Abstract
Telescopic spectacles (TS) magnify images of objects on the retina. Magnification improves visual acuity, provided the magnified images are sufficiently stable on the retina. Image motion across the retina with velocity greater than 2-3°/s causes a loss of visual acuity (Westheimer and McKee, 1975; Demer and Amjadi, 1993). When vision is not magnified, retinal image motion is minimized for a wide range of head movements by the vestibuloocular reflex (VOR) augmented by visually induced tracking. Magnification places an extraordinary burden on these mechanisms when viewing is attempted through high-power headborne magnifiers such as TS (Demer et al., 1991b). The result is that even small, involuntary head oscillations accompanying static postures (Demer et al., 1991a; Goldberg, 1992) induce retinal image motion of sufficient velocity to reduce visual acuity achieved with TS (Porter et al., 1989). Head oscillations of moderate velocities, similar to those observed during walking (Grossman et al., 1988; Demer et al., 1991a) induce acuity losses that can exceed any gains due to image magnification (Demer et al., 1988).
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Goldberg, J., Porter, F.I., White, J.M., Koval, A., Schmidt, K.A. (1995). Long-Term Adaptation of Dynamic Visual Acuity to Telescopic Spectacles by Low Vision Patients. In: Mergner, T., Hlavačka, F. (eds) Multisensory Control of Posture. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-1931-7_39
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DOI: https://doi.org/10.1007/978-1-4615-1931-7_39
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