Scanning electron microscopic study of episcleral arteriovenous anastomoses in the owl and cynomolgus monkey

In the present study we have analyzed the architecture of the episcleral microvasculature in the owl and cynomolgus monkey using scanning electron microscopy of resin casts. Due to the topical pretreatment with nitroprusside the complete vasculature including segments of the aqueous humor outflow channels could be visualized. We found that 1-3 mm posterior to the limbus corneae the episcleral vessels form numerous arteriovenous anastomoses (AVA) in the size of small arterioles and venules. These AVA are also located at the collector channels near Schlemm's canal and at the episcleral venous plexus which drains the collector channels. It is assumed that the AVA might influence not only the circulation in the episcleral venous plexus but also in the aqueous humor outflow routes.