Repeatability and reproducibility of retinal nerve fibre layer thickness measurements with the iVue-100 optical coherence tomographer

Abstract

Background: Accurate and repeatable measurements of the retinal nerve fibre layer (RNFL) thickness are important in the diagnosis and management of glaucoma and other disorders.

Objective: To assess the repeatability and reproducibility of the iVue-100 optical coherence tomographer (OCT).

Methods: The thickness of the RNFL was measured for 50 healthy participants using the iVue-100 OCT. Although both eyes per participant were measured, only right eyes were analysed here. Repeatability and reproducibility of the iVue-100 OCT were assessed using the intraclass correlation coefficient (ICC), coefficient of variation (CoV), paired t-tests and Bland-Altman analysis.

Results: Good intra-observer repeatability was obtained as indicated by the ICC of observer 1 (range: 0.941 - 0.976) and observer 2 (range: 0.829 - 0.953) as well by the CoV of observer 1 (range: 0.098 - 0.137) and observer 2 (0.091 - 0.132). In terms of inter-observer reproducibility, significant differences (p< 0.05) in mean measurements between the observers were noted for the average RNFL readings and in the superior and inferior quadrants as assessed with paired t-tests. Even though significant inter-session differences were found for the average RNFL thickness and the superior quadrant (p = 0.003 and p = 0.013, respectively), excellent ICCs were obtained for inter-session reproducibility (range: 0.914 - 0.979).

Conclusion: The iVue-100 OCT demonstrated good repeatability and reproducibility for RNFL thickness measurements.

Keywords: Retinal nerve fibre layer thickness; iVue-100 OCT; optical coherence tomography; repeatability; reproducibility.

Figure 1

RNFL thickness display of the optic nerve head scan

Figure 2

Bland-Altman plot comparing RNFL thickness measurements of the right eyes taken by observer one and observer two. The solid line represents the mean difference and the dashed lines represent the upper and lower LoA. Three points were outside the 95% LoA region.

Figure 3

Bland-Altman plot comparing average RNFL measurements of the right eyes taken by observer one in two separate sessions. The solid line represents the mean difference and the dashed lines represent the upper and lower LoA.