[Measuring the vascular caliber in diabetic retinopathy before and following photocoagulation].

The calibers of 4 retinal arterioles and 4 venoles of each of 58 patients with diabetic retinopathy (DR) were measured on fundus photographs before and after photocoagulation (PC). The measurements were repeated at approximately one-year intervals following photocoagulation (PC) of one eye of each patient. The mean caliber of arterioles and venoles of DR patients was 15.4% greater than in nondiabetic subjects. This finding may be interpreted as an autoregulatory response to relative tissue hypoxia. Following PC there was a significant reduction in both arterial and venous vessel caliber. In a multivariate regression analysis, the reduction in venous caliber correlated significantly with the number of coagulation spots. A weak correlation was found with arterial hypertension, change in visual acuity, and change in a calculated DR score. The reduction in pathologic vessel calibers following PC is indicative of an improvement in retinal hemodynamics. Photographic quantification of retinal vessel changes may be of prognostic value, i.e., for assessing the course of DR before and after treatment by PC.