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Negotiating a raised surface: gait adaptations when wearing multifocal compared to single vision distance spectacles in the elderly
Author(s) -
Elliott David B.,
Johnson Louise,
Buckley John G.,
Harley Clare
Publication year - 2008
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/j.1475-1313.2007.00530_2.x
Subject(s) - gait , heel , foot (prosody) , stairs , medicine , physical medicine and rehabilitation , optometry , anatomy , engineering , philosophy , linguistics , civil engineering
Purpose: The purpose of this study was to determine the effects of wearing multifocal compared to single vision distance spectacles upon gait characteristics and toe clearance parameters when negotiating a raised surface. Epidemiological evidence indicates that elderly multifocal‐wearers are at increased risk of falling, especially on curbs or stairs. Methods: Nineteen healthy older adults (72.7 ± 4.2 years) repeatedly approached and stepped up and along a raised platform (15.3 cm high, 3 m long, 1 m wide) whilst wearing bifocal, varifocal or single vision distance spectacles. Toe clearance parameters and gait characteristics from lead limb heel contact before the platform until lead limb foot contact on the platform were assessed using a 6‐camera, Vicon motion analysis system (Vicon, Oxford, UK). Results: When wearing multifocal compared to single vision distance spectacles the trail limb was placed further from the platform ( p = 0.05) and the lead foot landed closer to the step edge at the end of the crossing step ( p = 0.003). There was also greater variability in lead and trail foot‐platform distance ( p = 0.001) and platform‐lead heel distance ( p = 0.004), when wearing varifocal or bifocal compared to single vision spectacles. There was an increased incidence of ‘inadvertent’ step contacts when wearing multifocals (seven in bifocal, five in progressive addition lenses) when the lead heel or sole (but never the toe) accidentally scuffed the apex of the platform during swing phase of the crossing step. Conclusions: Adapted toe clearance and foot placement strategies are indicative of pro‐active control strategies aimed at decreasing the risk of tripping. Despite this, precision of control of foot placement prior to the crossing step deteriorated and this led to several inadvertent foot‐platform contacts occurring when wearing multifocal spectacles. These findings suggest that the optical effects inherent in the design of multifocal spectacles, result in unreliable visual information regarding the exact location and dimensions of a raised edge. Consequently, some elderly individuals who are at high risk of falling may benefit from wearing single vision distance rather than multifocal spectacles when walking. Acknowledgements: This study was funded by a Nursing & AHP Researcher Development Award from the Department of Health and NHS R&D (grant ref: R694) and by a Nursing & AHP Fellowship from the Health Foundation, UK (grant ref: 3991/3322).