[Vitreous substitutes as drug release systems].

Despite major improvements of vitreo-retinal surgical techniques proliferative vitreoretinopathy (PVR) remains a major challenge. Surgical therapy alone may not be sufficient in complicated cases of PVR. A combination of standard techniques such as pars plana vitrectomy with a vitreous substitute and a simultaneous adjuvant pharmacological treatment for the suppression of undesired proliferation of retinal cells and retinal scarring may be a promising therapeutic approach. However, due to the narrow therapeutic range and the short biological half-life of most anti-proliferative or anti-inflammatory drugs in the vitreous cavity, intravitreal slow-release systems for extended drug delivery are desirable. Vitrectomy for PVR normally requires a vitreous substitute. Consequently, a vitreous substitute that could also serve as a slow-release system for anti-proliferative or anti-inflammatory drugs would provide several advantages. This review gives an overview of recent developments of slow-release systems that may also be suitable as vitreous substitutes. Even standard internal tamponades such as silicone oils or gases may serve as extended drug-release systems under certain conditions. In the mean time polymerised hydrogels have been developed, which apart from providing an adequate tamponade effect, may facilitate an extended intravitreal release of various anti-proliferative and anti-inflammatory drugs for several weeks.