If we compare the eye to a watch, the cornea could be compared to the “transparent glass on top” through which we see. It is equipped with a specific curvature and, together with other ocular structures, it acts as a lens that allows light rays to pass through the eye. The cornea leads the light stimolous straigth to the central part of the retina. It can be affected by various diseases such as degenerations, infections, inflammations, abrasions and hereditary dystrophies. Astigmatism is instead a curvature alteration and in fact causes a visual deficiency in both far and close vision. The refractive laser surgery acts on the cornea to correct the main visual defects, by changing the curvature according to the need.