Diurnal Variation in Choroidal and Retinal Thickness of the Early Treatment of Diabetic Retinopathy Study Macular Subfields Determined Using Swept-Source Optical Coherence Tomography

PURPOSE: To describe diurnal variation in choroidal thickness (CT) and retinal thickness (RT) of the nine Early Treatment of Diabetic Retinopathy Study (ETDRS) macular subfields determined using swept-source optical coherence tomography. METHODS: A prospective study was conducted on 24 healthy Korean volunteers who underwent two sequential measurements of a randomly selected eye at 9 a.m., 1 p.m., and 6 p.m. The radial scan mode was used. To determine the repeatability and reliability, we applied intragrader agreement using the intraclass correlation coefficient (ICC). RESULTS: Significant diurnal variation in CT was observed. The highest mean CT was found at 9 a.m. The lowest mean CT occurred at 1 p.m. There was excellent intragrader agreement, with the ICC ranging from 0.961 to 0.997. There was no significant diurnal variation in RT. CONCLUSION: There was significant diurnal variation in CT. The choroid was thinner at 1 p.m. than at 9 a.m. and 6 p.m.