Tear Break-Up Time and Seasonal Variation in Intraocular Pressure in a Japanese Population

Purpose: To evaluate seasonal variation in intraocular pressure (IOP) with and without short tear break-up time (SBUT, BUT <= 5 s) since dry eye and IOP are known to have seasonal variation. Methods: This study enrolled 176 patients who visited one of six eye clinics, in Japan, four times for IOP measurement, in every season. The mean patient age was 67.9 years, including 79 males. Participants were divided into four groups based on the presence of glaucoma and/or SBUT and we compared the seasonal variation in IOP (winter and summer) among the four groups. Results: The IOP (mmHg) in winter and summer, respectively, was 12.8 +/- 3.7 and 12.8 +/- 3.1 for non-glaucoma patients without SBUT (n = 47, p = 0.964), 14.8 +/- 3.4 and 13.3 +/- 3.4 for non-glaucoma patients with SBUT (n = 57, p < 0.001), 14.3 +/- 3.2 and 14.1 +/- 3.4 for glaucoma patients without SBUT (n = 36, p = 0.489), and 13.3 +/- 3.0 and 11.6 +/- 2.9 for glaucoma with SBUT (n = 36, p < 0.001). Seasonal variation was largest across the seasons in the glaucoma with the SBUT group, and the magnitude of seasonal variation correlated with BUT (beta = 0.228, p = 0.003). Conclusions: Seasonal variation tended to be larger in patients with SBUT than those without SBUT.