Biomechanical and Histopathologic Effects of Pulsed-Light Accelerated Epithelium-On/-Off Corneal Collagen Cross-Linking

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Purpose:This study aimed to compare the biomechanical and histopathologic effects of transepithelial and accelerated epithelium-off pulsed-light accelerated corneal collagen cross-linking (CXL).Methods:A total of 24 New Zealand rabbits were analyzed after sham operation (control) or transepithelial or epithelium-off operation (45 mW/cm2 for both). The transepithelial group was treated with pulsed-light ultraviolet A for 5 minutes 20 seconds, and the epithelium-off group was treated for 90 seconds. Biomechanical testing, including ultimate stress, Young modulus, and the physiological modulus, was analyzed. Histological changes were evaluated by light microscopy and transmission electron microscopy.Results:The stress–strain curve was nonlinear in both accelerated transepithelial and epithelium-off CXL groups. The stress and elastic moduli were all significantly higher in both experimental groups compared with the control group (P < 0.05), whereas there were no significant differences between the 2 treatment groups (P > 0.05). Six months after the operation, hematoxylin and eosin staining and transmission electron microscopy showed that the subcutaneous collagen fibers were arranged in a regular pattern, and the fiber density was higher in the experimental groups.Conclusions:Both transepithelial and accelerated epithelium-off CXL produced biomechanical and histopathologic improvements, which were not significantly different between the 2 pulsed-light accelerated CXL treatments.

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