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Purpose: The primary objective of this study is to determine whether there are significant differences in visual and refractive outcomes between gas permeable (GP) and non-GP wearers following a 1-month period of overnight orthokeratology (OK)., Methods: The study included 14 subjects between the ages of 18 and 42 years. Group 1 consisted of six subjects wearing GP lenses for the correction of myopia for, at minimum, 1 year. Group 2 consisted of eight subjects wearing soft contact lenses or spectacles for the correction of myopia. All subjects were fit into the BE design in Boston XO material and lenses were worn for a period of 1 month. Unaided visual acuity using high (90%) and low (10%) contrast log MAR Bailey-Lovie vision charts, subjective refraction, corneal topography, and slit lamp evaluation were performed. Subjects were evaluated at day 1, 7, 14, 21, and 30., Results: One eye of each subject was considered for analysis; the eye with the better response was chosen based on post-OK measures. The mean post-OK spherical equivalent was 0.29 +/- 0.55 D in the GP group and 0.37 +/- 0.46 D in the non-GP group; the difference was statistically significant (p = 0.03). Baseline astigmatism decreased in the non-GP group after OK while there was no significant change in the GP group. The mean high contrast acuities were 0.06 +/- 0.12 in the GP group and 0.17 +/- 0.07 in the non-GP group (p = 0.05), whereas the low contrast acuities were 0.18 +/- 0.17 in the GP and 0.02 +/- 0.09 in the non-GP group (p = 0.01)., Conclusions: Although the non-GP group has higher post-OK visual acuity and spherical equivalent statistically, the GP group has attained an average unaided acuity of >20/20 and residual myopia <0.5 D. Clinically, this shows that OK can be a promising technique in GP wearers.

Purpose: 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., Methods: 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., Results: 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 which PAL wearers had better vision. Error scores for the binocular near visual task performance between the four groups revealed subjects with GP multifocal lenses and PAL wearers to have the least errors, followed by monovision users and then soft bifocal wearers with the most errors., Conclusion: Subjects wearing GP multifocals, soft bifocals, monovision, and PAL spectacles have good binocular contrast sensitivity, satisfactory binocular low and high contrast acuity, and increased sensitivity to glare. Presbyopic subjects requiring the use of contact lenses under dim light levels could benefit from GP multifocal lenses. Contrast and glare sensitivity evaluations provide significant information regarding the visual performance of the presbyopic contact lenses and should be included in regular presbyopic contact lens fitting.

The three-point Vernier alignment (or acuity) test was conducted on children from 5 to 9 years old. There is a significant difference between the 5-9 year old subjects and those in age groups 10 to 19 and 20 to 29 years in Vernier performance. These data were also compared with previously published data from older subjects (up to age 70). We conclude that Vernier function has not fully matured within the age range of 5 to 9 years; this finding is consistent with previous results reported in the literature.

A very useful clinical vernier acuity or vernier alignment test has been developed in this and associated laboratories over a span of two decades. We seek to refine further this test, to seek internal inconsistencies and to optimize parameters used in a variety of devices and environments. Vernier testing, and many aspects of this work have been considered by numerous able scientists over a long time period (not reviewed here), but none have encountered conditions faced by this group, particularly in the developing world. The three point vernier alignment (acuity) threshold test (3Pt VeA test) employed here has broad applications; it can be used as a clinical test of vision status, for triage, and as a reference standard for vision testing (in general). As one example, if sufficient luminance is employed, the test is applicable in the presence of truly dense media disorders, even advanced leucomas, mature cataracts, intraocular bleeds, as well as combinations of these disorders, with or without a window to the retina. Only retinal and centrally-based neural disorders, eccentricity from fixation, and about 50% of hypermature cataracts affect outcomes. With minor alterations, this test can be employed to assess the visual field. An analysis of variance (ANOVA) was performed on a defined set of parameters, to enable us to understand better the special properties and requirements associated with this test. Results are not significantly altered between ages 10-94 years (not assessed here). Employing settings well above threshold for test spot detection and well separated individual test spots, changes in test spot luminance, or background luminance (or adaptation level), contrast, veiling glare, test spot size, clear and variously degraded images, seem not to affect meaningfully measured outcomes. If an observer can define well a center of gravity for each test spot viewed, he can align the three points with remarkable precision.

With certain (but not all) vernier acuity (VeA) stimulus displays observers exhibit no or slight performance decrements with aging. Because three-point VeA test displays are much more easily applied experimentally and clinically, we examined visual performance on this task as a function of age. Ages of groups tested ranged from 20 to 70+ years (some individuals were 90+ years old). Eyes were examined monocularly. We tested three- and two-point sharply defined VeA arrays and a three-point ground-glass-degraded display (simulating a 20/100 nuclear cataract). Gap or feature separations were varied. Results obtained with the three-point display showed little alteration with age. Image degradation resulted in reduction in performance when small gap separations were used between the test points, but only slight decrements for large gap separations were recorded. The finding that performance with certain VeA targets is largely unaffected by age is confirmed and is expanded.

Problem: If changes are made to the optics of the eye (e.g., intraocular lens implants, contact lenses, etc.) how will they affect performance on clinical tests of vision?, Method: A phenomenological method is presented based on in vitro optical transfer function (OTF) and a simple model of human threshold detection., Results: The model is used to predict and the results are compared with clinical data (acuity, contrast sensitivity) obtained from pseudophakic patients implanted with a multifocal intraocular lens (IOL). A good qualitative agreement is found with the clinical data., Significance: This model predicts the relative change in clinical performance for a given change in the optical components of the human eye. This simple phenomenological model permits numerical prediction of clinical tests and is easily calculable.

Purpose/background: Many visual functions change with age. Hyperacuity vernier thresholds, however, seem to remain practically invariant with age., Methods: We critically review reports on age-related changes in hyperacuity thresholds and present new data using two and three-point vernier hyperacuity thresholds., Results: It appears as though the vernier (two dot or two line) alignment hyperacuity thresholds are not sensitive to age., Significance: Based on these studies we propose that hyperacuity (vernier) thresholds be used as a benchmark, or a gold standard for aging studies. This measurement can serve as a valuable control and reference for other clinical studies of aging.

Responses to hyperacuity stimuli are processed in quite a different manner by the central nervous system than many other stimuli such as resolution targets or increment threshold stimuli. With increased attention being paid to visual response in aging individuals, it is important to study how these response paradigms are affected by age. In this analysis, otherwise normal observers 20 to 85 years of age were studied. The hyperacuity gap test was used. As defined, this is a vernier test using a two-point test array. This particular format was chosen because the resultant data are less distorted by image blur, scatter, and astigmatism than other designs we have studied. The gap or feature separation between the two small targets (which were aligned vertically) was increased logarithmically using octave steps and the hyperacuity threshold (setting variance) was measured for each step. No systematic variation of vernier hyperacuity threshold was found with increasing age within the range of ages or gaps tested. This is important because it can serve as a valuable control and reference for other clinical studies of aging.

We have developed a new technique for quantification of metamorphopsia using a simplified and modified Amsler grid. Furthermore, the technique used is a bisection task, a form of hyperacuity determination. This allows for very fine assessments of metamorphopsia even in the presence of cataracts.