scléra

Scléra is the tough, white outer layer of the eyeball. It is a fibrous connective tissue that covers approximately five-sixths of the eyeball's surface, providing structural integrity and protection. The sclera is continuous with the cornea, the transparent front part of the eye, and the optic nerve sheath at the back.

Its primary function is to maintain the shape of the eye and serve as an attachment point for the extraocular muscles, which are responsible for eye movement. The sclera is relatively avascular, meaning it has few blood vessels, which contributes to its white appearance. However, it does contain a network of fine blood vessels that nourish the outer layers.

The sclera's thickness varies across the surface of the eye, being thinnest at the insertion points of the muscles and thickest at the posterior pole. Diseases affecting the sclera can lead to inflammation, known as scleritis, which can cause pain, redness, and blurred vision. Conditions like staphyloma, a bulging of the sclera, can also occur. The sclera is a crucial component of the eye's anatomy, essential for vision and ocular health.