Season, Weather, and Intraocular Pressure: A Monocentric Retrospective Analysis from 2016 to 2021

PURPOSE: We investigate the relationship between intraocular pressure (IOP) and environmental factors, such as daily mean temperature, daily cumulative sunshine duration, and daily mean atmospheric pressure. METHODS: = 199,804) in the Eye Center, University Hospital Freiburg, Germany. IOP values below 5 and above 30 mm Hg were excluded. No other exclusion criteria are applied. Analysis of variance was performed to assess seasonal variations in IOP. We fitted a multiple linear regression model to analyse the respective influences of age on the time of measurement, daily mean temperature, daily cumulative sunshine duration, daily mean atmospheric pressure, and time of day at measurement on IOP. We also performed cross-correlations to check for periodicity and time-lag between IOP and the aforementioned environmental factors. RESULTS: IOP was highest in January (15.0 ± 3.8 mm Hg) and lowest in July (14.6 ± 3.6 mm Hg). Cross-correlation and Fourier analysis support annual periodicity and a seasonal pattern of IOP. Multiple linear regressions revealed a significant negative correlation between daily mean temperature, age at measurement, and total sunshine duration of the preceding 10 days before measurement with IOP. Atmospheric pressure and time at measurement missed statistical significance. CONCLUSIONS: We observed an annual periodic IOP variation with an amplitude of ≈0.4 mm Hg. The variation is most likely attributable to a direct effect of environmental temperature and secondly to biological factors triggered by sunshine exposure over the preceding 10 days or secondary behavioral changes.