Ophthalmology Times.
The success of corneal crosslinking (CXL) for ectatic disease requires oxygen within the tissue, and this dependency likely explains the limited efficiency of high-intensity (rapid) and transepithelial treatment protocols, said Farhad Hafezi, MD, PhD. In a series of studies, Dr. Hafezi and colleagues at Geneva University, Switzerland, demonstrated that the biomechanical effect of CXL is (a) oxygen-dependent, and (b) declines in efficacy when intensity is raised and treatment time reduced, even when the total energy dose (fluence) remains the same.
“By definition, the corneal strengthening effect of treatment with riboflavin and ultraviolet A (UVA) requires oxygen because it arises from crosslinking of collagen and proteoglycans that is mediated by the generation of reactive oxygen species,” said Dr. Hafezi, professor and chairman, Department of Ophthalmology, Geneva University Hospitals, Switzerland, and adjunct clinical professor of ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles. “Previous research has shown that oxygen in the cornea is rapidly depleted during CXL irradiation and at a faster rate using higher intensities, raising concern that high irradiance/short irradiation time protocols or presence of an intact epithelial barrier limit the opportunity for adequate oxygen replenishment through diffusion.
