The sclera forms the outermost layer of the eye, it is "the white of the eye" that can be seen from the outside around the pupil and iris. It is therefore also called the white skin of the eye. Called "sclera" in Latin, the sclera protects the eye from external influences and ensures that it retains its shape.

The sclera is stretched by the intraocular pressure and encloses almost the entire eyeball: on the surface of the eye, it merges with the transparent cornea and opens on the back side at the optic nerve. In addition, the eye muscles, through which the eye moves, attach to the sclera. Through the white sclera, the eye movement and direction of gaze is recognizable in humans - thus it is an important component for non-verbal communication of humans.