Retinal Oximetry in Primary Open-Angle Glaucoma: Differences in Patients of African and European Descent

Abstract

Purpose: To determine whether retinal blood vessel oxygen saturation is different in patients with open-angle glaucoma (OAG) of African (AD) and European (ED) descent.

Methods: During a single study visit, retinal oxygen saturation in eight AD (Age 65.9±8.2, 6 female, 2 male) and 13 ED (Age 72.5±8.2; 4 male, 9 female) patients with OAG was measured in retinal blood vessels with a spectrophotometric retinal oximeter in darkness. Oxygen tension (PO2) was calculated from oxygen saturation values. Intraocular pressure (IOP), ocular perfusion pressure (OPP), calculated as 2/3 mean arterial pressure-IOP, and 24-2 sita standard visual fields were analyzed. Statistical analysis was performed using two-tailed student's t-test of unequal variance, with p<0.05 considered statistically significant.

Results: Mean oxygen saturation in retinal arteries was 89.9% ±8.9% in OAG patients of AD and 94.7% ±7.9% in OAG patients of ED (p=0.25). Mean oxygen saturation in venules was 65.5% ±10.7% in persons of AD compared to 58.3% ± 20.5% in ED (p=0.33). The mean arteriovenous difference in oxygen saturation was significantly lower in persons of AD (24.4% ± 9.3%) than in those of ED (36.4% ± 14.1%); (p=0.03). No significant differences were found in IOP (AD: 15.5 ±2.7; ED: 14.3 ±4.3); (p=0.47) or visual field mean deviation (AD: -7.55 ±7.9; ED: -4.67 ±7.53); (p=0.43) or pattern standard deviation (AD: 6.48 ±4.66; ED: 4.63 ±3.66); (p=0.39). Additionally, OPP was not significantly different between groups (AD: 45.75 ±5.82; ED: 51.04 ±6.36); (p=0.08).

Conclusions: OAG patients of AD present with significantly decreased arteriovenous difference in retinal oxygen saturation compared to OAG patients of ED. These differences were observed despite similar IOP, visual field defects and OPP. These data suggest that retinal oxygen metabolism is affected differently in OAG patients of AD compared to ED and may possibly be related to impaired vascular autoregulation and blood flow.

Keywords: 635 oxygen • 550 imaging/image analysis: clinical • 688 retina