Effect of pure O2-breathing on retinal blood flow in normals and in patients with background diabetic retinopathy.

The noninvasive Laser Doppler velocimetry technique was applied in normal volunteers and in patients with background diabetic retinopathy to determine retinal blood flow during pure oxygen breathing at atmospheric pressure. In normal subjects, five minutes of oxygen breathing produced a 63 +/- 6% decrease in retinal blood flow. In the diabetic patients blood flow decreased by only 36 +/- 15%. A significant correlation between the decrease in blood flow and that of the diameter of the veins was found in the diabetic patients. This was not the case for the normal subjects.