Photostress Recovery Time after Flash-Lighting Is Increased in Myopic Eyes

Background: It is well-known that non-pathological axial myopic eyes present physiological and functional differences in comparison with emmetropic eyes due to altered retinal anatomy. Photostress tests have shown very significant capabilities to discriminate a normal retina from an abnormal retina. Accordingly, the aim of this work was to investigate the differences between myopic and emmetropic eyes in the measured photostress recovery time (PSRT) after retinal light-flashing in a population of young healthy subjects. Methods: A coaxial illumination total disability glare instrument was employed to measure the recovery time after photostress was induced by a 240 milliseconds flash-lighting (535 nm) exposure on 66 myopic and 66 emmetropic eyes. The measurements were carried out for different combinations of glare angles and contrasts of the visual stimuli. Results: In general terms, PSRT in myopic eyes was found at a statistically higher than in emmetropic eyes (Bonferroni correction). For both groups, the measured recovery strongly depends on the contrast of the test object used to measure baseline recovery function and markedly less on the source of glare angles explored. When the PSRTs obtained for different glare angles are averaged, the differences between PSRTs drastically increase with the reduction in the contrast of the stimuli between both groups of study. Conclusions: PSRT is higher for myopic than for young healthy emmetropic eyes (1.2 s and 0.2 s for 5% and 100% contrast test object, respectively). Though seemingly small, the magnitude of this finding can be relevant when flash-lighting happens while driving a car or while performing actions where the reaction time after a visual stimulus can be critical.