Major Arterial Circle of the Iris

Description

Curving within the iris root near the ciliary body, the major arterial circle of the iris forms a continuous anastomotic ring at the junction of the iris and ciliary processes. Radial iris arterioles branch anteriorly from this circle and course toward the pupillary margin, running between the posterior pigmented epithelium and the anterior iris stroma. Anteriorly, the cornea and anterior chamber frame the iris and pupil, while posteriorly the lens sits immediately behind the pupillary aperture. A true circumferential landmark. Arising primarily from the long posterior ciliary arteries with contribution from the anterior ciliary arteries, this arterial circle is the key inflow to the iris circulation and a practical map for anterior segment surgery. During cataract extraction, intraoperative floppy iris syndrome, or iris manipulation in uveitis, disruption of these vessels can present as iris stromal hemorrhage or hyphema and can complicate pupil expansion maneuvers. The ring’s position at the iris base also explains why sectoral iris ischemia and postoperative iris atrophy often respect vascular territories, and why angle-based procedures near the ciliary body can influence anterior segment perfusion. Ophthalmology teaching files, anatomy courses covering the uveal tract, and medical publishing on anterior segment vascular supply will benefit from this focused rendering of the major arterial circle of the iris and its radial arteriolar pattern. It also suits surgical consent materials or slide decks discussing hyphema, uveitis-related rubeosis patterns, and the vascular basis of iris sphincter ischemia. Anatomical accuracy verified by SciePro's Medical Advisory Board.