Agreement and repeatability of the Sonogage ultrasound pachometer compared with a Mitutoyo micrometer

The agreement and repeatability of the Sonogage ultrasound pachometer was tested by comparing it with a Mitutoyo micrometer.

The thickness of five polymacon disks with thickness and ultrasonic properties similar to the human cornea and corneal epithelium were measured using both instruments. The mean values obtained using both instruments were compared and analyzed using a two-way analysis of variance, Bland-Altman analysis, and coefficient of variation.

The measurements of the Sonogage were found to be statistically indistinguishable from the micrometer for all disks combined (p = 0.25) and for the disks with thicknesses similar to the corneal epithelium (p = 0.10), Bland-Altman analysis reveal limits of agreement for all thicknesses with a lower limit of -4.23 microm and upper limit of 5.27 microm. The coefficient of variation was <4% for each thickness. Bland-Altman plots of thin and thick disks exhibit no systematic difference between the average micrometer and Sonogage measurements.

The measurements taken with the Sonogage pachometer are comparable with those taken with the micrometer when measuring polymacon disks with properties similar to corneal epithelium and total corneal thickness.