Abstract
Purpose :
It has been proposed that eye-movement related deformation of optic nerves could induce mechanical stress in the optic disc from which the retinal vasculature emerges. To study this phenomenon quantitatively we used OCTA for high-resolution 3D imaging of larger disc and peripapillary vessels during horizontal duction.
Methods :
Eight eyes of 5 normal adults were imaged in the 3×3 mm2 region centered on the disc using the Heidelberg Spectralis scanner in central gaze, and in 35° ab- and adduction. Deep learning was employed for automatic identification of blood vessels and Bruch’s membrane. Furthermore, we applied 3D scale-invariant feature transformation (SIFT) to extract feature points for the blood vessels. Among paired feature points in different gaze positions, we filtered for points with a distance <100 μm from large vessels. We registered vascular feature points to compute their displacements relative to the center of Bruch’s membrane opening (BMO). We reconstructed the plane of Bruch’s membrane whose normal vector defines the Z-axis (anterior-posterior). The X-axis (temporal-nasal) was defined by a line from BMO center to the fovea, and the Y-axis was perpendicular to X and Z.
Results :
In adduction, feature points in nasal disc and peripapillary region were displaced farther temporally by 10±9 μm (mean±SD), significantly more than 2±11 μm in the temporal region (p=0.0011, n=8 eyes); this indicates horizontal compression of the vascular arbor from the nasal side. Adduction also resulted 13±15 μm anterior displacement in nasal region that was significantly larger than 5±13 μm in the temporal region (p=0.0157), indicating tilting of the vascular arbor. However, in abduction temporal and anterior displacements were similar in the nasal and temporal regions, indicating absence of both horizonal compression and tilting of the vascular arbor.
Conclusions :
OCTA demonstrates that both ab- and adduction induce 3-dimensional deformations of major blood vessels emerging from the optic disc, but only in adduction is the vascular arbor tilted and horizontally compressed. These findings are consistent with optic nerve tethering in adduction but not abduction.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.