Sclera

The sclera is the posterior part of the fibrous layer of the eyeball. It covers the entire eyeball with the exception of the most anterior portion. It has a bluish-white appearance and plays a protective role. The sclera is composed of connective tissue interspersed with a few elastic fibers.

The sclera is poorly vascularized, mainly by episcleral vessels. It is perforated by vorticose veins, long posterior ciliary arteries, short posterior ciliary arteries, anterior ciliary arteries, posterior and anterior ciliary veins, long and short ciliary nerves and, notably, the venous plexus of sclera, which forms a circular ring through the sclera. The sclera allows optic nerve fibers to pass through the area cribrosa sclerae.