No / Purpose. To determine whether gait alterations due to monocular spherical lens blur were a safety strategy or driven by lens magnification. Methods. Adaptive gait and visual function were measured in 10 older adults (mean age, 74.9 4.8 years) with the participants' optimal refractive correction and when monocularly blurred with 1.00 DS and 2.00 DS lens over the dominant eye. Adaptive gait measurements for the lead and trail foot included foot position before the raised surface, toe clearance of the raised surface edge, and foot position on the raised surface. Vision measurements included binocular visual acuity, contrast sensitivity, and stereoacuity. Results. Equal levels of monocular positive and negative spherical lens blur led to very different stepping strategies when negotiating a raised surface. Positive blur lenses led to an increased vertical toe clearance and reduced distance of the lead foot position on the raised surface. Negative lenses led to the opposite of these changes. Conclusions. Findings suggest that step negotiation strategies were driven by the magnification effect provided by the spherical lenses. Steps appeared closer and larger with magnification from positive lenses and further away and smaller with minification from negative lenses and gait was adjusted accordingly. These results suggest that previously reported adaptive gait changes to monocular spherical lens blur were not safety strategies as previously suggested but driven by lens magnification. The significance of these findings in terms of prescribing large refractive changes in frail older patients is discussed.

No / Intervention trials that reduce visual impairment in older adults have not produced the expected improvements in reducing falls rate. We hypothesised that this may be caused by adaptation problems in older adults due to changes in magnification provided by new spectacles and cataract surgery. This study assessed the effects of ocular magnification on adaptive gait in young and older adults. Methods: Adaptive gait was measured in 10 young (mean age 22.3 ± 4.6 years) and 10 older adults (mean age 74.2 ± 4.3 years) with the participants' habitual refractive correction (0%) and with size lenses producing ocular magnification of ±1%, ±2%, ±3%, and ±5%. Adaptive gait parameters were measured when participants approached and stepped up onto a raised surface. Results: Adaptive gait changes in the young and older age groups were similar. Increasing amounts of magnification (+1% to +5%) led to an increased distance of the feet from the raised surface, increased vertical toe clearance and reduced distance of the lead heel position on the raised surface (p < 0.0001). Increasing amounts of minification (¿1% to ¿5%) led to the opposite of these changes (p < 0.0001). Adaptation to ocular magnification did not occur in the short term in young or older adults. Conclusion: The observed adaptive gait changes were driven by the magnification changes provided by the size lenses. The raised surface appeared closer and larger with magnification and further away and smaller with minification and gait was adjusted accordingly. Magnification may explain the mobility problems some older adults have with updated spectacles and after cataract surgery.