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PTK for keratoconus viable alternative to keratoplasty in select patients
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MINNEAPOLIS — A patient who continues to be contact lens intolerant after multiple fits may be an ideal candidate for phototherapeutic keratectomy (PTK) for keratoconus.
--- Good candidate for PTK: Keratoconus thinning, but with nodular elevation.
However, all reasonable attempts should be made to properly fit the patient before referral to a corneal specialist because "PTK is probably only successful in 30% to 50% of patients with keratoconus-type scarring," said David R. Hardten, MD, in group private practice here.
The depth of the scar and the consistency and irregularity of the scar are two variables in considering PTK. "It also depends on the thickness of the cornea once you remove the scar," explained Dr. Hardten, noting that too thin of a cornea will disqualify an otherwise suitable candidate.
Nodular indicator
Patients with anterior stromal scarring that forms a nodule appear to benefit most from the procedure, said Dr. Hardten, a clinical assistant professor of ophthalmology at the University of Minnesota. "Patients may be unable to tolerate a contact lens anymore because that nodule or elevation causes the contact lens to become uncomfortable or to teeter-totter back and forth on the anterior stromal scar," he said. "If these patients have sufficient cornea underneath their corneal scars, you can probably remove the scar with a laser, which, in turn, will make the scarred area level with the rest of the cornea. These patients can often return to a contact lens and wear it more comfortably with better vision."
Patients should be counseled about two options: PTK or penetrating keratoplasty. "PTK's goal is to return the patient to contact lenses," said Dr. Hardten. "The ideal candidate will have a relatively thick cornea and a solitary elevated nodule."
--- Bad candidate for PTK: Keratoconus thinning without nodule or scar.
In contrast, the patient with an extremely thin, ectatic cornea and diffuse scarring is more suitable for penetrating keratoplasty. "The penetrating keratoplasty is a little more predictable for the patient, but it also carries more risk."
Dr. Hardten cited the example of a recent patient who opted for PTK over keratoplasty. The 18-year-old man planned to play college baseball. "He couldn't wear his contact lenses anymore, and he couldn't see well out of glasses," Dr. Hardten said. "If we had performed a penetrating keratoplasty, it would have been unlikely that he could have played baseball this season because of the prolonged healing process (typically 6 to 18 months to achieve stable correction). Three weeks after PTK, though, he was back in a contact lens and playing baseball. He is doing just fine."
Stability key
"Clearly, when we perform PTK, we prefer to have a stable situation, in terms of age, refractive status and corneal curvature, so we can offer the patient a certain degree of predictability as to the amount of treatment and the kind of ablation we're going to achieve. This will likely result in a specific degree of correction of unassisted visual acuity," said James V. Aquavella, MD, clinical professor of ophthalmology at the University of Rochester in New York and director of its corneal research laboratory.
When counseling patients about PTK, Dr. Aquavella said that he cannot promise that the procedure will be helpful, or even that the outcome will not be worse. "If it doesn't make you a little bit better, at least it may defer keratoplasty for a period of time. In that sense, I'm very comfortable recommending PTK."
Some patients, however, choose grafting because they do not want the 2- to 3-month delay of PTK outcomes. "All patients must understand that kerotoplasty is the only option if PTK is not successful," said Dr. Aquavella.
For Your Information:
- David R. Hardten, MD, can be reached at 710 East 24th St., Suite 106, Minneapolis, MN 55404; (612) 336-5710; e-mail: drhardten@worldnet.att.net.
- James V. Aquavella, MD, can be contacted at the University of Rochester, 919 West Fall Rd., Rochester, NY 14618; (716) 461-8409. Neither Dr. Hardten nor Dr. Aquavella has a financial interest in any of the products mentioned in this article, and neither is a paid consultant for any of the companies mentioned.