What is cornea?

Cornea, commonly known as black eyeball, is the transparent part of the outer part of the eyeball wall, circular, accounting for one sixth of the outer layer area, about 1 mm thick, mainly composed of vascular connective tissue, which together with sclera constitutes the outer wall of the eyeball, plays a protective role on the intraocular tissue, histologically, cornea from front to back divided into five layers: epithelial cell layer, anterior elastic layer, stroma layer, posterior elastic layer and endothelial cell layer. Corneal tissue mainly has optical functions, external light can enter the eye through the cornea, refraction, the external objects through refraction bending to the retina imaging, and the protection of eye contents.