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Focus On Corneal Collagen Cross-linking | May 2012

Update on the US Status of CXL

A US study will evaluate accelerated cross-linking.

For the past 13 years, surgeons outside the United States have commonly performed corneal collagen cross-linking (CXL) as the first line of treatment to restore corneal stability in keratoconic and ectatic eyes. The traditional approach involves applying riboflavin solution to the eye for 30 minutes, followed by 30 minutes of exposure to ultraviolet A light at a fluence of 3 mW/cm2. Avedro, Inc., has submitted a new drug application to the FDA for a cross-linking study at these parameters, and recently, the company began a trial that will evaluate accelerated CXL (see Avedro's CXL Study). The American-European Congress of Ophthalmic Surgery (ACOS) is sponsoring the next accelerated CXL study, ACOS-KXL-001.


The Multi-Center, Randomized, Controlled Evaluation of the Safety and Efficacy of Corneal Collagen Cross-Linking in Eyes with Keratoconus or Corneal Ectasia after Refractive Surgery will be conducted at up to 100 investigational sites across the United States. The trial will enroll patients with keratoconus or post-LASIK ectasia. Investigators will evaluate and compare the safety and efficacy of three treatment regimens for CXL performed with VibeX (riboflavin ophthalmic solution) and the KXL System (agent and system from Avedro, Inc.) for reducing corneal curvature. Eyes will be randomized to one of the three treatment groups by treatment condition (keratoconus or corneal ectasia) and will all receive active treatment.

The ACOS study has several purposes. The large number of sites will enable patients all over the country to enroll in the trial and obtain potentially sight-saving treatment. Through this study, investigators such as myself will have rapid access to data from a large cohort of patients so that we may evaluate the dose response curve. A total of 8,000 eyes could undergo CXL in this study. We will test three doses of irradiation: 15, 30, and 45 mW/cm2. Which is most appropriate? Moreover, is CXL only ultraviolet A dose dependent, or does it also depend on duration? The information we gather will demonstrate how to balance the protocol for patients' safety, comfort, convenience, and outcomes.


Currently, there is no FDA-approved medical therapy to control the progression of keratoconus. CXL, however, has shown promising success internationally and in US clinical trials for stabilizing corneal curvature and slowing or stopping keratoconic progression. In the future, the procedure has great potential for a variety of corneal therapies. Already, international surgeons are incorporating accelerated CXL into their standard LASIK procedures and introducing it in antimicrobial applications. As the medical monitor of the ACOS trial, I look forward to bringing this promising procedure to a broad group of geographically diverse patients throughout 2012.

John A. Vukich, MD, is a partner at the Davis Duehr Dean Center for Refractive Surgery in Madison, Wisconsin. Dr. Vukich may be reached at (608) 282-2000; javukich@facstaff.wisc.edu.

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