Injury or disease of the cornea can make it opaque, stopping light from entering the eye and resulting in loss of vision. Some severe corneal diseases can also affect the eye's blink and tear mechanisms. Corneal injuries can be caused by direct trauma, including surgery, as well as chemical or thermal burns. Diseases that can cause corneal opacity include autoimmune diseases, bullous keratopathy, keratoconus, keratitis and corneal stromal dystrophies.
The standard treatment for significant corneal opacity is a corneal transplant (penetrating keratoplasty). Penetrating keratoplasty removes the opaque cornea using a trephine, replacing it with a donor cornea. Some patients cannot have a standard corneal transplant for reasons including: disease severity; severe involvement of the conjunctiva; a failed previous corneal transplant; or when measures needed to prevent graft rejection are contraindicated. For these patients, penetrating keratoplasty using an artificial cornea (keratoprosthesis) may be an option.