Routes of Ocular Drug Delivery - Conventional vs. Novel Routes

Drug delivery to the eye has conventionally involved two basic methods of drug administration i.e. the topical route and the systemic route. Both of these orthodox methods of drug delivery face a number of barriers limiting their effectiveness in attaining therapeutic levels at the target site. The tight junctions, tear dilution and rapid clearance by the blood supply in both the anterior and posterior segments of the eye, act as the major barriers. To overcome these barriers, novel routes for drug delivery have been tried out by ophthalmologists that can bypass these barriers. The novel routes possess multiple advantages on the conventional routes such as increased drug concentration at the target site. Some of the routes are less invasive than the conventional routes and also cause fewer side effects. Some of these routes when used for delivering specialized formulations can also allow for better controlled/sustained/targeted drug delivery. In this chapter the comparisons between these conventional and novel routes of drug delivery have been made describing the advantages and disadvantages of each route.

Keywords: Ocular drug delivery, anterior segment, posterior segment, routes, corneal pathway, non-corneal route, systemic route, blood-aqueous barrier, bloodretinal barrier, intravitreal, periocular.