Ophthalmic drug delivery is most interesting and challenging delivery system facing the pharmaceutical scientist. The anatomy, physiology, and biochemistry of the eye render this organ highly impervious to foreign substances. A significant challenge to the formulator is to circumvent the protective barriers of the eye without causing permanent tissue damage. These barriers affect the bioavailability of drugs. Development of newer, more sensitive diagnostic techniques and novel therapeutic agents continue to provide ocular delivery systems with high therapeutic efficacy. These includes iontophoresis, liposome bioadhesive gels, ocular insert, contact lenses, liposomes & a special one is microspheres. Microsphere is a well designed controlled drug delivery system can overcome some of the problems of conventional therapy and enhance the therapeutic efficacy of a given drug. This approach delivering a therapeutic substance to the target site in a sustained controlled release fashion & achive a good bioavalability in ocular delivery system.
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