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Design of multi-embedment contact lenses to mitigate corneal edema

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With the advance of micro-technology, the feasibility of fabricating circuit-embedded contact lenses to improve visualacuity or monitor health is under active study. However, embedded microcircuits and concomitant batteries exhibitsignificantly lower oxygen transmissibility than that of available silicone-based lens materials. Because corneal cellsreceive oxygen primarily from the atmosphere, corneal hypoxia and concomitant swelling (i.e., edema) is a majorsafety concern. To address this concern, we predict cornea edema, which is the clinical symptom of hypoxia, inducedduring wear of multi-embedded contact lenses. 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 metaboliteconcentrations of the cornea caused by the increased anaerobic metabolism during lens-induced hypoxia, theproposed model tracks the transport and kinetics of eight metabolites throughout the corneoscleral system. Changesin metabolite concentrations alter the chemical potential at the corneal endothelium. Via Kedem-Katchalsky membranetransport 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 transportacross 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. Figure2 provides the oxygen tension contour throughout the example lens, post-lens tear, and the cornea when the oxygenpermeabilities ( Dk) are 0, 30, and 160 Barrers for peripheral embedment, central embedment, and lens encasementrespectively. Oxygen deprivation within the cornea is shown below the embedded components. Even though thegreatest oxygen deprivation occurs below the peripheral embedded component, maximum swelling occurs at theregion closer to the central cornea due to limbal metabolic supply reducing the swelling at the periphery. Figure 3provides the swelling profiles when changing the oxygen Dk of the central embedment while keeping other parametersconsistent 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 otherparameters same as Figure 2. Due to limbal metabolic support, peripheral corneal edema significantly decreaseswhen 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. Asthe metabolic supply from the limbus reduces hypoxia near the lens periphery, any low oxygen-transmissibilityembedments should be placed near the lens periphery.

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