Effects of Daily Ambient Temperature on Intraocular Pressure: A Time-Series Analysis Using Generalized Additive and Distributed Lag Nonlinear Models.

Purpose: The purpose of this study was to investigate the potential nonlinear association between ambient temperature and intraocular pressure (IOP), as well as the short- to medium-term lagged effects of temperature exposure on IOP. Methods: A time-series study was conducted using 2018 to 2023 outpatient data from Shimane University Hospital in Izumo, Japan. Daily meteorological data were obtained from the Japan Meteorological Agency. We analyzed the association between ambient temperature and IOP using generalized additive models (GAMs) to assess nonlinearity, and distributed lag nonlinear models (DLNMs) to evaluate cumulative lag-effects. The main model was adjusted for time-related confounders (timeline, day of the week, public holidays, and season). Results: We analyzed 1269 observation days comprising 33,979 IOP measurements: 921 days with 8756 measurements in the non-glaucoma group and 1182 days with 25,173 measurements in the glaucoma group. In the non-glaucoma group, nonlinear associations with IOP were suggested for daily temperatures, with significant increase at average temperatures between 2.2°C and 12.2°C. In the glaucoma group, no nonlinear associations were detected. Cumulative exposure to warm average temperatures was associated with lower IOP in the non-glaucoma group (lag 0-6 = 15.6-21.1°C and lag 0-13 = 15.6-29.6°C), whereas colder ranges (lag 0-6 = 14.6-15.1°C and lag 0-13 = 13.1-15.1°C) increased IOP in the same group. Conclusions: Ambient temperature may be associated with IOP through nonlinear relationships and short-term cumulative effects, particularly in the non-glaucoma group. These findings suggest that monitoring ambient temperature is important for IOP management.