PLA and PLGA microparticles for intravitreal drug delivery: an overview

Disorders affecting the posterior segment of the eye are one of the major causes of blindness in western countries. Treatments of these pathologies often require multiple intravitreal injections to achieve effective concentrations in the vitreous cavity. However, repeated injections are poorly tolerated and are frequently associated with cataract formation, retinal detachment, and endophthalmitis. Furthermore, the risk of adverse effects increases with the frequency of intravitreal administration. Injectable microparticles offer a good alternative to multiple injections because they can be administered as conventional intraocular formulations. Among them, microspheres prepared from biodegradable polymers such as poly(lactic) (PLA) acid and poly(lactic-co-glycolic)acid (PLGA) have the advantage of disappearing from the site of administration once the active substance has been delivered. This work describes relevant in vitro and in vivo parameters and variables related to the intravitreal administration of PLA and PLGA microspheres for the treatment of diseases affecting the posterior segment.