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Corneal cross-linking would be welcome addition to treat keratoconus
 Richard L. Lindstrom |
Keratoconus is a common problem confronting the corneal specialist and comprehensive ophthalmologist. Patients with keratoconus are especially common among the 40 million Americans who wear contact lenses, and as many as 5% of patients requesting corneal refractive surgery present with topography suggestive of early keratoconus. In addition, a small number of patients continue to develop corneal ectasia after excimer laser refractive surgery.
Classical treatment has been a progression from glasses to contact lenses. Usually, patients with significant keratoconus require rigid gas permeable contacts for best vision, and in many cases, specialized contact lens fitting is required to keep these patients seeing well enough to function. In recent years, many patients have been helped with Intacs (Addition Technology), in some cases combined with conductive keratoplasty, and in others, conservative treatment with PRK. When all these modalities fail, lamellar or penetrating keratoplasty is necessary, and today, keratoconus is the No. 1 indication for PK, according to Eye Bank Association of America statistics.
Collagen cross-linking is potentially a welcome addition to the treatment alternatives for this significantly disabling problem. Clinical observation has taught us that keratoconus progression usually slows as the patient ages. This slowing and, in many cases, stabilization of corneal topography is secondary to the natural aging of the cornea’s collagen, accelerated by exposure to sunlight, which results in natural collagen cross-linking. Through the brilliance of Theo Seiler, MD, PhD, and his research group, it has become possible to accelerate this process through the application of ultraviolet light to a cornea pre-saturated with riboflavin to enhance the energy absorption. The science is convincing that a much more rigid cornea is created by this treatment, retarding ectasia progression.
The risks, which include the expected damage to living cells, including the epithelium if not removed, stromal keratocytes and endothelium, seem manageable through proper patient selection and surgical technique. A superficial haze develops in most patients, but like the reticular haze in excimer laser PRK, seems to fade with time and is rarely visually significant. Most exciting is the possibility that corneal cross-linking might be applied, either sequentially or simultaneously, with Intacs, CK or PRK to further benefit the patient’s visual function.
This treatment, while not available in the U.S., is available elsewhere, including Canada, Latin America and Europe. Patients with significant corneal ectasia that is progressing may be candidates for referral abroad for treatment.
It is hoped that the regulatory and financial barriers are not too high to prevent this promising treatment’s approval by the FDA, but, sadly, collagen cross-linking may represent another promising treatment that is just not potentially profitable enough to justify the extraordinary costs of U.S. regulatory approval. I hope this is not the outcome.