Ioannis M Aslanides1, Claudia Dessi2, Panagiotis Georgoudis1, Georgios Charalambidis3, Dimitris Vlassopoulos2, Athanassios G Coutsolelos3, George Kymionis4, Achyut Mukherjee5, Theofanis N Kitsopoulos6. 1. Emmetropia Mediterranean Eye Clinic Crete, Greece. 2. Department of Materials Science and Technology, University of Crete, and Institute of Electronic Structure & Laser, Foundation for Research and Technology Hellas (FORTH), Crete, Greece. 3. Department of Chemistry, Laboratory of Bioinorganic Chemistry, University of Crete, Crete, Greece. 4. Department of Ophthalmology, School of Medicine, University of Athens, Athens, Greece. 5. Emmetropia Mediterranean Eye Clinic Crete, Greece 5Cardiff University School of Optometry, South Glamorgan, United Kingdom. 6. Department of Chemistry, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Crete, Greece.
Abstract
PURPOSE: The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. METHODS: Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. RESULTS: For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). CONCLUSIONS: We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.
PURPOSE: The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. METHODS: Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. RESULTS: For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). CONCLUSIONS: We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.
Authors: Cristina Rosell-Valle; María Martín-López; Fernando Campos; Jesús Chato-Astrain; Rafael Campos-Cuerva; Miguel Alaminos; Mónica Santos González Journal: Front Bioeng Biotechnol Date: 2022-08-23
Authors: Mitchell A Kirby; John J Pitre; Hong-Cin Liou; David S Li; Ruikang K Wang; Ivan Pelivanov; Matthew O'Donnell; Tueng T Shen Journal: Ophthalmol Sci Date: 2021-09-22