Custom crosslinking—an evolution of standard corneal cross-linking (CXL)—is customized to a patient’s specific corneal topography, and appears to result in greater normalization of cornea curvature for keratoconus than standard CXL treatment performed using the original Dresden protocol, said Theo G. Seiler, MD, PhD.
Customized CXL is a tomography-guided procedure that focuses the treatment on the weak area of the keratoconic cornea. The procedure, which Avedro has been marketing as CuRV, is performed using a proprietary adjustable ultraviolet A light device (Mosaic System, Avedro) that features an integrated eye tracker and enables projection of customized irradiation patterns with customized energy profiles onto the cornea.
The concept of performing customized CXL arose from findings of biomechanical modeling undertaken by Abhijit Sinha Roy, PhD, and William J. Dupps Jr., MD, PhD, who proposed that the biomechanical change in keratoconus is focal, not generalized [Invest Ophthalmol Vis Sci. 2011;52:9174-9187].
“Previously, it was thought that because keratoconus is a genetic disease, the defect would be present throughout the entire cornea, and therefore, the entire cornea would need to undergo CXL,” said Dr. Seiler, professor of ophthalmology, University of Zurich, and chairman, Institute for Refractive and Ophthalmic Surgery (IROC), Zurich, Switzerland.
Proof of concept for performing customized CXL was provided by a study conducted by Giuliano Scarcelli, PhD, and colleagues who evaluated the mechanical properties of keratoconic corneas using tissue removed during keratoplasty [Invest Ophthalmol Vis Sci. 2013;54:1418-1425]. Using Brillouin optical microscopy, they showed mechanical loss was generally localized to the area of the cone, whereas outside the cone the Brillouin shift was similar to that measured in healthy control eyes.