Effect of Atropine Eye Drops on Choroidal Thinning Induced by Hyperopic Retinal Defocus

PURPOSE: To investigate the effects of atropine on choroidal thinning induced by hyperopic retinal defocus. METHODS: Ten young adults with myopia (−1.00 D to −5.00 D) viewed a video at 6 metres for 60 minutes on successive days. On day 1, one eye (control) was distance corrected with a contact lens; the other (experimental) eye wore a contact lens imposing 2.00 D of hyperopic retinal defocus. Sub- and perifoveal choroidal thickness (SFCT, PFCT) were monitored with optical coherence tomography. On day 2, the procedure was repeated but the experimental eye had received one drop of 0.5% atropine 22 hours earlier. RESULTS: On day 1, eyes exposed to hyperopic defocus developed progressively thinner choroids (SFCT (baseline) = 253 ± 32 μm versus SFCT (40 mins) = 244 ± 31 μm, p = 0.004), whereas SFCT and PFCT in control eyes did not change (p > 0.17). On day 2 (22 hours after instilling atropine), baseline SFCT and PFCT were not different to day 1 (p > 0.05) and hyperopic defocus failed to thin the choroid (max change in SFCT = +2 ± 2 μm, p = 0.36). CONCLUSIONS: Atropine abolished choroidal thinning induced by hyperopic defocus without changing baseline choroidal thickness. The results suggest that atropine inhibits signals associated with hyperopic defocus, for example, from lag of accommodation during near work. This trial is registered with ACTRN12617001519347.