Background: Investigation of retinal blood flow in patients with and without diabetic retinopathy (DR). Retinal blood flow is measured with the non-invasive 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 non-diabetic persons.
Methods: Cross-sectional study of retinal capillary perfusion in eighty diabetic patients and forty-nine control persons, non-invasively measured with the Heidelberg scanning laser Doppler flowmeter.
Results: In the control group, HRF measurements could be performed in all subjects. In the diabetes group some patients had media opacities or were not able to maintain stable fixation. Therefore HRF measurement was only possible in 79%, 75% and 60% of the subjects for the nasal, papillo-macular and foveal areas respectively. Retinal 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 preproliferative DR (level 3). Blood flow was not correlated with age, systemic blood pressure, intra-ocular pressure and perfusion pressure in either group. A significant negative correlation with the actual blood glucose level was found in the perifoveal area (R = -0.585, P = 0.0001).
Conclusions: The HRF offers an interesting non-invasive method for measurement of retinal blood flow. In this cross-sectional study variations in retinal blood flow could be detected in various stages of DR in relation to clinically visible funduscopic changes.