Interaction of atropine and retinal image defocus on choroidal thickness in children with myopia

Abstract

Purpose: Both atropine and retinal image defocus modify myopia progression in humans. The choroid has been implicated in eye growth and myopia development, particularly in animals. This study investigates the interaction of atropine and imposed retinal defocus on subfoveal choroidal thickness (SFCT) in children. Methods: Twenty Taiwanese children (aged 6 to 14 years) with myopia (-0.75 to -4.00 D) participated in the study. During distance viewing, SFCT was monitored by Optical Coherence Tomography (OCT) in both eyes while 2.00D of hyperopic and myopic retinal defocus (randomly ordered) was imposed in the Experimental eye for 60 minutes, with the contralateral Control eye fully corrected for distance. These protocols were repeated before 0.3% atropine treatment and after 1 week, 3 and 6 months of atropine treatment to both eyes. Results: Before atropine, experimental eyes exposed to 60 minutes of 2.00D myopic and hyperopic defocus developed thicker and thinner choroids respectively (Myopic: SFCT(baseline) = 271 ± 72 µm vs SFCT(60 mins) = 283 ± 73 µm, p < 0.01, and Hyperopic: SFCT(baseline) = 274 ± 72 µm vs SFCT(60 mins) = 262 ± 72 µm, p < 0.01), whereas SFCT in Control eyes did not change (p > 0.20). After 1 week of atropine, baseline SFCT (without defocus) in both eyes had increased by ~20 µm, and 60 minutes of hyperopic defocus failed to cause choroidal thinning, although myopic defocus caused a further increase in SFCT. These effects remained essentially the same after 3 and 6 months of atropine treatment. Conclusions: The normal reduction in SFCT in response to hyperopic retinal defocus is inhibited by 0.3% atropine, while the normal increase in SFCT with myopic defocus is unaffected. This may imply that choroidal thinning and thickening are mediated by different mechanisms. These changes are superimposed on an increased baseline SFCT caused by atropine. The additive effect of myopic defocus and atropine on choroidal thickening suggests that combining optical and pharmaceutical therapies into dual therapies is likely to provide more effective myopia control than either therapy alone.