Enhanced Detection of Open-angle Glaucoma with an Anatomically Accurate Optical Coherence Tomography–Derived Neuroretinal Rim Parameter

Abstract

Objective Neuroretinal rim assessment based on the clinical optic disc margin (DM) lacks a sound anatomic basis for 2 reasons: (1) The DM is not reliable as the outer border of rim tissue because of clinically and photographically invisible extensions of Bruch’s membrane (BM) inside the DM and (2) nonaccountability of rim tissue orientation in the optic nerve head (ONH). The BM opening-minimum rim width (BMO-MRW) is a parameter that quantifies the rim from its true anatomic outer border, BMO, and accounts for its variable orientation. We report the diagnostic capability of BMO-MRW. Design Case control. Participants Patients with open-angle glaucoma (n = 107) and healthy controls (n = 48). Methods Spectral-domain optical coherence tomography (SD-OCT) with 24 radial and 1 circumpapillary B-scans, centered on the ONH, and confocal scanning laser tomography (CSLT) were performed. The internal limiting membrane (ILM) and BMO were manually segmented in each radial B-scan. Three SD-OCT parameters were computed globally and sectorally: (1) circumpapillary retinal nerve fiber layer thickness (RNFLT); (2) BMO-horizontal rim width (BMO-HRW), the distance between BMO and ILM in the BMO reference plane; and (3) BMO-MRW, the minimum distance between BMO and ILM. Moorfields Regression Analysis (MRA) with CLST was performed globally and sectorally to yield MRA1 and MRA2, where “borderline” was classified as normal and abnormal, respectively. Main Outcome Measures Sensitivity, specificity, and likelihood ratios (LRs) for positive and negative test results (LR+/LR−). Results The median (interquartile range) age and mean deviation of patients and controls were 69.9 (64.3–76.9) and 65.0 (58.1–74.3) years and −3.92 (−7.87 to −1.62) and 0.33 (−0.32 to 0.98) dB, respectively. Globally, BMO-MRW yielded better diagnostic performance than the other parameters. At 95% specificity, the sensitivity of RNFLT, BMO-HRW, and BMO-MRW was 70%, 51%, and 81%, respectively. The corresponding LR+/LR− was 14.0/0.3, 10.2/0.5, and 16.2/0.2. Sectorally, at 95% specificity, the sensitivity of RNFLT ranged from 31% to 59%, of BMO-HRW ranged from 35% to 64%, and of BMO-MRW ranged from 54% to 79%. Globally and in all sectors, BMO-MRW performed better than MRA1 or MRA2. Conclusions The higher sensitivity at 95% specificity in early glaucoma of BMO-MRW compared with current BMO methods is significant, indicating a new structural marker for the detection and risk profiling of glaucoma.

Clustering of Combined 24-2 and 10-2 Visual Field Grids and Their Relationship With Circumpapillary Retinal Nerve Fiber Layer Thickness

“…The fovea is usually located below the ONH center in fundus images, and the degree varies among individuals. 14,32 We set the reference line as the fovea-ONH center axis to minimize the influence of the variability, although the effect was not fully determined. [33][34][35][36] The 24-2 VF grid has four test points between (and including) fixation and the optic disc (i.e., test point numbers 34, 35, 44, and 45 in Fig.…”

A Global Shape Index to Characterize Anterior Lamina Cribrosa Morphology and Its Determinants in Healthy Indian Eyes

“…In addition to the LC morphological parameters, the mean minimum rim width from the BMO (BMO-MRW) was measured, as it has recently been suggested to be an anatomically accurate biomarker for glaucoma. 35 The mean shortest 3D distance from the BMO to the ILM (previous studies were in 2D 35,36 ) was measured using custom code and reported as BMO-MRW (Fig. 1D).…”

Strategies to improve early diagnosis in glaucoma

“…In order to more accurately detect structural abnormalities, it is important to choose measures that reference anatomically accurate landmarks. Following clinical observations and histological and SDOCT studies in nonhuman primates, Chauhan and colleagues recently proposed a novel, anatomically sound, structural measure for glaucoma, known as the Bruch's membrane opening-minimum rim width (BMO-MRW) (Chauhan et al, 2013). Traditionally, the outer border of the neuroretinal rim is defined by the optic disc margin; however, this is not an anatomically accurate landmark as measurements from disc margin to inner rim are affected by tissue orientation and the neuroretinal rim may extend inside the disc margin.…”

“…The BMO-MRW is a measure of minimum rim width from the true outer border of the rim, which is Bruch's membrane opening (BMO). In a study of 107 patients with early glaucoma (average MD of À3.92 dB) and 48 healthy controls, Chauhan and colleagues reported BMO-MRW to have a sensitivity of 81% for detecting glaucoma at 95% specificity, compared to a sensitivity of only 70% for cpRNFL thickness for similar specificity (Chauhan et al, 2013). In another study of 151 glaucoma patients from the same research team, Danthurebandara and colleagues report that the structure-function relationship with BMO-MRW was not significantly different from that of cpRNFL (Danthurebandara et al, 2014).…”