Test—retest variability of glaucoma imaging devices

This article reviews the methods adopted to evaluate the test-retest variability of glaucoma imaging devices. The author also discusses their use in judging disease progression and determining the testing frequency required to detect a predetermined progression rate within a specified period.

He says that information relating to the test-retest variability of measurement results provided by each imaging device is indispensable in determining whether or not glaucomatous damage has progressed from baseline and in estimating the optimal frequency of testing needed to confirm disease progression. Such information enables the clinician to use these devices in clinical practice.

The test-retest variability of a glaucoma imaging device is usually estimated using Bland-Altman analysis and by calculating the coefficient of variation (CV), intraclass correlation coefficient (ICC) and minimum detectable changes (MDC).

The author systematically reviews the reported CV, ICC and MDC values for glaucoma-related structural parameter measurement results of stereo-disc photographs, confocal scanning laser ophthalmoscopes, scanning laser polarimeters, time-domain optical coherence tomography (OCT), spectral-domain OCT (SD-OCT), anterior-segment OCT and ultrasound biomicroscope. This information will enable clinicians to interpret measurement results provided by each glaucoma imaging device and thus be useful in practice.

The author notes that although SD-OCT systems may be currently prevailing because of the volume of information provided and their relatively better test-retest variability, these systems need improvement in their test-retest variability measurement capabilities.

This article concludes that structural parameters provided by glaucoma imaging devices should be free from a patient's subjective response, and test-retest variability of results of glaucoma imaging devices should be further improved, along with improvement of the technology.