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Balwantray C. Chauhan, Neil O'Leary, Faisal AlMobarak, Alexandre S. Reis, Hongli Yang, Glen P. Sharpe, Donna M. Hutchison, Marcelo T. Nicolela, Claude F. Burgoyne; Enhanced Glaucoma Detection With An Anatomically Accurate Spectral Domain OCT Derived Neuroretinal Rim Parameter. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1745.
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Rim assessment based on the clinical disc margin (DM) lacks a solid anatomical basis for two reasons. 1) the DM is not a reliable outer border of rim tissue due to clinically and photographically invisible extensions of Bruch’s membrane (BM) inside the DM1 and 2) rim tissue orientation in the ONH is unaccounted for. We introduced a parameter, BM opening-minimum rim width (BMO-MRW),2 that quantifies the rim from its true anatomical outer border and accounts for its variable trajectory in the measurement plane. Here we report its diagnostic capability.
Glaucoma patients (n = 107) and normal controls (n = 48) had Spectralis SD-OCT imaging (24 B-scans centred on the optic nerve head). The median (IQR) age and mean deviation were 69.9 (64.3, 76.9) and 65.0 (58.1, 74.3) yrs, and -3.92 (-7.87, -1.62) and 0.33 (-0.32, 0.98) dB respectively. The internal limiting membrane (ILM) and BMO were manually segmented in all B-scans and two parameters (Fig 1) derived with custom software: 1) BMO-horizontal rim width (BMO-HRW), the distance between BMO and ILM in the BMO reference plane, akin to current BMO-based measurements and 2) BMO-MRW, the minimum distance between BMO and ILM. Global and 6 sectoral Moorfields Regression Analysis (MRA) from Heidelberg Retina Tomograph scans yielded MRA1 and MRA 2 where "borderline" was classified as normal and abnormal respectively. Diagnostic performance was evaluated in Receiver Operating Characteristics (ROC) space.
In controls, BMO-MRW was significantly more correlated to age than BMO-HRW (r = -0.26 and -0.06, P <0.01) or BMO area (r = -0.46 and -0.07, P < 0.01). Global BMO-MRW had consistently higher discrimination than global BMO-HRW (Fig 2). At 95% specificity, the sensitivity of BMO-MRW was 83% and BMO-HRW, 25%. Both MRA1 and MRA2 performed substantially worse. Sectorally, at 95% specificity, the sensitivity of BMO-MRW ranged 56-81%, and BMO-HRW, 10-46%. BMO-MRW performed better than MRA1 or MRA2 in all sectors.
The >3-fold higher sensitivity at 95% specificity in early glaucoma of BMO-MRW compared to current methods is clinically significant, indicating a new structural marker for the detection and risk-profiling glaucoma.1Reis et al, Ophthalmology (in press)2Reis et al, submitted
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