Intraocular drug delivery

Abstract

One of the key limitations of systemic therapy in the management of intraocular inflammation is the need for high doses of the drugs used to achieve meaningful intraocular concentrations, which may result in a high frequency of side effects and intolerance. Local therapy has been used for many years in the form of periocular injections of corticosteroid formulations, delivered either as an orbital floor injection (OFI) or a posterior sub-Tenon’s injection (PST). These types of injection result in a high concentration of the drug in the orbit. The mechanism by which the corticosteroid enters the eye is not clear, but may involve a number of different pathways, including transscleral penetration, the most likely route. Response rates to this form of drug delivery are variable with some studies reporting visual improvement from 67 to 85 %. The use of intraocular injection of corticosteroids bypasses all potential barriers and produces a very high concentration of the corticosteroid in the intraocular compartment. Also anti-VEGF drugs like Avastin can be injected into the vitreous. The effect of all injections is short-live and repeated procedures are needed with an increasing risk of complications.