Anterior chamber angle measurement with optical coherence tomography: Intraobserver and interobserver variability

Purpose

To assess intraobserver and interobserver variability of anterior segment optical coherence tomography (AS-OCT) as an objective diagnostic tool to quantify the anterior chamber angle and opening width.

Setting

University Eye Clinic, Lübeck, Germany.

Methods

The anterior chamber angle and opening width were assessed in 18 eyes of 9 healthy volunteers by 2 observers. Intraobserver reproducibility was evaluated by calculating an intraclass correlation coefficient (ICC) in a mixed model. Each observer had a separate model using information from 5 scans. Interobserver variability was determined by Bland-Altman analysis. The ICC was calculated in a mixed model using a residual maximum likelihood method. The results of 3 and 5 repeated scans were evaluated to indicate the change to 1 measurement application.

Results

The mean anterior chamber angle measurement was 35.9 degrees ± 5.7 (SD) for observer A and 36.2 ± 5.7 degrees for observer B. The ICC was 0.94 and 0.91, respectively. The mean opening width was 315 ± 62 μm for observer A and 317 ± 60 μm for observer B. The ICC was 0.97 and 0.93, respectively. Interobserver comparisons showed a mean difference between anterior chamber angle measurements of −0.27 ± 1.6 degrees, a limit of agreement (LOA) interval from −3.52 to 2.98 degrees, and an ICC estimate of 0.96. The mean difference in opening width measurements was 2.40 ± 12.40 μm, the LOA from −27.20 to 22.40 μm, and the estimated ICC 0.96. Using 1 instead of the mean of 5 measurements, the LOA range increased by 3.46 degrees for the anterior chamber angle and 30.0 μm for the opening width.

Conclusion

Anterior chamber angle and opening width measurements by OCT showed low intraobserver and interobserver variability, indicating OCT is a valuable technique for quantitative assessment that provides reproducible measurements and objective documentation by different examiners.