Data-Driven Redefinition of Normal Intraocular Pressure in Nonglaucomatous Korean Adult Population.

Purpose: To characterize the population-based normative distribution of intraocular pressure (IOP) in Korean adults using survey-weighted data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2019 to 2021. Design: A cross-sectional, population-based study using nationally representative data. Participants: Adults aged ≥19 years who completed the KNHANES ophthalmic examination during the 2019 to 2021 cycles. Individuals with glaucoma, missing IOP or refractive data, or implausible IOP values (<5 or >40 mmHg) were excluded. Methods: The ophthalmic examination included rebound tonometry and noncycloplegic autorefraction using a standardized national protocol. Glaucoma status was determined through centralized expert panel review based on the International Society of Geographical and Epidemiological Ophthalmology criteria. Refractive error was classified using spherical equivalent (SE): hyperopia (SE > +0.50 diopters [D]), emmetropia (-0.50 to +0.50 D), mild myopia (-0.50 to -3.00 D), moderate myopia (-3.00 to -6.00 D), and high myopia (<-6.00 D). Diabetes and metabolic syndrome (MetS) were defined using established clinical criteria. All analyses incorporated ophthalmic examination weights to account for differential sampling and nonresponse. Weighted mean IOP and weighted 95th percentiles were estimated across demographic and clinical subgroups. Main Outcome Measures: Weighted mean IOP and weighted 95th percentile for each age, sex, refractive, and metabolic subgroup. Results: A total of 10 625 nonglaucomatous adults were included. Across most age-sex strata, the weighted 95th percentile of IOP ranged from 18.1 to 19.2 mmHg, substantially lower than the conventional reference value of 21 mmHg. Men aged 30 to 39 years showed a higher 95th percentile value (20.5 mmHg). Increasing myopia was associated with a trend toward higher values in the IOP distribution; high myopic men exhibited the highest 95th percentile value (20.75 mmHg). Metabolic syndrome was associated with modest increases in the upper percentile of IOP (approximately 0.2-0.5 mmHg), although absolute values remained below 20 mmHg for most subgroups. Conclusions: In this nationally representative Korean sample, the physiologic 95th percentile of IOP was closer to 18 to 19 mmHg for most adults, with modest elevations observed in highly myopic or metabolically unhealthy individuals. These findings indicate that ethnicity- and phenotype-specific IOP distributions provide a useful contextual framework for interpreting IOP values in populations with high rates of normal-tension glaucoma. Financial Disclosures: The authors have no proprietary or commercial interest in any materials discussed in this article.