7 Those simulations suggest that ON tethering force is concentrated on the temporal disc and peripapillary tissue, in the typical location where peripapillary atrophy occurs in patients with primary open angle glaucoma (POAG). This reflects duction-related peripapillary tissue deformation probably related, at least in part, to optic nerve tethering in adduction.įinite element analysis has been used to simulate mechanical stress and strain in the ONH and the peripapillary retina during horizontal eye rotation, 5, 6 and we have shown this to be especially the case in adduction. Horizontal duction compresses the temporal peripapillary choroid, more in adduction than in abduction and more in younger than older subjects. Volume reduction was greatest near the disc and significant up to three disc radii from it in younger and 1 radius in older subjects but was insignificant in abduction. Relative volume reduction in adduction was 7.5% ± 0.6% in younger ( P < 0.001) and 1.3% ± 0.6% in older ( P < 0.02) subjects. In adduction, regional choroidal volume decreased by 42.4 ± 3.4 nanoliters (nL) (standard error of the mean) in younger ( P < 0.0001) and 6.2 ± 2.6 nL in older ( P < 0.02) subjects. Regional volume changes from central gaze were determined in adduction and abduction. The choroid temporal to the optic disc underlying the region between the Bruch's membrane opening and fovea was segmented into regions that were multiples of the disc radius for determination of local choroidal thickness. In 25 younger (18–33 years) and 15 older (50–73 years) normal subjects, the disc and the peripapillary choroid were imaged with optical coherence tomography (OCT) in central gaze and 35° adduction and abduction. We investigated the effect of horizontal ocular duction and subject age on choroidal volume at the macular side of the optic disc. The optic nerve becomes tethered in adduction in most people, which deforms the disc.
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