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Luke Reyes, Ruojin Ren, Juan Reynaud, Hongli Yang, Stuart Gardiner, Brad Fortune, Shaban Demirel, Claude Burgoyne; Variability of the Foveal-Bruch’s Membrane Opening centroid (FoBMO) axis angle in patients with ocular hypertension and early glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4842.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the range and measurement variability of the FoBMO angle relative to the horizontal meridian of the acquired image frame (AIF) in 191 eyes of patients with glaucoma and high-risk ocular hypertension.
Spectral domain optical coherence tomography (SDOCT, Heidelberg Engineering) scans were obtained in 191 patients (46 -90 years of age, using a pattern of 48 radial 30° B-scans centered on the optic nerve head (ONH). In the data from one eye per patient, the BMO was delineated within every other radial B-scan (24 total) and its centroid was determined. The fovea was then independently marked within the corresponding infrared reflectance image by two delineators and then re-marked by one delineator to measure inter and intra-delineator variability. The linear distance between the BMO centroid and fovea and the angle between FoBMO and the AIF horizontal (negative below, positive above) were calculated for each delineation of each eye.
The average FoBMO axis was -6.4 ± 4.0° relative to the AIF horizontal (range -16° to +6.4°. Figure 1). The average FoBMO distance was 4365 ± 280 µm (range 3599 to 5200 µm). The FoBMO axis was ≥ 10 degrees below the AIF horizontal in 21% of eyes and equal to or above the AIF horizontal in 6% of eyes. Delineation of the FoBMO axis angle was highly correlated within a delineator (R2=0.86) and between delineators (R2=0.90). Bland-Altman limits-of-agreement for intra- and inter-delineator repeatability, respectively, were 2.7° and 3.4° for FoBMO axis angle and 368 µm and 432 µm for FoBMO distance.
The range of FoBMO axis angles within this cohort is substantial and similar to a recent report (Patel, OVS 2012). These results indicate that the FoBMO axis measured using this method is sufficiently repeatable to permit reliable analysis of 30° ONH sectors oriented to this landmark. Because the FoBMO axis influences axon bundle paths and is an anatomical reference shared by nearly all human eyes, using it (rather than the AIF axes) to regionalize ONH data may personalize the interpretation of SDOCT ONH imaging.
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