The Weiss Ring, a Major Confounding Factor For Measurements of Peripapillary Retinal Nerve Fiber Layer Thickness: Short title: The Impact of the Weiss Ring On RNFL Thickness Measurements

Abstract

To identify how the Weiss ring affects the measurement of mean and sectoral peripapillary retinal nerve fiber layer (pRNFL) thicknesses. Retrospective, cross-sectional study. Subjects were divided into two groups: controls (control group) and subjects in which a Weiss ring was visible on optical coherence tomography fundus images (WR group). Mean and sectoral pRNFL thicknesses were compared between the two groups. A total of 205 eyes were enrolled: 131 eyes in the control group and 74 eyes in the WR group. The mean pRNFL thicknesses of the control group and WR group were 97.2 ± 6.7µm and 94.6 ± 10.8 µm, respectively (P=.042). In sectoral thickness, the inferior sector of the WR group was 112.1 ± 23.2 µm, which was significantly thinner than that of the control group (125.5 ± 13.3 µm; P < .001). The Weiss ring was located in 10 eyes (13.5%) in the superior sector, 7 eyes (9.5%) in the temporal sector, 40 eyes (54.1%) in the inferior sector, and 17 eyes (23.0%) in the nasal sector. In analyses of reproducibility, the coefficient of variation and intraclass coefficient of the inferior sector measurement were 10.90% and 0.409, respectively, indicating low reliability of the measurement. Eyes with a Weiss ring showed thinner mean and inferior pRNFL thicknesses than normal controls, which would be a measurement error caused by the Weiss ring. This could be a major confounding factor for analyses of pRNFL changes, especially in glaucoma patients.