EXPERIMENTAL RATIONALES OF THE EFFICACY OF DIFFERENT METHODS OF RIBOFLAVIN DELIVERY INTO THE CORNEAL STROMA AS THE INITIAL STEP OF CORNEAL UV CROSS-LINKING

Purpose. To study experimentally the penetration of a 0.1% riboflavin solution in the balanced salt solution (BSS) into the corneal stroma during the simulation of various UV cross-linking techniques and to assess an alteration of anterior corneal surface using a new device for dosed corneal epithelium scarification.Material and methods. We used the infra-red Fourierspectroscopy with the registration of reflectance spectra to assess the Riboflavin penetration into the corneal stroma. The study was performed in 9 human donor eyes (3 groups of 3 eyes in each) which were not acceptable for transplantation. A classic UV cross-linking technique with the complete removal of the epithelium was simulated in the first group, a transepithelial technique – in the second group, a technique of a dosed corneal epithelium disruption using a new model of scarifier device – in the third group. Donor eyes were fixed in a holder, the 0.1% riboflavin solution was instilled during 30 minutes in a rate of 1 drop per minute. In the second group the 0.1% riboflavin solution and the 0.5% proximetacaine solution (containing benzalkonium chloride) were instilled simultaneously to break the tight junctions between the epithelial cells. The alteration of anterior corneal surface was assessed in 3 cadaver eyes using the light microscopy after application of a new scarifier.Results. The analysis of infra-red spectra, registered from the endothelial side of the corneas in the first and the second groups showed a significant increase in intensity of the band at 1542 cm-1, which is typical for riboflavin. This fact demonstrates its full penetration to the corneal stroma and it complete impregnation. The increase of this index in the 1st and the 2nd groups was 7.3±0.5% and 7.8±0.6%, respectively (p>0.05). In the third group a relative intensity of the spectra did not differ significantly from those of control measurements (before instillation of riboflavin solution). The morphologic study of the corneas after use of a new scarifier showed the alteration of all epithelial layers up to the Bowman’s membrane without damaging of its integrity.Conclusions. We have proved a full impregnation of the corneal stroma with the 0.1% riboflavin solution using the method of dosed corneal epithelium scarification, comparable to that after a full corneal deepithelialization. The efficacy and safety of the new scarifier device were also substantiated.