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Corneal Transplants



Ophthalmologists perform more than 40,000 corneal transplants each year in the United States.  Of all transplant surgery done today, including heart, lung and kidney, corneal  transplants are the most successful.

The cornea is the clear front window of the eye that covers the colored iris and the round pupil.  Light is focused while passing through the cornea so we can see.

The cornea is the normally clear, front window of the eye that covers the colored iris and round, dark pupil.  Light is focused while passing through the cornea, allowing us to see.

Our cornea is made up of three layers:

  • The outer or epithelial layer;
  • The middle or stromal layer (this layer accounts for about 95 percent of the cornea's total thickness)
  • The inner or endothelial layer.

A healthy, clear cornea is necessary for good vision.


HOW CAN AN UNHEALTHY CORNEA AFFECT VISION?

If your cornea is injured or affected by disease, it may become swollen or scarred, and its smoothness and clarity may be lost.  Scars, swelling or an irregular shape can cause the cornea to scatter or distort light, resulting in glare or blurry vision.

The function of the endothelial cells is to pump fluid out of the cornea, keeping it crystal clear and thin.  When many endothelial cells are injured or lost, the fluid that circulates inside the eyeball seeps into the cornea, causing it to become cloudy and swollen.  When this condition occurs, medical treatments usually will not help, and a corneal transplant is recommended.

WHAT CONDITIONS MAY CAUSE THE NEED FOR A CORNEAL TRANSPLANT PROCEDURE?

  • Corneal failure after another eye surgery, such as cataract surgery
  • Karatoconus, a steep curving of the cornea
  • Hereditary corneal failure, such as Fuch's dystrophy
  • Scarring after infections, especially after herpes
  • Rejection after a first corneal transplant
  • Scarring after injury

There are many conditions that can affect the clarity of the entire cornea, including trauma, infections or hereditary diseases.

Some conditions can affect the cornea's endothelial cells, including Fuchs' dystrophy and pseudophakic bullous keratopathy, as well as previous eye surgery.

Many people who require corneal transplant surgery have diseases that only affect the cornea's inner lining of endothelial cells.  If the remaining corneal layers are clear and healthy, endothelial keratoplasty (EK) may be considered to improve vision.

WHAT HAPPENS IF YOU DECIDE TO HAVE A CORNEAL TRANSPLANT?

BEFORE SURGERY

Once you and your doctor decide you need a corneal transplant, you will be scheduled for surgery.  Most of the time a donor cornea will be available for your surgery, but sometimes the surgery will need to be postponed if a suitable donor cornea is not available, or if your doctor has special requirements for donor tissue.

Before a cornea is released for transplant, the eye bank test the human donor for the viruses that cause hepatitis, AIDS and other potentially infectious diseases.  The cornea is also carefully checked for clarity.

Your doctor may request that you have a physical examination and other special tests.  If you usually take medications, ask your doctor if you should continue using them.

THE OPERATION

The eyelids are gently opened. Your doctor will view your eye through a microscope and measure your eye for the corneal transplant.  The diseased or injured cornea is carefully removed from the eye.  Any necessary additional work within the eye, such as removal of a cataract, is completed.  Then the clear donor cornea is sewn into place.

When the operation is over, your doctor will usually place a shield over your eye.

After surgery, you may go home after a short stay in the recovery area.  You should plan to have someone drive you home.  An examination at your doctors office will be scheduled for the following day.

You will need to:

  • Use the eye drops as prescribed
  • Be careful not to rub or press on your eye
  • Use over the counter pain medicine if necessary
  • Continue normal daily activities but avoid strenuous exercise or activities until cleared
  • Wear eyeglasses or an eye shield for protection as advised
  • Ask when you can start driving again
  • Call if you have any questions about your home care instructions

Your doctor will decide when to remove the stitches, depending upon the health of your eye and rate of healing.  Usually it will be one year before stitches are removed, but this varies depending on the specific technique used.  Often, stitches are left in place permanently.

FULL-THICKNESS CORNEAL TRANSPLANT VS. EK PROCEDURE

With traditional full-corneal transplant surgery (know as penetrating keratoplasty), a circular portion is removed from the center of the diseased cornea.  A matching circular area is removed from the center of a healthy, clear donor cornea, placed into position and stitched into place.

It may take as long as one year or more to recover from a full corneal transplant.  It is also possible to have a significant irregular curvature of the cornea because of the stitches.  In many cases, a contact lens must be worn for the best vision.  Also, a transplanted cornea can be prove to damage years after the procedure, meaning that even a minor trauma can cause the transplant to dislocate from its position.

With the EK corneal transplant procedure, only the abnormal inner lining of the cornea is removed. 
A thin disk of donor tissue containing the healthy endothelial cell layer is placed on the back surface of the cornea.  An air bubble pushes the endothelial cell layer into place until it heals in an appropriate position.

The EK surgical procedure takes less time, requires a smaller incision, uses fewer (or no) stitches, has a shorter recovery time, and restores vision faster than with traditional corneal transplant.  Also, because stitches usually are not used, the structure of the cornea remains intact, resulting in less visual distortion (astigmatism) than full-thickness corneal transplant.

WHAT HAPPENS DURING THE EK PROCEDURE?

The EK procedure is done in an outpatient setting under local anesthesia (eye drops or numbing injections are placed around the eye).  Relaxing medications are given in a vein.

The procedure takes approximately 45 minutes.  A tiny incision is made in the sclera (white portion of the eye)  A thin button of healthy endothelial cell layer from a donor is inserted into the eye through the incision and placed on the back surface of the cornea.  An air bubble is injected to push this new tissue into place and help it heal in the proper position.  The endothelial cells have a natural "pumping" action, which creates suction and rapidly bonds the new donor tissue to the cornea.

Your doctor may want you to lie flat on your back facing the ceiling as much as possible for the first 24 hours after surgery.  This will help the air bubble keep the new corneal tissue in place.  You will be given eye drops to use for comfort and to prevent infection.  Vision is usually better within one week.  After one month, approximately 80 percent of the healing has occurred, but vision may continue to improve over the next four to six months.

WHAT ARE THE RISKS AND COMPLICATIONS OF EK?

 Risks and complications associated with EK can include:

  • Bleeding in the eye
  • Infection
  • Swelling of the retina, causing temporary or permanent blurring of vision
  • Retinal detachment
  • Glaucoma or high pressure in the eye
  • Chronic inflammation
  • Droppy eyelid
  • Loss of corneal clarity
  • Poor vision or total loss of vision
  • Loss of the eye

There is also risk of rejection, where the body's immune system starts to fight against the donated corneal tissue. Symptoms of rejection are redness, blurry vision and light sensitivity.  This can happen at any time, months or years after the transplant, and can occur after EK as well as traditional penetrating keratoplasty.

Another complication that can occur from the EK procedure is a graft dislocation, where the circular disc slips from position, requiring surgery to reposition it.

If EK fails, a full-thickness corneal transplant can still be performed.

EK is not for everyone.  Some people with corneal scarring or other conditions are not suitable candidates for the procedure.  Your doctor will discuss your condition with you and explain the best treatment options.

CORNEAL TRANSPLANTS ARE A GENEROUS GIFT OF SIGHT.

Corneal transplants would not be possible without the thousands of generous donors and their families who have donated corneal tissue so that others may see.  This gift, along with the development of endothelial keratoplasty, provide another treatment option for people with corneal disease.

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