We studied effects of age and horizontal duction on deformation of the optic nerve (ON) head and peripapillary retina as reflected by displacement of vascular landmarks to explore the influence of adduction tethering.Cross-sectional study.Setting: University.Single eyes of 20 healthy young adults (average age 23.9±3.9 SD) years were compared to 20 older subjects (average age 61.4±9.3) years. Observational Procedure: The disc and peripapillary retina were imaged by scanning laser ophthalmoscopy in central gaze, and 35° abd- and adduction.Deformations of the disc and adjacent PPR were measured by comparing positions of epipapillary and epiretinal blood vessels.Vessels within the ONH of younger subjects shifted temporally during adduction and nasally during abduction. Displacement of the nasal hemi-disc in adduction was greater at 38.5±1.7μm (SEM) than the temporal half at 4.1±2.1μm (P<0.001). Peripapillary retina within one radius of the disc margin underwent 7.6±1.6μm average temporal displacement in adduction in young subjects. In abduction, the young temporal hemi-disc shifted 4.4±0.6μm nasally without significant displacement in the nasal half. Older subjects' ONH showed less temporal shift and less displacement in the PPR within one disc radius (P<0.0001) in adduction; the nasal hemi-disc shifted 24.5±1.3μm compared with 4.4±2.1μm in the temporal half. There were no significant deformations of the disc during abduction by older subjects.Large horizontal duction, particularly adduction, deforms the disc and peripapillary vasculature. This deformation, which is larger in younger than older subjects, may be due to ON tethering in adduction.