Repeatability and Reproducibility of Corneal Epithelial Thickness Mapping with iVue SD-OCT

Abstract

Purpose : Corneal epithelium can be affected by conditions such as contact lens wear, dry eye, laser refractive surgery (LRS) and keratoconus (KCN). iVue SD-OCT provides high-resolution cross-sectional imaging of the cornea and automated segmentation of the pachymetry scan for corneal epithelial boundary. The purpose of this study is to evaluate the performance of the epithelial thickness mapping (ETM) in normal eyes and eyes of patients with corneal conditions.

Methods : Three repeated pachymetry scans were acquired on 3 different iVue SD-OCT devices (Optovue, Fremont, CA) with device-designated operators from consented subjects enrolled in an IRB-approved study. Manual editing for segmentation artifacts was permitted at operator discretion. Epithelial measurements were derived automatically from the ETM software. Repeatability (based on the random error of repeated scans) and reproducibility (including the random error of repeated scans and the instrument/operator variability) were assessed based on 17 sector parameters (see Map below) derived from a 6 mm diameter corneal epithelial thickness map centered on the pupil.

Results : A total of 59 eyes of 59 subjects (12 Normal, 12 Contact Lens, 11 Dry Eye, 12 Post-LRS, and 12 KCN) qualified for final analysis. Seventy one out of 598 total acquired scans (11.9%) were excluded from R&R analysis due to the following scan quality issues: decentration of the scan, eyelid artifacts, cropped OCT image, low signal and motion artifacts. The percentage of disqualified scans was similar across Normal eyes (10.7%) and Corneal Patients eyes (12.1%). Out of 527 scans qualified for final analysis, 40 (7.6%) scans required manual edits of the segmentation lines. Repeatability and Reproducibility results are similar (see Table below) indicating minimal device/operator variability for both Normal and Cornea Patient groups.

Conclusions : The study showed good corneal epithelial thickness mapping repeatability and reproducibility in normal eyes and eyes of patients with corneal conditions in all map zones.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Pachymetry scan pattern centered on pupil (left) and thickness map derived from automated segmentation of epithelium (right).

 

Repeatability and Reproducibility results for Normal and Cornea patient eyes summarized for central 2mm (blue), 2-5mm parafovea (yellow, divided into 8 sectors) and 5-6mm perifovea (green, divided into 8 sectors) zones.