Modern drug delivery systems for targeting the posterior segment of the eye

Some of the most dangerous diseases of the eye are related to the posterior segment. Diseases such as age-related macular degeneration, cytomegalovirus retinitis, diabetic retinopathy, posterior uveitis and retinitis pigmentosa are difficult to treat using classical methods because of the many internal barriers of the eye which affect the drug efficiency. In this review, we will summarize the main research directions in the field of medicamentous treatment of posterior eye disorders belonging to the controlled drug delivery concept. The review is starting with the most important knowledge regarding anatomy and pathology of the posterior segment of the eye and is continuing with the current treatment methods of the eye posterior segment illnesses and drawbacks of these methods, the drugs administration pathways to the posterior segment of the eye. The last three sections present the state of the art regarding the latest discoveries including the commercial products in the modern drug delivery systems; the main classes of materials treated in the present review are implants, hydrogels and nano- microparticulate systems.