The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber consisting of highly specialized tissue. The difference of refractive indices between air and tear film/cornea renders the cornea the part with the highest dioptric power in the optical system of the eye (ca. 43 D). The average cornea is ca. 0.5 mm thick and consists of five layers (corneal epithelium, Bowman’s layer, corneal stroma, Descemet’s layer, corneal endothelium). The corneal epithelium is of ectodermal origin; the other layers are of mesodermal origin.