Ocular surface parameters repeatability and agreement —A comparison between Keratograph 5M and IDRA

Purpose

To evaluate the repeatability and agreement in dry eye measurements using Oculus Keratograph 5M (K5M) and SBM Sistemi IDRA (IDRA).

Methods

A total of 108 participants were enrolled and 108 eyes were evaluated. Tear meniscus height (TMH) and first and average non-invasive break-up time (NIBUT) were measured using the K5M and IDRA (order randomly assigned). TMH was measured using the built-in caliper tool while NIBUT was computed by the automatic algorithm of the instruments.

Results

The Bland Altman plots analysis showed a good agreement between the two instruments for TMH (95 % Limits of Agreement (LoA), −0.17 to 0.16), but not the first NIBUT (95 % LoA, −8.13 to 14.79) and average NIBUT (95 % LoA, −7.89 to 10.32). The values of the first and average NIBUT measured using IDRA were significantly shorter than in K5M (difference = median (IQR) −2.75 (−6.48- −0.28)s, p < 0.001 and difference = median (IQR) −1.65 (−3.97–1.89)s, p = 0.008 respectively). The TMH (p = 0.037) and NIBUT average (p = 0.033) measured by K5M, as well as the TMH (p = 0.040) measured by IDRA, exhibited unstable measurements across the three measurement times. The remaining parameters exhibited stability with three repeated measurements.

Conclusion

The NIBUT measurements are not interchangeable between IDRA and K5M, while the TMH was little difference between the two instruments. It is important to exercise caution when using different ocular surface analyzers to minimize errors in comparing multiple measurements.