Mathematical Models of Contact Lens Drug Delivery: Blinking and Lens Design
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Eye drops are typically used to deliver ophthalmic drugs that treat disorders such as glaucoma. However, drugs delivered by this method quickly leave the tear film due to blinking and drainage. Drug-eluting contact lenses are an alternative that have been studied mathematically and experimentally for decades, but therapeutic options remain limited. To join theoretical and experimental information, we design models of contact lens drug delivery to align with experimental systems and consider factors such as blinking and lens design. The models couple partial differential equations for linear diffusion of drug inside the contact lens with ordinary differential equations governing the dynamics of compartments such as the pre- and post-lens tear films, the eyelid region, and drug delivery target tissues like the retina. To study blinking, we model the effect of a blink on the pre- and post-lens tear film drug concentrations, investigating mechanisms such as partial or full sweep out of drug by the eyelid, and squeezing or sliding of the lens. The most likely scenario is identified by comparing to model eye data [1]. To study lens design, we model drug-polymer films encapsulated in lens hydrogels, where the drug-laden region appears as an annulus in a top-down view. We investigate the dependence of drug release time on lens design properties and identify drug delivery transport mechanisms by comparing to in vivo data [2]. We recover drug cumulative release profiles from experimental systems and determine the effects of blinking and lens design properties on cumulative release. This can inform our understanding of the mechanics of contact lens drug delivery and predict targeted tissue transport of drug. REFERENCES [1] Phan, C.-M., Shukla, M., Walther, H., Heynen, M., Suh, D., and Jones, L. Development of an in vitro blink model for ophthalmic drug delivery, Pharmaceutics, Vol. 13(3), pp. 300, 2021. [2] Ross, A.E., Bengani, L.C., Tulsan, R., Maidana, D.E., Salvador-Culla, B., Kobashi, H., Kolovou, P.E., Zhai, H., Taghizadeh, K., Kuang, L., et al. Topical sustained drug delivery to the retina with a drug-eluting contact lens, Biomaterials, Vol. 217, pp. 119285, 2019.
