Meta-analysis: biometry measurements with different devices not equivalent

This meta-analysis found that biometry measurements taken with different devices are not equivalent, with some exceptions.

The authors analyzed data from 216 articles comparing 24 different devices with reference devices in the following parameters: mean, steep and flat curvature of the anterior and posterior cornea; central corneal thickness; anterior chamber depth; and axial length.

A device was equivalent with the reference device within the thresholds set by the measurement error in only 17 of the 70 comparisons. More lenient thresholds, based on a change in calculated refraction of ±0.25 D, increased this number to a maximum of 25/50 comparisons (excluding pachymetry). High degrees of inconsistency were seen in the reported results, which could partially explain the low agreement between devices.

They recommend avoiding mixing devices while following individual patients to prevent inter-device differences from obfuscating any real evolutions in pathology.

They say that equipment differences between participating centers could potentially influence outcomes in clinical studies and suggest that studies include all interested centers and consider centers (rather than equipment) as a between-subjects factor in the statistical analysis, thus correcting for potential equipment and calibration bias.