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Rithambara Ramachandran, Cindy X. Cai, Dongwon Lee, Benjamin C. Epstein, Kirsten G. Locke, David G. Birch, Donald C. Hood; Reliability of a Manual Procedure for Marking the EZ Endpoint Location in Patients with Retinitis Pigmentosa. Trans. Vis. Sci. Tech. 2016;5(3):6. doi: https://doi.org/10.1167/tvst.5.3.6.
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We developed and evaluated a training procedure for marking the endpoints of the ellipsoid zone (EZ), also known as the inner segment/outer segment (IS/OS) border, on frequency domain optical coherence tomography (fdOCT) scans from patients with retinitis pigmentosa (RP).
A manual for marking EZ endpoints was developed and used to train 2 inexperienced graders. After training, an experienced grader and the 2 trained graders marked the endpoints on fdOCT horizontal line scans through the macula from 45 patients with RP. They marked the endpoints on these same scans again 1 month later.
Intragrader agreement was excellent. The intraclass correlation coefficient (ICC) was 0.99, the average difference of endpoint locations (19.6 μm) was close to 0 μm, and the 95% limits were between −284 and 323 μm, approximately ±1.1°. Intergrader agreement also was excellent. The ICC values were 0.98 (time 1) and 0.97 (time 2), the average difference among graders was close to zero, and the 95% limits of these differences was less than 350 μm, approximately 1.2°, for both test times.
While automated algorithms are becoming increasingly accurate, EZ endpoints still have to be verified manually and corrected when necessary. With training, the inter- and intragrader agreement of manually marked endpoints is excellent.
For clinical studies, the EZ endpoints can be marked by hand if a training procedure, including a manual, is used. The endpoint confidence intervals, well under ±2.0°, are considerably smaller than the 6° spacing for the typically used static visual field.
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