PURPOSE: To assess the overdiagnosis of open-angle glaucoma (OAG) and to investigate associated factors.METHODS: This was a cross-sectional, population-based study of an urban Caucasian population in northern Greece. Randomly selected subjects ≥60 years (n = 2554) participated in the Thessaloniki Eye Study. The definition of OAG required the presence of structural and functional damage, irrespective of intraocular pressure (IOP). Non-OAG subjects were classified as overdiagnosed with OAG if they had reported at least one of the following (self-reported glaucoma): (i) prior diagnosis of glaucoma, (ii) prior laser for glaucoma, (iii) prior glaucoma surgery. Factors associated with the overdiagnosis of OAG were investigated using a logistic regression model.RESULTS: Of 57 (2.2%) subjects with self-reported glaucoma, 34 (60%) were overdiagnosed with OAG, corresponding to a prevalence of 1.3% (34/2554). In a logistic regression model among non-OAG subjects, worse visual acuity (VA) (20/200 or worse versus 20/25 or better; odds ratio (OR) = 4.30, 95% Confidence Intervals (CI), 1.13-16.35), family history of glaucoma (OR = 8.69, 95% CI, 2.83-26.67) and history of cataract surgery (OR = 11.50, 95% CI, 3.85-34.36) were statistically significantly associated with the overdiagnosis of OAG. Age, sex, higher IOP, higher vertical cup-to-disc ratio and pseudoexfoliation were not statistically significant.CONCLUSION: The overdiagnosis of OAG was substantial in this elderly, Caucasian population. The overdiagnosis of glaucoma has not been previously addressed in population-based studies and needs to be further explored.