Potential vision testing – the relationship between visual acuity and Vernier acuity in the presence of simulated cataract

Abstract

To evaluate the utility of a computer controlled two-bar Vernier acuity measurement as a predictor of visual function in the presence of cataract we measured logMAR visual acuity and Vernier acuity in a group of 40 young normal observers under various levels of dioptric blur (0-3 D in dioptre steps). The Vernier thresholds were resistant to dioptric blur up to 2 D, but performance degraded with blur of 3 D for non-optimised Vernier stimulus parameters. The stimulus parameters, bar length and bar separation, were further investigated in two subjects under conditions of blur. By extending the Vernier bar length and increasing the bar separation the effect of blur could be further reduced even under the most blurred condition. The relationship between visual acuity and Vernier acuity was determined. Vernier acuity was measured in the presence of Vistech cataract simulating lenses and a prediction of visual acuity was made for three observers, two with no ocular abnormality and one with age-related maculopathy. The cataract simulating lenses affected the measured visual acuity in all three subjects, but had less effect on Vernier acuity. Predicted visual acuities were all within six letters (0.12 log units) of the visual acuity without the simulated cataract. As expected, the subject sufferng from age-related maculopathy, whilst showing similar levels of Vernier acuity to the two ocularly healthy subjects at 1.5 degrees of retinal eccentricity, showed much poorer Vernier acuity for stimuli presented at fixation.

Distance and near visual performance in pseudophakic eyes with simulated spherical and astigmatic blur

“…Myopic defocus (+1.00 DS) degraded distance HCVA by ~30% less than astigmatism, close to the power strength ratio (0.71) prediction . The spherical blur was less than that found in phakic eyes, possibly related to the extended depth‐of‐focus interval in pseudophakic eyes . For near vision, spherical refraction changes near VA by ~0.18 logMAR/DS compared with the ~0.10 logMAR/DC provided by the astigmatic refraction.The present data suggests that a pseudophakic eye with 1.00 DS of myopia will have better distance and approximately the same near VA as an astigmatic eye with 2.00 DC.…”

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

“…Quaid et al ( 2002 ) reported a correlation coefficient between Vernier acuity and optotype acuity of r = 0.8 for normal subjects. In our total population, we find that r = 0.52 ( p < 0.001); for our controls, we find r = 0.55 ( p = 0.0025); and for ASD, we find r = 0.57 ( p = 0.0057).…”

Stereopsis in end-stage renal disease (ESRD)

“…22 The effects of contrast reduction are greater on stereoacuity than on Vernier acuity. 20 Thus the differences we found between the stereoblind and stereoscopic subgroups could result from some optical degradation (perhaps refractive error, cataract, and/or deposits in the cornea) which was large enough to produce a differential effect on Landolt acuity and stereoacuity, but not large enough to affect Vernier acuity differentially. This notion is also supported by the correlation between Landolt acuity and stereoacuity in the stereoscopic patient subgroup.…”

“…In contrast, our data from the Landolt test, showing greater impairment in the stereoblind subgroup, appear to be consistent with differences within the eyeball, either optical or retinal, between the two patient subgroups. For example, Quaid et al 20 showed that blurring with positive lenses or with contact lenses which simulate cataracts had a greater effect on letter than on Vernier acuity. In their study, blurring had little effect on Vernier acuity below two dioptres.…”