EyeWorld Asia-Pacific December 2017 Issue

Seeing clearer with CXL by Vanessa Caceres EyeWorld Contributing Writer AT A GLANCE • CXL has generated much interest since its U.S. approval for progressive keratoconus and ectasia. • Further studies of CXL are focusing on accelerated CXL and transepithelial CXL. • Research is underway abroad on the use of CXL with refractive surgery, and similar research is beginning in the U.S. • Results are mixed regarding CXL to treat infectious keratitis. continued on page 33 September 2017 Dec EWAP SECONDARY FEATURE 31 Where the U.S. market stands now, what approaches could be used in the future T he U.S. Food and Drug Administration (FDA) approval of corneal crosslinking (CXL) last year for progressive keratoconus and ectasia brought an additional welcome treatment to the U.S. market, physicians said. “It’s a very important ap- proval,” said Peter Hersh, MD , director of the Cornea and Laser Eye Institute, Teaneck, New Jersey; professor, Rutgers Medical School, Newark, New Jersey; and visiting research collaborator, Princeton University, Princeton, New Jersey. “Because of its unique ability to decrease progression of KC and ectasia, we’ve seen widespread incorporation into ophthalmic practice, especially among cor- nea surgeons. It’s been adopted very quickly.” Dr. Hersh was the medical monitor for the U.S. clinical trials for approval that were done by Avedro (Waltham, Massachusetts), the only company in the U.S. that currently offers FDA-approved CXL via its Pho- trexa Viscous, Photrexa, and KXL System. About 10,000 CXL treatments have been performed with the Avedro system since the FDA ap- proval, said Rajesh Rajpal, MD , chief medical officer of Avedro, and founder of See Clearly Vision Group, Washington, DC area. Evolving treatment parameters Currently, there’s an acceler- ated CXL study underway that has completed enrollment and should be submitted to the FDA in the near future, said J. Bradley Randleman, MD , professor of clinical ophthalmology, director of cornea, external disease, and refractive surgery, and medical director, USC Roski Eye Institute, Beverly Hills, California. The study uses the Avedro KXL proto- col with 30 mW treatment. “The most basic process in the works is standard accelerated protocols, where total irradiance remains constant, but fluence increases and treatment time de- creases,” Dr. Randleman said. He contrasts this with higher irradi- ance accelerated protocols, where both fluence and total irradiation increase. “The concept is that accelerated protocols may not provide the same total treatment effect and depth as the standard protocol, so increasing fluence for a reduced time may allow for equal treatment efficacy but also maintain safety,” he said. There is also research on the use of pulsed CXL. “The hypoth- esis is that the CXL reaction has multiple pathways, and one of these is oxygen-dependent,” Dr. Hersh said. “It’s thought that by using pulsed UV light during the dark phases, there will be replen- ishment of oxygen, and it will have a more robust crosslinking reaction.” Another area under inves- tigation is transepithelial CXL (or epithelium-on) and its rela- tive effectiveness; the current FDA approval is for epi-off. At Dr. Hersh’s practice, there is a physician-sponsored investiga- tional new drug study regarding the transepithelial technique, as well as the use of CXL and Intacs (Addition Technology, Lombard, Illinois). The latter study looks at the safety, efficacy, and timing of CXL and Intacs, either done the same day or performed sequen- tially over 3 months. These results will be available shortly. There’s interest in the use of devices with a higher power along with epi-on treatments for shorter treatment duration of CXL; clini- cal trials in the U.S. for this are being planned, Dr. Rajpal said. Other areas under investiga- tion include the use of oxygen to varying degrees with the CXL procedure and the use of other carriers beyond dextran, includ- ing HPMC, for riboflavin. CXL and refractive surgery One area with much interest for CXL is with refractive surgery. Avedro is planning its first U.S.- based trial for photorefractive intrastromal corneal collagen CXL (PiXL) for low myopia, followed by one for presbyopia. With PiXL, myopic errors are treated with topical ribofla- vin and then cornea exposure to ultraviolet light delivered by Avedro’s Mosaic device, which has a CE mark in Europe and approval from Health Canada but is not yet approved in the U.S. “Presbyopia is something most ophthalmologists would like to treat, and we have preliminary data to show it may be possible with PiXL,” Dr. Rajpal said. Imaging of corneal ectasia after LASIK