Systemic Blood Pressure and Ocular Perfusion Pressure affect Retrobulbar Blood Flow Differently in Glaucoma Patients of European and African Descent

Abstract

Purpose: To examine differences in the relationship between systemic blood pressure (BP) and ocular perfusion pressure (OPP) with localized ocular blood flow in the central retinal artery (CRA) and ophthalmic artery (OA) in glaucoma patients of European descent (ED) and African descent (AD).

Methods: 75 patients with open-angle glaucoma (OAG) (19 of AD, 56 of ED) were assessed at baseline and after three years follow up. Blood flow velocities and vascular resistance were assessed using color Doppler imaging (CDI). Systolic (SBP) and diastolic (DBP) blood pressure were measured using automated ambulatory measurements, intraocular pressure (IOP) was measured using Goldmann tonometry, and OPP was calculated using the following equation: OPP=2/3[mean arterial pressure (MAP)]-IOP. Systolic (SPP), diastolic (DPP) and mean (MPP) perfusion pressures were also calculated as SBP-IOP, DBP-IOP and mean arterial pressure-IOP respectively. Pearson correlations were calculated to evaluate the associations between measurements at baseline and between the changes in measurements between baseline and 3 years with p values <0.05 considered statistically significant.

Results: Changes in SBP, MAP, SPP were more strongly correlated to CRA peak systolic blood flow velocity (PSV) and end diastolic velocity (EDV) in OAG patients of AD versus ED [r=-0.38 to -0.47 (AD); r=0.23 to 0.17 (ED)] with statistically significant differences between groups in every parameter (P=0.0110 to 0.0330). In patients of ED, changes in OA EDV positively correlated with changes in SBP (r=0.45, p=0.0013), MAP (r=0.43, p=0.0025), SPP (r=0.41, p=0.0040), OPP (r=0.31, p=0.0365), and MPP (r=0.35, p=0.0147) over three years. These same relationships were negative and not statistically significant for patients of AD (p>0.05). The differences between the groups were statistically significant for each correlation (p<0.0413; p<0.0368; p<0.0356; p<0.0490; p<0.0416, respectively).

Conclusions: In OAG patients of AD, CRA blood flow was more strongly correlated to blood pressure and perfusion pressure than in OAG patients of ED. OA changes were more strongly correlated to ED than AD OAG patients. This indicates that retinal blood flow may not be sufficiently autoregulated during changing blood and perfusion pressure in OAG patients of AD.

Keywords: 464 clinical (human) or epidemiologic studies: risk factor assessment • 436 blood supply • 550 imaging/image analysis: clinical