Interobserver variability of an open-source software for tear meniscus height measurement.

Abstract

Different values of the lower tear meniscus height (TMH) can be obtained depending on the method and technique of measurement employed. The aim of this study was to analyse the interobserver variability of a method for measuring TMH by using an open source software. On a group of 176 subjects, two videos of the central lower tear meniscus, first under slit-lamp illumination and ten minutes later under Tearscope illumination, were generated by a digital camera attached to a slit-lamp. Images were extracted from each video by a masked observer. Two further observers measured in a masked and randomized order the TMH in each illumination method by using an open source software based on Java (NIH ImageJ). TMH was measured from the lower lid to the upper limit of the tear meniscus for both slit-lamp (TMH-SL) and Tearscope (TMH-Tc) illumination methods. Subsequently, in different order, observers assigned a four-grading and a healthy/abnormal subjective classification to each central meniscus. No significant differences were found between the TMH measurements obtained by both investigators in slit-lamp or Tearscope image datasets (t-test; both p≥0.136). When comparing TMH measurements stratified by grade, only interobserver significant differences were observed for grades 3 and 4 with silt-lamp (t-test; both p≤0.009). Significant differences on TMH results between subjective subgroups were observed for both illumination techniques (ANOVA, all p≤0.045). This study showed a useful tool to objectively measure TMH by photography.