[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. Despite several corneal transporters that take part in permeation of some drugs, increasing bioavailability of ophthalmic drugs in general remains a question of current importance. Liposomes are an option. These vesicular structures consist of the outer lipid bilayer and the inner aqueous compartment, which can be filled with a medication solution. This peculiarity of liposomes ensures their penetration through both hydro- and lipophilic mediums of the eye, including the barriers of the anterior and posterior segments. Liposomes are effective means of vectored drug delivery into the anterior chamber. This paper presents a review of the current knowledge on the interaction of drugs and ocular surface barriers as well as the prospects for the use of liposomes for transcorneal drug delivery.