Liquid-gel transition.

  Eye, which is the most vital organ of the body suffer from various eye problems like glaucoma, endopthalmitis, dry eye syndrome, trachoma, keratitis, conjunctivitis etc. 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 because of dilution and rapid drainage. Prolonged drug delivery can be achieved  by various new dosage forms like in-situ gel, collagen shield, minidisc, ocular film, ocusert, nanosuspension, nanoparticulate system, liposomes, niosomes, dendrimers, ocular iontophoresis etc. The most successful of these is the in-situ forming ophthalmic drug delivery systems prepared from polymers that exhibit reversible liquid-gel phase transition .The aim of this article is to present a concise review of in-situ gelling system to overcome all above problems. This review also summarizes various temperature, pH, and ion induced in-situ forming polymeric systems used to achieve prolonged contact time of drugs with the cornea and increase their bioavailability.