Architecture of the lid-cornea juncture.

The details of the lid-cornea-tear film juncture influence the encounter of the lid with the top edge of an interpalpebrally fit rigid gas permeable contact lenses. During blink, fluid circulation at right angles to the globe can be hypothesized in the tear prism of the upper lid. This circulation prevents formation of a stratified tear layer, although lipid may always be present at the air interface. Water soluble or dispersed materials will be uniformly distributed in the tear film of the open eye. The collection of tears in the upper margin during a blink is shown to favor movement of tears away from the center of the upper lid. Tears on the temporal side of the center move along the upper lid to the fornix and then along the lower lid to the lower punctum. Tear fluid on the nasal side of center moves directly to the upper punctum.