Microcirculation of the retina and its microvascular characteristic patterns

Retinal microvasculature is of great interest in biomedical research for its peculiar mechanisms of blood pow regulation, closely connected with the variable activation of the retina. Moreover, retinal vessels are notoriously affected in a number of local and systemic diseases. For this reason, the knowledge of the retinal vascular patterns in man and laboratory animals is important for the understanding of both the physiology and the pathology of this district. Male Wistar rats and Cynomolgus monkeys were used in this study. Vascular casts (vee) and partially digested tissue specimens were observed by scanning electron microscopy (SEM). Rat retinal microvasculature shows the following characteristics: a) the laminar distribution of capillaries which also reach the anterior edge of the sensory retina; b) the prevalence, especially at the posterior pole, of side branching arterioles which allow preferential pow in the most vitreal layers of the retina. Microvascular arrangement of the monkey posterior retina appears as follows: 1) Capillaries have a laminar distribution. Most vitreal ones are favored as they are more directly vascularized by side branching arterioles. 2) around the foveal avascular zone, capillaries show a round course and likely function as arterial-venous anastomoses. In both species peculiar Luminal restrictions of arterioles and capillaries -related to the presence of pericytes -further determine preferential flow and may represent sites of fine blood pow regulation