Seasonal fluctuation in intraocular pressure and its associated factors in primary open-angle glaucoma

Background/Objectives To evaluate seasonal fluctuations in intraocular pressure (IOP) in primary open-angle glaucoma (POAG) and its associated factors. Subjects/Methods POAG patients treated only with glaucoma eye drops were enroled. Winter and summer IOPs were evaluated. The Seasonal fluctuation rate of IOP was defined as follows: (mean winter IOP-mean summer IOP)/mean IOP in all seasons. Multiple linear regression analysis was used to explore factors associated with the seasonal IOP fluctuation rate including: age, gender, family history of glaucoma, type of glaucoma, number of eye drops, type of eye drops, mean deviation (MD) value, MD slope, disc haemorrhage, central corneal thickness and spherical equivalent. Results Winter IOP was higher than summer IOP in 204 POAG eyes of 204 patients, including 162 eyes with normal tension glaucoma (NTG) (13.2 +/- 2.7 vs. 12.0 +/- 2.3 mmHg, P < 0.001). The mean age and follow-up duration were 63.3 +/- 11.4 years and 140.0 +/- 66.9 months. Initial MD and MD slope were -2.1 +/- 3.4 dB and -0.07 +/- 0.50 dB/year, respectively. POAG was positively associated with the rate of seasonal IOP fluctuations compared to NTG (beta = 5.29, P = 0.013). Family history, and timolol and carteolol use were also factors associated with the IOP fluctuation rate (beta = -6.27, P = 0.007; beta = 4.94, P = 0.030; and beta = 4.51, P = 0.042, respectively). Conclusions We confirmed seasonal IOP fluctuations in POAG. Type of glaucoma, family history of glaucoma, and beta-blocker use might influence IOP fluctuations.