Precision of Pachymetry Measured With a Portable High-Resolution Ultrasound, a Standard Ultrasound, and Two...

To assess the precision (repeatability and reproducibility) and agreement of central corneal thickness (CCT) measurements by a high-resolution ultrasound (E-pach), a standard ultrasound, and two Scheimpflug pachymeters in healthy eyes.

Instrument diagnostic test study. A total of 100 healthy volunteers were enrolled to measure right-eye CCT by a high-resolution ultrasound (E-pach), a standard ultrasound (A-scan device), and two Scheimpflug pachymeters (Pentacam and Corvis ST). To assess repeatability and reproducibility, the test-retest repeatability (TRT) and intraclass correlation coefficient (ICC) were calculated. The agreement among the four devices was evaluated with Bland-Altman plots.

The high-resolution ultrasound (E-pach) showed repeatability (ICC = 0.9981), interobserver reproducibility (ICC = 0.9971), and intersession reproducibility (ICC = 0.9825); the standard ultrasound and two Scheimpflug pachymeters also showed similar repeatability (all ICC ≥ 0.9679), interobserver reproducibility (all ICC ≥ 0.9730), and intersession reproducibility (all ICC ≥ 0.9647). However, the high-resolution ultrasound yielded CCT values that were obviously lower than those of the standard ultrasound and Pentacam (p < 0.001) but higher than those of the Corvis ST (p < 0.001). The 95% limits of agreement (LoA) in the Bland-Altman plots were 44.5 µm (high-resolution ultrasound vs. standard ultrasound), 34.9 µm (high-resolution ultrasound vs. Corvis CT), and 32.5 µm (high-resolution ultrasound vs. Pentacam).

The high-resolution ultrasound is a portable, reliable, and inexpensive pachymeter. However, the CCT values obtained from the high-resolution ultrasound are not interchangeable with those from Pentacam, Corvis ST, and standard ultrasound.