Riboflavin concentrations at the endothelium during corneal cross-linking (CXL) in humans

Session Details

Session Title: Corneal Cross-Linking

Session Date/Time: Monday 16/09/2019 | 16:00-18:00

Paper Time: 16:42

Venue: South 5

First Author: : T.Seiler SWITZERLAND

Co Author(s): :    A. Batista   B. Frueh   K. Koenig                       

Abstract Details

Purpose:

To determine the riboflavin concentration in the posterior corneal stroma, Descemet´s membrane and endothelium prior to UV-irradiation in CXL in humans.

Setting:

Laboratory study, Universitätsklinik für Augenheilkunde, Inselspital Bern. Switzerland

Methods:

Five human de-epithelialized cadaver corneas were mounted into artificial anterior chambers. After the establishment of stable physiological hydration, two-photon imaging with a certified multiphoton tomograph was used to determine fluorescence intensity and Second Harmonic Generation-signals from collagen throughout each cornea by optical sectioning with a step size of 2.5µm. Afterwards, 0.1% riboflavin solution was applied onto the anterior corneal surface similar to the standard corneal crosslinking (CXL) protocol. To determine the absolute riboflavin concentration immediately before UV-irradiation, corneas were measured by two-photon imaging just at the end of the riboflavin-imbibition and a third time after riboflavin saturation.

Results:

The topical application of 0.1% riboflavin results in a riboflavin concentration that is decreasing in the posterior stroma to 0.035%. Inside Descemet´s membrane and endothelium, the concentration drops further to only about 0.015% at the endothelial level. Local riboflavin distribution indicates a predominantly paracellular passive diffusion of riboflavin into the anterior chamber.

Conclusions:

The experimentally determined riboflavin concentration of 0.015% at the endothelium shows a substantial discrepancy of a factor of 1.7 to the previously theoretically calculated 0.025%. A lower riboflavin concentration at the endothelium may enable higher radiant exposures and further improve the efficacy of CXL.

Financial Disclosure:

None