CXL research focuses on evolving techniques, emerging indications

Zurich, Switzerland-Corneal crosslinking (CXL) using the current standard technique is safe and effective for stabilizing eyes with progressive corneal ectasia, but new treatment protocols and new indications are emerging, according to Theo Seiler, MD, PhD.

Dr. Seiler, who introduced CXL, spoke on the topic of “Crosslinking in the year 2020: What will the future hold?” He noted that there is interest in developing treatment techniques that are more efficient, do not require removal of the epithelium, and provide better crosslinking outside of the central cornea. Dr. Seiler is professor of ophthalmology, University of Zurich, and Chairman, IROC, Zurich, Switzerland.

Research conducted so far indicates that it is feasible to shorten the irradiation time to just 5 or 10 minutes by using higher irradiation power, probably in a range between 10 and 25 mW/cm². Additionally, new UVA light sources that maintain the intensity of light delivered in the mid-peripheral cornea can increase the efficacy of crosslinking.

While efforts to develop strategies for epithelium-on CXL have fallen short so far, Dr. Seiler expressed hope that this challenge will be met successfully in the future. However, due to the diffusion constant of riboflavin, it does not appear possible to shorten the imbibition time.

Dr. Seiler discussed novel approaches for performing CXL that are under investigation, looking at glucose as an alternative to riboflavin or substituting sunlight exposure for irradiation with a UVA light source. Interest is also turning to new applications for CXL, including treatment of corneal melts and microbial keratitis.

“It is well appreciated that CXL has a biomechanical effect on the cornea mediated by the creation of new chemical bonds between neighboring molecules. However, it is sometimes forgotten that CXL also has biochemical and cytotoxic effects,” Dr. Seiler said.

“After CXL, the cornea becomes more resistant to the activity of digesting enzymes, and so it may be used to treat corneal melts by shifting the balance between catalysis and synthesis. In addition, the free radicals produced during the procedure kill microorganisms [as well as] keratocytes, so that CXL may be used to treat corneal infections,” he concluded.

This article is adapted from Dr. Seiler’s delivery of the Dohlman Lecture during the 2012 Cornea Subspecialty Day at the annual meeting of the American Academy of Ophthalmology.

For more articles in this issue of Ophthalmology Times eReport, click here.