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

J Cataract Refract Surg. 2006 Nov;32(11):1803-8. doi: 10.1016/j.jcrs.2006.07.014.


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 microm for observer A and 317 +/- 60 microm 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 microm, the LOA from -27.20 to 22.40 microm, 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 microm 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.

MeSH terms

  • Adult
  • Anterior Chamber / anatomy & histology*
  • Ciliary Body / anatomy & histology*
  • Diagnostic Techniques, Ophthalmological*
  • Female
  • Humans
  • Iris / anatomy & histology*
  • Male
  • Observer Variation
  • Reproducibility of Results
  • Tomography, Optical Coherence / methods*
  • Trabecular Meshwork / anatomy & histology