Progress of Research on Ocular Barriers of Topical Drug Delivery and Strategies to Overcome the Barriers

The ocular bioavailability is extremely low after topical administration due to complex structure of the eye. Nanocarrier-based ophthalmic drug delivery systems, which can overcome ocular barriers more easily, make it possible for topical administration to deliver drugs to the eye efficiently. This article reviews the ocular barriers after topical administration and common strategies to overcome these barriers, and summarizes the clinical progress of new dosage forms for eye diseases, with a prospect of ocular drug delivery systems via topical administration, so as to provide new insights for the treatment of eye diseases.