Diurnal variation in retinal thickening measurement by optical coherence tomography in center-involved diabetic macular edema

Abstract

Objective: To evaluate diurnal variation in retinal thickness measured with optical coherence tomography (OCT) in patients with center-involved diabetic macular edema. Methods: Serial OCT3 measurements were performed in 156 eyes of 96 subjects with clinically diagnosed diabetic macular edema and OCT central subfield retinal thickness of 225 μm or greater at 8 AM. Central subfield thickness was measured from OCT3 retinal thickness maps at 6 points over a single day between 8 AM and 4 PM. A change in central subfield thickening (observed thickness minus mean normal thickness) of at least 25% and of at least 50 μm at 2 consecutive points or between 8 AM and 4 PM was considered to have met the composite outcome threshold. Results: At 8 AM, the mean central subfield thickness was 368 μm and the mean visual acuity was 66 letters (approximately 20/50). The mean change in relative central subfield retinal thickening between 8 AM and 4 PM was a decrease of 6% (95% confidence interval, -9% to -3%) and the mean absolute change was a decrease of 13 μm (95% CI, -17 to -8). The absolute change was significantly greater in retinas that were thicker at 8 AM (P