Time of Day Effects of Contact Lens-Induced Full-Field and Peripheral-Field Defocus on Choroidal Thickness: A Pilot Study in Adults

PURPOSE: To determine the effects of contact lens-induced full-field and peripheral-field myopic defocus on choroid thickness and variation with time of day in young adults. METHODS: In this prospective, randomized, crossover study, 16 adults (age 28.2±6.3 years) participated in four experimental sessions (two morning and two evening). At each session, optical coherence tomography (OCT) was performed before and 60 min after distance viewing with either full-field or peripheral-field +2.50 D contact lens-induced defocus in the left experimental eye and distance correction in the right eye. Recovery was assessed after 20 min with distance correction in both eyes. Choroidal thickness was analyzed using a custom MATLAB program and two-factor repeated-measures ANOVAs. RESULTS: Mean spherical equivalent refraction was -1.7±1.7 D in right eyes and -1.9±2.0 D in left eyes (P=0.20). Baseline choroidal thickness was greater in the morning (326±71 μm) than evening (316±72 μm, P=0.006). No significant changes occurred after 60 min for either full field or peripheral-field in the morning or evening (P>0.05 for all). CONCLUSION: One-hour exposure to full-field or peripheral myopic defocus did not alter choroidal thickness, irrespective of time of day, in young adults with a range of refractive errors. Studies in children, particularly with longer durations of imposed defocus, are needed to determine whether short-term structural responses may serve as clinically meaningful biomarkers.