Disruption of the tear film by the application of small drops of saline and surfactant.

The effects of disrupting the tear film by placing 5 or 10 microl drops of saline and mild surfactant solution (SS) directly onto the tear films of 10 subjects were observed and are described here. Disruption of the tear film was only transient, with restoration of the film occurring within about two to three blinks for saline drops, and four to six blinks for SS drops. When a drop of SS was placed on a cornea, two types of black spots/areas may be observed: black areas apparently similar to those observed in the TBUT test, and black areas forming outside the border of the pattern of the spreading SS drop. In general, staining of the black areas formed in the fluorescein-stained tears did not occur even when blinking was inhibited for up to 13 s. Stained areas on the corneal surface did not have a tendency to form black spots first; the tear film over these areas did not appear to be less stable than on other areas of the corneal surface.