Comparative Human Aqueous Dynamics Study between Black and White Subjects with Glaucoma

Abstract

To compare the baseline aqueous humor dynamics in white Caucasians and patients of African origin with previously untreated primary open-angle glaucoma (POAG) or ocular hypertension (OHT). Ninety-one participants were enrolled in this prospective, observational controlled study: 34 black subjects with POAG or OHT, 32 white Caucasian participants with POAG or OHT, and 12 black and 13 white healthy volunteers as the controls. All aqueous humor parameters were taken between 9 AM and 12 noon on the same day. Intraocular pressure (IOP) was measured by pneumatonometer; morning aqueous humor flow rate was measured by fluorophotometry and trabecular outflow facility by electronic Schiøtz tonography. Uveoscleral outflow was calculated by using Goldmann's equation with assumed episcleral venous pressure of 8, 9, 10, and 11 mm Hg. Differences among groups were analyzed with parametric and nonparametric tests and the relationship between aqueous dynamics parameters were evaluated with linear regression analyses. The POAG/OHT groups had similar IOP (white, 24.6 ± 3.0 mm Hg; black, 24.3 ± 4.0 mm Hg; comparison by Holm's sequential Bonferroni method (HBonf): P(HBonf) = 0.51), outflow facility (white, 0.13 ± 0.09 μL/min/mm Hg; black, 0.13 ± 0.07 μL/min/mm Hg; P(HBonf) = 0.87), aqueous flow (white, 2.36 ± 0.63 μL/min; black, 2.35 ± 0.53 μL/min; P(HBonf) = 0.95), and uveoscleral outflow (white, 0.42 ± 1.59 μL/min; black, 0.58 ± 1.17 μL/min; P(HBonf) = 1.78). POAG/OHT groups had significantly higher IOP and lower outflow facility than their healthy counterparts (P < 0.01). Black participants had significant thinner corneas (540 ± 37 μm vs. 564 ± 36 μm) than those of white participants (P = 0.002). The aqueous humor dynamics of black African and white Caucasian patients with POAG or OHT have no significant differences. However, the significantly thinner corneas of the black patients may be masking potential differences in outflow facility and IOP measurements between the racial groups.