Effect of Optical Defocus on Choroidal Thickness in Healthy Adults With Presbyopia

PURPOSE. To investigate changes in subfoveal choroidal thickness (SFCT) induced by retinal defocus in presbyopic adults. METHODS. Thirty-seven healthy presbyopic subjects (age 57.74 +/- 4.06 years) with low refractive errors (+0.08 +/- 1.09 Diopters [D]) viewed a distant target (video movie at 6 m) for 60 minutes on two occasions while SFCT was monitored with optical coherence tomography every 20 minutes. On each occasion, both eyes were optimally corrected for distance: one eye acted as control, while the other (experimental) eye viewed through an additional ophthalmic lens: a +2.00 D lens imposing myopic defocus on one occasion and a -2.00 D lens imposing hyperopic defocus on the other occasion. RESULTS. Baseline SFCT was not different between experimental and control eyes (226 +/- 72 mu m vs. 232 +/- 75 mu m; P 1/4 0.28). Myopic defocus caused a significant (P < 0.001) increase in SFCT in the defocused eye by 20 minutes (and +10 +/- 5-mu m increase at 60 minutes: P < 0.001), while hyperopic defocus caused a significant decrease in SFCT by 20 minutes (and -10 +/- 5-mu m decrease at 60 minutes: P < 0.001) with no change in control eyes. CONCLUSIONS. In presbyopic subjects, imposed myopic retinal defocus caused thickening of SFCT, while hyperopic defocus caused thinning of SFCT. This implies that uncorrected presbyopia, which is associated with hyperopic retinal defocus for near objects and which is highly prevalent in the developing world, would likely be associated with choroidal thinning and possibly reduced choroidal blood flow with prolonged periods in a near visual environment.