Differences in the Relationship Between Ocular Blood Flow, Retinal Structural Damage and Visual Field in Caucasian versus African American Glaucoma Patients

Abstract

Purpose: : To assess differences in predictors of visual field progression between Caucasians and African Americans with open angle glaucoma (OAG) based on the Indianapolis Glaucoma Progression Study.

Methods: : 113 patients (age 66.9 (10.0), 68 females, 84 Caucasians; 29 African Americans) with OAG participating in the Indianapolis Glaucoma Progression Study were assessed for retinal nerve fiber layer (RNFL) thickness, retinal microcirculation, retrobulbar blood flow, intraocular pressure (IOP), ocular perfusion pressure (OPP) and visual field progression. Data were analyzed by Mann-Whitney U test and Spearman rank-correlation test. Rank-transformed data were used for multivariate linear regression analysis.

Results: : There were no statistically significant differences between Caucasian and African-American OAG patients with respect to age, gender, IOP, OPP, peak systolic (PSV) and end-diastolic (EDV) blood flow velocities of ophthalmic artery (OA), central retinal artery (CRA), and nasal and temporal posterior ciliary arteries (NPCA and TPCA). Mean RNFL thickness and cross-sectional area was higher in African-Americans than in Caucasians (P=0.051 and P=0.014, respectively) as was inferior retinal blood flow (P=0.011). In bivariate analysis, mean RNFL thickness and cross-sectional area negatively correlated with age (P=0.009 and P=0.020, respectively) and positively correlated with CRA EDV (r=0.238, P=0.029 and r= 0.291 P=0.008, respectively) and NPCA EDV (r= 0.381, P<0.001and r= 0.346, P=0.001, respectively) among Caucasians. In African-American OAG patients, mean RNFL thickness and cross-sectional area correlated positively and significantly only with mean superior retinal flow (r=0.47, P=0.009). Multivariate linear regression analysis revealed that mean RNFL thickness was the independent predictor of AGIS score in Caucasians (adjusted model r²=0.233) (partial rho=-0.477, P<0.001). IOP was the independent predictor of AGIS score among African-American patients (adjusted model r²=0.116) (Partial rho=0.397, P=0.045).

Conclusions: : Retrobulbar circulation appears to be the main determinant of RNFL thickness in Caucasains, while retinal microcirculation appears to be the main determinant of RNFL in African Americans. The relationship between the RNFL thickness, IOP and AGIS score appears to differ between Caucasian and African-American patients with OAG.

Keywords: blood supply • nerve fiber layer • visual fields