Retinal blood flow changes in diabetic retinopathy measured with the Heidelberg scanning laser Doppler flowmeter

Background: Investigation of retinal blood flow in patients with and withou t diabetic retinopathy (DR). Retinal blood flow is measured with the non-in vasive Heidelberg Retinal Flowmeter (HRF). The clinical suitability of the HRF in patients with diabetes mellitus is investigated, and measured blood flow is compared with blood flow in a group of nondiabetic persons, Methods : Cross-sectional study of retinal capillary perfusion in eighty diabetic p atients and forty-nine control persons, noninvasively measured with the Hei delberg scanning laser Doppler flowmeter. Results: In the control group, HR F measurements could be performed in all subjects. In the diabetes group so me patients had media opacities or were not able to maintain stable fixatio n. Therefore HRF measurement was only possible in 79%, 75% and 60% of the s ubjects for the nasal, papillo-macular and foveal areas respectively. Retin al blood flow as measured in the perifoveal and nasal areas was associated with the level of diabetic retinopathy. In patients with proliferative DR ( levels 4 and 5) the blood flow was reduced, in comparison with that of the patients with exudative or non-proliferative DR (levels 1 and 2) and prepro liferative DR (level 3). Blood flow was not correlated with age, systemic b lood pressure, intra-ocular pressure and perfusion pressure in either group . A significant negative correlation with the actual blood glucose level wa s found in the perifoveal area (R=-0.585, P=0.0001). Conclusions: The HRF o ffers an interesting non-invasive method for measurement of retinal blood f low. In this cross-sectional study variations in retinal blood flow could b e detected in various stages of DR in relation to clinically visible fundus copic changes.