Abstract
Purpose :
Epithelial thickness measurements (ETM) may play a role in the detection of early keratoconus, which is a contraindication for laser refractive surgery. Epithelial thickness also contributes to corneal power which can affect the accuracy of refractive and intraocular lens surgery.This study reports on the repeatability and reproducibility (R&R) of ETM from CIRRUS™ HD-OCT 5000 (ZEISS, Dublin, CA).
Methods :
This was a retrospective study where three Pachymetry scans on each of three CIRRUS HD-OCT devices were acquired on one eye of 137 subjects. Three operators each were assigned to one device only. The operator-device order in which the subjects were scanned was randomized. All study procedures were done for three study groups: Normal Cornea, Post-LASIK and Corneal Pathology. Enrolled corneal pathology subjects had one of the following diagnoses in Table 1. Each scan was analyzed with a quality metric algorithm to determine whether the scan was acceptable or not and unacceptable scans were excluded from the analysis. The quality metric exclusion reasons include poor scan quality, B-scan taken at a suboptimal position, or large motion. The scan was analyzed using an algorithm to generate ETM in 25 sectors.
Results :
Normal: Analysis was performed on 279 qualified scans from 45 eyes of 45 normal subjects (Table 2). The coefficient of variation (CV) is better than 6% for all sectors. The reproducibility limit would allow detection of changes of 3-7 microns.
Post-LASIK: Analysis was performed on 360 qualified scans from 40 eyes of 40 post-LASIK subjects (Table 2). The CV is better than 7.5% for all sectors. The reproducibility limits would allow detection of changes of 3-9 microns for most sectors.
Pathology: Analysis was performed on 333 qualified scans from 37 eyes of 37 subjects, with corneal pathology (Table 2). The CV is better than 6.5% for all sectors. The reproducibility limits would allow detection of changes of 5 to 8 micrometers in general.
Conclusions :
The results of the precision analyses for ETM show good reproducibility and coefficients of variation across the 3 study groups: Normal corneas, Corneas with Pathology, and Post-LASIK corneas. All repeatability and reproducibility limits are clinically acceptable. The ETM feature on CIRRUS HD-OCT may be useful for detecting patients with keratoconus.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.