Retinal hemodynamics in proliferative diabetic retinopathy. A laser Doppler velocimetry study.

PURPOSE This study investigated retinal hemodynamic changes associated with different pathologic features observed on fundus color and fluorescein angiography in patients with proliferative diabetic retinopathy. METHODS Retinal circulatory characteristics were investigated in 25 eyes of 23 diabetic patients with proliferative retinopathy using a combination of bidirectional laser Doppler velocimetry and monochromatic fundus photography. RESULTS Eyes with severe capillary nonperfusion had 32% less average volumetric blood flow rate (Q) than eyes with less severe nonperfusion (P = 0.0005). In addition, eyes with severe vessel staining with fluorescein had 20% less average Q than eyes without staining (P = 0.0508). Eyes with severe fluorescein leakage in the macula had a 17% larger total venous cross-section than eyes with milder leakage (P = 0.027). Eyes with clinically significant macular edema had 11% larger average venous diameter than eyes without this feature (P = 0.0085). CONCLUSIONS Severe capillary nonperfusion and vessel staining with fluorescein are associated with decreased retinal blood flow rates. Vasodilatation may be an important factor for increased vascular permeability and macular edema in proliferative diabetic retinopathy.