Current Perspective on microneedles for ocular drug delivery

Many ocular inflammatory and proliferative diseases require long-term pharmacological intervention/treatment. However, delivery of drugs in therapeutic levels to the back of the eye is challenging using conventional topical application, due to the poor efficacy. Systemic injections of drugs pose severe adverse effects. Direct injection into the eye may need surgical intervention. In the recent years, small size microneedles are fabricated to insert into various ocular tissues depending upon the complexity and state of disease to be treated. Microneedles are capable of delivering drugs through cornea or sclera in a minimally invasive way. There are few reports that large molecules, proteins, vaccines could be delivered into eye using microneedles. Drug delivery to the posterior segment of the eye is a significantly challenging task due to the various ocular barriers and precorneal factors. In this review, the targeted drug delivery to the ocular tissues via minimally invasive approach is discussed.