A Combined Clinical and Langmuir Film Study of Natural Tear Films

The Langmuir technique has been applied to the study of natural tears and the results obtained from surface pressure-area isotherms have been correlated with those of clinical tests (the Schirmer and the TFBUT tests). The population studied only included people aged over 45. Natural tears were collected from Schirmer strips, which were placed in contact with the water subphase of a Langmuir trough for recording the surface pressure-area isotherms. These isotherms have been classified as good or weak according to the characteristics obtained. From the isotherms, characteristic values such as π limit , C S -1 max and π max were also obtained. The analysis from the Chi-squared test indicates dependence between the Schirmer test and the type of isotherms (P 0.05 indicates that the independence cannot be discarded with the significance criteria imposed. Working with the same criteria of significance, we obtain moderate or good Pearson correlation coefficients with statistical significance (P limit , C S -1 max and π max values. On the other hand, we obtain low Pearson correlation coefficients with no statistical significance (P>0.05) between the values of the TFBUT test and the π limit , C S -1 max and π max values.