[Transcorneal drug delivery: prospects for the use of liposomes].

Anatomical and physiological ocular surface barriers are responsible for low bioavailability of topical ophthalmic drugs. The unique structure of the cornea, epithelial cells and hydrophilic stroma in particular, impedes permeation of hydro- and lipophilic drugs via common routs of administration. The tear film with its proteins and enzymes also acts as a barrier.