Keratoconus 

Keratoconus is an uncommon condition, which causes a bulging of the cornea from its normal round shape to a bulged cone shape. This is caused by a progressive thinning and steepening of the central cornea. As the cornea steepens and thins, the patient experiences a decrease in vision which can be mild to severe depending on the amount of corneal tissue affected. Keratoconus, "what is keratoconus", corneal transplant, Rose-K lens