Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 82

In most species, the major arterial circle of the iris is formed by the nasal and temporal long posterior ciliary arteries. The iris and ciliary body receive approximately 1% and 10%, respectively, of the total ocular blood flow. In humans and rabbits, additional iridal blood flow occurs from the anterior ciliary arteries via the extraocular muscles (EOMs). Blood flow to the ciliary body in most species that have been studied is provided by the iridal major arterial circle, branches of the anterior ciliary arteries, and branches of the long posterior ciliary arteries. The cat and monkey iris and ciliary body have autoregulation of their blood flow. Carbon dioxide dilates the anterior uveal vessels, and sympathetic α‐adrenergic receptors cause vasoconstriction in the anterior uvea. Parasympathetic muscarinic receptors and prostaglandins, however, cause vasodilation. Prostaglandins E₁ and F_2α appear to cause a two‐ to threefold increase in blood flow to the anterior uvea when applied topically.