Atrium Health Navicent Ophthalmology Macon

Corneal Transplants

A corneal transplant or keratoplasty is a surgical procedure in which all or part of a diseased or scarred cornea is removed and replaced with healthy corneal tissue from a donor.

Approximately 46,000 corneal transplants are performed in the United States every year. Corneal transplants have been able to restore vision for more than half of all recipients for periods longer than 10 years.

The Cornea's Role in Vision

The cornea plays two important roles in the vision process. First, the cornea controls and focuses the amount of light that enters the eye and works with the lens to focus light rays on exactly the right part of the retina. Second, the cornea helps shield sensitive eye structures from dust, grit, and microorganisms.

The Anatomy of the Cornea

The cornea is found in both eyes. It consists of three layers of cells separated by two membranes.

Epithelium

The outermost corneal layer is composed of epithelial cells that function to safeguard the eye from foreign matter and to absorb nutrients. Nutrients and oxygen diffuse into the cornea by means of tears and the aqueous humor, which is a watery fluid in the space in front of the iris. While the cornea is the only living tissue in your body that is not served by blood vessels, its epithelial layer contains thousands of nerve cells, which is why your eye hurts so much if it's scratched.

Bowman's Membrane

Bowman's membrane is a transparent collagen film that can form scars if it is injured.

Stroma

The stroma is the corneal layer responsible for light conduction. It is composed of strong collagen fibers and water, and if it is injured, it cannot heal itself. The stroma is the thickest corneal layer.

Descemet's Membrane

Descemet's Membrane is a thin, highly elastic sheet of tissue that is made of collagen. Descemet's Membrane provides an additional safeguard against infection and injuries.

Endothelium

The endothelial layer functions to pump excess water out of the stroma. The cell density of this layer depletes slowly as you age, and it cannot heal itself. If too many endothelium cells are destroyed by trauma, disease or aging, your only recourse if you want to save your sight may be a corneal transplant.

Corneal Injuries and Diseases

Considering its lack of blood vessels, the cornea responds surprisingly well to minor abrasions. If a scratch penetrates the epithelial layer, healthy cells move in quickly to patch the area before infection can set in and vision is affected. Deeper scratches, however, can impair vision since the cornea's two inner layers cannot repair themselves. When trauma injuries these layers, a corneal transplant may be indicated.

Corneal transplants may also be indicated in a number of inherited conditions and diseases, including:

Keratoconus

Keratoconus is an inherited condition that affects approximately one of every 2,000 people in the United States, many of whom are young adults. It involves a progressive thinning in both eyes so that the corneas are no longer able to maintain their distinctive domelike shape. Several technologies like specialized contact lenses and new technologies like collagen crosslinking are available for keratoconus. However, sometimes the cornea is so thinned and scarred that only a corneal transplant will help the problem.

Fuch's Dystrophy

Fuch's dystrophy is another progressive condition that may be linked to genetics. It causes a gradual deterioration of corneal endothelial cells and typically affects individuals in their 50s and 60s. Severe cases may need to be treated with corneal transplants.

Keratitis

Keratitis is an umbrella term for corneal infections. Following injuries to the eye, microorganisms can enter the cornea and cause inflammations and ulcerations. Bacteria, viruses, and fungi can also enter the cornea as the result of systemic infections. Some individuals have developed keratitis as the result of injuries related to wearing contact lenses. Severe ulcerations may result in scarring that requires a corneal transplant.

Herpes

Herpes simplex - the same virus that causes fever blisters around your lips - can also cause tiny blisters in your eyes. Herpes zoster or shingles are the viri that cause chicken pox. This virus can also cause ocular ulcerations. In some cases, ulceration may produce scarring that is so severe; a corneal transplant is called for.

Corneal Transplant Surgery

Corneal transplant surgery, which is also called corneal grafting consists of two types: Penetrating keratoplasty in which the entire thickness of the cornea (all five tissue layers) is replaced with a donor tissue and lamellar keratoplasty which involves removing only partial layers of the cornea. Donor corneas are provided through eye banks that obtain corneas from decedents who signed consent forms authorizing the removal of their corneas for this purpose.

Penetrating traditional corneal transplants may still be the most viable option for individuals who are suffering from severe corneal scarring. More recently, however, ophthalmologic surgeons have opted to replace selected corneal layers rather than all corneal layers when a corneal disease is restricted to a particular layer of the cornea.

Corneal transplants are typically performed on an outpatient basis. Your surgeon will use a specially engineered microscope and several fine delicate instruments to perform the surgery. You will be required to use medicated eye drops to prevent rejection of the graft.

The long-term success rates for corneal transplants are high. Approximately 90 percent of patients with keratoconus, 70 percent of patients with Fuch's dystrophy, and 60 to 70 percent of patients with severe corneal scarring enjoyed a marked improvement in their vision after penetrating keratoplasties that lasted for at least 10 years.