Ocular drug delivery by conventional routes of administration does not maintain therapeutic drug concentrations in the target tissues for a long duration because of various anatomical and physiological barriers. Treatment of diseases of the posterior segment of the eye requires novel drug delivery systems that can overcome these barriers for efficacious delivery, provide controlled release for the treatment of chronic diseases, and increase patient's and doctor's convenience to reduce the dosing frequency and associated side effects. Thereby, an increasing number of sustained-release drug delivery devices using different mechanisms have been developed. This article discusses various current and future sustained-release drug delivery systems for the posterior segment disorders.
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