An update on intravitreal implants in use for eye disorders

Advanced biotechnological techniques and new polymers have led to the development of many innovative intravitreal drug delivery systems. Some designs are still in an experimental phase while others have gained widespread acceptance and are commercially available. Since steroids are a mainstay of therapy for uveitis and macular edema, new intravitreal implants have been developed to provide continuous release of corticosteroids over prolonged spans of time with reduced systemic adverse effects. Today, three long-acting corticosteroid implants are commercially available: the fluocinolone acetonide implants Retisert® and Iluvien® and the dexamethasone drug delivery system Ozurdex®. They offer an alternative route in the management of macular edema due to uveitis, retinal vein occlusion, diabetes and pseudophakia. Their advantage over treatment with steroid injections and the anti-vascular endothelial growth factor ranibizumab is the long-term control of inflammation and macular edema with a reduced frequency of administration. Their potential side effects are cataract and glaucoma, therefore, careful patient selection and monitoring is essential. Further studies are warranted to define the relative efficacy and indications for each treatment option. The development of new devices is a future challenge in the strive to improve drug delivery systems.