An investigation of the surface chemical properties of the tear film system is proposed both in normals and in patients with insufficient or unstable tear film ("dry eyes" in the broadest sense). The purpose of the study is to discern whether the tear film abnormality is due to a decrease in the surface activity of the macro-molecular components of the aqueous tears, a change in the spreading properties of the meibomian lipids, or possibly a combination of these factors. The degree of wettability of the corneal surface in dry eye patients will be determined. In subjects having a continuous tear film for at least several seconds, the surface tension of the tear film will also be measured.