Structural dissociation of optic disc margin components with optic disc tilting: a spectral domain optical coherence tomography study.

PURPOSE: To investigate the dissociation of the Bruch's membrane opening (BMO) from the scleral canal opening (SO) of the optic disc.

METHODS

In this prospective, cross-sectional, observational study, 101 eyes from 101 patients or suspected subjects of primary open angle glaucoma were included. Enhanced depth imaging spectral domain optical coherence tomography images along the long axis of the optic disc were used to visualize better the deep structures around the optic disc on both the temporal and nasal sides. The distances between the BMO and SO were measured at the temporal and nasal sides of the optic disc, and their correlations with age, axial length, intraocular pressure, disc size, disc ovality index, disc torsion degree, and visual field mean deviation were investigated.

RESULTS

The temporal and nasal distances of BMO from SO correlated significantly with each other (R = 0.632, P < 0.0001). By multiple linear regression analysis, significant correlations were found for disc ovality index (temporal: β = -0.691, P < 0.0001; nasal: β = -0.420, P < 0.0001) and axial length (temporal: β = 0.224, P = 0.002; nasal: β = 0.310, P = 0.001). The other factors did not show any significant correlation.

CONCLUSION

Locations of the SO at not only the temporal, but also the nasal side of the optic disc are nasally shifted from the BMO with optic disc tilting and axial length elongation in glaucomatous eyes, and are significantly correlated to each other. The nasal shift of the deep structures of the optic disc should be considered especially when assessing myopic eyes with optic disc tilt.