Cornea Transplant Surgery

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There are approximately 40,000 Corneal Transplants performed each year in the United States. This is actually a small number when compared with approximately 2,000,000 cataract procedures each year in this country. Of all transplant surgery done today, including heart, lung and kidney, corneal transplants are by far the most common and successful. Richard A. Erdey, M.D., a Corneal Specialist, has been performing Corneal Transplant Surgery since 1988.

The Normal Cornea

Infections, trauma, or dystrophic conditions can involve any layer of the cornea and may result in thinning or scarring that, if severe can cause loss of transparency and blindness.

Cross-section of the cornea. The normal cornea is about 0.55 millimeters (mm) thick in its center and consists of five microscopic layers as labeled above.  The thickness may increase to 0.68 mm or greater if swelling occurs because of endothelial cell loss.

We are born with a complement of cornea endothelial cells (3000 to 3500 cells/ mm²) that line Descemet’s membrane. These cells are responsible for “pumping” fluid out of the cornea, maintaining cornea transparency. As we mature, the concentration of these specialized cells may decrease by 1/3 but this quantity is still sufficient to maintain corneal clarity throughout life. Unfortunately, corneal endothelial cells are one of the few cells in the human body that are not capable of regeneration and if damaged or lost are not replaced.

If the cornea endothelial cell concentration falls below a certain critical threshold, as can occur in Fuchs’ Corneal Dystrophy, after cataract surgery or after eye trauma, the cornea swells and loses transparency leading to blurry vision or eventually, blindness.

Fuchs' corneal dystrophy is a progressive condition that gradually affects both eyes. It is slightly more prevalent in women than in men. The condition rarely affects vision until people reach their 50s and 60s although an eye doctor can sometimes detect the early signs of Fuchs' dystrophy at age 30 to 40 years. The pathology in Fuchs' corneal dystrophy occurs when the endothelial cells are gradually lost over the years.

At first, a person with Fuchs' corneal dystrophy may awaken with blurry vision that gradually clears later in the morning or by noon. The reason for this is during sleep the closed eyelids prevent evaporation; once the patient awakens, the open eyelids allow corneal surface evaporation to occur, allowing the cornea to thin and vision to improve. As the disease progresses, corneal swelling will remain constant and vision remains poor throughout the day.

Eventually, the epithelium also swells with fluid and may form tiny blisters, causing eye irritation, foreign body sensation and severe visual impairment. If these blisters burst they can cause severe pain.

To treat the disease, your doctor may initially try to reduce corneal swelling with hypertonic salt drops or ointment which extracts the fluid from the cornea. If the condition becomes painful, bandage soft contact lenses may be implemented. In early stages of this condition, a hair dryer held at arm's length and directed parallel to face and be used to temporarily dry and thin the cornea. This easy procedure may temporarily improve symptoms and can be repeated several times a day.

Once the disease interferes with daily activities because visual performance is reduced and/or persistent pain occurs, your doctor may recommend corneal transplantation to restore sight and eliminate discomfort.
 

The Diseased Cornea – Corneal Transplantation

Corneal Transplantation may be necessary if your cornea is damaged due to injury or disease. Since there is no artificial substitute for corneal tissue, a human donor cornea is transplanted to restore sight. The Central Ohio Lions Eye Bank typically provides the corneal tissue for our patients.

As in any kind of surgery, many different complications can occur. One unique to most varieties of corneal transplantation is rejection of the donated tissue. The major signs of cornea graft rejection are redness of the eye or worsening of vision. Presence of these signs after corneal transplantation mandates prompt return to your ophthalmologist, even if it is years after the original operation!

A successful Corneal Transplant requires special, ongoing care and attention on the part of both patient and physician. However, no other surgery has so much to offer when the cornea is deeply scarred or afflicted with disease. View: Testimonials

“Don't take your organs to heaven...heaven knows we need them here! “

Corneal Transplant Surgery would not be possible without the hundreds of thousands of generous donors and their families who have donated corneal tissue so that others may see. If you would like more information on becoming a donor, please contact the Central Ohio Lions Eye Bank at (614) 293-8114 or (800) 301-4960

Corneal Transplantation - Variations

Dr. Erdey may recommend one of the following surgical variations of corneal transplantation at the time of your consultation:

• Penetrating Keratoplasty (PK)
• Descemet’s Stripping Endothelial Keratoplasty (DSEK)
• Deep Anterior Lamellar Keratoplasty (DALK)
  
  

Penetrating Keratoplasty (PK)

Penetrating Keratoplasty (PK) is a traditional full-thickness corneal transplant. This may be required in cases where the cornea is scarred, swollen or excessively thin (Keratoconus).

Return of best vision after standard full thickness corneal transplantation may take up to a year or more after the operation. It is dependent on how long it takes for the grafted cornea to begin functioning as a lens; it must become transparent and it must have a regular surface curve. These important characteristics permit light to properly bend (refract) as it passes through the cornea, bending further as it passes through the crystalline lens and comes to focus on the retina.

The newly grafted cornea, if successful, only takes a few weeks to become thin and transparent but far more time is usually required until light is properly refracted through it.

The healthy cornea is transparent because it does not contain the fine blood vessels (capillaries) present in other tissues of the body. However, this lack of blood supply has a downside when cornea graft wound-healing is required. The cornea takes years to heal as compared to a superficial wound in the skin of your arm, which heals in only about a week! For this reason cornea graft sutures must be left in place for a year or more while the cornea graft-host interface heals. The tension generated by the sutures within the cornea often cause distortion of the curvature of the graft, causing the refraction of the eye to shift unpredictably. If the cornea surface is regular, and the prescription of the other eye is not too different, it is sometimes possible to prescribe glasses during this early rehabilitation period but the prescription lenses may need to be periodically changed as the cornea heals.

Some patients with significant corneal surface distortion may need to wait a year or more until the sutures can be removed before the actual graft curvature becomes obvious and spectacles prescribed. However, if after suture removal significant cornea graft distortion remains, spectacles will not help. Instead, hard contact lenses may be suggested, but fitting can be challenging and is not always successful.

Other individuals require laser vision correction to reduce inadequate graft curvature or imbalances between the prescriptions of both eyes to maximize optical visual rehabilitation.

Of course, a good visual outcome is also dependent on general eye health and requires the absence of other visually limiting conditions such as cataract, glaucoma, or macular degeneration.

Descemet's Stripping Endothelial Keratoplasty (DSEK)  View: 10TV News Report

Descemet’s Stripping Endothelial Keratoplasty (DSEK) is a newer, cornea-sparing transplant procedure that is indicated for patients without corneal scarring and with disease limited to the inner corneal layer (endothelium) such as Fuchs’ Endothelial Dystrophy or Pseudophakic Bullous Keratopathy.

Only the inner cornea layer is transplanted, leaving the patient’s cornea mostly intact. Only a small scleral incision is made and few sutures are required. The cornea heals very quickly and is less susceptible to injury or rupture as compared to standard PK. Visual recovery is much faster since the cornea’s original curvature is essentially unchanged resulting in little refractive shift. In contrast, after standard PK, patients often experience large changes in the amount of nearsightedness, farsightedness, and astigmatism. In fact, Dr Erdey prefers DSEK and no longer recommends PK for suitable candidates with Fuchs’ Endothelial Dystrophy or Pseudophakic Bullous Keratopathy.

Cornea after DSEK: Note partial thickness donor graft (arrow) applied to inner cornea surface. Cornea transparency is restored.

Deep Anterior Lamellar Keratoplasty (DALK)

Deep anterior lamellar keratoplasty (DALK) is a partial thickness graft that preserves the TWO inner most layers of the cornea: Descemet's membrane and the endothelium.

The goal of the procedure is to retain the endothelial layer of the host. This layer keeps the cornea clear by removing fluid from the bulk of the cornea.

Retaining this layer greatly reduces the risk of potentially blinding Graft Rejection that can occur with PK. If the endothelial layer is normal, then it is worth preserving.

Patients with anterior cornea scarring or Keratoconus who are contact lens intolerant and who are poor candidates for INTACS might be the most suitable candidates for this procedure.

Advantages:

• Closed eye surgery
• No chance of potentially blinding endothelial rejection because the recipients own endothelial layer is retained
• Can always perform a PK if visual results are not satisfactory

Disadvantages:

• Technically challenging and conversion to full thickness PK often required
• Potential for interface scarring (and reduced visual clarity)
  
  

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The Diseased Cornea – Research

Various Stem Cell Research projects may hold the promise of finding ways to stimulate corneal endothelial cell regeneration. This is the “holy grail” that could eventually eliminate cornea transplantation in cases of endothelial cell loss.Other research is dedicated to developing better artificial corneas or eventually regenerating entire living corneas for transplantation.