Tear film lipid layer thickness as a function of blinking.

Alterations in the tear film lipid layer as a function of blinking were investigated using a custom-designed specular reflection monitoring system. The tear film lipid layer of 104 subjects under conditions of normal ("baseline") blinking and "forceful" blinking was quantitated on the basis of specific interference colors. Deliberate, forceful blinking was found to significantly increase the lipid layer thickness (LLT) of the tear film. The magnitude of increase was found to be correlated with the baseline LLT values; individuals with baseline LLT values of 75-150 nm demonstrated a mean increase in LLT of 33 nm following forceful blinking, whereas subjects with baseline LLT values < or = 60 nm experienced a mean increase of 19 nm. The difference in the magnitude of increase between the groups was highly significant (p = 0.0001). The data suggest that, in addition to playing a role in the spreading of lipid across the tear film, the blinking mechanism may be important in the maintenance of the lipid layer by augmenting the expression of lipids from the meibomian glands.