Multi-embedded lens architectures were designed with Comsol Multiphysics 5.4 platform (Comsol Inc., Burlington MA), and incorporated into a 2D continuum diffusion-reaction computational model. To determine changes in metabolite concentrations of the cornea caused by the increased anaerobic metabolism during lens-induced hypoxia, the proposed model tracks the transport and kinetics of eight metabolites throughout the corneoscleral system. Changes in metabolite concentrations alter the chemical potential at the corneal endothelium. Via Kedem-Katchalsky membrane transport relations, the endothelium transports excess water from the aqueous humor into the cornea causing swelling. We calculate central-to-peripheral corneal edema with different types of embedded lenses based on oxygen transport across the lens and post-lens tear film. We investigate lens oxygen permeability, number of embedded components, and location of the embedded components.
Figure 1 provides an example encasement scleral lens containing two transparent axisymmetric embedments. Figure 2 provides the oxygen tension contour throughout the example lens, post-lens tear, and the cornea when the oxygen permeabilities (Dk) are 0, 30, and 160 Barrers for peripheral embedment, central embedment, and lens encasement respectively. Oxygen deprivation within the cornea is shown below the embedded components. Even though the greatest oxygen deprivation occurs below the peripheral embedded component, maximum swelling occurs at the region closer to the central cornea due to limbal metabolic supply reducing the swelling at the periphery. Figure 3 provides the swelling profiles when changing the oxygen Dk of the central embedment while keeping other parameters consistent to that of Figure 2. As the central embedment decreases in oxygen Dk, an increase in swelling is apparent. Figure 4 provides the difference in swelling by changing the location of the peripheral embedment while keeping other parameters same as Figure 2. Due to limbal metabolic support, peripheral corneal edema significantly decreases when the peripheral embedment is closer to the limbus.
We have devised a computational design tool to evaluate the safety of embedded contact lens against corneal edema. Oxygen transmissibility of an embedded component plays a significant role on the localized swelling of the cornea. As the metabolic supply from the limbus reduces hypoxia near the lens periphery, any low oxygen-transmissibility embedments should be placed near the lens periphery.
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