Repeatability and agreement of two A‐scan ultrasonic biometers and IOLMaster in non‐orthokeratology subjects and post‐orthokeratology children

Abstract

Purpose: Our aim was to determine the repeatability of measurements of axial length (AL) and anterior chamber depth (ACD) made with two ultrasonic biometers and the IOLMaster in a group of non‐orthokeratology (ortho‐k) adult subjects and to investigate the agreement among instruments in children undergoing ortho‐k therapy and in children wearing spectacles.Methods: To determine repeatability, AL and ACD were measured twice in 22 non‐ortho‐k young adults using two A‐scan ultrasonic biometers (A‐5500 and A‐2500) and the IOLMaster. To determine agreement, AL and ACD were measured with the same instruments in 30 children undergoing ortho‐k therapy and 30 spectacle‐wearing children.Results: In the adult subjects, there were no significant differences in ACD and AL measurements obtained from the three instruments (repeated measures ANOVAs, p > 0.05). There was also no significant between‐measurement difference for each instrument. The between‐measurement agreement was better for the IOLMaster (95% limits of agreement (LA): ‐0.04 and +0.05-mm for both AL and ACD) than for the two A‐scan ultrasonic biometers (95% LA: ‐0.12 and +0.11-mm for AL; ‐0.22 and +0.27-mm for ACD). Among the children, AL measurements with all three instruments were not significantly different from each other for both the children undergoing ortho‐k therapy and those wearing spectacles (repeated measures ANOVAs, p > 0.05). The 95% LA of differences obtained from any two instruments were also comparable for both groups of subjects (within ‐0.20-mm and +0.20-mm). ACD measurements of the children were significantly different among the three instruments (repeated measures ANOVAs, p < 0.05). No significant differences in ACD measurements were found between A‐5500 and A‐2500 for both groups of children (paired t tests, p > 0.017).Conclusions: The repeatability of AL and ACD measurements with the IOLMaster was very good, and was better than with the A‐scan ultrasonic biometers. The agreements in AL measurements between A‐scan ultrasonic biometers and IOLMaster were comparable in both the ortho‐k and the spectacle‐wearing subjects, and were comparable to the repeatability of the A‐scan ultrasonic biometers. ACD measurements between A‐scan ultrasonic biometry and the IOLMaster were not comparable. AL measurements with the IOLMaster can replace the measurements from the two A‐scan ultrasonic biometers used, however, the reverse is not true. AL and ACD measurements with all three instruments were unaffected by the flattened cornea following ortho‐k lens wear.