Ultrasound-enhanced Penetration of Topical Riboflavin into the Corneal Stroma

Abstract

Purpose: : To determine whether ultrasound treatment can promote the permeation of topical riboflavin into the corneal stroma.

Methods: : Fresh cadaveric rabbit eyes with intact corneal epithelium were placed in a solution of 0.1% riboflavin at 37C. Continuous wave ultrasound at 1 W/cm2 was applied to the central cornea for 5 minutes, and the eyes were then left in riboflavin solution for an additional 40 minutes. Control eyes received the same exposure to riboflavin solution without ultrasound treatment. Corneas were then excised, and confocal microscopy was performed to detect the presence of riboflavin in the cornea.

Results: : At a depth of 200 microns, average fluorescence intensity of riboflavin was 162 in treated eyes (n = 12), and 69 in control eyes (n=5). The confocal images suggested the existence of some areas of epithelial cell damage on the anterior surface of ultrasound-treated eyes.

Conclusions: : Ultrasound treatment facilitated the entry of topical riboflavin into the corneal stroma despite the presence of a previously intact epithelial barrier. This approach may offer a means of achieving clinically useful concentrations of riboflavin in the cornea without removing the corneal epithelium, thereby improving the risk profile of corneal cross-linking procedures.

Keywords: cornea: clinical science • keratoconus • cornea: basic science