JUN 05, 2009
By J. Bradley Randleman, MD
Refractive Mgmt/Intervention
This study included 14 keratoconic patients enrolled for penetrating keratoplasty (PKP) and 16 warm-stored sclerocorneal rings unsuitable for transplantation. Half the PKP specimens were debrided, and half were left with the epithelium in situ. One sample from each group was not exposed to riboflavin (controls). Samples in both groups were soaked with 0.1% riboflavin-dextran 20% solution instilled every two minutes for five, 15 and 30 minutes.
Using high-performance liquid chromatography, they demonstrated that stromal concentrations of riboflavin increased with exposure time only if the epithelium was removed. In exposed samples with epithelium, the mean riboflavin concentration was 91.88 ng/g after 5 minutes of exposure, 95.60 ng/g after 15 minutes, and 94.92 ng/g after 30 minutes. In the debrided samples, the mean riboflavin concentration was 14.42 μg/g, 20.92 μg/g, and 24.06 μg/g, respectively.
They conclude that a theoretically safe and effective riboflavin concentration of15 µg/g was obtained for ultraviolet A-induced corneal crosslinking only after the epithelium was removed and after at least 10 minutes of riboflavin application every two minutes.
Ultimately a prospective clinical trial of both techniques would be valuable for resolving the issue of whether to leave the epithelium intact.
Dr. Randleman receives lecture fees from Alcon Laboratories, Inc., Allergan, Inc. and Ista Pharmaceuticals.