CORNEA & CONTACT LENS Q&A

LASIK on a Graft?
Concepts You Must Grasp

Edited by Joseph P. Shovlin, O.D.

Question: I've heard LASIK can improve vision in patients after they've had corneal transplantation. What guidelines should I follow in deciding which patients to refer?

Answer: First, try to improve the patient's vision with contact lenses. If the patient is unsuccessful with contact lenses, can't tolerate the lenses or doesn't want to wear them, then consider referring him or her for LASIK.

Two indications for LASIK—astigmatism and anisometropia—often occur following transplant. You might be able to correct each eye with spectacle lenses, but the considerable difference in the two Rxes causes different retinal image sizes. The brain can't fuse those images, resulting in visual discomfort for the patient. LASIK could help reduce the anisometropia and balance the two eyes, says refractive surgeon Frederic B. Kremer, M.D., of King of Prussia, Pa.

You'll need to counsel this patient to expect results different from those a conventional LASIK patient would expect. Says Rockville Center, N.Y., surgeon Eric D. Donnenfeld, M.D.: "The visual goal for LASIK following transplant is resolving anisometropia, myopia and high astigmatism to the point where the patient can comfortably wear glasses. It's not unaided visual acuity." He says that about one in five of his patients who have undergone both transplant and LASIK see 20/30 or better uncorrected.

Also educate the patient that LASIK is less predictable on a graft than on a virgin cornea, and that the enhancement rate is somewhat higher in post-transplant patients. These patients also are more likely to develop irregular astigmatism than a LASIK patient without a transplant, says optometrist Paul Karpecki of Hunkeler Eye Centers in Kansas City, Mo.

Patients who have astigmatism greater than 6.00D or significant irregular astigmatism are not ideal LASIK candidates. To decide whether your patient would benefit from LASIK, find the best corrected spectacle acuity in each eye. If spectacle acuity is not good, the patient will not see well after LASIK either. However, if the patient achieves 20/20 or 20/25 with spectacles, he or she will likely do very well with LASIK. As topography-linked ablation systems become available, patients with irregular astigmatism might then do better with LASIK.

For patients with high amounts of astigmatism, astigmatic keratotomy (AK), also referred to as a relaxing incision, may be an alternative to LASIK, says Cleveland optometrist Loretta B. Szczotka. AK, sometimes with the use of compression sutures, decreases the astigmatism so you can then fit those patients in contact lenses more easily.

Another contraindication for LASIK: a history of graft rejection. "The eyes have to be quiet, and the grafts have to be in good shape," Dr. Donnenfeld says. "I wouldn't offer this to a patient who had three different rejections or inflammation in the eye."

Some additional guidelines:

• Patients should wait at least a year after transplant before having LASIK. This enhances their wound-healing abilities, says Daniel S. Durrie, M.D., of Hunkeler Eye Centers. The suction ring of the microkeratome often raises IOP to more than 100mm Hg, so you want the wound to be very solid. Dr. Szczotka suggests waiting even two years, since there's increased risk of wound dehiscence.

• Sutures should be out for at least six months so that the cornea has time to develop its true shape, Dr. Donnenfeld says.

• Patients should have a stable refraction without contact lens wear at three months apart to make sure their myopia or astigmatism is not changing, adds Dr. Durrie.

• You or the surgeon should make sure the patient will have at least 250 microns of cornea left in the stromal bed after LASIK, says Dr. Karpecki.

• Ideally, you want to refer to an experienced LASIK surgeon who may also specialize in corneal transplants. However, it's most important to have a skilled LASIK surgeon. "You don't want to send them to a beginning LASIK surgeon just because he's a transplant surgeon," Dr. Durrie says.

Question: Are there any special considerations when comanaging corneal transplant patients who undergo LASIK?

Answer: You comanage them as you would any other LASIK or transplant patient. The first week, you want to make sure there's no post-op infection and that the LASIK cap is smooth, Dr. Kremer says.

You'll also need to monitor the patient for any signs of graft rejection, as you would for any post-transplant patient. Dr. Szczotka instructs all transplant patients to return annually once they're stable, sooner if there are any signs of rejection. Keep in mind, post-transplant patients who undergo LASIK may not achieve stability for the first few years. Topography and spectacle refraction may constantly change during this time, so you'll need to repeat topography often, Dr. Szczotka adds.

These doctors say LASIK does not necessarily increase the likelihood of rejection. However, the possibility still exists. "Any time you stir up the eye, you can stir up the immune system," says Dr. Karpecki. "When you stir up the immune system, you can certainly increase the risk of rejection."

Transplant patients should continue using any anti-rejection medications before and after the LASIK, warns Dr. Durrie. If they use antibiotic drops, these should be in addition to, not in place of, the anti-rejection meds.

Dr. Donnenfeld also puts these patients on steroids for about two weeks after the LASIK, longer than his other LASIK patients. He then tapers the dosage over an additional week or two.

If the patient has a history of herpetic eye disease, use oral antivirals before and after LASIK. Instances of reactivation following LASIK have been reported, possibly resulting from the trauma of lamellar dissection or the ultraviolet light from the excimer laser.1

As one final precaution, Dr. Donnenfeld advises his post-transplant patients to wear a protective shield at night for at least four days after LASIK to ensure that the flaps adhere well.

Send your questions to Review of Optometry, 201 King of Prussia Road, Radnor, PA 19089; or e-mail them to reviewofoptometry@jobson.com.

1. Davidorf JM. Herpes simplex after LASIK. J Refractive Surg 1998;14:667.