The Langmuir Technique Applied to the Study of Natural Tears

Abstract

As a new proposal, natural tears collected from the Schirmer strips were studied using surface pressure-area, π-A, isotherms obtained with the Langmuir technique. Parameters such as limit surface pressure, πlimit, elastic modulus at the maximum, CS−1max, and surface pressure at the maximum, πmax, were correlated with clinical tests, such as the Schirmer (SCH) and the tear film breakup-time (TFBUT) tests. The analysis from the chi-square test indicates dependence between the SCH test and the type of isotherms with a value of P < 0.05. A moderate Pearson correlation coefficient with statistical significance (P < 0.05) between the values of the SCH test and the πlimit was obtained. On the other hand, a low Pearson correlation coefficient with no statistical significance (P > 0.05) between the values of the TFBUT test and the πlimit was obtained. Additionally, considering only the isotherms classified as good, moderate Pearson correlation coefficients with statistical significance (P < 0.05) between the values of the TFBUT test and πlimit or πmax can be obtained. This study shows that the isotherms obtained with the Langmuir technique correlate well with the tear secretion, and when the later is moderate or good, the isotherm parameters afford information about the tear film stability and the behaviour of the tear lipids.