The treatment of vitreoretinal disorders has been problematic because it is difficult to gain access to the posterior segment of the eye. Topical instillation of eye drops has little therapeutic effect on posterior structures which cannot be maintained without frequent administration. Intraocular injections could be an alternative, but the fast flowing blood supply in this region, associated with the rapid clearance rates, causes the drug concentration to fall rapidly below therapeutic levels. In order to obtain therapeutic levels over longer time periods, polymeric sustained-drug release systems, implanted into the vitreous, are being studied for the treatment of vitreoretinal disorders. These systems are prepared using different kinds of polymers that can be biodegradable or nonbiodegradable. The polymers derived from lactic and glycolic acids have been the most promising for drug delivery systems because of their biocompatibility and biodegradation. According to previous studies, the polymers can be manufactured in the form of rods, discs or membranes, using the following methods: molding, extrusion or preparation of films. In this review, we present the technology and some preliminary studies of biodegradable implants in relation to intraocular drug delivery systems.
Drug implants; Absorbable implants; Drug delivery system; Delayed-action preparations; Technology, pharmaceutical
