The sclera has a structural function and protective: it keeps the shape of the eyeball, while protecting the structures contained therein, and allows the insertion of so-called extrinsic muscles (which control the movement of the eyes) before and continues with the cornea. The sclera is composed of two layers: the outer one is called episcleritis and is rich in connective tissue and blood vessels, the innermost layer is the sclera itself, formed by a loose connective tissue.