Energetics of corneal epithelial cell-ocular mucus-tear film interactions: some surface-chemical pathways of corneal defense.

The role of ocular mucous gel in the corneal epithelial hydration, lubrication, cleansing, wettability and defense against pathogens, is investigated based on a modified DLVO theory that accounts for the apolar, as well as polar, "acid-base" surface interactions. A strong polar repulsion keeps mucus in the form of highly hydrated "sloppy" gel, which does not adhere to the normal epithelium. Due to its strong electron donor type monopolarity, the mucus gel can form an effective barrier against contamination of the underlying epithelium by both the apolar (e.g., tear film lipids, cell debris) and the polar (e.g., hydrophilic bacteria) entities. In the absence of mucus, epithelial contamination becomes energetically favorable, which can also compromise its wettability by tears. Finally, a loss of polar surface properties can lead to adhesion of mucus to the cornea.