International Journal of Keratoconus and Ectatic Corneal Diseases

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VOLUME 11 , ISSUE 1 ( January-December, 2024 ) > List of Articles

Original Article

In Vitro Histological Analysis of the Human Cornea Undergoing Conventional and Accelerated Cross-linking Protocol: From the Microscope to Clinical Application

Cosimo Mazzotta, Stefano Baiocchi, Maria M De Santi, Mohamed Hosny, Mohamed S Shaheen, Adel Barbara

Keywords : Accelerated cross-linking, Cross-linking, Fluence, Histology, Keratoconus

Citation Information : Mazzotta C, Baiocchi S, De Santi MM, Hosny M, Shaheen MS, Barbara A. In Vitro Histological Analysis of the Human Cornea Undergoing Conventional and Accelerated Cross-linking Protocol: From the Microscope to Clinical Application. Int J Kerat Ect Cor Dis 2024; 11 (1):1-8.

DOI: 10.5005/jp-journals-10025-1204

License: CC BY-NC 4.0

Published Online: 15-02-2025

Copyright Statement:  Copyright © 2024; The Author(s).


Abstract

Purpose: In vitro assessment of the photo-oxidative effects induced by conventional cross-linking (CXL) and accelerated cross-linking (ACXL) at 5.4 J/cm2 energy dose (fluence). Methods: A total of 20 eye-bank human corneas were treated with different epithelium-off (EPI-OFF) CXL UV-A protocols: five EPI-OFF at 3 mW/5.4 J/cm2 for 30 minutes (Dresden protocol), five at 15 mW/5.4 J/cm2 for 12 minutes pulsed light (Siena ACXL protocol), and five at 30 mW/5.4 J/cm2 pulsed light for 6 minutes. Five corneas were used as control group. Semi-thin and ultrathin sections were examined by a Philips transmission electron microscope at the Department of Human Pathology of Siena University. Histology overview included Bowman's lamina thickness measurement, CXL depth, collagen fibers density, and CXL-induced photo-oxidative damage. Results: The study provides descriptive histological evidences of in vitro corneal changes induced by ACXL, identifying the differences between treatment depths based on different UV-A power settings and exposure times. The higher UV-A power with the shorter exposure time induced a lower photo-oxidative CXL penetration, while the longer exposure time increased CXL treatment photo-oxidative depth. Increased fiber density induced by higher UV-A power was observed only in the anterior 50 µm of corneal stroma in all cases. Conclusion: Cross-linking photo-oxidative damage is fluence-dependent. Keeping a constant fluence, the longer exposure time increased the treatment depth due to more oxygen diffusion, while the higher UV-A power with shorter exposure time without increasing the fluence resulted in reduced treatment depth due to less oxygen diffusion. The higher reduction of collagen fibrils distance in the anterior 50 µm stroma appears to be independent from UV-A power and exposure time.

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