Electroretinogram response changes in a guinea pig myopia model treated with different atropine concentrations.

PURPOSE: We used electroretinography (ERG) to assess whether different concentrations of atropine alter the electrical activity of retinal cells during inhibition of myopia progression. MATERIAL AND METHODS: Myopia was established in 14-day-old guinea pigs using -10.00 diopter spectacle lenses in the right eye. Topical atropine eye drops (0.01% and 1%) and sterile water (vehicle) were subsequently administered to the right eyes starting at 2 weeks postnatally. All animals in each group underwent refraction and ERG measurements at weeks 2, 4, 6, and 8. RESULTS: The degree of myopia decreased in atropine-treated eyes in a dose-dependent manner. The ERG results revealed that atropine did not significantly affect scotopic or photopic a-wave amplitudes or implicit times at any time point in lens-induced guinea pigs. Similarly, the scotopic b-wave in lens-induced guinea pigs was unaffected by atropine treatment. By contrast, atropine significantly increased photopic b-wave amplitudes in a dose-dependent manner in treated lens-induced eyes, but only at weeks 6 and 8. The b/a ratio decreased sequentially in the 1% atropine, 0.01% atropine, and vehicle groups on photopic ERG. In the vehicle group, no statistically significant differences in photopic b-wave amplitude or b/a ratio from the left and right eyes were observed at any experimental time point; however, significant differences were observed at weeks 6 and 8 in the 0.01% and 1% atropine groups. CONCLUSIONS: The results imply that atropine acts on photopic ERG b-wave-producing cells during the process of retarding lens-induced myopia, raising the possibility that atropine may affect the depolarization of bipolar cells in myopic guinea pigs.