Reproducibility of retinal nerve fiber layer parameters measured with scanning laser polarimetry in healthy eyes

Purpose To determine the variability of retinal nerve fiber layer (RNFL) parameters measured with scanning laser polarimetry (SLP) with enhanced corneal compensator (GDx ECC) in healthy eyes. Methods Eighty-two healthy individuals were prospectively selected. Only one eye per subject was randomly included in the study. All participants had intraocular pressure less than 21 mmHg and normal standard automated perimetry (Humphrey 24-2 SITA Standard). Peripapillary RNFL parameters were measured using the GDxPRO (Carl Zeiss Meditec, Dublin, CA) 3 consecutive times on the same session. Left eye data were converted to a right eye format. The same operator performed all acquisitions with the same device. Intraclass correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability were calculated for all SLP parameters: TSNIT average, superior average, inferior average, TSNIT standard deviation and the nerve fiber indicator (NFI). Results Mean age was 56.08 ± 9.4 years. The ICC was higher than 0.928 for all SLP parameters. The TSNIT average had the highest ICC (0.967), while the TSNIT standard deviation showed the lowest ICC (0.928). The COVs ranged from 2.4% (TSNIT average) to 21.8% (NFI). Test-retest variability was 6.55 for the NFI and 2.51 for the TSNIT average. Conclusion The reproducibility of RNFL measurements acquired with the GDxPRO was excellent. Variability was higher for NFI than for other SLP parameters.