Purpose
Evaluating seasonal intraocular pressure (IOP) fluctuation is important in managing glaucoma patients, especially in patients who experience a large increase of IOP in winter. The purpose of this study was to investigate IOP seasonality in patients with various types of glaucoma from a large, 16-year clinical dataset.
Methods
This study involved a total cumulative number of 68,980 pieces of data from 3,108 eyes of 3,108 Japanese glaucoma patients (1,713 males and 1,395 females; mean age: 62.0±15.3 years). Inclusion criteria included subjects who 1) visited the outpatient clinic of Kyoto Prefectural University of Medicine, Kyoto, Japan between January 1997 and December 2012, 2) were diagnosed and followed up by glaucoma specialists based on several ophthalmic examinations, and whose 3) IOP was measured reliably by Goldmann applanation tonometer. Patients were divided into five categories depending on their glaucoma type as follows: 1) primary open-angle glaucoma (POAG), 2) normal tension glaucoma (NTG), 3) primary angle-closure glaucoma (PACG), 4) steroid induced ocular hypertension (StG), and 5) secondary glaucoma except StG (SG). Right-eye data was selected if both eyes were available, and data from the last visit was chosen for the individual representative value of that month if several visits were observed within the same month. Individual IOP from 1 eye in each group was then averaged monthly. Relative seasonal variation and seasonal index were calculated utilizing the deviation from linearized trend line, and periodicity was examined using the Friedman test.
Results
Seasonal index of each glaucoma type showed the IOP to repeatedly be low in summer and high in winter, and that index was shared by all five glaucoma types. Autocorrelation showed a periodicity of 1 peak per each 12 month period, and the Friedman test showed statistical significance in all types of glaucoma (POAG, p<0.0001; NTG, p<0.0001; PAC/G, p<0.0001; StG, p<0.0001; and SG, p=0.0002).
Conclusions
Retrospective examination of a collected large IOP dataset proved that IOP in different types of glaucoma showed simultaneous statistically significant seasonality, which is high in winter and low in summer.