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Dexi Zhu, Yuheng Zhou, Zi Jin, Meixiao Shen; Assessing the biomechanical properties of cross-linked cornea in vivo with optical coherence elastography. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6821. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Riboflavin and UV induced corneal collagen cross-linking (CXL) has been recognized as an effective treatment to increase corneal stiffness and retard the progression of keratoconus. This study presents a noncontact air-puff combined optical coherence elastography (OCE) to assess the biomechanical properties after different corneal collagen CXL irradiance solutions.
Nine corneas of white Japanese rabbit were infiltrated with 0.22% riboflavin solution for 30 minutes after removing the epithelium. The CXL treatment was then performed with three irradiation solutions: 3mW/cm2 for 30 minutes, 9mW/cm2 for 10 minutes and 18mW/cm2 for 5 minutes. High speed swept source optical coherence tomography (OCT) with central wavelength of 1.0 μm, axial resolution of ~5 μm in tissue and acquisition rate of 100 kHz was used to image the sample. An air-puff dilivery was used as the stimulation to induce shear wave on the tissue at frequency of 1 kHz. By M-B mode scanning of OCT synchronizing with air-puff system, the shear wave propagation was detected by calculating the phase shift between two successive A-lines based on phase-resolved Doppler algorithm. The shear wave velocity as well as the Young's modulus of tissue then can be calculated. The measurements of biomechanical properties were implemented at time of pre-operation, post-operation immediately and one week later after the CXL treatment.
Figure 1 shows the average percent changes of Young's modulus at post-operation and one week later comparing with the pre-operation for three irradiance groups. The group 3mW/30min, which has identical irradiate with well-known Dresden solution, shows a 170.8% increase in Young's modulus at post-operation. The group 9mW/10min and group 18mW/5min are less effective than group 3mW/30min, with 153.5% and 146.6% increase in Young's modulus at post-operation, respectively. A slight increase of Young's modulus was observed in all groups after one-week recovery process.
A shear wave OCE system was developed with simultaneous air-puff system and phase resolved OCT detection. The results in this study demonstrate the ability of our OCE system for evaluating the changes in corneal biomechanical properties in vivo after different CXL irradiance solutions noninvasively.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
figure1. Average percent changes of unified Young's modulus of cornea at each pre-operative IOP.
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