RETINAL BLOOD-FLOW CHANGES IN TYPE-I DIABETES - A LONG-TERM, FOLLOW-UP-STUDY

Purpose. The authors previously reported that blood speeds in the reti nal arteries were significantly lower in patients with type I diabetes than in controls without diabetes. The purpose of this long-term, fol low-up study was to characterize the natural course of changes in bloo d speed and blood flow in these patients. Methods. Twenty-four patient s were followed up with serial annual measurements of the blood flow i n a temporal retinal artery using the bidirectional laser Doppler tech nique and monochromatic photography. The follow-up period ranged from 2 to 6 years (mean, 3.8 years). Using standardized color fundus photog raphy and fluorescein angiography, a retinopathy score was generated f or each eye studied. Linear regression analysis was used to compute th e slope of the change in retinal blood flow for each patient during th e follow-up period. Results. Retinal blood flow slopes were negative i n 15 patients and positive in 9 patients. Multiple linear regression a nalysis showed that the retinal blood flow slopes were significantly r elated to the retinal blood flow measured at entry to the study and to the median duration of diabetes during the follow-up period (R(2) = 0 .56; P = 0.0002). There was a positive correlation between the retinal blood flow slopes and the median retinopathy score during the follow- up period (P = 0.47; P = 0.02). Conclusions. As duration of diabetes b ecomes longer and retinopathy becomes more severe, there is a transiti on from negative to positive retinal blood flow slopes. This bimodal r elationship between the change in retinal blood flow and the duration of diabetes reflects the complex pathologic alterations that occur in the diabetic retina.