Ocular Drug Delivery- Recent approaches in the formulation

Ophthalmic products are formulated using essentially the same scientific principles and technology as dosage forms developed for other target organs. Despite numerous scientific efforts, efficient ocular drug delivery remains a challenge for pharmaceutical scientists.  Most ocular diseases are treated by topical drug application in the form of solutions, suspensions and ointment. These conventional dosage forms suffer from the problems of poor ocular bioavailability. The major diseases affecting the eye are age-related macular degeneration, diabetic macular edema, cataract, proliferative vitreoretinopathy, uveitis, cytomegalovirus, and glaucoma. A myriad of advances have been made to overcome these physiological barriers for the targeted ocular delivery of drugs. Various approaches that have been attempted to increase the bioavailability and the duration of therapeutic action of ocular drugs can be divided into two categories. The first is based on use of the drug delivery systems, which provide the controlled and continuous delivery of ophthalmic drugs. The second involves, maximizing corneal drug absorption and minimizing precorneal drug loss. This review provides an insight into various noval techniques employed in prolonging the ocular residence time and therefore bioavailability of drugs like mucoadhesive systems, Insitu gelling systems, microemulsions, lipid based nanocarriers, Nanosuspensions, Ocular iontopherosis.