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The cornea can be transplanted, either as a full thickness graft, a procedure known as PENETRATING KERATOPLASTY, or as only a partial thickness graft of the outer layers of corneal tissue, known as a LAMELLAR KERATOPLASTY. PENETRATING KERATOPLASTY may be necessary when the cornea loses its clarity by being scarred or swollen, or when the cornea loses its shape (which is normally nearly round) by becoming abnormally thin. Corneal thinning can be the result of infection or inflammation, and PENETRATING KERATOPLASTY under these circumstances is a means of preventing perforation of the cornea with resultant disastrous explusion of intraocular contents. Anti-inflammatory and/or antibiotic medications are used in conjunction with surgery to control the inflammatory or infectious process. PENETRATING KERATOPLASTY is also used to treat conditions where the cornea becomes thin without apparent inflammation. These diseases include KERATOCONUS, PELLUCID MARGINAL DEGENERATION, and KERATOGLOBUS, which all involve thinning causing distortion of the normal corneal shape; the cause is unknown and no medications are effective as treatment. CONTACT LENSES are useful in most cases, but if the corneal distortion is very severe, PENETRATING KERATOPLASTY may be required. LAMELLAR KERATOPLASTY may be performed when inflammation of the cornea has caused thinning in the periphery of this clear tissue, which is amenable to a crescent shape graft being placed to support the cornea and prevent perforation. Occasionally, the sclera may be thinned dangerously by inflammation (SCLERITIS) and require additional support to maintain the eyewall structure. Under these circumstances, a SCLERAL PATCH GRAFT may be placed, using sclera from a cadaveric donor. The CONJUNCTIVA is the clear membrane that covers the white part of the front of the eye. The conjunctiva can be grafted from one part of the ocular surface to another or from one eye to another in cases where surgery has created a large defect that needs assistance healing. This procedure is known as a CONJUNCTIVAL AUTOGRAFT. The LIMBUS is the area where the CORNEA meets the
SCLERA, and this ring shaped area contains STEM CELLS that help
maintain the integrity of the corneal surface. When the corneal
surface and limbus of one eye have both been injured, the corneal
surface integrity may not heal unless STEM CELLS from the limbus
of the other eye-or from the eye of a donor-are transplanted to
the injured eye. This procedure is known as a LIMBAL STEM CELL TRANSPLANT.
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