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Navid Amini, Sara Nowroozizadeh, Arezoo Miraftabi, Ji Woong Lee, Sharon Henry, Norman Chung, Joseph Caprioli, Kouros Nouri-Mahdavi; Influence of The Disc Area on The Anatomical Relationship of the Clinical Disc Margin and Bruch’s Membrane Opening in Normal Subjects. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1016.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the mismatch between the clinical disc margin and Bruch’s membrane opening (BMO) as a function of clinical disc area (CDA) in normal eyes.
36 eyes of 36 normal subjects with optic nerve head (ONH) SD-OCT images with Spectralis SD-OCT (24 radial scans, 768 scans over 6 mm) and Cirrus HD-OCT (200x200 Optic Disc Cube) were enrolled. Eyes with a tilted or anomalous disc were excluded. The inner tip of Bruch’s membrane (BM) and the clinical disc margin were marked on radial scans and digital optic disc photographs by 2 masked clinicians. The location of the inner tip of BMO on B-scans was projected onto SD-OCT en face infrared images. The marked infrared images and optic disc photographs were registered by i2K Retina software. Magnification-corrected disc area measurements were calculated with Bennett’s formula. The main outcome measures were the regional Bruch’s membrane overhang (i.e. CDA BMO mismatch) and the difference between CDA and BMO area.
The average CDA corrected for magnification was 1.94+/-0.38mm2. A BM overhang was observed most commonly in the superotemporal (86%), superonasal (86%), and nasal sectors (72%). Eyes were divided into two groups of large and small disc area as a function of the median corrected CDA (1.93mm2). The corrected BMO area was smaller than CDA (p=0.006). The difference between the BMO and CDA was not a function of CDA (p =0.24). There was no difference in the frequency of Bruch’s membrane overhang (mismatch) in any of the sectors between the two groups (p >0.47).
BMO area was significantly smaller than CDA; however, the difference was not a function of CDA. BMO mismatch was frequent in this group of normal eyes. Eyes with smaller CDA tended to have more frequent BM mismatch in inferotemporal and nasal sectors compared to eyes with larger CDA. These relationships need to be explored in glaucomatous eyes.
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