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

We used electroretinography (ERG) to assess whether different concentrations of atropine alter the electrical activity of retinal cells during inhibition of myopia progression.

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.

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.

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.