Circulus aeriosus iridis major is formed by the anastomosis of

Anterior ciliary aeries: These are derived from the muscular branches of ophthalmic aery. These aeries pass anteriorly in the episclera, give branches to sclera, limbus and conjunctiva; and ultimately pierce the sclera near the limbus to enter the ciliary muscle; where they anastomose with the two long posterior ciliary aeries to form the circulus aeriosus major, near the root of iris. Reference :- A K KHURANA; pg num:-136