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What every eye doctor should know about collagen cross-linking
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For nearly 15 years, collagen cross-linking of the cornea has been practiced in Europe, and its use in the U.S. has slowly grown through its availability at various study sites. To date, no treatment platform has yet been approved by the FDA. Some controversies have arisen in this field, but here I would like to present three truths that are fairly accepted across the cornea community.
Cross-linking works. Across all studies, there seems to be agreement that collagen cross-linking, when properly performed, almost always halts the progression of ectatic disorders, including keratoconus and surgically or traumatically induced ectasia. The mechanism of action is by causing covalent bonds to form across layers of collagen in the cornea — a process that imitates but significantly accelerates age-related cross-linking. Furthermore, in most studies, about half of patients experience a meaningful improvement in uncorrected visual acuity or at least an improvement in the regularity of the astigmatism, which allows easier correction with contact lenses or spectacles.
It is safe and becoming more patient-friendly. All the initial protocols for collagen cross-linking involved removing the corneal epithelium. This so-called epi-off approach, while successful, is accompanied by a longer healing time and the potential for corneal scarring that comes with delayed re-epithelialization. With epi-on techniques, most studies by experienced surgeons seem to suggest the same outcomes as epi-off, and complication rates (due to faster healing) are much lower. Some studies are also examining higher-intensity UV light treatment, which reduces exposure time from 30 minutes down to as little as 5 minutes. Most patients experience some pain on the night of the procedure but fairly uneventful healing after this.
Cross-linking’s role is expanding. Beyond treating ectatic disorders, collagen cross-linking has been found successful for reducing diurnal fluctuations in refraction and vision that occur in post-RK patients. This happens because cross-linking collagen across the incision sites leads to less diurnal swelling and refractive shift. Additionally, some protocols are examining the role of UV light exposure in treatment of corneal infections, in which aggressive cases of microbial keratitis can be brought under control more quickly with the adjunctive and sterilizing use of UV light. Anecdotal reports have shown impressive results so far. As these techniques become more common, we will learn more about how and when they are most effective.
Long story short, collagen cross-linking is here to stay and has already become a game changer for patients with ectasia and a growing list of other disorders. At this point, patients who have keratoconus, particularly if it is progressive, regardless of age, might benefit from knowing that cross-linking is available at limited sites across the U.S.