Topical administration is the most common method of ocular medication, but it is generally difficult for the drug to pass through the cornea, and the bioavailability of the drug is low. Nanocarrier drugs were used in eyes in the 1980s, and liposomes and lipoids vesicles (Niosomes) interacted with ocular surface mucins to prolong the residence time of the drug on the ocular surface. Nanoemulsion surfactants can release the tight junctions of corneal epithelial cells, form transport openings, and inhibit the degradation of pharmaceutically active proteins by cell surface glycoprotein P (Pgp). Nanoparticles pass through the corneal and conjunctival epithelium without causing toxicity. Nanocapsules internalize deeper into the corneal epithelium (at 50 μm). Polymeric micelles self-assemble into core-shell nanocarriers to enhance the ability of drugs to penetrate the cornea. Anionic high-generation poly-amidoamine (PAMAM) dendrimers enhance drug permeability. Neutral and cationic low-generation dendrimers mediate higher drug permeability through clathrin pathway. Nanocrystal, in addition to enhancing drug solubility and dissolution rate, its high adhesion ability helps drug retention and penetration into ocular tissues. Nanostructured materials are closely related to dry eye and provide a choice for the treatment and diagnosis of dry eye.
