Analysis of which device is reliable for measuring central corneal thickness in novice examiner

Abstract

Purpose : Ultrasound pachymetry (USP) is the most commonly used and gold standard for measuring central corneal thickness (CCT), but it can be difficult for novice examiner. We evaluate the most reliable device to measure CCT for a novice examiner using four different methods.

Methods : A novice examiner and an expert examiner measured CCT in 17 healthy eyes using dual rotating Scheimpflug camera, optical coherence tomography (OCT), noncontact specular microscopy (NCSM), and USP. CCT of the same subject was measured twice by a novice, and once by an expert. The paired t-test was used to compare CCT values of expert and novice examiner. Inter-examiner repeatability was evaluated by intraclass correlation coefficient (ICC). Agreement among the devices measured by novice examiner was analyzed using Pearson’s correlation coefficient and Bland–Altman analysis.

Results : The CCT measurements were not statistically different between the measured value of the expert and the mean value of the novice for all devices. The mean value of the CCT measured twice by the novice examiner using dual rotating Scheimpflug camera, OCT, NCSM and USP were 533.38 ± 41.45 μm, 504.38 ± 39.01 μm, 490.38 ± 37.62 μm and 521.73 ± 39.26 μm, respectively. The ICCs of dual rotating Scheimpflug camera, OCT, NCSM and USP were 0.972, 0.996, 0.988 and 0.990. A significant linear correlation was observed among all devices (r > 0.900, p < 0.001), except NCSM and USP (r = 0.875, p = 0.086). Bland-Altman analysis demonstrated low mean biases between devices.

Conclusions : All CCT measurements using 4 devices have no significant differences between expert and novice, and the OCT was the least different. For novice, the values of the CCT measured by four devices show good repeatability and strong correlation with each other.