Overview of the repeatability, reproducibility, and agreement of the biometry values provided by various ophthalmic devices.

PURPOSE

To present an overview of the measurement errors for various biometric devices, as well as a meta-analysis of the agreement between biometric devices using the Pentacam, Orbscan, and IOL Master as a reference.

DESIGN

Meta-analysis of the literature.

METHODS

The meta-analysis is based on data from 216 articles that compare a total of 24 different devices with the reference devices for the following 9 parameters: mean, steep and flat curvature of the anterior and posterior cornea; central corneal thickness; anterior chamber depth; and axial length. After the weighted average difference between devices has been determined, the "two one-sided t test" was used to test for equivalence between devices within certain thresholds defined by the measurement errors and the influence of these differences on the calculated refraction.

RESULTS

In only 17 of the 70 comparisons a device was equivalent with the reference device within the thresholds set by the measurement error. More lenient thresholds, based on a change in calculated refraction of ±0.25 diopter, 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.

CONCLUSION

As a rule, biometry measurements taken by different devices should not be considered equivalent, although several exceptions could be identified. We therefore recommend that clinical studies involving multiple device types treat this as a within-subject variable to avoid bias. The follow-up of individual patients using different devices should be avoided at all times.