ABSTRACT
Only a few commercially available ophthalmic drug delivery systems have been forthcoming since the introduction of the topical eye drop. However, delivery systems that attempt to increase the residence time in the eye have been extensively studied in the literature. Among these are pre-soaked soft contact lenses (1-7), soluble polymer gels (8,9) and emulsions (10-12), bioerodible ocular inserts (13), diffusional devices or nonerodible inserts (14), and osmotic systems (15). Of these delivery systems, the Ocusert
system (Alza Corporation, Palo Alto, CA), which was introduced in 1975, provided a virtual zero-order release of the drug over a long period of time. Although it was technologically advanced, the Ocusert system was not well accepted by patients.
