Ophthalmic Drug Delivery Systems for the Treatment of Corneal Diseases

Abstract

The role of nanotherapeutics as it applies to the treatment and management of current corneal pathology is evolving to provide increased therapeutic concentration , targeted therapy, and reduced toxicity. The current limitations to such novel therapies are based on structural and functional barriers of a lipophilic corneal epithelium and a hydrophilic stroma. This chapter provides a detailed review of the corneal anatomy to help facilitate discussion into how nanotherapeutics may be applied in certain clinical conditions. Current modes of ophthalmic drug delivery to the cornea such as solutions, suspensions, and ointments have their own inherent fl aws including lower bioavailability, lower contact time, and bypass of fi rst-pass metabolism. In contrast, the development of colloids such as liposomes, microemul-sions, and niosomes overcomes many of these limitations by providing a biphasic environment with lipophilic and hydrophilic properties. Furthermore, they allow for sustained release of pharmacotherapy and higher bioavailability. Current innovative applications include using voriconazole microemulsions and cyclosporine micelles in the treatment of fungal keratitis and dry eye syndrome, respectively. This chapter further details the use of transporter proteins, by manipulating their infl ux and effl ux transport properties, it becomes possible to deliver antiviral medications for the treatment of herpetic corneal disease. The use of an electrical stimulus, via ionto-phoresis or ultrasound, via sonophoresis to drive pharmacologic agents through tissue planes is also discussed in this chapter with several examples of current experimental models. Finally, we describe the use of microneedles to introduce gene therapy to potentially treat corneal disease.