Diagnostic discrepancies in glaucoma: underdiagnosis, overdiagnosis and missed opportunities in a nationwide South Korean population.

BACKGROUND/AIMS: To investigate glaucoma prevalence and diagnostic discrepancies-undiagnosed glaucoma, missed diagnostic opportunities and false-positive diagnoses-in South Korea and to identify factors contributing to these errors. METHODS: This nationwide cross-sectional study used data from the Korea National Health and Nutrition Examination Survey 2019-2021. Participants aged ≥20 years who had gradable ophthalmic examinations were included. Glaucoma was adjudicated by specialists using International Society of Geographical and Epidemiological Ophthalmology criteria. Survey-weighted logistic regression analyses were performed to identify factors associated with undiagnosed glaucoma and missed diagnostic opportunities. RESULTS: The final analytical cohort comprised 18 710 participants. The weighted prevalence of glaucoma was 3.9% (95% CI 3.6% to 4.2%). The awareness rate was only 17.1%, leaving 82.9% (95% CI 80.4% to 85.4%) of cases undiagnosed. Notably, 44.7% (95% CI 41.0% to 48.3%) of undiagnosed cases represented a missed diagnostic opportunity. Multivariable analysis identified high myopia as the strongest predictor of a missed diagnostic opportunity (OR 23.53, 95% CI 5.65 to 98.09, p<0.001), alongside younger age (OR 0.98, p=0.039), rural residence (OR 1.97, p=0.047) and thicker retinal nerve fibre layer (OR 1.09, p<0.001). The lowest household income quartile was associated with undiagnosed glaucoma (OR 1.87, p=0.019). CONCLUSION: Diagnostic discrepancies present a dual burden: profound underdiagnosis coexists with frequent false-positive diagnosis. High myopia, milder disease phenotype and rural residence are central drivers of missed diagnostic opportunities. Reducing discrepancies will therefore require efforts at both the clinical-professional and health system levels.