Collagen Corneal Shields
Collagen corneal shields are useful as a delivery system to prolong the contact between a drug and the cornea. For the creation of these shields, porcine scleral tissue is extracted and molded into contact lens–like shields. Drugs can be incorporated into the collagen matrix during the manufacturing process, absorbed into the shield during rehydration, or applied topically while the shield is in the eye. Because the shield dissolves in 12, 24, or 72 hours, depending on the manufacturing process for collagen crosslinking, the drug is released gradually into the tear film, and high concentrations are maintained on the corneal surface and in the conjunctival cul-de-sac.
Recent attempts to create collagen shields have focused on using metal oxide nanoparticles as agents for collagen crosslinking. In one study, an initial rapid release, or burst release, due to adsorption of the drug on the shields, was followed by a constant release over the next 13 days, which was due to diffusion of the drug from the collagen matrix. Additional crosslinking with ultraviolet light achieved a slower rate of drug release.
Collagen shields have been used for the early management of bacterial keratitis, as well as for antibiotic prophylaxis. They have also been used to promote epithelial healing after ocular surgery, trauma, or spontaneous erosion. Despite these therapeutic benefits, collagen shields are poorly tolerated because they are very uncomfortable.
Agban Y, Lian J, Prabakar S, Seyfoddin A, Rupenthal ID. Nanoparticle cross-linked collagen shields for sustained delivery of pilocarpine hydrochloride. Int J Pharm. 2016;501(1–2): 96–101.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.