Posters

Intraobserver reproducibility and interobserver agreement of demarcation line depth measurements in keratoconic eyes following accelerated epi-off corneal cross-linking

Poster Details

First Author: A.Tzamalis UK

Co Author(s): R. Vinciguerra   V. Romano   E. Arbabi   M. Batterbury   S. Kaye        

Abstract Details

Purpose:

The aim of this study was to evaluate the intraobserver reproducibility of demarcation line depth (DLD) measurement in keratoconic patients after epithelium-off CXL and assess the interobserver variability/agreement among examiners of various experience levels.

Setting:

St. Paul's Eye Unit Royal Liverpool University Hospital Liverpool, UK

Methods:

56 eyes of 56 patients undergoing corneal collagen cross linking for progressive keratoconus were enrolled. After 4 weeks, all patients underwent an anterior segment optical coherence tomography in the cross-linked eye by four masked examiners (2 medical students [S1, S2] and 2 corneal fellows [F1, F2]) in order to identify and measure the DLD in experienced and non-experienced users. The intraclass correlation coefficient (ICC) and the coefficient of variation (CV) were calculated. Agreement between raters was evaluated using Bland-Altman plots, ICC and weighted kappa statistics comparing raters in pairs.

Results:

The average DLD of all measurements was 254.34 ± 72.3 μm, varying from 84 to 459 μm. The intraclass correlation coefficient (ICC) evaluating the reproducibility of measurements for the F1 was calculated 0.9379 (95% confidence intervals [CIs]=0.9035-0.9619), while for the second (F2) it was 0.9837 (95% CI=0.9743-0.9901). The overall ICC among all four observers was 0.8706 (95% CI= 0.8061 to 0.9185). The coefficient of variation for repeated measurements was 5.981μm (95% CIs=3.966–7.471) and 3.312μm (95% CIs=2.468-3.981) for F1 and F2 raters respectively.

Conclusions:

The reproducibility of DL measures although very good (ICC>0.9), yielded a difference between the two experienced raters. Furthermore, the novice raters did not reach an excellent level of agreement with the expert ones showing greater variability in their recordings.

Financial Disclosure:

None