Measurement of the Optic Nerve Head Descending Fibers at Bruch’s Membrane Opening Level with Spectral Domain Optical Coherence Tomography in Normal and Glaucoma Eyes.

Abstract

Purpose : This study aims to evaluate a novel structural parameter: the descending fibers width at the Bruch’s membrane opening level (DF-BMO) and its association with other structural and functional parameters in normal and glaucoma patients.

Methods : Subjects with glaucoma presenting typical optic nerve head (ONH) findings, high intraocular pressure with or without visual field damage and normal controls were included. Patients underwent 24-2 perimetry (Humphrey Field Analyzer) and SD-OCT (Spectralis). A vertical B-scan of the ONH with the largest cup extension was obtained for the measurements. The mean width between the BMO and the innermost portion of the descending fibers in the inferior and superior portions of the cup constituted the DF-BMO (Figure 1). Automated individual macular layers were checked for proper segmentation and plotted using the average of sectors from the ETDRS grid circle. Statistical analysis was performed using generalized estimating equations (GEE) to allow for clustered observations. Age, gender, presence of glaucoma, disc area and cup extension were accounted in the model. The area under the receiver operating characteristics curve (AUROC) to discriminate between glaucoma and normal eyes for DF-BMO was also calculated.

Results : 109 eyes (67 subjects) qualified for the study. The number of eyes was 95 in the glaucoma and 14 in the control group. The mean DF-BMO was 260.04 ± 106.06 µm and 476.14 ± 124.70 µm, for glaucoma and normal eyes, respectively. Other characteristics are described in Table 1. In the GEE models, DF-BMO was significantly associated with cRNFL (P=0.001) and the inner circle of the GCIPL (P=0.006). The inferior portion of the DF-BMO was associated with the inferior cRNFL (P<0.001), whereas their superior counterparts were not (P=0.674). Age and gender weren’t significant in any of the models. The AUROC for the DF-BMO was 0.896 (P<0.001). At the cutoff value of 365 µm, the sensitivity and specificity were 83.2% and 78.6%, respectively, with a positive predictive value of 96.3%.

Conclusions : The DF-BMO was significantly associated with structural glaucoma parameters (cRNFL and inner circle of GCIPL) and differentiated well between normal and glaucoma patients. This parameter may constitute an additional OCT biomarker for the structural diagnosis and monitoring of glaucoma.

This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.

 

Figure 1

 

Table 1