A large nationwide cohort study from Japan found that myopia is associated with a substantially increased long-term risk of developing open-angle glaucoma and of requiring subsequent glaucoma surgery. Using health insurance claims data from more than 14 million adults aged 40 years or older followed for up to 7.5 years, the analysis provides quantitative estimates of glaucoma incidence and surgical intervention across refractive error categories in routine clinical practice.
According to the study, published recently in Ophthalmology, participants were categorized into 3 groups based on validated diagnostic algorithms: nonmyopia, myopia, and high myopia, defined as a spherical equivalent of −6.0 diopters or worse. Of the total cohort, nearly 7.5 million patients had myopia, and 373,232 were classified as having high myopia. The nonmyopia group was older on average (mean age 68.8 years) compared with the myopia (56.8 years) and high myopia (52.9 years) groups. Women accounted for more than 60% of participants across all groups, and systemic comorbidities such as diabetes, hypertension, and dyslipidemia were more prevalent in the nonmyopic population.
During follow-up, the incidence of newly diagnosed open-angle glaucoma differed by refractive status. After adjustment for age, sex, diabetes, hypertension, and dyslipidemia, myopia was associated with a 44% higher hazard of glaucoma development compared with nonmyopia (adjusted hazard ratio [aHR] 1.44; 95% confidence interval [CI], 1.43-1.45). The association was stronger for high myopia (aHR 2.67; 95% CI, 2.62-2.73). Kaplan-Meier analyses demonstrated earlier and progressively higher cumulative incidence of glaucoma in both myopic and highly myopic groups compared with nonmyopic patients, with statistically significant separation of curves across age strata (younger than 65 years and 65 years and older).
The researchers also evaluated the need for glaucoma surgery as a clinical endpoint. Any glaucoma surgery was more common among individuals with myopia, with an aHR of 1.71 (95% CI, 1.67-1.75) that increased to 3.07 (95% CI, 2.91-3.25) in those with high myopia.
When stratified by procedure type, nonfiltering surgeries—including trabeculotomy and minimally invasive glaucoma surgery—showed an aHR of 1.62 (95% CI, 1.57-1.66) for myopia and 2.74 (95% CI, 2.57-2.93) for high myopia. Filtering surgeries such as trabeculectomy or tube shunt implantation demonstrated the largest relative differences: an aHR of 2.03 (95% CI, 1.94-2.11) in the myopia group and 4.03 (95% CI, 3.67-4.42) in the high myopia group, compared with nonmyopic patients.
The definitions of myopia and high myopia were validated using electronic medical record data from 10 Japanese institutions. Myopia diagnosis showed an overall sensitivity of 79.6% and specificity of 86%, while high myopia had lower sensitivity (39.5%) but very high specificity (99.4%). Glaucoma onset was identified using a previously validated claims-based algorithm that required both a diagnostic code and a prescription for glaucoma medication.
The authors noted that glaucoma severity and progression could not be assessed directly, and refractive error could not be modeled as a continuous variable because the National Database does not include granular ophthalmic measurements such as intraocular pressure, axial length, visual acuity, visual field indices, or continuous refractive error values. Although validated algorithms were used to define myopia, high myopia, and open-angle glaucoma, some degree of misclassification is possible. Diagnostic codes for high myopia, as well as mild or moderate myopia, and glaucoma subtype codes also presented limitations. Because detailed cataract type and lens status data were unavailable, some cases of lenticular myopic shift—such as that associated with nuclear cataract—may have been misclassified as myopia, despite the exclusion of patients with prior cataract surgery. Finally, the authors wrote, the analysis could only establish associations between myopia and glaucoma or surgical outcomes; it could not establish causality because of its retrospective observational cohort design.
According to the authors, “this study is the first to provide quantitative evidence on the relationship between myopia and the need for glaucoma surgery.” By using a nationwide claims database with near-complete population coverage, they continued, the study provides precise estimates for relatively infrequent outcomes, including filtering glaucoma surgery, across a broad age range of adults in routine clinical care. They added, “future research should focus on elucidating the mechanisms underlying this association and exploring effective strategies for early detection and management of glaucoma in myopic populations.” GP