Presenter(s)

Alyssa Hood

Abstract or Description

Purpose

Minimum visible (detectable) acuity (MDA) is the thinnest line one can detect on a specific background. We developed a cone specific measure of MDA reported in the nature Journal EYE (https://doi.org/10.1038/s41433-024-03377-7). Our purpose was to extend this research to determine if cone specific MDA improves with color vision correcting lenses.

Rationale and Significance

Hereditary color vision deficiency(CVD) is a non-progressive X-linked condition affecting 8% of males and 1/200 females. It reflects a shift in peak sensitivity of either red (long wavelength, L) or green (middle wavelength, M) cones or in more severe cases the absence of either L or M cones. MDA is the finest black line visible on a white background and can be thin as 1” of arc, much less than diameter of a human cone (30” of arc) and hence may be considered a hyperacuity processed in the visual cortex. Our cone specific test of MDA, based on stimulation of specific cone types used in the cone contrast test (https://www.innovasystemsusa.com/), reveals hereditary CVD.Herein we show that color vision correcting lenses (CCLs, www.enchroma.com) significantly improve cone specific MDA.

Methodology

Fifteen CVDs (confirmed by Ishihara, cone contrast test, age 26 ± 8, 13 green, 2 red CVDs) participated after written informed consent in accord with our IRB approved protocol. MDA stimuli: 1.4° vertical, horizontal, or oblique lines centered on a Microsoft Surface display (3. 7° x 2.1°) at 4 m in a dark room. Each line was an increase in L, M, S cone or luminance (grey) stimulation against a grey background (24.7 cd/m2, x,y = .32, .36) converted to cone or luminance contrast. Weber contrasts for L, M, luminance:16%, S cones:128%. Line thickness varied from 60" to 10" of arc in 0.16 log steps. On each trial a single line appeared on the display. Subjects reported color and orientation (.01 log units/trial) with color andorientation varied across trials. Log MDA thresholds were distributed normally for CVDs (Jarque Berra test, P > 0.69without CCLs, P > 0.45 with CCL). Parametric analyses were used with Bonferroni correction for multiple comparisons.

Findings

Two-way repeated measures ANOVA across cone type (normal, abnormal, S cone, luminance, F = 2.26 P > 0.09) and spectacle correction (with vs. without CCLs, F = 3.69, P > 0.05) both approached significance. However post-hoc t tests revealeda significant improvement in mean MDA threshold with CCLs for the abnormal cone type (mean MDA threshold 1.37 log sec, 23.6”) compared to the MDA threshold without CCLs (1.53 log sec, 34.2”, mean difference 0.16 log CS, 11”, 95% CI 0.06 –0.26, P < .006). Wilcoxon signed rank test: 80% of CVDs showed improvement with CCLs, P < .002). These findingsprovide the first definitive results that CCLs can improve color vision in a novel MDA hyperacuity test. The cortical basis of this metric provide a powerful index of the efficacy of CCLs for improvement of performance in CVDs.

Mentor

Dr. Jeff Rabin