Effect of short-term exposures to near work environments on photopic electroretinography

Purpose To investigate the changes in photopic retinal electrophysiological
responses after near work under different environments in terms of scene defocus profiles based on the dioptric uniformity hypothesis.
Methods Eighteen healthy myopic Asian young adults age 19–24 years (mean ± SD: 20.99 ± 1.5 years) were recruited. In each of the 3 visits, participants viewed a 30-min video under exposure to one of 3 simulated near work visual scenes with low, mid, and high level of scene defocus dispersion (SDd); these were anticipated to impose an increasingly myopiagenic stimulus to the participant.
Photopic standard full-field flash and the 30-Hz flicker ERG were measured before and after scene exposure. Normalized percentage changes in amplitude and implicit time of a- and b-waves and flicker responses were extracted for analysis.
Results The spherical equivalent refraction of subjects ranged from - 1.00 D to - 5.38 D (- 3.20 ± 1.39 D; 8 had low myopia of lower than - 3.00 D and 10 had moderate myopia greater than or equal to - 3.00 D). There was no significant difference in the percentage change in either the amplitude or implicit time of the a- or b-wave under different SDd. The percentage change in amplitude of the
30 Hz flicker ERG was stratified by myopia severity, and statistically significant reduction was obtained under high SDd exposure in moderate myopes (mixed ANOVA, SDd*myopia severity: F2,32 = 3.68, p = 0.04) but not in low myopes.
Conclusions Significant reduction in the 30-Hz flicker ERG, representing post-receptoral function of the cone pathway, was found in moderate myopes after 30 min of near work under high SDd conditions. Our results implied that dispersed defocus profile in the environment may weaken inner retinal activity in moderate myopes and may relate to myopiagenic risks.