Repeatability and Reliability of Quantified Ultrasound Biomicroscopy Image Analysis of the Ciliary Body at the Pars Plicata

Abstract

Most of the ciliary body and ciliary processes of the eye cannot be directly visualized in vivo because of the posterior location of the pars plicata to the posterior chamber and iris. However, ciliary anatomy can be effectively imaged using ultrasound biomicroscopy (UBM) by placing the probe close to the limbus, perpendicular to this structure. Previous studies measuring ciliary body parameters in meridian UBM images found that these parameters were measured with poor reliability and repeatability. This study evaluates the intra-observer reliability and inter-observer agreement of a standardized protocol for measuring six ciliary parameters in transverse or quadrant UBM images that capture an entire row of ciliary processes. All six ciliary parameters have high intra-observer reliability, with ciliary body thickness, ciliary process length and ciliary process density measurements being the most consistent for each observer. The coefficient of variation for each observer ranged from 1.4%–15%. Inter-observer agreement was also high for all six parameters, with an intra-class correlation coefficient >0.8. Utilizing transverse UBM images of the pars plicata allows for consistent quantitative analysis in control subjects.