Sunita Chaudhary

Eye is the most exclusive organ of the body and various drug delivery systems are used to deliver drug into eye. Eye diseases are commonly encountered in day to day life, which are cured or prevented through the conventionally used dosage forms like eye drops, ointments. Delivery to the internal parts of the eye still remains troublesome due to the anatomical and protective structure of the eye. To improve ocular drug contact time, bioavailability and residence time, and to reduce the patient discomfort, frequency of dose, as well as to slow down the elimination of the drug there are significant efforts concentrating towards newer drug delivery systems for ophthalmic administration. This review focuses on the various new drug delivery systems applied in eye like inserts, in-situ gel, the newly developed particulate and vesicular systems like liposomes, pharmacosomes and discomes, niosomes, nanoparticles, iontophorosis, corneal shields, drug embedded contact lenses, ocular wafers etc  and the most recent advanced approaches of the ocular delivery systems like the delivery of the genes and proteins to the internal structures which were used in treating the diseases caused due to genetic mutation, along with safety evaluation of ocular drug delivery formulations with some case studies.

Drug targeting is the ability to direct a therapeutic agent specifically to desired site of action with little or no interaction with nontarget tissue. Niosomes are one of the best carriers for drug targeting. Niosomes are microscopic lamellar structures formed on admixture of non-ionic surfactant of the alkyl or dialkyl polyglycerol ether class and cholesterol with subsequent hydration in aqueous media. Niosomes are biodegradable, relatively nontoxic, more stable and inexpensive, an alternative to liposomes. Niosomes can be SUV (Small Unilamellar Vesicles), MLV (Multilamellr Vesicles) or LUV (Large Unilamellar Vesicles). The method of preparation of niosome is the based on liposome technology. The basic process of preparation is the same i.e. hydration of the lipid phase by aqueous phase. Niosomes are characterized by vesicle size, bilayer formation, number of lamellae, membrane rigidity and entrapment efficiency. A method of in-vitro release rate study includes the use of dialysis tubing. Niosomal drug delivery is potentially applicable to many pharmacological agents for their action against various diseases including cancer and leishmaniasis.