Seasonal Fluctuation in Intraocular Pressure and Retinal Nerve Fiber Layer Thinning in Primary Open-Angle Glaucoma

Purpose: To detect seasonal fluctuations in intraocular pressure (IOP) in healthy eyes and eyes with primary open-angle glaucoma (POAG) and to evaluate whether these seasonal fluctuations affect retinal nerve fiber layer (RNFL) thinning in eyes with POAG. Design: Observational, retrospective cohort study. Participants: Healthy population who underwent a comprehensive health check-up and patients with POAG using only topical medications were enrolled. Methods: Kaplan-Meier survival analysis was used to compare the cumulative incidence probabilities of RNFL thinning between different seasonal IOP fluctuation groups. A Cox proportional hazards model, with adjustments for potential confounding factors, was used to evaluate the association between seasonal fluctuations in IOP and RNFL thinning. Main Outcome Measures: Intraocular pressure fluctuation rate calculated from winter and summer IOPs and RNFL thinning as determined by event-based analysis with high-definition OCT. Results: A total of 12 686 healthy eyes and 179 eyes of 179 POAG patients showed a significantly higher IOP in winter than in summer (healthy, 13.2 +/- 3.0 mmHg vs. 12.5 +/- 2.9 mmHg [P < 0.001]; POAG, 13.1 +/- 2.7 mmHg vs. 11.8 +/- 2.3 mmHg [P < 0.001]). In POAG patients, the mean age at initial OCT and follow-up duration were 55.1 +/- 11.7 years and 98.4 +/- 26.4 months, respectively. The mean deviation (MD) at first visit, MD slope, and RNFL thinning rate were-2.2 +/- 3.4 dB, -0.07 +/- 0.44 dB/year, and -0.44 +/- 0.88 gm/year, respectively. During the study period, 85 eyes (47.5%) showed RNFL thinning progression. Kaplan-Meier analysis showed that a high seasonal IOP fluctuation rate significantly suppressed RNFL thinning (P < 0.05, log-rank test). After adjusting for confounders in the Cox analysis, the seasonal IOP fluctuation rate still showed a significantly negative association with RNFL thinning (hazard ratio, 0.98; 95% confidence interval, 0.96-0.99; P = 0.005). Conclusions: Winter IOP was higher than summer IOP in both healthy and POAG eyes. The temporary IOP decline in summer, rather than a constant IOP throughout the year, may prevent glaucoma progression. (C) 2020 by the American Academy of Ophthalmology.