Altered retrobulbar hemodynamic oxygen reactivity in early diabetic retinopathy patients as measured by color Doppler imaging

Purpose. We previously demonstrated that early diabetic retinopathy patients have altered retinal vascular oxygen reactivity as measured by scanning laser ophthalmoscopy (ARVO: 1994). In this study, oxygen reactivity for the ophthalmic and central retinal artery was tested using color Doppler imaging (CDI). Methods. Nine insulin-dependent diabetic patients with no or mild pre-proliferative retinopathy (less than 10 microaneurysms per eye) and 9 visually normal subjects were tested. The two groups were comparable for sex and age: diabetic (6 male/3 female; average age 29 ± 9 years), normal (5 male/4 female; average age 30 ± 6 years). Using CDI, peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI) were determined for the ophthalmic (OA) and central retinal arteries (CRA) on both groups under conditions of room air and hyperoxia (100% oxygen breathing). Results. There was no difference in retrobulbar hemodynamics between groups under room air conditions. The diabetic group showed no change between the room air and hyperoxia condition, however, the normal group demonstrated a significant decrease in CRA EDV (p = .031) and a significant increase in CRA RI (p = .030) during hyperoxia. This different response between groups provided for a significant difference between groups for CRA EDV (p = .013) and CRA RI (p = .007) during hyperoxia. Conclusions. Normal patients have reduced CRA EDV and increased CRA RI under conditions of hyperoxia, while early diabetic patients show no such effect. Diabetic retinopathy patients may present with altered retrobulbar oxygen reactivity due to impaired hemodynamic autoregulation.