Adaptive gait changes in older people due to lens magnification.

PURPOSE

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.