Purpose
To assess the magnitude and direction of mismatch between BMO and ASCO within SDOCT ONH scans of 131 ocular hypertension and glaucoma patients.
Methods
Both eyes of 131 patients (aged 33-90) underwent SDOCT (Heidelberg Spectralis, 870nm) ONH imaging (48 high-resolution, ONH centered, radial B-scans). Data from one eye per patient was chosen based on optimal scan quality. BMO and ASCO were manually delineated within each SDOCT data set (Figure 1) and 12 ONH sectors were established based on the Foveal-BMOcentroid (FoBMO) axis. Eyes without visible BMO or ASCO in any sector were eliminated from the study. The direction and magnitude of the BMO-ASCO centroid axis was determined and the mean BMO and ASCO radii were quantified for each of the 12 sectors. The average BMO and ASCO radii and the distribution of differences (ASCO-BMO) among all 131 eyes were analyzed by sector.
Results
All sectors showed significant mismatch (p<0.001) between BMO-ASCO except the inferior temporal and temporal inferior sectors (Fig 2a). Mismatch between BMO and ASCO was greatest in the nasal superior, nasal, superior nasal, nasal inferior, and superior sectors (Mean difference ± SD: 145 ± 87.5, 135 ± 94.0, 127 ± 72.5, 113 ± 90.1, 96 ± 57.4, respectively) with substantial variation across eyes and locations (Fig 2b).
Conclusions
This is the first characterization of SDOCT detected BMO-ASCO mismatch in eyes of glaucoma patients. Our data suggest that in the subset of eyes that could be studied, the frequency and magnitude of BMO-ASCO mismatch is greatest in the superior and nasal sectors, however in some eyes it extends along the superior nasal- inferior temporal axis or less commonly involves all 12 segments of BMO. Since the ASCO and BMO are connected by the Border Tissues of Elshnig (BTE), ASCO-BMO mismatch contributes to the regional location of “internally oblique” and “externally oblique” BTE as previously described by Strouthidis, et al, IOVS 2009 and Reis, et al, Ophthalmology. 2012. The implications of these findings for cross-sectional and longitudinal studies of SDOCT ONH imaging are under study.
Keywords: 629 optic nerve •
708 sclera •
438 Bruch's membrane