Atropine Affects the Outer Retina During Inhibiting Form Deprivation Myopia in Guinea Pigs

Abstract

Purpose: Atropine has been proven to be effective in retarding myopia progression. However, the underlying mechanism remains unknown. Our purpose was to detect morphological and functional changes caused by atropine during myopic inhibition. Method: Twenty 2-week-old guinea pigs were randomly assigned to either the saline group (n = 10) or the atropine group (n = 10). Form-deprived myopia (FDM) and intravitreal injections were applied on the right eyes. The injections were given every 3 days, lasting for 2 weeks. The left eyes served as control. Ocular refraction, axial length, retinal, and choroidal thickness were collected at the start and the end of the experiment. Retinal function was evaluated via full-field electroretinogram (ERG) at the end of treatment. Results: The interocular differences (experimental eye minus control eye) of refraction error (RE), vitreous chamber depth (VCD), and axial length (AL) in the saline group were significantly greater than those in the atropine group (RE, VCD: P < .001, AL: P < .0001). The differences in choroidal thickness between the two groups did not reach statistical significance. However, a decreasing trend of choroidal thickness was observed in the saline group but not in the atropine group. Furthermore, the interocular differences of total retinal and outer retinal thickness in the atropine group were much thicker than in the saline group (P < .001 and P < .01, respectively). The treatment did not affect inner retinal thickness. In photopic ERG, the atropine-treated FDM eyes showed significantly greater a-wave amplitudes compared to the saline group. Conclusion: During the process of inhibiting FDM, atropine showed an effect on the outer retina, most likely on the cones, in guinea pigs.