Innovative drug delivery in ophthalmology

Ocular drug delivery (topical or intraocular) is hindered by physiological barriers, including the mucus layer, surface epithelium, tear drainage, enzyme metabolism, and the blood–aqueous and blood–retina barriers. Conventional dosage forms face problems related to short retention time and poor drug bioavailability. The development of nanoparticles as drug delivery systems is an advantageous strategy that could overcome these limitations. Nanoparticles can prolong the retention time on the ocular surface, allowing more effective contact with the epithelium. In addition, they can reduce the side effects of drugs due to their capability to release the drug at a desired rate. Finally, nanoparticles can improve the solubility of poorly water-soluble drugs, further enabling their absorption. The present review summarizes recent research on the development of three types of nanoparticles as carriers for ophthalmic drug delivery, particularly polymeric micelles, nanogels, and nanocrystals.