The transparent layer in front of the iris layer, which is the colored part of the eye, is called the cornea. After the rays coming to the eye first pass through this tissue, they reach the nerve layer we call retina and vision occurs. Corneal transplant, also known as corneal graft, is a surgical procedure in which a damaged or diseased cornea is replaced with donated corneal tissue (graft). Keratoplasty means cornea surgery. Light rays passing through a damaged cornea can be struck and alter your vision.
Scarring due to corneal injury or infection
Medical condition that makes your cornea swollen (keratoconus)
Hereditary eye diseases such as Fuchs' dystrophy and others
Problems arising from early eye surgery