Available online through www.jpronline.info

Efficiency of ocular therapy depends on presence of suitable drug at site of action in an effective concentration for desired period of time. Depending on the disorder site of action may be any ocular tissue or cell. Hence there are many sites within eye that should be targeted. Tear production, non productive absorption, transient residence time and impermeability of corneal epithelium leads to poor bioavailability of drug from ocular dosage form. The primitive ophthalmic solutions, suspensions and ointment dosage forms are less efficient to combat various ocular diseases. This article explores the importance of niosome as potential ocular drug delivery system, its formulation aspects and its characterization in in vito and in vivo. Drug delivery in ocular therapeutics is challenging task. The main objective is to improve existing ocular dosage forms and exploit newer delivery system for improving the ocular bioavailability of existing molecules. The tendency today is to find ocular delivery systems that are ‘patient-friendly’. Most ocular diseases are treated with a topical application of drug solutions administered as eye drops. The relative percentages are 62.4% for solution, 8.7% suspensions and 17.4% ointments. These conventional dosage forms account for nearly 90% of the currently accessible marketed formulations. One of the major problems encountered with the topical delivery of ophthalmic drugs is the rapid and extensive precorneal loss caused by the high tear fluid turnover as well as the relatively large volume of the administered eye drop (approximately 50µl versus 7µl of cornea1 tear film), lead to a high rate of lacrimal drainage. Due to the resulting elimination rate, the precorneal half life of drugs applied by these pharmaceutical formulations is considered to be between about 1-3 min. As a consequence, only the very small amount of about l-3% of the dosage actually penetrates through the cornea and is able to reach intraocular tissues. The poor productive absorption, on the other hand, results in a high amount of drug that is drained into the nose or into the gut. Especially the nose but also the gut is very efficient absorption organs of the body. This in turn leads to an extensive systemic absorption and may result in unwanted side effects and toxicity of the drug. In recent years, vesicles have become the vehicle of choice in drug delivery. Lipid vesicles were found to be of value in immunology, membrane biology, diagnostic techniques, and most recently, genetic engineering. 1 Vesicles can play a major role in modeling biological membranes, and in the transport and targeting of active agents. Vesicular systems not only help in providing prolonged and controlled action at the corneal surface but also help in providing controlled ocular delivery by preventing the metabolism of the drug from the enzymes present at the tear/corneal epithelial surface. Moreover, vesicles offer a promising avenue to fulfill the need for an ophthalmic drug delivery system that has the convenience of a drop, but will localize and maintain drug activity at its site of action. The penetration of drug molecules into the eye from a topically applied preparation is a complex phenomenon. In vesicular dosage forms the drug is encapsulated in lipid vesicles, which can cross cell membrane. Vesicles therefore, can be viewed as drug carriers and as such they change the rate and extent of absorption as well as the disposition of the drug. Vesicular drug delivery systems used in ophthalmic broadly include liposomes and niosomes 2 . Niosomes are a novel drug delivery system, in which the medication is encapsulated in a vesicle. The vesicle is composed of a bilayer of non-ionic surface active agents and hence the name niosomes. The niosomes are very small and microscopic in size. Although structurally similar to liposome, they offer several advantages over them 3