New Ocular Drug Delivery Systems

The need for sustained ocular drug delivery systems grows with the increasing number of people with visual impairments. Drug delivery to the posterior segment poses unique challenges that a variety of systems have been developed to overcome. Currently, small-molecule drugs and protein therapeutics are mainly administered as topical solutions and intravitreal injections, respectively. Small-molecule drugs have a short half-life and diffuse easily throughout the eye, making it challenging to deliver a localized, and maintained, therapeutic dose. The main challenge of delivery protein therapeutics is maintaining a sustained therapeutic level of protein during manufacture and release since most protein therapeutics depend on their complex structural integrity to be effective. Due to these limitations, repeated doses of small-molecule drugs and protein therapeutics are given to maintain a therapeutic range. Thus, developing new drug delivery systems (DDSs) that have a controlled, extended, and localized release of drug and maintain drug stability would reduce the frequency of administration. This chapter discusses new DDSs for small-molecule and macromolecular biological drugs, particularly protein therapeutics, in the form of ocular implants, ocular inserts, microneedles, cell-based systems, injectable nano/microparticles, injectable hydrogels, and composite systems. Many of these advances in drug delivery will help to play a role in improving anatomic and visual outcomes for various forms of macular surgery.