A dry eye may be defined as the eye which exhibits an abnormal corneal epithelium secondary to an abnormal precorneal tear film (Baum, 1976). Such a broad clinical definition includes the etiological factors of tear film abnormalities due to deficiency of tear film composition, the corneal and conjunctival surface abnormalities, and the mechanical factors which may not allow proper dispersion of tear film on the cornea. In the last two conditions there is generally adequate tear secretion. The common essential feature is, however, an area of corneal dry surface.