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B. Audrey Nguyen, Mohammad Arif Hossain, Jun Liu, Cynthia J Roberts; Biomechanical impact of the sclera on corneal deformation response to an air-puff: a finite-element study. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3142.
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Many studies have examined corneal and scleral biomechanics, but none have examined the contribution of varied scleral properties to corneal deformation response. It has been shown that the corneal biomechanical response to an air-puff is significantly different between a cornea mounted on an anterior chamber and the cornea of a whole globe. We present a finite element (FE) model to explore the impact of changing scleral properties on corneal biomechanical behavior under loading by an air-puff.
A 2D axisymmetric model of the human cornea, limbus, and sclera surrounded by an air region was created in COMSOL based on average dimensions. The spatial and temporal velocity profiles of the unobstructed CorVis ST air jet were previously determined by hot wire anemometry. In the FE model, the pressure profile of the air-puff was computed and applied to the cornea, then replicated in a computational fluid dynamic model with a non-deformable cornea to validate the interaction between the air-puff and an obstruction. This validated pressure profile was applied to the corneal surface in the coupled deformation study. The Young’s moduli of the cornea and limbus were kept constant, while the loading due to IOP and the scleral Young's modulus were varied such that the ratio of scleral to corneal moduli was 1.5, 2 or 5. The maximum apical displacement of the cornea was recorded for each simulation.
Figure 1 shows the result of a single simulation, and table 1 summarizes the data. For each value of IOP tested (10, 20, 35 mmHg), increasing the ratio of Young’s moduli resulted in decreasing maximum apical displacement. Further, the model showed that increasing the IOP while keeping all other factors constant resulted in decreasing maximum apical displacement, which is consistent with literature reports.
The FE model demonstrates that scleral material properties have an important impact on the biomechanical deformation response of the cornea in air-puff induced deformation. The observed relationship between scleral properties and corneal deformation parameters is expected to persist with improvements in the model.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig. 1: (Left) Air-puff profile used in loading (Right) Resultant von Mises stress and deformation
Table 1: Simulation input values and resulting max apical displacement
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