Effect of Weiss ring on peripapillary retinal nerve fiber layer thickness measurements using SD-OCT

Abstract

Spectral-domain optical coherence tomography (SD-OCT) must accurately identify and measure the peripapillary retinal nerve fiber layer (pRNFL) thickness to improve the repeatability and reproducibility, and reduce measurement errors. Because Weiss ring can be located in front of the optic disc, we hypothesized that it may affect pRNFL thickness measurements obtained using SD-OCT. We retrospectively reviewed the medical records of patients with (group W) and without (group N) Weiss ring, observed on OCT fundus image and an RNFL map devised using SD-OCT. Optic disc cube scans (200 x 200) were obtained to measure pRNFL thicknesses (superior, temporal, inferior, nasal, and average) at two consecutive visits. Pearson's correlation coefficient (r), intraclass correlation coefficient (ICC), and coefficient of variation (CV) were calculated. The r and ICC values for the pRNFL thickness measurements at the two visits were lower for group W compared to group N, but statistical significance was reached only for inferior pRNFL thickness. In addition, CV values were greater for group W compared to group N, but the differences were significant only for inferior and average pRNFL thickness measurements (p < 0.001 and p = 0.004, respectively). Weiss ring located near the optic disc can affect pRNFL thickness measurements and repeatability thereof, especially the inferior quadrant and average values. Therefore, it is important to identify the presence of Weiss ring when analyzing pRNFL thickness values.