Light enters the eye through the cornea, where it is then transmitted to the lens and pupil. The cornea is therefore also called the "window of the eye" and is an important component of the optical system.
The refractive power of the cornea is quite strong at about 43 diopters and is thus an important factor in producing an image on the retina. Due to its evenly arranged and fine tissue structures, the cornea is transparent and forms a crystal clear dome on the surface of the eye. It is protected by the eyelids.
Many people have astigmatism - a natural irregularity of the cornea. This can be corrected with glasses and contact lenses, but also with laser eye surgery and the use of an artificial lens.