Posterior and Anterior Ciliary Arteries
Approximately 16–20 short posterior ciliary arteries and 6–10 short ciliary nerves enter the globe in a ring around the optic nerve (Figs 1-17, 1-18, 1-19). Usually, 2 long posterior ciliary arteries and 2 long ciliary nerves enter the sclera on either side of the optic nerve, close to the horizontal meridian. They course anteriorly in the suprachoroidal space, terminating at the major arterial circle of the iris.
The posterior ciliary vessels originate from the ophthalmic artery and supply the entire uvea, the cilioretinal arteries, the sclera, the margin of the cornea, and the adjacent conjunctiva. Occlusion of the posterior ciliary vessels (as in giant cell arteritis) may have profound consequences for the eye, such as anterior ischemic optic neuropathy.
The anterior ciliary arteries also arise from the ophthalmic artery and usually supply (in pairs) the superior, medial, and inferior rectus muscles (Figs 1-20, 1-21). After emerging from the surface of the rectus muscles, the anterior ciliary vessels perforate the sclera anterior to the rectus muscle insertions, where they anastomose with the long posterior ciliary arteries at the major arterial circle of the iris.
Within the eye, the posterior ciliary vessel forms the intramuscular circle of the iris, branches of which supply the major arterial circle (which is usually discontinuous). This circle lies within the apex of the ciliary muscle, which it supplies together with the iris (Fig 1-22). The iris vessels have a radial arrangement that, in lightly pigmented blue irises, is visible upon slit-lamp examination. This radial arrangement can be distinguished from the irregular new iris vessels formed in rubeosis iridis.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.