Reproducibility of scanning laser polarimetry (GDx) of peripapillary retinal nerve fiber layer thickness in normal subjects

Abstract.

Purpose: To assess the reproducibility of measurement of retinal nerve fiber layer (RNFL) thickness among subjects using the GDx Nerve Fiber Analyzer (NFA). Methods: One eye of each of five young and healthy volunteers was imaged by three newly trained technicians (R.-H.P, K.-R.K., and S.-T.K.). Each volunteer was scanned six consecutive times for five independent times within a 1-month period. One composite image was selected out of three best images per session. Intra- and interoperator reproducibilities were calculated and the influence of placement of measurement ellipse by a single operator on interobserver reproducibility was also investigated. Results: Mean coefficients of variation for total integral value of RNFL were 3.67±1.47%, 3.86±2.13%, and 4.16±1.97%, respectively for the three technicians. Interoperator variability was not statistically significant (P=0.075), and the difference was even less if a single ellipse drawn by one operator was used in all measurements (P=0.1528) by repeated-measures analysis of variance (ANOVA). Conclusions: The results suggest that GDx NFA may provide acceptable intraoperator as well as interoperator reproducibility among Asian eyes.