Theo G Seiler1,2,3, Ana Batista4,5, Beatrice E Frueh1, Karsten Koenig4,5. 1. Universitätsklinik für Augenheilkunde, Inselspital, Universität Bern, Bern, Switzerland. 2. Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland. 3. Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States. 4. JenLab GmbH, Berlin, Germany. 5. Lehrstuhl für Biophotonik und Lasertechnologie, Universität des Saarlandes, Saarbrücken, Germany.
Abstract
Purpose: To determine the riboflavin concentration in the posterior corneal stroma, Descemet's membrane, and endothelium prior to UV irradiation in corneal cross-linking (CXL) in humans. Methods: Five human deepithelialized 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 2.5 μm. Afterward, 0.1% riboflavin solution was applied to the anterior corneal surface, similar to the standard 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 after riboflavin saturation. Results: The topical application of 0.1% riboflavin results in a riboflavin concentration that decreases to 0.035% in the posterior stroma. Inside Descemet's membrane and endothelium, the concentration drops further to only approximately 0.015% at the endothelial level. Local riboflavin distribution indicates a predominantly paracellular passive diffusion of riboflavin into the anterior chamber. Conclusion: 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.
Purpose: To determine the riboflavin concentration in the posterior corneal stroma, Descemet's membrane, and endothelium prior to UV irradiation in corneal cross-linking (CXL) in humans. Methods: Five human deepithelialized 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 2.5 μm. Afterward, 0.1% riboflavin solution was applied to the anterior corneal surface, similar to the standard 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 after riboflavin saturation. Results: The topical application of 0.1% riboflavin results in a riboflavin concentration that decreases to 0.035% in the posterior stroma. Inside Descemet's membrane and endothelium, the concentration drops further to only approximately 0.015% at the endothelial level. Local riboflavin distribution indicates a predominantly paracellular passive diffusion of riboflavin into the anterior chamber. Conclusion: 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.
Authors: Majid Moshirfar; Uma Vaidyanathan; Grant C Hopping; Yasmyne C Ronquillo; Phillip C Hoopes Journal: Med Hypothesis Discov Innov Ophthalmol Date: 2019
Authors: Arie L Marcovich; Jurriaan Brekelmans; Alexander Brandis; Ilan Samish; Iddo Pinkas; Dina Preise; Keren Sasson; Ilan Feine; Alexandra Goz; Mor M Dickman; Rudy M M A Nuijts; Avigdor Scherz Journal: Transl Vis Sci Technol Date: 2020-05-11 Impact factor: 3.283