Analytical Performance, Spatial Dynamics and Clinically Meaningful Change Thresholds for Automated Non-invasive Tear...

Area of Science:

• Ophthalmology
• Optometry
• Biomedical Engineering

Background:

• Automated topographers are increasingly used for non-invasive tear film assessment.
• Device-specific analytical performance requires thorough characterization for reliable clinical application.

Purpose of the Study:

• To quantify the analytical performance of the Oculus Keratograph 5M for non-invasive break-up time (NIKBUT) and tear meniscus height (KTMH).
• To evaluate the agreement of these metrics with conventional methods.
• To characterize the spatial dynamics of tear film break-up using the Keratograph 5M.

Main Methods:

• Thirty-five participants (18 symptomatic, 17 asymptomatic) underwent three daily visits.
• NIKBUT, KTMH, fluorescein break-up time (FBUT), and slit-lamp tear meniscus height (TMH) were measured multiple times per eye.
• Precision (CV), reliability (ICC), SEM, and MDC₉₅ were calculated; method agreement assessed via Bland-Altman analysis.
• Spatial distribution of break-up events was analyzed by corneal zone.

Main Results:

• KTMH demonstrated excellent precision (CV=8.8%) and good reliability (ICC=0.73), with an MDC₉₅ of 0.173 mm.
• NIKBUT exhibited poor precision (CV=53.6% for First, 42.8% for Average) and symptom-dependent reliability.
• Bland-Altman analysis revealed significant bias and wide limits of agreement between NIKBUT and FBUT.
• Spatial analysis showed NIKBUT break-up occurred paracentrally, while FBUT occurred centrally, indicating distinct phenomena.

Conclusions:

• KTMH is the most analytically robust Keratograph metric for longitudinal monitoring, with changes needing to exceed its MDC₉₅.
• NIKBUT shows poor precision, with only large changes being significant.
• NIKBUT and FBUT measure distinct biophysical processes and are not interchangeable.
• Established benchmarks for KTMH and NIKBUT performance should guide clinical interpretation and study design.