Racial Differences in Ocular Structure and Retrobulbar Blood Flow Over Time in Patients with Glaucoma

Abstract

Purpose: : To examine racial differences in patients with open angle glaucoma (OAG) of African descent vs. European descent in terms of the relationships between change in ocular structure and retrobulbar blood flow after 2 years of follow-up.

Methods: : Patients with OAG of African descent (n=24) vs. European descent (n=73) were analyzed for ocular structure and retrobulbar blood flow at baseline and after 2 years follow up. Associations between the changes in ocular structure and blood flow parameters were evaluated using Pearson correlation coefficients separately for patients of African and European descent.

Results: : Change in ophthalmic artery (OA) resistive index (RI) was positively correlated with optic nerve cup area (r=0.49, p=0.0131), optic nerve cup volume (r=0.52, p=0.0081), and optic nerve cup/disk area ratio (r=0.49, p=0.0140) as measured by HRT3 in persons of African descent. OA end diastolic velocity (EDV) was negatively correlated with optic nerve cup volume (r=-0.44, p=0.0320) as measured by HRT3 in persons of African descent. These correlations were not found to be statistically significant in OAG patients of European descent (r=-0.18 for OA RI and cup area, r=-0.20 for OA RI and cup volume, r=-0.17 for OA RI and cup/disk area ratio, and r=0.05 for OA EDV vs. cup volume), and were significantly different from the correlations in OAG patients of African descent (p=0.0036 for OA RI and cup area, p=0.0018 for OA RI and cup volume, p=0.0047 for OA RI and cup/disk area ratio, and p=0.0386 for OA EDV vs. cup volume.

Conclusions: : An increase in OA vascular resistivity is associated with an increase in optic nerve cup area, cup volume, and cup/disk area, indicating damage to the optic nerve, in persons of African descent. Furthermore, a decrease in OA perfusion as measured by the EDV is associated with an increase in optic nerve cup volume. Thus, decreased blood flow in the OA may be associated with structural deterioration in persons of African descent. This indicates a possible stronger vascular contribution in OAG pathophysiology in persons of African descent compared to European decent.

Keywords: blood supply • imaging/image analysis: clinical • optic nerve