Changes in refractive components after a short exposure to astigmatic blurs in young adults

Abstract

Purpose : Astigmatism is a very common refractive error in Native American and Asian Chinese. Recent studies have reported the effects of optically imposed astigmatism on ocular parameters in humans and chickens. This study investigated the effect of astigmatism on refractive changes in young Chinese adults. Methods : Nineteen non-/ low-myopic young adults (age: 18-24 years; spherical-equivalent error: 0DS to –5.00DS, cylindrical error <= 0.75DC) with unremarkable ocular health were recruited. Participants wore a trial frame to watch a movie for 60 minutes, with one eye chosen randomly as the treated eye and the fellow eye served as control. In three separate visits, while the control eye was fully corrected optically, the treated eye was exposed to one of three defocused conditions in random sequence : 1. Myopic defocus (SPH): +3.00 DS 2. With-The-Rule (WTR) astigmatism: +3.00 DC x 180° 3. Against-The-Rule (ATR) astigmatism: +3.00 DC x 90°Before and after watching the movie, spectacle over-refractions were measured by a Shin Nippon open-field autorefractor. Results : A significant interaction effect (treatment*time) was found for the interocular difference in J0 astigmatic component (p < 0.001): the interocular difference significantly reduced in magnitude for both the WTR condition (Change: -0.25 ± 0.10 D, p = 0.022) and the ATR condition (Change: +0.39 ± 0.15 D, p = 0.017), suggesting an active refractive compensation to reduce the difference in the perceived astigmatic blur between fellow eyes. However, the change was not significant in the SPH condition (p = 0.129). There was also no such effect in the J45 astigmatic component, spherical-equivalent error, and other biometric parameters (all p > 0.372). Conclusions : Optically imposed astigmatic blur for an hour led to bi-directional changes in the astigmatic component, suggesting that young adults are susceptible to refractive changes in response to orientation-dependent astigmatic blur.