SEM studies of the functional morphology of the ciliary process vasculature in the cynomolgus monkey: reactions after application of epinephrine.

In the ciliary processes of the cynomolgus monkey three vascular territories with discrete arterioles and venules were found by means of scanning electron micrographs of vascular resin casts. The first vascular territory, which is located at the anterior end of the major processes, is drained posteriorly by long isolated venules, which pass the ciliary body without greater connections to the venules of the major ciliary processes, whereas the second and third territories comprise the vasculature of the major and minor ciliary processes drained posteriorly by veins which are located at the internal edge of the ciliary processes. With the functional resin casting method it could be demonstrated that 15 min after application of 20 micrograms of epinephrine into the conjunctival sac the terminal arterioles supplying the first vascular territory constricted most intensely, whereas the terminal arterioles related to the middle and posterior vascular territory of the ciliary processes constricted to a lesser extent. Twenty-five minutes after topical application of epinephrine only the posterior vascular territory and the capillaries of the ciliary muscle appeared filled in the resin casts. The vasculature of the anterior territories remained empty because of strong vasoconstriction of the supplying arterioles. The three morphologically different vascular territories with their different sensitivities to epinephrine may reflect a functional differentiation in respect to aqueous humour formation and resorption.