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Kirill Larin, Manmohan Singh, Jiasong Li, Zhaolong Han, Chih-Hao Liu, Chen Wu, Raksha Raghunathan, Salavat Aglyamov, Srilatha Vantipalli, Michael D Twa; Noncontact depth-resolved quantification of riboflavin/UV-A and rose-bengal/green light cross-linking of rabbit cornea by optical coherence elastography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):899. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Utilize noncontact optical coherence elastography (OCE) to evaluate and compare the depth-resolved changes in the biomechanical properties of the rabbit cornea in situ before and after corneal collagen cross-linking by two techniques: UV-A/riboflavin (UV-CXL) and rose-bengal/green light (RGX).
Low-amplitude (≤ 10 µm) elastic waves were induced in fresh mature rabbit corneas by a focused air-pulse. The elastic wave propagation was imaged by a home-built phase-stabilized swept source OCE (PhS-SSOCE) system with fixed intraocular pressure. Following epithelial debridement, the corneas were then cross-linked by two methods: UV-CXL (n=4 ; Instill 0.1% Riboflavin for 30min followed by UV irradiation (365nm, 3mW/cm2) with riboflavin instillation for 30min) and RGX (n= 4; Instill 0.1% Rose bengal solution for 20min followed by green light exposure (560nm, 0.25W/cm2) with rose bengal instillation for 10min). The phase velocities of the elastic waves were fitted to a previously developed modified Rayleigh-Lamb Frequency Equation (RLFE) to obtain the viscoelasticity of the corneas before and after the cross-linking treatments. The micro-scale depth-resolved phase velocity distribution revealed the depth-wise heterogeneity of both cross-linking techniques.
UV-CXL and RGX increased the stiffness of the corneas by ~54% and ~5% (P<.05) and reduced the shear viscosity by ~42% and ~17% (P>.05), respectively. The depth-wise phase velocities showed that UV-CXL affected the anterior ~34% of the corneas, while RGX only affected the anterior ~16% of the corneas. The average central corneal thickness changed 31% and 6% after UV-CXL and RGX treatments, respectively.
UV-CXL strengthens the cornea noticeably more than RGX, and the effects of cross-linking by UV-CXL reach deeper into the cornea than cross-linking by RGX under similar conditions
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
OCE experimental setup. ADC: analog to digital converter. DAC: digital to analog converter.
(a) Young’s modulus and (b) shear viscosity as estimated by the OCE-measured phase velocities. Statistical significance (P<0.05 by a paired t-test) is indicated by the asterisk, and the error bars represent the inter-sample standard deviation.
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