Terauchi and colleagues have conducted a prospective study in which 204 eyes of 204 subjects with medically treated open-angle glaucoma underwent IOP measurement in both the summer and the winter to assess possible seasonal variation in IOP. Mean IOP was higher in the winter than in the summer by about 1 mmHg (p < 0.001). Factors associated with seasonal IOP variability included glaucoma type (POAG more so than NTG), family history of glaucoma, and the use of topical beta-blockers.
The significance of this finding is unclear, and as with all interesting research, this study raises more questions than it answers. Is true IOP higher in winter? Why might this be? How might this affect our assessment and management of patients throughout the year? Further study is warranted to more fully explore this finding, as it may shed light on the factors that regulate IOP variability, which in turn may be a risk factor for glaucoma progression.