Assessment of retinal vascular oxygenation and morphology at stages of diabetic retinopathy in African Americans

BACKGROUND: Diabetic retinopathy (DR) is a microvascular complication of diabetes and a leading cause of blindness in working-age adults. The likelihood of visual impairment associated with DR is two-fold higher in the African-American (AA) compared to non-Hispanic white. Although alterations in retinal vessel oxygenation and morphology have been reported in DR, there is limited knowledge about these vascular changes in AA subjects. The purpose of the current study was to investigate alterations in retinal vascular oxygen saturation (SO(2)), vessel diameter (D) and tortuosity at severity stages of DR in AA subjects. METHODS: A nested case-control study of 56 AA subjects was conducted. Right eyes were grouped as non-diabetic (ND) (N = 26), no clinical DR (NDR) (N = 19), or moderate/severe non-proliferative DR (NPDR) (N = 11). Imaging was performed using a commercially available scanning laser ophthalmoscope. Images were analyzed to determine retinal arterial and venous SO(2) (SO(2A) and SO(2V)), diameter (D(A) and D(V)), and vessel tortuosity index (VTI) (VTI(A) and VTI(V)). RESULTS: SO(2V) and D(V) were higher in NPDR compared to ND and NDR groups (P < 0.05). There were no significant differences in SO(2A) and D(A) among ND, NDR, and NPDR groups (P > 0.8). Maximum VTI(A) was higher in diabetics (NDR and NPDR) compared to non-diabetics (P < 0.03). There was no significant difference in maximum VTI(V) among the 3 groups (P = 0.5). CONCLUSIONS: The findings advance our understanding of DR pathophysiology in the AA population and may propel identification of race-specific retinal vascular biomarkers for improved diagnosis and monitoring of DR.