Test Lens Research Articles

Phosphorylcholine Impairs Susceptibility to Biofilm Formation of Hydrogel Contact Lenses

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.

Designing clinical trials for triple negative breast cancer: evidence and issues

In a dynamic postural task, visual information plays a fundamental role in the selection of the balancing strategy. While standing on a platform oscillating in the antero-posterior direction, subjects almost fix their head in space when vision is allowed and oscillate with the platform with eyes closed. We investigated two competing hypotheses regarding the relationship between visual acuity and balance control strategy. One hypothesis refers to the existence of a threshold value of visual acuity as a turning point between the eyes-open and eyes-closed strategy. The other assumes that the change from eyes-open to eyes-closed behavior is continuous and parallels the progressive worsening of visual acuity. Ten subjects balanced on the mobile platform wearing an examination frame and a facemask occluding peripheral vision. Seven different test lenses were used in different trials to modify visual acuity, from a visus value of 10/10 to severely blurred vision. Head stabilization in space progressively worsened with the decrease in visual acuity and turned toward the eyes-closed behavior when vision was blurred. The increase in head oscillation as a function of visual acuity was best fitted by a logarithmic function. In five of the subjects, additional trials were performed without facemask, to add peripheral vision to each visual acuity level, and with black lenses to allow peripheral vision alone. Addition of peripheral vision gave a significant contribution to head stabilization. With peripheral vision alone, head stabilization was intermediate between the eyes-closed and 10/10 visus value condition. We conclude that, in order to stabilize the head in space, visual information of the environment must be definite and worsening of central vision leads to a graded modification of the ‘head fixed in space’ behavior. Thus, the more conservative hypothesis of two different fundamental balancing strategies is not supported. Instead, the body exhibits a continuous mode of balancing patterns as a function of visual acuity. The findings support the notion that the central mechanism for head stabilization operates through linear integration of the central-field visual input with the general somesthetic feedback.

Graded changes in balancing behavior as a function of visual acuity

In a dynamic postural task, visual information plays a fundamental role in the selection of the balancing strategy. While standing on a platform oscillating in the antero-posterior direction, subjects almost fix their head in space when vision is allowed and oscillate with the platform with eyes closed. We investigated two competing hypotheses regarding the relationship between visual acuity and balance control strategy. One hypothesis refers to the existence of a threshold value of visual acuity as a turning point between the eyes-open and eyes-closed strategy. The other assumes that the change from eyes-open to eyes-closed behavior is continuous and parallels the progressive worsening of visual acuity. Ten subjects balanced on the mobile platform wearing an examination frame and a facemask occluding peripheral vision. Seven different test lenses were used in different trials to modify visual acuity, from a visus value of 10/10 to severely blurred vision. Head stabilization in space progressively worsened with the decrease in visual acuity and turned toward the eyes-closed behavior when vision was blurred. The increase in head oscillation as a function of visual acuity was best fitted by a logarithmic function. In five of the subjects, additional trials were performed without facemask, to add peripheral vision to each visual acuity level, and with black lenses to allow peripheral vision alone. Addition of peripheral vision gave a significant contribution to head stabilization. With peripheral vision alone, head stabilization was intermediate between the eyes-closed and 10/10 visus value condition. We conclude that, in order to stabilize the head in space, visual information of the environment must be definite and worsening of central vision leads to a graded modification of the ‘head fixed in space’ behavior. Thus, the more conservative hypothesis of two different fundamental balancing strategies is not supported. Instead, the body exhibits a continuous mode of balancing patterns as a function of visual acuity. The findings support the notion that the central mechanism for head stabilization operates through linear integration of the central-field visual input with the general somesthetic feedback.

Light Scatter on the Surface of AcrySof® Intraocular Lenses: Part II. Analysis of Lenses Following Hydrolytic Stability Testing

To investigate the surface light scatter and optical quality of AcrySof lenses (Alcon Laboratories, Inc., Fort Worth, TX) following simulated aging of 20 years. AcrySof lenses were exposed to exaggerated thermal conditions to simulate up to 20 years of aging and were tested for surface light scatter and optical quality (modulation transfer function). There were no significant differences from baseline for either the surface light scatter or optical quality of the lenses over time. The current study demonstrated that surface light scatter on AcrySof lenses did not increase under conditions simulating 20 years of aging. Because the simulated aging environment contained no protein, this work indirectly supports the finding that surface light scatter is due to the deposition of a biomaterial on the lens surface rather than changes in the material. Optical performance integrity of the test lenses was maintained under severe environmental conditions.

The role of an acousto-optic grating in determining the refractive index of a lens

A technique for measuring the refractive index of a lens is described in this paper. In the present paper, an innovative technique has been proposed in which acousto-optics is involved. A new formula for evaluating the refractive index of a lens glass material is reported which is independent of lens parameters. A rectangular glass cell filled with liquid has been used as a photo-sonar device, which also has a piezoelectric crystal for generating ultrasonic waves. The test lens is immersed inside the ultrasonic cell. The focal length of the test lens has been varied by immersing it inside the ultrasonic cell filled with known liquid. The laser light travelling through the lens inside the glass cell gets diffracted when the ultrasonic waves are generated. Thus an interaction between sound and light wave occurs, resulting in a grating-like action, and the diffraction dots are displayed on a screen. A relation between the refractive index of liquids and the velocity of ultrasonic waves has been derived which also involves the separation of diffraction dots.

A 12-month prospective clinical trial of comfilcon A silicone-hydrogel contact lenses worn on a 30-day continuous wear basis

Purpose To evaluate the clinical performance of comfilcon A (Biofinity) during 12 months of continuous wear compared to other silicone-hydrogel lenses. Method Forty-five subjects were fitted in one eye with the comfilcon A (test) lens. For 22 subjects, the other eye was fitted with lotrafilcon A (group A) and for the remaining 23 subjects the other eye was fitted with balafilcon A (group B). Twelve-month data are presented on 48 measured variables. Results There were no serious adverse events during the course of the study. A total of 33 subjects completed the study, with only 4 discontinuations for lens-related reasons, spread proportionately between the lenses. On preference scales, the test lens was superior to both control lenses for comfort ( p < 0.05) and overall preference ( p < 0.05) and in group A for vision ( p < 0.05). On grading scales, the test lens scored better than both control lenses for overall comfort ( p < 0.1 for group A, p < 0.05 for group B), comfort during the day ( p < 0.05), end-of-day comfort ( p < 0.05) and overall preference ( p < 0.05), and better in group A for general vision quality ( p < 0.01), night vision quality ( p < 0.01) and handling ( p < 0.05). All lenses performed to a comparable degree on the basis of microcysts and corneal staining. There were significant differences between lenses in producing limbal redness ( p < 0.05), bulbar conjunctival hyperemia ( p < 0.1) and conjunctival NaFl staining ( p < 0.01) with the control lens in group A showing the greatest effect and the control lens in group B the least. Conclusion Comfilcon A offers performance advantages over first generation silicone-hydrogel materials for continuous wear.

Measurement of parameters of simple lenses using digital holographic interferometry and a synthetic reference wave

The use of digital holographic intrerferometry in the testing of simple thin lenses is explored. Focal length, radius of curvature, and refractive index are the lens parameters that can be determined using this method. The digital holograms using the lens under test are recorded at various positions of the test lens using off-axis geometry. This is combined with a digitally computed plane wavefront to determine the curvature of the light beam emerging from the test lens. Focal length is the position of the test lens where a single fringe results. The radius of curvature of the test lens is also determined similarly using a long focal length lens to concentrate a collimated beam onto the test lens. The nonuniformities on the lens surface could also be found by using this method. The implementation of the method is shown by using computer simulations in the case of biconvex lenses. The method can be utilized to measure the parameters of plano-convex and concave lenses also.

Novel Method for Determining Hydrogel and Silicone Hydrogel Contact Lens Transmission Curves and Their Spatially Specific Ultraviolet Radiation Protection Factors

Anterior ocular tissues exposed to high levels of toxic ultraviolet (UV) radiation may undergo physiologic changes leading to diseases that can alter the ocular surface, particularly in the stem cell-rich limbal region. UV radiation-blocking hydrogel contact lenses provide protection across the ocular surface, which varies according to the lens thickness. A novel fiber optic spectrophotometer front-end system has been developed to measure lens transmission curves at test points across lens surfaces to determine optical properties based on the Beer-Lambert law. Factors determining the transmission curves include the hydrogel lens used, its refractive index, whether a UV radiation-blocking dopant is incorporated, the water content, and the thickness of the lens. Test lenses of equal power were placed over a detecting fiber optic and illuminated by a deuterium source, and transmission spectra were recorded. The small optical sampling size allowed the spectral transmission profile to be determined across the lens surface, and comparisons were made with different lenses. Transmission curves across the lenses showed greater UV radiation-blocking capacity at the thicker peripheral region, with the 50% cutoff wavelength moving toward the visible spectrum by 10 nm from the center to the periphery. In addition, the ability to determine the spatially specific absorption coefficient and the related UV radiation protection factor was demonstrated. The system measures spatial variation in lens transmission and comparing different lens types while overcoming many of the handling limitations of cuvette-based spectrophotometer methods. The data show good agreement with published transmission curves and allow intralens and interlens comparisons.

The use of defocussed position of a Ronchi grating for evaluating the refractive index of lens

This report describes a Ronchi-grating shearing interferometric collimation method for determining the refractive index of a lens. A new formula has been deduced for the refractive index of the lens, which is independent of lens parameters. This newly developed device has two lenses. One of them collimates the light from a point source while the other acts as a decollimator. The point source acting as a test target is situated in the front focal plane of the collimator. The test lens is placed inside a glass cell in the back focal plane of the collimator. The Ronchi grating is exactly placed in the back focal plane of the decollimator, and a fringe-free space is observed in the common region. When the test lens is immersed in a liquid cell, it disturbs the focal point and hence interference fringes are observed. The combined system consisting of the test lens and the decollimator is moved to bring the focal point on the Ronchi grating. Thus, the difference between the two settings gives the amount of defocusing.

Self-calibration for transmitted wavefront measurements

Micro-optic components and subsystems are becoming increasingly important in optical sensors, communications, data storage, and many other diverse applications. To adequately predict the performance of the final system, it is important to understand the element's effect on the wavefront as it propagates through the system. The wavefront can be measured using interferometric means, however, random and systematic errors contribute to the measurement. Self-calibration techniques exploit symmetries of the measurement or averaging techniques to separate the systematic errors of the instrument from the errors in the test lens. If the transmitted wavefront of a ball lens is measured in a number of random orientations and the measurements are averaged, the only remaining deviations from a perfect wavefront will be spherical aberration from the ball lens and the systematic errors of the interferometer. If the radius, aperture, and focal length of the ball lens are known, the spherical aberration can be calculated and subtracted, leaving only the systematic errors of the interferometer. We develop the theory behind the technique and illustrate the approach with a description of the calibration of a microinterferometer used to measure the transmitted wavefront error of micro-optics.

Aberraciones ópticas en ojos con lentes de contacto medidas con el sistema de trazado de Rayos

To evaluate the impact of disposable soft contact lenses upon visual performance by comparing the optical aberrations of myopic eyes with and without the use of contact lenses. The optical aberrations of a set of 18 eyes were measured by a laser ray tracing system, an objective measurement method, enabling comparison of the findings of the naked eye, the eye plus a test lens, and the eye plus a disposable contact lens. There was a large variability among subjects, but the general tendency was that test lenses did not modify aberrations, whereas contact lenses tended to increase the ocular aberrations for large pupils by an average of 40%. There was a lower increase for smaller pupils. This study predicts there will be no significant adverse effects on the quality of vision from the use of disposable contact lenses worn under daylight conditions, but a small decline in night vision.

Relative performance of soft contact lenses having lathe-cut posterior surfaces with and without additional polishing

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.

Acinetobacter and Staphylococcus Aureus Ulcerative Keratitis After Laser in situ Keratomileusis Treated With Antibiotics and Phototherapeutic Keratectomy

To report a method of treatment for through-the-flap multibacterial ulcerative keratitis after laser in situ keratomileusis (LASIK). Bacterial ulcerative keratitis after LASIK was treated with topical and systemic antibiotics followed by flap lifting, cleaning, and phototherapeutic keratectomy (PTK). Follow-up examinations included in vivo confocal microscopy, corneal topography, and wavefront analysis. Rapid recovery of the ulcerative keratitis was observed after flap lifting and cleaning of the interface and PTK combined with topical and systemic antibiotics. Two years postoperatively, corneal topography showed a slight depression of the ulcer area and decentration of the photoablation. Wavefront analysis revealed an irregular scan with a pronounced coma-like aberration, which with a wavefront-guided custom test lens correction provided 20/16 visual acuity. Ulcerative bacterial keratitis is a possible sight-threatening complication of LASIK refractive surgery. Lifting and rinsing the flap combined with cleaning of the flap interface with PTK may be helpful in these conditions when regression of the ulcer does not occur with topical and oral antibiotic treatment.

Long‐term Lens Organ Culture System with a Method for Monitoring Lens Optical Quality¶

ABSTRACTThe Scan Tox™ System is a method for monitoring lens optical quality (focus or lack of focus) in culture conditions, which mimic conditions inside the eye. The ocular lens is an ideal organ for long‐term culture experiments because it has no direct blood supply and no connection to the nervous system. The Scan Tox™ System makes it possible to keep lenses for long‐term studies of up to a few weeks. The use of cultured lenses, mainly bovine, replaces the need for testing the effects of potentially damaging agents on live animals. This optical monitoring apparatus uses a computer‐operated scanning laser beam, a video‐camera system and a video frame analyzer to record the focal length and transmittance of the cultured lens. The scanner is designed to measure the focal length at points across the diameter of the lens. The lens container permits the lens to be exposed to a vertical laser beam from below. The laser source projects its light onto a plain mirror, which is mounted at 45° on a carriage assembly. The mirror reflects the laser beam directly up through the test lens. The mirror carriage is connected to a positioning motor, which moves the laser beam across the lens. The camera sees the cross section of the beams and, by examining the image at each position of the mirror, Scan Tox™ software is able to measure the quality of the lens by calculating the back vertex distance for each beam position. The cultured lenses continue to maintain their original refractive function. When foreign substances are introduced to a cultured lens, the Scan Tox™ System measures the resulting optical response. This provides a very sensitive means to follow early damage to the eye lens. Because the lens is maintained in an intact state in solutions that are similar to those inside the eye, the lens retains its normal recuperative powers. So in addition to measuring early damage, this system allows measurement of recovery from damage.

Self-imaging pitch variation applied to focal length digital measurements

Several approaches were developed in the literature for focal length measurements. In our experimental arrangement, a collimated laser beam illuminates a test lens with a Ronchi grating placed against this lens. This procedure gives rise to a series of classical Talbot images, although magnified due to the non-parallel illumination. In this configuration, we propose to relate the self-images positions and pitches to obtain the focal length. We designed a software that helps first to precisely focus each self-image plane by a best-contrast algorithm and then to take an intensity histogram along a direction perpendicular to the grating lines. A theoretical explanation, experimental results and error analysis are presented.

Long-term lens organ culture system with a method for monitoring lens optical quality

The Scan Tox System is a method for monitoring lens optical quality (focus or lack of focus) in culture conditions, which mimic conditions inside the eye. The ocular lens is an ideal organ for long-term culture experiments because it has no direct blood supply and no connection to the nervous system. The Scan Tox System makes it possible to keep lenses for long-term studies of up to a few weeks. The use of cultured lenses, mainly bovine, replaces the need for testing the effects of potentially damaging agents on live animals. This optical monitoring apparatus uses a computer-operated scanning laser beam, a video-camera system and a video frame analyzer to record the focal length and transmittance of the cultured lens. The scanner is designed to measure the focal length at points across the diameter of the lens. The lens container permits the lens to be exposed to a vertical laser beam from below. The laser source projects its light onto a plain mirror, which is mounted at 45 degrees C on a carriage assembly. The mirror reflects the laser beam directly up through the test lens. The mirror carriage is connected to a positioning motor, which moves the laser beam across the lens. The camera sees the cross section of the beams and, by examining the image at each position of the mirror, Scan Tox software is able to measure the quality of the lens by calculating the back vertex distance for each beam position. The cultured lenses continue to maintain their original refractive function. When foreign substances are introduced to a cultured lens, the Scan Tox System measures the resulting optical response. This provides a very sensitive means to follow early damage to the eye lens. Because the lens is maintained in an intact state in solutions that are similar to those inside the eye, the lens retains its normal recuperative powers. So in addition to measuring early damage, this system allows measurement of recovery from damage.

The impact of lens choice in the relief of contact lens related symptoms and ocular surface findings

Purpose : The aim of this study was to compare the efficacy of hioxofilcon A and omafilcon A soft contact lenses for the reduction of signs and symptoms of contact lens related dryness among contact lens wearers who presented with symptoms and signs at baseline. Methods : Forty dry eye subjects, 37 females and 3 males, were enrolled in this prospective, single-center, randomized, contra-lateral, cross-over study. Subjects were randomly dispensed hioxifilcon A and omafilcon A lenses for contra-lateral eyes. Lenses were worn daily wear for 3 months; for 6 weeks (2-week lens replacement) then lens types were crossed over to opposite eyes for 6 more weeks. Clinical examinations took place at baseline, 1 and 6 weeks in each cycle. Ocular surface signs and symptoms were evaluated by self-administered questionnaire. Results : Compared to baseline symptoms with habitual lenses, dryness, discomfort, and blurry vision were reported at a lower frequency and intensity with both test lens types ( p < 0.05, all comparisons, Wilcoxon Signed Ranks Test). Compared to baseline signs, there was an improvement in overall fluorescein staining for both lenses ( p < 0.05). Lissamine green staining showed improvement with omafilcon A lenses only ( p < 0.05). There was no change in tear break up time or bulbar redness. Conclusion : Symptoms and ocular surface staining associated with contact lens related dryness can be significantly alleviated by the use of hioxofilcon A or omafilcon A lenses, which yielded similar findings in this study.

Pseudomonas aeruginosa Corneal Binding After 24-Hour Orthokeratology Lens Wear

To examine the effect of short-term 24-hr orthokeratology lens (OKL) wear on Pseudomonas aeruginosa binding, epithelial surface cell morphology, epithelial sheet thickness, and stromal thickness in a rabbit model. Seventeen New Zealand white rabbits were treated according to the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. Partial membranectomy was performed on all rabbits 1 week before the experiments. Baseline values for epithelial and stromal thickness and epithelial surface cell size were determined by in vivo confocal microscopy in one randomly chosen eye (n = 6). One week later, rabbits were fitted in the same eye with a hyper oxygen-transmissible OKL. Twenty-four hours later, confocal microscopy was repeated. The second group of rabbits (n = 6) was fitted with an OKL in one randomly chosen eye for 24 hr. P. aeruginosa binding to the corneal epithelium was assessed for the control corneas and those exposed to the test lens. Scanning electron microscopy was performed on a third group of rabbits to assess epithelial surface damage (n = 5). There was a statistically significant difference (P<0.001) in P. aeruginosa binding between the control (1.11 +/- 0.74 x 10(5) colony-forming units per cornea) and the OKL-wearing eyes (2.74 +/- 0.69 x 10(5) colony-forming units per cornea). The central epithelium thinned by 6.5% after lens wear (48.2 +/- 1.9 microm to 45 +/- 1.7 microm, P=0.005); however, central stromal thickness increased by 7.3% (322 +/- 22 microm to 345 +/- 29 microm, P=0.006). Compared with the baseline value, central epithelial cell size increased significantly from 1,253 +/- 140 mm(2) to 1,627 +/- 393 mm(2) (29.4%, P=0.02). Scanning electron microscopy showed increased surface epithelial damage associated with OKL wear. This prospective, masked, pilot study showed that 24-hr hyper oxygen-transmissible OKL wear induced a statistically significant increase in P. aeruginosa binding to the epithelium of the rabbit cornea, accompanied by central epithelial thinning, stromal thickening, and surface cell damage assessed by scanning electron microscopy. Collectively, the data suggest that despite adequate lens oxygen transmissibility, the mechanical pressure inherent in the OKL design exerted on the corneal surface appears to be associated with increased adherence of P. aeruginosa to surface corneal epithelial cells, which may pose an increased risk for lens-related microbial keratitis, especially in overnight (i.e., closed-eye) wearing conditions. Future studies are needed to determine whether these results are similar in human wear and how P. aeruginosa binding during OKL wear compares with other lens-wearing modalities, such as daily or continuous soft lens wear.

Tolerancing and budget in design and production of test lenses for calibration of focimeters.

A focimeter is one of the basic clinical instruments used in every optometric practice, and verification of the accuracy and calibration of the instrument are of the utmost importance. Calibration is accomplished using special test lenses. These lenses must be of high quality and of nominal ophthalmic power that is known with high accuracy. The standard ISO 9342:1996 Optics and Optical Instruments: Test Lenses for Calibration of Focimeters imposes stringent requirements on permitted deviation from nominal ophthalmic power of test lenses. In this study, the influence of tolerancing and uncertainties in design and production of standard test lenses for calibration of focimeters was analyzed. Two approaches were used. First, the paraxial approximation was used to relate the lens parameters with ophthalmic power and to calculate the uncertainty budget. Second, exact ray tracing using a professional optical design program and tolerancing sensitivity analysis in conjunction with Monte Carlo simulation were used to evaluate the uncertainty budget and balance the required tolerances. The results of both approaches are compared and discussed in detail. The customary uncertainty budgeting based on simple paraxial approximation does not guarantee the compliance with the requirements of the ISO 9342:1996 standard. Consequently, such an approach is inadequate for characterization and tolerancing of test lenses for calibration of focimeters.

Topographical Thickness of the Epithelium and Total Cornea after Overnight Wear of Reverse-Geometry Rigid Contact Lenses for Myopia Reduction

To investigate topographical thickness changes of the epithelium and total cornea measured with optical coherence tomography (OCT) after overnight wear of rigid gas-permeable lenses. Reverse geometry design CRT (Dk=100) rigid (test) lenses (Paragon Vision Sciences, Mesa, AZ) were randomly fitted on one eye of each of 20 neophyte subjects (mean age, 24.6 +/- 2.7 years) and the other eye was fitted with an alignment tricurve rigid lens of the same material (control). Epithelial and total corneal thickness was measured at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after overnight wear. Refractive error was measured with an autorefractor. These measurements were repeated 20 and 60 minutes and 3, 6, and 12 hours after lens removal. After one night of lens wear, myopia decreased in the test eye by 1.18 +/- 0.81 D, which was significantly different from baseline (P<0.001). No significant change was found in the control eye. Twelve hours after removal, two thirds of the myopic reduction was still present. Different topographical swelling patterns were induced by the two lens designs, with greatest swelling occurring in the center with the control lens and in the midperiphery with the test lenses (polynomial regression: P<0.005). Significantly greater central corneal swelling was found with the control lens than the test lens (6.9% +/- 3.1% vs. 4.9% +/- 2.0%, respectively, P=0.006). The effect on epithelial thickness differed between lenses and depended on both position and time (F(48,912)=2.3; P=0.000). Immediately after removal of the test lens, the central epithelium was 5.1% +/- 4.5% thinner than baseline, and all other locations (P<0.005 post hoc tests) and the epithelium in the midperiphery showed significant thickening (1.9% on the temporal side and 2.4% on the nasal side, both P<0.006 compared with the baseline). There were no significant changes in epithelial thickness with the control lens during the study period (post hoc tests: P>0.05). The optical coherence tomograph is a sensitive instrument that can detect small changes in epithelial and corneal thickness across the entire cornea. Topographical thickness changes of the epithelium and total cornea induced by one night of reverse-geometry lens wear appear to be associated with the decrease of myopia.