A central issue to the treatment of retinal disease in humans is how to deliver therapeutic concentrations of a drug without side effects. While agents targeting the retina are frequently injected directly into the vitreous, vision threatening complications may occur. Systemic administration can get the agents to posterior segment of the eye but, it may lead to serious side effects. Topical drug delivery to the retina would be highly desirable however, the necessity for penetration across the various ocular barriers prevents its efficacy. Many other methods have been also considered including subconjunctival injection, iontophoresis, liposomes, microparticulates, gene therapy and using transporters.