Variability of Epithelial Thickness Measurements by iVue SD-OCT in Dry Eye Patients and its Correlation with Disease Severity

Abstract

Purpose : To investigate the correlation between the severity of dry eye disease and the variability of epithelial thickness (ET) measurements by the iVue SD-OCT.

Methods : Scans were acquired on 3 different iVue SD-OCT devices from 12 normal and 12 dry eye patients. Epithelial measurements were derived automatically from the ET analysis software and measured in 17 sectors. Repeatability (based on the random error of repeated scans) and reproducibility (including the random error and the instrument/operator variability) were assessed. The severity of the dry eye condition for each study subject was clinically determined and documented using Ocular Surface Disease Index (OSDI) score and Tear Break Up Time (TBUT). The coefficient of variation (CoV) in each of the 17 regions measured was compared between the dry eye patients and normal subjects. The standard deviation (SD) of the ET scans in each sector from each individual subject was also calculated. The SD values were then correlated with the patient's OSDI and TBUT.

Results : Ninety-eight scans of 12 dry eye patients and 108 scans of 12 normal subjects were included in the study. The mean central ET was similar in both groups (normal eyes ET: 52.9±3.4 , dry eyes ET: 51.7±3.4 microns, p=0.395). The mean of the OSDI score was 48.8 (range, 14.6-83.3). Reproducibility of 15 of the 17 ET measurements was significantly better in the normal group compared to the dry eye group (Figure 1). The variability of the maximal ET (representing the maximum thickness value within 5mm diameter of a map area) measured in the dry eye group was positively correlated with a high OSDI score (p=0.02). In addition, the variability of the thickness measured at the supero-temporal 2.5 mm of the cornea was positively correlated with a higher TBUT (p=0.008).

Conclusions : This study shows good corneal ET mapping repeatability and reproducibility in normal eyes and dry eye patients in all corneal mapping zones. The reproducibility of the ET measurements is however significantly lower in dry eye patients in comparison to normal subjects. The severity of dry eye disease may affect the variability of ET measurements.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Coefficient of Variation (%) epithelial thickness in dry eye patients and normal subjects.
(* represents p value < 0.05 for difference between Dry Eye and Normal Eye Groups)