Eyeworld

EW FEATURE 88 Corneal collagen crosslinking • September 2016 AT A GLANCE • Research suggests a potential place for CXL in treating infectious keratitis. • Several published reports have found CXL could help vision fluctuation in post-RK patients. • Evidence for CXL's effectiveness in Terrien's marginal degeneration is limited. • CXL can be effective in treating recurrent keratoconus in corneal grafts. by Rich Daly EyeWorld Contributing Writer Surgeons outline the promise and known limits of crosslinking in new therapeutic areas E merging science is explor- ing the potential for col- lagen corneal crosslinking (CXL) to provide therapeu- tic benefits in several areas beyond those for which the treat- ment recently received U.S. regulato- ry approval. Beyond a treatment for progres- sive keratoconus, which received ap- proval from the U.S. Food and Drug Administration (FDA) in April, the use of riboflavin ophthalmic solu- tions and systems to irradiate with ultraviolet A light have increasingly therapeutic keratoplasty appears imminent. "That having been said, effec- tiveness seems greater for more mild and superficial infections," Dr. Hersh said. "In infectious keratitis with corneal thinning, it's also important to understand the risk to the endo- thelium of treating thin corneas." Dr. Hersh noted when following the FDA approval's limitation of crosslinking to corneas thicker than 400 microns, he has not found risk to the endothelium from CXL. The mode of action of CXL in infectious keratitis may be two- fold, Dr. Hersh said. First, photo- active products, such as oxygen free radicals and activated riboflavin, may help directly kill the organ- isms. Second, amid corneal melting disorders, the increased resistance in CXL-treated eyes to enzymatic diges- tion may support the corneal stroma and decrease melting. Dr. Hersh said CXL may be more effective in bacterial infections than in amoebic, fungal, or mycobacterial infection, "but this remains anec- dotal, and more work is required to refine parameters for treatment and adjunctive care." Elmer Tu, MD, professor of clin- ical ophthalmology, University of Illinois Eye and Ear Infirmary, Chi- cago, agreed that CXL for bacterial keratitis seems more promising, but said that larger studies need to be done before it can be recommended. "The mechanism for its action remains unclear since laboratory studies show little effect of the CXL Pushing the limits of corneal collagen crosslinking Monthly Pulse Corneal collagen crosslinking T The topic of this Monthly Pulse survey was "Corneal collagen crosslinking." We asked about the devices physicians have in their practice to enable assessment of keratoconus progression, and the majority said they have Placido disc topography and corneal tomography. We asked, "Now that corneal crosslinking is approved by the FDA, which statement best describes your practice?" The majority of respondents to this survey said, "I was performing crosslinking already prior to FDA approval." As a physician, if you had a diagnosis of keratoconus and were 25 years old, what would you want to do? When asked this question, the majority of respondents said they would undergo crosslinking immediately. Finally, we asked, "Which of the following options do you think could benefit young keratoconus patients who want to improve their uncorrected visual acuity?" The majority answered crosslinking with topography-guided PRK. " Since cornea infections have a wide range of causes and presentations, it is difficult to fully assess the safety and efficacy of CXL for these uses. " –Peter Hersh, MD been examined for other ophthalmic treatments. The treatment, which aims to strengthen the chemical bonds in the cornea, also has been examined as a treatment for corneal infections for several decades, given the known microbicidal properties of ultraviolet light, said W. Barry Lee, MD, cornea and refractive service, Eye Consul- tants of Atlanta, and co-medical director, Georgia Eye Bank, Atlanta. Known as photoactivated chromophore for infectious keratitis, corneal collagen crosslinking (PACK- CXL) has successfully treated bacte- rial corneal ulcers, viral keratitis, and Acanthamoeba keratitis as a first line agent with avoidance of emergent keratoplasty, according to published research. 1 "CXL can also be used as an ad- junct to topical and oral antimicro- bial therapy for infectious keratitis in cases recalcitrant to treatment," Dr. Lee said. Peter Hersh, MD, Cornea and Laser Eye Institute, Hersh Vision Group, Teaneck, New Jersey, noted that efficacy in other published reports was mixed. "Since cornea infections have a wide range of causes and presenta- tions, it is difficult to fully assess the safety and efficacy of CXL for these uses," Dr. Hersh said. The literature suggests a poten- tial place for CXL in infectious kera- titis, especially in those cases where

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