[The corneal epithelial barrier]

The corneal epithelium is an stratificated pavimentous epithelium. The epithelial cells are grouped in 3 levels: superficial cells, intermediate cells, basal cells. The superficial cells are solidarised by there type of junctional complexes: desmosomes, impermeable junctions, and communicating junctions. Because the corneoconjunctival surface is colonised by microorganisms and every minimal lesions can favorise an infection, the epithelial integrity plays a protective role. The corneal epithelium constitute the main way of intraocular penetration of topical drugs. There are two ways of drugs penetration through corneal epithelium: intracell and pericell way. The penetration speed was influenced by ocular factors (epithelial lesions) and drugs features (solubility, molecular mass, molecular structure, pH, pK, concentration, contact time).