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Keyton Clayson, Elias Pavlatos, Xueliang Pan, Yanhui Ma, Jun Liu; Corneal Deformation Before and After Corneal Crosslinking (CXL) in Response to Ocular Pulse. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1391.
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© ARVO (1962-2015); The Authors (2016-present)
To measure and compare corneal deformation induced by the ocular pulse before and after UVA-riboflavin crosslinking.
Seven porcine and four human whole globes were tested within 72 hours post-mortem. Porcine globes were deswelled in a 10% dextran solution for 1 hr and immersed in a 3.0% Poloxamer 188 solution (P188) to preserve corneal thickness during testing. Human globes were deswelled in a 3.5% P188 solution at 4oC for 18 hours and remained in this solution during testing. The baseline intraocular pressure (IOP) was set to 15 mmHg. After epithelium removal and preconditioning, ocular pulses (1 Hz, 3 mmHg amplitude) were introduced via a syringe pump. Ultrasound scans of the central 5.7 mm of cornea in the nasal-temporal direction were obtained using a 50 MHz probe (Vevo 2100, VisualSonics). The cornea was then subjected to a clinical crosslinking protocol using VibeX Rapid (0.12% riboflavin, Avedro) and UVA radiation (Vega CBM-X-Linker, CSO Italia) followed by repeated testing. Corneal through-thickness (TT) strains were calculated using an ultrasound speckle tracking algorithm (Tang & Liu, J Biomech Eng 2012, 134(9)), and ocular pulse stiffness index (OPSI) was calculated using the model OPSI=-IOP2/k, where k is the regression slope of the strain verses pressure change (Pavlatos et al, IEEE Trans Med Imag 2017, in press). The responses before and after CXL treatment were compared using paired t-tests.
In porcine corneas, peak axial displacements, peak TT strain, and OPSI were significantly different after CXL treatment (all p<0.05, Fig. 1), indicating corneal stiffening. Human corneas had significant reductions in peak axial displacement and OPSI (p<0.05, Fig. 2), but the change in peak strain did not reach statistical significance (p=0.167, Fig. 2).
Corneal deformation in response to the ocular pulse changed after CXL. High frequency ultrasound speckle tracking may detect and quantify CXL-induced corneal stiffness changes based on measuring the cornea’s response to intrinsic ocular pulse.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1: a. Average peak strain, displacement, and OPSI in porcine globes, b. peak strain maps before and after CXL, and c. cyclic displacements during 5 ocular pulses in a typical porcine globe
Fig. 2: a. Average peak strain, displacement, and OPSI in human globes, b. peak strain maps before and after CXL, and c. cyclic displacements during 5 ocular pulses in a typical human globe
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