Polymeric, injectable, intravitreal hydrogel devices for posterior segment applications and interventions

Posterior segment diseases are commonly implicated in the occurrence of curable as well as incurable diseases which could lead to blindness. An example of one such disease is age-related macular degeneration, which would require chronic treatment over an extended period and as such the development of an intravitreal drug delivery system that would optimize patient outcomes is essential. The major contributor of the difficulty in treating diseases in the posterior segment is the structure of the eye, particularly the blood–ocular barriers. This review will focus on the various biodegradable and non-biodegradable injectable intravitreal polymeric hydrogel devices, such as poly(ethylene glycol), poly(lactic-co-glycolic acid), silica, hyaluronic acid/dextran, silk, chitosan/alginate and poly(N-isopropylacrylamide)-based polymers, their compositions as well as the effects and results of these polymeric components on the device as a whole. Furthermore, it will briefly discuss therapeutic agents used in these devices, such as ranibizumab, dexamethasone, Avastin®/bevacizumab and aflibercept, and a potential way forward by employing intelligent polymeric systems.