The objective of the present study is to develop quantitative indicies of microvascular structure and function that could be used clinically in patients with diabetes to evaluate the severity of the disease and its response to therapy. Morphometric procedures have been applied to determine changes in the microvascular network as visualized in the bulbar conjunctiva of the eye. The entire temporal aspect of the conjunctiva is photographed with a special medical Nikor lense using a 25 mm camera. Enlargements on paper of up to 65 x are used to scan the network visually and to determine total vascular length or vascular density. Computer based image enhancement procedures have been used to make such measurements and to enter the scanned photographs onto computer tape for subsequent analysis. The studies to date (on 25 individuals) show that diabetics have a poorly perfused capillary network and a much lower vascular count than age-matched non-diabetic controls. At the same time the larger venules are much more prominent and resemble the changes seen in older controls (above 50-55 years). These changes persist in older patients, especially the ischemic tendency that becomes more striking.