Diurnal Variation of Choroidal Thickness in Primary Open-angle Glaucoma

Purpose: To investigate, in primary open-angle glaucoma (POAG) and healthy subjects, the pattern and magnitude of diurnal variation in macular choroidal thickness (mCT). Methods: A prospective study was conducted on Koreans comprising 21 patients with POAG and 17 healthy subjects. All underwent mCT, systemic blood pressure (BP), and intraocular pressure measurements during the daytime at 5 time points (8 am, 11 am, 2 pm, 5 pm, and 8 pm). The mCT was determined at 5 sites using swept-source optical coherence tomography. Results: In the healthy subjects, the mean mCT was 233.63 +/- 50.98 mu m at 8 am, which then decreased gradually to 2 pm (206.02 +/- 45.91, P=0.015) and increased again in the evening (8 pm; 228.12 +/- 51.69, P=0.030). The mean mCT in the POAG patients at 8 am, 246.50 +/- 48.94 mu m, also decreased to 226.77 +/- 51.48 at 2 pm (P=0.027) but did not increase in the evening (229.07 +/- 50.87; P=0.566). However, the overall diurnal variation of mean mCT was not statistically significant in either group (P=0.179 and 0.164, respectively). The systolic BP, diastolic BP, and mean ocular perfusion pressure of the POAG had the peak value at 8 am and the trough value at 8 pm (P=0.001, 0.002, and <0.001). Conclusions: The mCT in the POAG patients did not increase in the evening relative to the healthy subjects' pattern. However, the diurnal mCT values measured in the healthy subjects and POAG patients were not statistically significant.