Light is focused while passing through the cornea so sight can occur. To stay clear the cornea must be healthy. If the cornea becomes damaged or diseased, the resulting scars and swelling may cause clouding and distortion of vision. A corneal transplant may be needed if vision cannot be corrected with glasses or painful swelling cannot be relieved. A corneal transplant replaces the damaged cornea with a distortion-free, clear cornea.
Vision improves markedly in most cases.