Because there are no proven treatments to prevent the progression of keratoconus, corneal crosslinking (CXL) is attractive as a viable alternative to keratoplasty and other surgical procedures, with impressive early results.
Because there are no proven treatments to prevent the progression of keratoconus, corneal crosslinking (CXL) is attractive as a viable alternative to keratoplasty and other surgical procedures, with impressive early results. While approved and commercially available in Europe and Asia since the early part of the current decade, corneal crosslinking was only recently approved by the U.S. Food and Drug Administration in April 2016.
The Eye Bank Association of America has estimated that more than 40% of the corneal transplants in the U.S. − or more than 6,800 transplants − could be avoided if an approved device for crosslinking were approved to treat keratoconus.
CXL procedures involve the administration of vitamin drops (typically, riboflavin) into the cornea, followed by ultraviolet light irradiation. During this process, the cornea’s crosslink fibers are increased, thereby increasing the biomechanical rigidity of the cornea by up to 300%.
Human studies of UV-induced CXL began in Germany in 2003, with an initial pilot study of 16 patients. Most of these patients saw a halt to progression of keratoconus. Numerous subsequent trials reproduced these findings, with many reporting high rates of improvement in visual acuity within 3-6 months following the procedure. Improvements in topographical and wavefront parameters have also been seen out to 7 years of follow-up.
Collagen crosslinking (CXL) uses a natural photosensitizer, riboflavin (vitamin B2), combined with ultraviolet light to reinforce the structural weakness found in the corneal stromal in patients with keratoconus.Reported side effects of CXL include corneal edema, anterior chamber inflammation, and recurrent corneal erosions. Retreatment rates in clinical trials have been low – typically <10% − although this will need to be followed over a longer term.
In addition to keratoconus, other diseases for which CXL is being studied include Pellucid Marginal Degeneration, Terrien’s Marginal Degeneration, and post-refractive surgery (ie, LASIK).