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BLOG: CXL, refraction correction an ideal combination
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The U.S. approval of corneal collagen cross-linking for ectatic disorders provided hope for so many patients with keratoconus, but the real benefit of CXL is if it can be combined with a refractive procedure to give spectacle freedom.
Topographic-guided PRK ablation patterns, which are now approved on the Alcon WaveLight platform, have successfully corrected irregular astigmatism and higher-order aberrations already in many patients undergoing cross-linking, but our knowledge is far from complete.
A debate relating to the timing of PRK exists: Should it be performed before cross-linking or after a few months of healing have occurred? There are reasonable arguments to be made on both sides, but one thing is clear: Most ectatic corneas can be safely treated with laser (even LASIK in some cases) and will remain stable and free from further ectasia.
Why is this important? Between 5% and 10% of patients presenting with interest in corneal refractive surgery are turned down because of evidence of ectasia or forme fruste keratoconus. Many of these patients have irregular astigmatism and have failed with spherical and toric soft contact lenses and even gas permeable lenses; they want better vision through surgery.
For some time, my colleagues in the CXLUSA study have performed a combination of collagen cross-linking with conductive keratoplasty, centering the CK treatment over or adjacent to the steepest area of the cone. This treatment would flatten the cone and give permanent improvement in irregular astigmatism once cross-linking was performed. Topographic-guided PRK offers an even more precise method of reshaping the cornea to lessen irregularity.
Not all corneas can be completely corrected. Some ectatic eyes are extremely myopic, and only so much tissue can safely be removed by PRK, even in a cross-linked cornea. But debulking the irregularity and refractive area in these patients gives them a major advantage and enables them to consider soft or soft toric contact lens wear in the future.
Another option that may offer hope is a small aperture IOL. AcuFocus is developing and has begun U.S. clinical trials of a lens implant that has a pinhole aperture similar to the Kamra corneal inlay. While its primary approval will be for correction of presbyopia, this technology clearly has off-label benefits for patients with irregular corneas caused by ectasia or other disorders. For some patients with keratoconus, cross-linking may be the first step followed by lens implantation. Time and clinical experience will tell us how much irregularity the small aperture can correct.
Meanwhile, many patients with keratoconus are ready and willing to undergo PRK treatment to improve their refractive error and irregular astigmatism. The technology is available and approved, and a growing body of evidence supports its safe use. I am one surgeon who is ready to get started.
Disclosure: Hovanesian reports he is a consultant to Alcon.