Objective: Investigate the relationship between body mass index (BMI) and primary open-angle glaucoma (POAG) in an African ancestry cohort from the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study.

Methods: Retrospective, cross-sectional "case-control" comparison study. Methods: A total of 6,634 POAAGG study subjects were eligible: 2,977 cases and 3,657 controls. Ocular and demographic data were collected from on-site exams, standardized interviews, and electronic medical records. BMI was calculated: weight(kg)/height(m)2, and categorized as low (<18.5), moderate (18.5-24.9), high (25.0-29.9), or very high (≥30). Structural and functional POAG progression were assessed by annual rate of change in retinal nerve fiber layer thickness and visual field mean deviation, respectively, using a linear mixed-effects model. Regression analyses evaluated associations of BMI with POAG status, phenotype, and progression.

Results: Lower BMI was associated with increased POAG risk (aOR[95% confidence interval], 1.02 [1.007,1.023] per kg/m2 decrease in BMI, p = .0003). In cases, low BMI was associated with larger cup-to-disc ratio (p = .007) and worse visual acuity (p = .04). Fast functional POAG progressors had a significantly lower mean BMI than slow progressors (25.7 vs. 30.0 kg/m2, p = .04).

Conclusions: In this African ancestry cohort, low BMI was associated with increased POAG risk. POAG cases with low BMI were more likely to have larger cup-to-disc ratios, worse visual acuity, and faster functional progression, indicating more severe glaucoma.