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Yanhui Ma, Keyton Clayson, Elias Pavlatos, Xueliang Pan, Jun Liu; 3D inflation response of the corneoscleral junction in porcine and human eyes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1402.
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Anatomically, the cornea is continuous with the sclera at the region of the limbus. The biomechanical boundary conditions in this region however are not well-understood. This study aims to measure the 3D inflation response of the corneoscleral junction including the peripheral cornea, the limbus and the sclera in whole porcine and human donor globes using high-resolution ultrasound speckle tracking to gain insight into the in situ biomechanical responses of this region.
The globes were secured in a custom-built holder with needles inserted into the anterior chamber to control and monitor the intraocular pressure (IOP). The IOP was increased from a baseline of 12 mmHg to 13.5, 15, 17, and 19 mmHg consecutively in five porcine globes and three human donor globes. A 50 MHz ultrasound probe (Vevo2100, VisualSonics) was used to scan a volume of the corneoscleral region (9.7 mm × 7.0 mm). The distributive displacements were calculated using a 3D ultrasound speckle tracking algorithm (Cruz et al, J Biomech 2014, 47(5)). Three regions (cornea, limbus, and sclera) were manually marked based on ultrasound B-mode images (Fig. 1).
Axial displacement maps at 19 mmHg in a representative porcine and human eye are shown in Fig. 1. Average axial, lateral and elevational displacements for each region in response to IOP elevation in porcine and human eyes are shown in Fig. 2. In the porcine eye, the average axial displacement from 12 to 19 mmHg in the limbal region was significantly larger than that in the sclera (24.4±21.5 μm vs 10.6±15.8 μm, p=0.008, paired t-test). In the human eye, the displacement patterns were variable among the three tested globes, with the limbal region appearing more distinct from the sclera in the lateral and elevational directions (Fig. 2B).
The 3D displacement profile in the corneoscleral junction during IOP elevation revealed a transition region between the cornea and sclera whose biomechanical properties may be distinct from either the cornea or the sclera. This experimental data provides guidance for future biomechanical modeling of the in vivo boundary conditions of the cornea.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1. B-mode image and axial displacement map with labeled regions in a representative porcine (left) and human (right) eye at 19 mmHg
Fig. 2. Average axial, lateral and elevational displacements in different corneoscleral regions in (A) porcine and (B) human eyes
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