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.
