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James Bradley Randleman, Hongyuan Zhang, mehdi roozbahani, ANDRE LUIS PICCININI, Giuliano Scarcelli; Depth-dependent analysis of corneal cross-linking performed over or under the LASIK flap by Brillouin microscopy. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2145.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the impact of corneal cross-linking (CXL) performed over the flap or under the flap on regional corneal stiffness using Brillouin microscopy.
CXL was performed intact fresh porcine eyes after LASIK flap creation using either the standard technique of epithelial removal followed by riboflavin drop application to the corneal surface followed by UV exposure with the flap in place using 3mW/cm2 for 30 minutes (S-CXL) or a modified technique with riboflavin application to the posterior stroma after reflecting the flap, followed by replacing the flap and UV exposure with the flap in place using 3mW/cm2 for 30 minutes (flap-CXL). LASIK flaps were created using a mechanical microkeratome. Depth profile of stiffness variation and averaged elastic modulus of anterior, middle and posterior stroma were determined by analyzing Brillouin maps. Corneas were cut into strips to conduct mechanical stress-strain tests after Brillouin microscopy to verify stiffness difference between S-CXL and flap-CXL. Each eye served as its own control.
Based on Brillouin maps, S-CXL had maximal stiffening impact at the corneal surface and extended through the anterior 40% of the cornea, well below the depth of the LASIK flap, while flap-CXL had maximal stiffening impact at the LASIK flap interface, extending less than 50 microns above and below the interface. Maximal stiffening effect was significantly less overall and in the interface region using flap-CXL as compared to S-CXL.
The standard CXL technique for treatment after LASIK flap creation generates significantly greater stiffening effect than using a modified protocol with riboflavin administration under the flap. Minimal posterior corneal stiffening occurs with either protocol.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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