Purpose: To indirectly measure stromal riboflavin penetration using commercially available riboflavin solutions and new and existing epithelium-off, trans-epithelial and iontophoresis-assisted delivery protocols.
Methods: Forty porcine eyes were divided into eight groups. Group 1: Ricrolin applied to the de-epithelialised cornea for 30 min; Group 2: epithelium-intact, no treatment; Groups 3-5: epithelium-intact, 30-min application of Ricrolin TE, Mediocross TE or ParaCel/Vibex, respectively. Group 6: epithelium-intact, Ricrolin(+) iontophoresis-assisted delivery for 5 min; Group 7: epithelium-intact, Ricrolin(+) iontophoresis-assisted delivery for 5 min with a 20-min riboflavin soak; and Group 8: epithelium-intact, Ricrolin(+) iontophoresis-assisted delivery for 5 min, 15-min soak and another 5 min of iontophoresis. After a saline wash, light transmission spectra were obtained from each cornea, before and after epithelial removal.
Results: Corneas in groups 1 and 8 showed a distinct riboflavin absorption peak between 400 and 520 nm. The optical density of the corneas in groups 3-7 did not differ significantly from that of the untreated corneas (group 2).
Conclusions: A modification to the standard iontophoresis trans-epithelial technique resulted in successful penetration of riboflavin into the stroma and appears to offer the most promise for epithelium-on cross-linking.
Keywords: cornea; cross-linking; iontophoresis; spectrophotometry.
© 2015 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation and European Association for Vision & Eye Research.