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Keyton Clayson, Xueliang Pan, Elias Pavlatos, Jun Liu; 2D Regional Inflation Strains in Porcine Cornea. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4340.
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© ARVO (1962-2015); The Authors (2016-present)
To measure and compare the inflation response of the central, paracentral and peripheral cornea and sclera using high-resolution ultrasound speckle tracking.
Ten porcine globes were tested within 48 hours postmortem. Whole globes were pretreated in 10% dextran solution, secured to a custom-built holder and immersed in 0.9% saline. The anterior chamber was infused with Optisol via a syringe pump to control intraocular pressure (IOP). Globes were preconditioned with 20 pressure cycles from 5 to 30 mmHg and then equilibrated at 5 mmHg for 20 minutes. IOP was raised in 0.5 mmHg steps between 5-20 mmHg and 1 mmHg steps between 20-30 mmHg consecutively, with nasal-temporal images acquired at each step using a 50 MHz ultrasound probe (VisualSonics MS700). After acquiring images of the central cornea, the probe was translated peripherally and the procedure was repeated. Regional through-thickness and in-plane strains were calculated using an ultrasound speckle tracking technique (Tang and Liu, ASME 2012). Linear mixed models with repeated measures were used to compare the strain between regions while accounting for the association of the measures at different regions in the same globe.
Average through-thickness compressive and in-plane tensile strains for each region are shown in Figure 1. Maps of strain by region in a representative eye are shown in Figure 2. Through-thickness compressive strains were not different in the central, paracentral and peripheral cornea (p>0.05 in all cases), while the anterior sclera had significantly less compression than the cornea (p<0.01). In-plane strains were significantly larger in the central and paracentral regions than the peripheral and scleral regions (p<0.05).
The porcine cornea showed a fairly similar through-thickness compression from central to periphery, while in-plane stretch was smaller in the periphery. The anterior sclera had smaller deformation compared to the cornea in the same eye. Future studies will investigate the anterior coat in human eyes which may show a different profile due to the different collagen organization.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig. 1: Average in-plane (a) and through-thickness (b) strains of n=10 porcine eyes in different corneal regions and anterior sclera
Fig. 2: B-mode image of anterior globe with labeled regions (a) and through-thickness (top blue) and in-plane (bottom red) strain maps in the central (b) and peripheral (c) regions in a representative cornea at 30 mmHg
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