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Kimberly Metzler, Cynthia Roberts, Steven Whitaker, Michael Lawrence, Jennifer Malik, Jeffrey Bons; Modeling corneal response to an air puff using deformation data to derive Young’s modulus. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1629.
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To create and validate a computational model that describes the deformation characteristics of human donor corneas mounted in an artificial anterior chamber in response to an air puff.
A 2-dimensional COMSOL Multiphysics model of an air jet impinging on a human donor cornea mounted in an artificial anterior chamber was created. The physical air jet was generated by the CorVis ST, a device used clinically to evaluate deformation response in living corneas. This air jet was characterized with hot wire anemometry to acquire spatial flow velocity data. The hot wire was placed at the jet exit on the CorVis, and then moved outward with micrometer control to distances of 3, 6, 9, 12, 15, 20, and 25 mm along the centerline. The duration of the hot wire anemometry recordings lasted 40 ms. Preliminary data of the temporal profile shows that the peak velocity along the centerline during the air puff as it exits the device (distance x = 0) is over 100 m/s. At distances between 9 and 12 mm from nozzle of the CorVis ST, the peak velocity reaches above 90 m/s. Accordingly, the model inlet velocity representing the CorVis ST was set at 100 m/s. Corneal dimensions were modeled by constructing an ellipse inside an 8mm sphere that was sectioned to have a width of 12 mm. The cornea section was mounted onto a rigid body within the model, representing the Barron’s Artificial Anterior Chamber. Intraocular pressure was manipulated to be 10, 20, 30, 40, and 50 mmHg. Deformation data from a donor corneal-scleral rim mounted on an artificial anterior chamber at these pressures was used to validate the model. The model was run iteratively at each pressure to determine the Young’s modulus required to produce experimentally determined deformations.
Maximum deformation amplitude for the model was matched to experimental deformation data within 0.01% error. The Young’s moduli were 1.569, 1.740, 1.899, 2.099, and 2.250 MPa for pressures of 10, 20, 30, 40, and 50 mmHg, respectively.
This model supports the known relationship that as IOP increases, the cornea will become stiffer. Future studies will include developing a 3D model as well as modeling the whole globe.
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