Drug Delivery to the Posterior Segment of the Eye

Drug delivery into the posterior segment of the eye is complicated by the existence of the blood-ocular barrier. Strategies for delivering drugs to the posterior segment include systemic administration, modification of the barrier, and local drug delivery (including transcorneal, transscleral, and intravitreal). The most commonly used method for drug delivery into the posterior segment is by intravitreal injection. Other routes that can be used to achieve therapeutic drug levels in the posterior segment include topical, iontophoretic, and juxtascleral delivery. Extended-release intravitreal drug delivery systems can achieve sustained therapeutic levels with the goal of providing a prolonged clinical benefit with significantly fewer interventions.