Role of Corneal Epithelium in Riboflavin/Ultraviolet-A Mediated Corneal Cross-Linking Treatment in Rabbit Eyes

Abstract

Purpose. To evaluate the role of corneal epithelium in riboflavin/ultraviolet-A (UVA) mediated corneal collagen cross-linking treatment. Methods. Fifty New Zealand rabbits were divided into 5 groups: UVA treatment with or without corneal epithelium, UVA+riboflavin treatment with or without corneal epithelium, and control without any treatment. All rabbits were sacrificed after irradiation and subsequently 4 mm × 10 mm corneal strips were harvested for biomechanical evaluation. Results. UVA irradiation alone did not enhance the maximal stress and Young's modulus of corneal specimens with (3.15 ± 0.56 mpa, 1.00 ± 0.09 mpa) or without (3.53 ± 0.85 mpa, 0.94 ± 0.21 mpa) the corneal epithelium, compared to specimens in the control group (4.30 ± 0.68 mpa, 1.03 ± 0.24 mpa). However, UVA irradiation combined with riboflavin significantly increased the maximal stress and Young's modulus of corneal specimens with (5.27 ± 1.09 mpa, 1.23 ± 0.23 mpa, P < 0.05) or without (7.16 ± 1.88 mpa, 1.42 ± 0.16 mpa, P < 0.05) corneal epithelium when compared to the control group. The maximal stress and Young's modulus of cornea in UVA+riboflavin and “epithelium-off” group were 35.9% and 15.4% higher compared to the UVA+riboflavin and “epithelium-on” group, respectively (P < 0.05). Conclusions. Our study shows that UVA+riboflavin treatment significantly affects the biomechanical properties of the cornea with and without epithelial removal. However, corneas without epithelium seem to benefit more compared to corneas with the epithelium.

Ultraviolet Corneal Crosslinking

“…показали, что CXL-обработанные роговицы кроликов с сохраненным эпителием, так же как и сшитые стандарт-ным способом, демонстрируют увеличение модуля Юнга и механической прочности, хотя и в несколько меньшей степени [61].…”

Corneal Cross-Linking: An Example of Photoinduced Polymerization as a Treatment Modality in Keratoconus

“…As an alternative to this, the epi-on procedure, without the removal of the cornea, has been proposed [22][23][24]. Different studies have shown that epi-on CXL does affect the biomechanical properties of the cornea.…”

“…Different studies have shown that epi-on CXL does affect the biomechanical properties of the cornea. However, corneas without the epithelium seem to benefit more compared to corneas with it [22][23][24]. Noticeably better results were obtained with epi-on CXL using iontophoresis, but the relative efficacy of that technique compared to standard epithelium-off CXL still remains to be determined [25].…”

Keratoconus und dessen Behandlung mit Hornhautvernetzung und Kontaktlinsen: ein Überblick

“…Stromale Narben und Zellen wurden in der Nähe dieser Defekte festgestellt und KeratozytenApoptose wurde nachgewiesen [46][47][48]. Die in-vivo confocale Mikroskopie hat verminderte subbasale Nervendichte gezeigt, die mit verminderter Hornhautsensibilität und verminderter Basal-Epithelzelldichte einhergeht [49].…”

“…Keratozyten liefern ja die Grundsubstanz des Kollagens, aus dem Unseres Wissens gibt es derzeit noch keine in vivoStudien, welche die Auswirkungen der CXL-Therapie auf die menschlichen limbalen Epithel-Stammzellen evaluierten. Der Schutz der limbalen Stammzellen während der CXL-Prozedur sollte in Erwägung gezogen werden, insbesondere deshalb, weil bei KC a priori die zentrale Epithelzelldichte vermindert ist [46,68].…”