Reliability of a manual procedure for marking the EZ endpoint location in patients with retinitis pigmentosa

Rithambara Ramachandran, Cindy X. Cai, Dongwon Lee, Benjamin C. Epstein, Kirsten G. Locke, David G. Birch, Donald C. Hood

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Purpose: 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). Methods: 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. Results: Intragrader agreement was excellent. The intraclass correlation coefficient (ICC) was 0.99, the average difference of endpoint locations (19.6 lm) was close to 0 lm, and the 95% limits were between-284 and 323 μlm, 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. Conclusions: 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. Translational Relevance: 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.

Original languageEnglish (US)
Article number6
JournalTranslational Vision Science and Technology
Issue number3
StatePublished - May 2016
Externally publishedYes


  • Ellipsoid zone (EZ)
  • Optical coherence tomography
  • Receptors
  • Retinitis pigmentosa

ASJC Scopus subject areas

  • Biomedical Engineering
  • Ophthalmology


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