A Summary of the Advances in Ophthalmic Drug Delivery via Iontophoresis and Microneedles

Drug delivery to the posterior segment of the eye is a significantly challenging task due to the underlying physiological, anatomical and metabolic constraints. Delivery of drugs through ophthalmic route is significantly hindered by multiple physiological processes including potential static and dynamic barriers. Moreover, efflux pumps expressed on ocular tissues severely restrict the intra-ocular penetration of drugs, especially into the posterior ocular tissues. However, severe ocular complications which may be sight threatening, pose an urgency for the intervention/ treatment. Currently, invasive intravitreal injections are widely used to drugs/drug candidates to retina and vitreous body. Therefore, non-invasive drug delivery strategies that overcome the barriers encountered in the ocular milieu should be developed and explored. Various topical formulation approaches are being designed in order to address the safety and patient compliance issues associated with invasive routes. In this review, the targeted drug delivery to the ocular posterior segment via minimally invasive approaches is discussed.