Clinical features and glaucoma according to optic disc size in a South Korean population: The Namil study

Purpose: To assess the proportion of glaucomatous eyes based on the association between optic disc (OD) size and its clinical determinants in the resident population of Namil-myon, Central South Korea. Methods: Of the 1,532 participants in the Namil study, we included 1,410 Koreans (2,734 eyes) with legible fundus photographs in this study. Following the estimation of OD size on the photographs using Image J software, we corrected for image magnification. Associations between the clinical features, such as age, sex, axial length (AL), spherical equivalent (SE), and central corneal thickness, and the estimated OD size were assessed for individual eyes. After adjusting for the influencing factors, the proportion of glaucoma was compared among three categories of measured OD size (small, medium, and large OD groups). Results: After adjusting for the potential confounders using a linear mixed model, age, sex, AL, and SE were correlated with the OD size estimates (P = 0.003, P = 0.029, P < 0.001, and P < 0.001, respectively). The percentage of glaucomatous eyes was 3.77 % in the small disc group, which was higher than in the other groups (P = 0.054). In particular, normal tension glaucoma (NTG) was statistically significantly more frequent in this group (odds ratio = 1.86, P = 0.042). Conclusions: These results suggest that clinical features such as age, sex, AL, and SE might need to be considered for an accurate evaluation of the OD. In addition, in individuals with a small OD, the presence of NTG must be carefully investigated in the South Korea population.