ABSTRACT
The complex nature of the eye makes ocular drug delivery a challenge. Conventional systems like eye drops, suspensions, and ointments are not optimal in the treatment of vision threatening ocular diseases. More than 90% of marketed ophthalmic formulations are in the form of eye drops, which mainly target anterior segment eye diseases. Topical drug delivery is often impaired by innate protective characteristics of the eye against entry of foreign compounds. Due to the removal mechanism (blinking and tears) and complex composition and dynamic character of the lachrymal fl uid (Attama et al. 2008), the bioavailability of an instilled formulation is generally low with only a small fraction reaching the target site (< 5%). The major challenge in ocular drug delivery is to get adequate amount of the drug to the target site and maintain contact with the ocular tissue of interest.
