The effect of tints on distance stereoacuity under varying retinal illuminations

Abstract

Background: Stereopsis is the accurate awareness of relative depth necessary for efficient hand-eye coordination and navigation. A popular brand of sunglasses claims to enhance depth perception. Aim: This study set out to investigate the effect of tinted lenses on distance stereoacuity under varying retinal illumination. Setting: This study was set at the Discipline of Optometry, University of KwaZulu-Natal. Methods: A pretest-post-test research design was used. Forty participants were recruited using convenience sampling. The Howard-Dolman apparatus was used to measure distance stereoacuity with different tints of a popular sporting brand under varying retinal illumination. The tinted lenses and their respective transmission values used included persimmon (61%), light grey (38%), G30 (30%) and black iridium (10%). The placebo comprised of a white lens (100% transmission). Habitual distance stereoacuity was measured with no lens as the control. Retinal illumination was varied with neutral density filters to simulate mesopic and scotopic conditions. The Friedman and paired t-tests were used to analyse the data. Results: The mean stereoacuity for each lens was significantly different across the three retinal illumination levels (p < 0.05). A statistically significant difference (p = 0.012) was found with only the light grey tint under scotopic conditions when compared to the habitual stereoacuity. However, clinically significant differences were noted with the persimmon, light grey and black iridium tints. Overall, poorer stereoacuity was noted in mesopic and scotopic conditions compared to photopic for all five lenses. Conclusion: Tinted lenses used had no statistically significant effect on distance stereoacuity but clinically significant changes were noted. However, the change in retinal illumination adversely affected distance stereoacuity.