Reproducibility of Cornea Measurements in Anterior Segment OCT Images Analysed With the Zhongshan Assessment Program (ZAP)

Abstract

Purpose: : To determine the interobserver and intraobserver measurement reproducibility of cornea parameters using the Zhongshan Assessment Program (ZAP, Guangzhou, China) on Visante anterior segment OCT (AS-OCT) images.

Methods: : This was a prospective study of 24 healthy volunteers with no previous ophthalmic history. All participants underwent 2 sets of AS-OCT scans (in both the horizontal and vertical meridians), 1 week apart. AS-OCT images were independently analysed by 2 examiners using the ZAP software. Parameters examined were anterior chamber depth (ACD), central corneal thickness (CCT), posterior corneal curvature (PCC) and posterior corneal arc length (PCAL), a novel parameter defined as the posterior corneal border distance between scleral spurs. Interobserver and intraobserver reproducibility of the above parameters was calculated in terms of limits of agreement (LOA; mean of differences +/- 1.96 x standard deviation of differences).

Results: : Horizontal ACD was successfully measured in 23 of 24 images, and vertical ACD similarly was successfully measured in 23 of 24 images The ZAP software successfully measured all other parameters in all 24 sets of images.. Interobserver variation showed the range of LOA to be 87.5% to 95.83%, and p-values from 0.446 to 0.999. Intraobserver variation showed the range of LOA to be 91.67% to 95.83%, and p-values from 0.082 to 0.946. All individual parameters examined are tabulated in Table 1.

Conclusions: : There was highly reproducible inter and intra observer measurements of corneal parameters using the ZAP. ZAP may serve as a new investigatory tool for accurately evaluating the anterior segment and corneal parameters for lamellar and refractive procedures.

Keywords: cornea: clinical science • imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)