with 2D gel electrophoresis and subsequently with MS, thus making examination of individual patients possible. The protein composition appeared homogeneous between the test persons which is a necessity for additional comparison analysis. The molecular masses of the identified proteins indicate that protein degradation occurs only as a minor event. Myopic patients were investigated in this pilot study, but the combined techniques can easily be applied to other eye diseases. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
Bagheri, Abbas; Abbasi, Hamed; Tavakoli, Mehdi; Sheibanizadeh, Abdolreza; Kheiri, Bahareh; Yazdani, Shahin
To determine the effect of rigid gas permeable contact lenses (RGPCL) on involuntary eye movements and visual function in hyperopic patients with infantile nystagmus syndrome. This prospective interventional case series was conducted on 16 patients with infantile nystagmus and hyperopia equal or more than +0.5 D and astigmatism more than -1 D over a 2-year period. A complete ophthalmological examination including determination of best corrected visual acuity (BCVA), contrast sensitivity, and videonystagmography was performed for all patients before and after at least 3 months of RGPCL use, and the outcomes were compared. Thirty-two eyes of 16 patients with mean age of 18.6±4.9 years were enrolled. Mean spherical equivalent refractive error was +1.5±2.35 (range +1 to +6.25) diopters (D); corresponding values were +2.45±2.44 D (range +0.5 to +7.5) for spherical error and +1.90±0.83 D (range +1 to +4) for astigmatism. Monocular BCVA improved from 0.56±0.23 to 0.51±0.23 Log MAR (P=0.007), and binocular BCVA improved from 0.54±0.25 to 0.48±0.24 Log MAR (P=0.01) after fitting RGPCL. Following the use of RGPCL, contrast sensitivity was significantly improved at low (P=0.02) and intermediate (P< 0.001) frequencies but not at high frequencies (P=0.6). The frequency, amplitude, and intensity of nystagmus were decreased significantly after RGPCL use (P<0.001). RGPCL improved monocular and binocular BCVA and contrast sensitivity in hyperopic patients with infantile nystagmus syndrome. Motor indices of nystagmus (frequency, amplitude, and intensity) were also significantly improved after RGPCL use.
... about special eyewear you can wear on the field. With glasses, you'll also want to find out how to clean them properly. And it helps if you have a glasses case and put them in it when you're not wearing them. The last thing you want is to sit on your ...
González-Méijome, José M; López-Alemany, Antonio; Lira, Madalena; Almeida, José B; Oliveira, M Elisabete C D Real; Parafita, Manuel A
The purpose of the present study was to develop mathematical relationships that allow obtaining equilibrium water content and refractive index of conventional and silicone hydrogel soft contact lenses from refractive index measures obtained with automated refractometry or equilibrium water content measures derived from manual refractometry, respectively. Twelve HEMA-based hydrogels of different hydration and four siloxane-based polymers were assayed. A manual refractometer and a digital refractometer were used. Polynomial models obtained from the sucrose curves of equilibrium water content against refractive index and vice-versa were used either considering the whole range of sucrose concentrations (16-100% equilibrium water content) or a range confined to the equilibrium water content of current soft contact lenses (approxi