Telescopic spectacles are frequently prescribed for visually impaired patients, but clinical observation reveals that low vision patients often do not achieve expected functional use of these costly visual aids. This may be a result of patients’ inability to maintain adequate stability of magnified images on the retina during unintended head movements caused by ambulation, tremor, and postural instability. Although the visual-vestibulo-ocular reflex (VVOR) produces eye movements that partially compensate for head movements, this compensation is incomplete when images are magnified by head-mounted telescopes.1 It has been demonstrated in normally sighted subjects wearing telescopic spectacles that head motion significantly decreases dynamic visual acuity (DVA), the acuity during head motion.2 We hypothesized that insufficient compensation of head instability might cause reduced DVA and motion sickness, and might thus predict failure of low vision patients to make functional use of telescopic spectacles. We have been testing this retinal image instability hypothesis to develop methods that may be useful in prediction of the successful use of telescopic spectacles.