RESEARCH OBJECTIVES: A colony of diabetic rhesus monkeys has been established in the University of Illinois Medical Center in the past five years. These animals were made diabetic with the streptozotocin technique, and some have started to develop diabetic retinopathy. The overall objective of this project is to study the pathologic changes, the circulatory dynamics, and the breakdown of blood-retinal barrier in the retinopathy of these diabetic rhesus monkeys. Fundus photography, fluorescein angiography, and vitreous fluorophotometry will be used to guage the clinical progress of the diabetic retinopathy. Angiography with fluorescein-labelled dextrans of various molecular weights will be employed to assess the disruption of the blood-retinal barrier. The ophthalmoscopic changes and the physiologic alterations in the diabetic retinopathy of these animals will be correlated with the histologic and ultrastructural changes in the retina. The nature of the breakdown of blood-retinal barrier will be further examined using the horseradish peroxidase tracer technique. Lensectomy and/or vitrectomy will be performed on the proven diabetic animals to evaluate the effect of these surgical procedures on the retinopathy. Therapeutic effects of aspirin and reversal of diabetes by islet cell transplantation will be evaluated and the relationship of therapeutic effects to diabetic retinopathy will be examined.