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.
Highlights
Stereopsis is the fusion of horizontal retinal image disparity which gives rise to the perception of relative depth and distance.[1]
Stereoacuity is often measured in a clinical setting and has applications in the assessment of binocular vision including screening for amblyopia, aniseikonia and anisometropia.[6]
The habitual stereoacuity was significantly different at the three illumination levels (c 2 = 12.636, p = 0.002) where better stereoacuity was noted in photopic compared to mesopic and scotopic conditions
Summary
Stereopsis is the fusion of horizontal retinal image disparity which gives rise to the perception of relative depth and distance.[1] Even though not essential for the perception of depth, stereopsis allows for the accurate judgement of distances between two objects which complements efficient hand–eye coordination and navigation, at intermediate distances.[2,3,4] Stereoacuity, the clinical measurement of stereopsis, is expressed in seconds of arc (arcsec) and represents the smallest horizontal retinal image disparity resulting in the perception of depth.[5] The lower the stereoacuity, the better the stereopsis. 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
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