CORNEAL TRANSPLANT INFORMATION
The cornea is the clear dome-shaped "window" in the front of the eye. Behind this clear window lies the iris, or coloured portion of the eye. The cornea serves two purposes:
It forms the front part of the eye's outer wall or shell and focuses images on the retina at the back of the eye. With its curved shape, the cornea acts like a camera lens to transmit light and focus images on the back of the eye.
Following disease or injury, the cornea may become weakened, cloudy, or irregular in shape. If medicines are ineffective, in some cases, the damaged cornea can be replaced with a healthy cornea from a deceased person. This replacement procedure is called a "corneal transplant" or "penetrating keratoplasty".
This information is designed to accompany but not replace the discussions with your surgeon before and after the surgery. If you have further questions, please ask your doctor. It is important that you take as much time as you need to understand your condition and possible treatments.
The Donor Tissue
Corneal tissue for transplantation comes from an eyebank. The process begins at the death of someone who has been generous enough to donate his or her eyes. The eyebank carefully screens the donor tissue to rule out any disease that might be transmitted to the recipient.
It is the policy of all eyebanks that the donor remains anonymous. There is no incompatibility of donor and recipient tissue on the basis of sex or race, or need for glasses, the color of the donor eye is also irrelevant, since only the transparent dome in the front of the eye is replaced, and not the colored iris behind it.
Indications for Surgery
Corneal transplants are done to improve vision, relieve pain, and protect the inner structure of the eye.
The transplant repairs the damage from injuries or infections. Knives, pencils, other sharp objects, fireworks, and chemicals can cause severe injury to the cornea. Bacterial, viral, and fungal infections are frequent causes of severe corneal scarring and ulceration.
Abnormal steepening of the cornea (keratoconus), occasional degeneration after cataract surgery, and some aging processes can also damage the cornea. Inherited abnormalities (dystrophies) can lead to corneal clouding and loss of sight.
Preparing for Surgery
A general medical examination and routine laboratory tests ensure that you are well enough to undergo surgery. Aspirin is not used for 2 weeks prior to surgery, since it tends to cause bleeding during surgery.
In most cases, the surgery can be done on an outpatient basis. A small weight is placed on the closed eye to soften the eye. An IV line and EKG monitoring are standard safety precautions.
Local or general anaesthesia can be used, based on age, general health, length of surgery, and patient preference. Local anaesthesia consists of two small injections, one behind the ear, and one in the lower eyelid. Sufficient sedation is given so that the local anaesthetic is hardly felt.
The eyelids are carefully washed and covered with a sterile plastic drape. Fresh oxygen is provided by a plastic tube placed near the nose.
The entire procedure is done under a microscope. A circular blade called a trephine is used like a cookie cutter to remove the center of the diseased cornea. A "button" of similar size is cut from the donor cornea. This donor tissue is then sewn in place with extremely fine nylon sutures.
If it has been determined before surgery that a cataract (cloudy lens) is present, the cataract may be removed and replaced with a clear plastic lens during the corneal transplant operation. Your surgeon will have discussed this with you prior to surgery.
If the eye has previously had cataract surgery, but the plastic lens implant is damaging the cornea, the faulty lens implant can be replaced with a new one at the time of the corneal transplant surgery.
At the conclusion of the procedure, a patch and shield are applied to protect the eye.
Pain varies from person to person. Typically there is either no pain or only slight soreness for a few days, relieved by Tylenol.
The surface epithelium is healed, usually in 1 to 4 days. After the patch is removed, it is important to wear something hard on front of the eye (glasses or a metal shield) at all times to give it protection. Typically, patients wear their glasses during the day. A shield is worn at night for several weeks.
Sleeping on the operated side is acceptable. After the first day, brushing teeth, bathing, light housework, bending over, walking, reading, and watching TV will not hurt the eye. Showering, shampooing, sexual activity, and vigorous exercise can be resumed after one week.
Since the new cornea is delicately sutured in place, a direct poke to the eye must be avoided. Contact sports are discouraged after corneal transplant. Otherwise, normal activity can be resumed within a few days.
Because the cornea has no blood supply, the transplant heals relatively slowly. Sutures are left in place for three months to one year, and in some cases they are left in permanently. The sutures are buried and therefore do not cause discomfort. To reduce astigmatism (irregular shape of the cornea), suture tension may be adjusted as early as three weeks after surgery. Suture adjustment and removal are simple, painless office procedures.
Vision gradually improves as the new cornea heals. There is often useful vision within a few weeks. However, in some cases it may take several months to one and half years' for full vision to develop. Usually you will require glasses or even a contact lens to achieve your best vision in that eye.
To prevent rejection of the new cornea, steroid drops are placed in the eye for several months after surgery. In some cases, low dosage steroid drops are continued indefinitely. Unlike oral steroids, steroid eye drops cause no side effect elsewhere in the body. Occasionally, other eye medications are necessary.
It is important to call immediately (including weekends, evenings and holidays) for any unusual symptoms including: Redness, Sensitivity to lights, Vision loss or Pain ("RSVP"). Flashing lights, floaters, and loss of peripheral vision should also be reported immediately. Post-operative care is extremely important and by far the most time-consuming part of having a corneal transplant. The eye is checked the day after surgery, several times in the first two weeks, at gradually longer intervals over the first year, and usually yearly thereafter.
Risks and Complications
No surgical procedure is completely free of risk. Possible complications include, but are not limited to, astigmatism, infection, bleeding, retinal detachment, glaucoma, and cataract. Occasionally, the donor cornea is rejected (becomes cloudy). Following such complications, vision may end up the same or worse after surgery.
Problems unrelated to the corneal transplant surgery, such as retinal scarring (macular degeneration) or optic nerve damage from increased eye pressure (glaucoma) may lead to poor vision even if the corneal transplant operation is successful.