Abstract
Purpose :
To measure spatial configurations of the anterior scleral canal opening (ASCO) and the Bruch’s membrane opening (BMO) in normal and glaucomatous eyes.
Methods :
The optic nerve heads of 193 glaucoma cases (95 primary open angle glaucoma [POAG] and 98 primary angle closure glaucoma [PACG]) and 497 healthy controls were obtained with spectral domain optical coherence tomography (Spectralis, Heidelberg, Germany). BMO and ASCO points were manually segmented from each B-scan and were fitted into ellipses. The centroid and area of BMO and ASCO were then calculated. The ASCO/BMO offset magnitude was measured as the length of the projection of the ASCO/BMO centroid vector on the BMO plane (Figure). The neural canal obliqueness was defined by the angle between the ASCO/BMO centroid vector and a vector passing through the BMO centroid and perpendicular to the BMO plane. These parameters were compared between two primary glaucoma subtypes and healthy controls using t-tests and multivariate linear regression models with age, gender, intraocular pressure, axial length, central cornea thickness, and diagnosis as independent variables.
Results :
Both the ASCO and BMO areas were larger in eyes with POAG and PACG compared to normal eyes, even after adjusting for other factors in the multivariate regression analysis. The mean ASCO/BMO offset magnitude was higher in eyes with POAG (155.55±119.48 μm) than that in eyes with PACG (101.23±107.84 μm, P=0.0017) and healthy eyes (102.17±68.25 μm, P=0.0002). The nasal-temporal component of the ASCO/BMO offset magnitude was also higher in POAG subjects but the superior-inferior component did not differ between groups. The neural canal obliqueness was 38.84±17.06°, 46.65±19.64° and 37.20±17.78° in healthy controls, POAG and PACG, respectively. In the multivariate analysis, ASCO/BMO offset magnitude was significantly associated with being male (β=26.81 μm, P<0.001), axial length (β=32.49 μm, P<0.001), and presence of POAG (β=25.6 μm, P=0.01). Neural canal obliqueness was only associated with age, gender, and axial length in the multivariate analysis.
Conclusions :
Increased ASCO/BMO offset magnitude and neural canal obliqueness are characteristics of eyes with POAG. This specific spatial configuration of the optic nerve head may have an impact on its biomechanical environment.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.