A New Method to Measure Ocular Surface Sensitivity: Repeatability and Reproducibility of the Liquid Jet Esthesiometer

Abstract

Objectives: To assess the reliability of the liquid jet esthesiometer (LJA) for measurement of corneal sensitivity. Methods: Two separate studies were conducted to assess intrasession repeatability (study 1) and intersession reproducibility (study 2) of corneal sensitivity measured using the LJA. Thirty participants (13 female and 17 male participants, age 23±6 years) participated in study 1 and another 30 (18 female and 12 male participants, 35±10 years) participated in study 2. For study 1, mechanical sensation threshold of the central cornea was measured three times on the same day, with a 30-min break between repeats. For study 2, central corneal sensation threshold was measured on five different days by one of eight randomly assigned examiners. Results: Corneal sensation thresholds obtained in studies 1 and 2 were 2.3±1.0 and 2.5±1.2 μL, respectively. No significant differences between repeated measurements were obtained in either study (P≥0.19). Thresholds were lower (i.e., corneal sensitivity was higher) in female than male participants (2.1±1.0 vs. 2.7±0.9 μL in male participants, P=0.02) but were not affected by contact lens wear. Clinical reliability of the LJA was good for intrasession repeatability (coefficient of repeatability ±1.6 μL, intraclass correlation coefficient 0.74, within-subject coefficient of variation (CVW) 24%) and moderate for intersession reproducibility (Coefficient of Reproducibility ±2.2 μL, CVW 32%). Measurement variability was independent of threshold level (P=0.84). Conclusions: The LJA offers good clinical repeatability and is a reliable tool to measure corneal sensitivity in different population groups, regardless of stimulus thresholds. Day-to-day fluctuations in corneal sensitivity probably account for the relatively lower reproducibility.