Prevalence and Factors Associated with Optic Disc Tilt in the Primary Open-Angle African American Glaucoma Genetics Study

Abstract

Purpose: To investigate the prevalence and factors associated with optic disc tilt in the eyes of Black Americans with glaucoma.

Design: Cross-sectional.

Participants: Subjects with glaucoma participating in the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study.

Methods: Stereo pairs of optic disc images were assessed independently by POAAGG-certified nonphysician graders for quantitative features including maximum and minimum linear disc diameters, and qualitative features including gradeability of images, shape of the cup, rim plane position, β-peripapillary atrophy, sloping region adjacent to the outer disc margin, and rim pallor. Discrepancies were adjudicated by an ophthalmologist. Descriptive statistics and P values were generated for associations of tilt with demographic and ocular characteristics. Stepwise multivariable analysis was performed with logistic regression using Generalized Estimating Equations (GEEs) to account for inter-eye correlation within subjects.

Main outcome measures: Tilt Ovality Index (TOI) of >1.30 and Stereoscopically Identified optic disc Tilt (SIT).

Results: Among 1251 subjects with data on both eyes, 104 (8.3%) had TOI. Subjects with TOI were less likely to be male (adjusted odds ratio [aOR], 0.46, 95% confidence interval [CI], 0.29-0.74, P < 0.001). Eyes with TOI were less likely to have large cup disc ratios (aOR, 0.18, 95% CI, 0.06-0.53, P < 0.001) and less likely to have cylinder-shaped cups compared with conical-shaped cups (aOR, 0.31, 95% CI, 0.19-0.49, P < 0.001). Among 1007 subjects with data on both eyes, 254 (25.2%) had SIT. Subjects with SIT were younger (aOR, 0.95, 95% CI, 0.93-0.96, P < 0.001), and eyes with SIT were more likely to have oval-shaped discs compared with round discs (aOR, 1.82, 95% CI, 1.32-2.52, P < 0.001), more likely to have a sloping region adjacent to the outer disc margin instead of being flat (aOR, 3.26, 95% CI, 2.32-4.59, P < 0.001), and less likely to have cylinder-shaped cups compared with conical-shaped cups (aOR, 0.59, 95% CI, 0.41-0.85, P < 0.001). Both TOI and SIT were not associated with myopia.

Conclusions: There are substantial numbers of tilted optic discs in glaucoma patients with African ancestry. They occur more frequently in female subjects and younger subjects and are associated with several ocular features but not with myopia.

Keywords: Black Americans; Open-angle glaucoma; Ovality Index; Stereoscopically Identified optic disc Tilt; Tilted optic discs.