Old technique, new delivery

Orlando-Results of a preclinical pilot study demonstrate ocular iontophoresis accelerates transfer of topically applied riboflavin into the cornea compared with conventional application, said George O. Waring IV, MD.

“There is a lot of debate about the best way to deliver riboflavin to the cornea for corneal collagen crosslinking,” said Dr. Waring, medical director, Division of Ophthalmology, St. Joseph’s Translational Research Institute, Atlanta. “This proof-of-concept study indicates that iontophoretic application of riboflavin should decrease patient treatment time and may eliminate the need for corneal de-epithelialization before treatment.”

The efficacy and safety of the iontophoretic technique was investigated in an animal study in which 12 New Zealand rabbits were divided into four groups. In two groups 0.1% riboflavin was delivered with iontophoresis using application times of 3 or 5 minutes and a current of 1 mA/cm². One group received riboflavin delivery by passive imbibition with a bioenhancer to loosen the tight junctions, and a control group underwent 5 minutes of iontophoresis with application of normal saline instead of riboflavin.

Stromal concentrations of riboflavin were measured after 15 minutes by high-performance liquid chromatography and showed the iontophoretic delivery of riboflavin depended on iontophoresis time, and the highest concentration was achieved in the 5-minute iontophoresis group. Confocal analysis of the cornea showed no irregularities in corneas where the electric current was 1 mA/cm². Some opacities were observed when the current was increased to 2.5 mA/cm², although they were reversible.

“Based on this study, 1 mA/cm² appears to be a safe current level,” Dr. Waring said. “Higher currents may be considered potentially to shorten delivery time, but further studies are needed.”

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