Precision of Pachymetry Measured With a Portable High‐Resolution Ultrasound, a Standard Ultrasound, and Two Scheimpflug Pachymeters

Subject 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. Methods 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. Results 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). Conclusions 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.