Date of Award

August 2012

Degree Type

Thesis

Degree Name

Master of Science

Department

Occupational Therapy

First Advisor

Roger O. Smith

Second Advisor

Kurt Beschorner

Committee Members

Dennis Tomashek, Inga Wang

Abstract

Background: It is estimated that over 85% of adults over the age of 45 develop a condition called presbyopia (Holden et al., 2008). Multifocal lenses (MfLs) are used to functionally adapt to this condition to allow for convenient near and distance vision. However, this causes vision distortion in the lower part of the visual field at ground level while walking. Since safe ambulation relies on the lower visual field to detect obstacles (Marigold et al., 2008), and vision acts as a moderating factor for increased fall rates as individuals age (Heasley et al., 2005), there is a need to investigate the connection between MfLs, falls, and age.

Objective: This study hypothesized that when wearing MfLs, both young and middle-aged individuals would experience a significant decrease in functional gait performance when compared to wearing single lenses. In addition, non-experienced MfLs wearers would both show similar within group gait performance decrement.

Methods: Sixteen 18-35 year olds and seven 45-60 year old novice MfL wearers with no history of balance or gait impairments participated. A within-between subjects repeated measures ANOVA and t-tests evaluated the effects of MfLs and age on toe clearance, step force, and functional gait (the Dynamic Gait Index-Modified).

Results: A statistically significant difference in toe clearance and DGI-m scores were found for young and middle-aged individuals between lens conditions. Young group: increase in toe clearance (t=4.801, p=.000) and decrease in DGI-m scores (t=-3.9, p=.001); Middle-aged group: increase in toe clearance (t=3.230, p=.018) and decrease in DGI-m (t=3.092, p=.021). No significant difference between groups was found (DGI-m F=.020, p=.836, toe clearance F=.015, p=.905, and maximum force F=.463, p=.505). Due to the multiple t- tests performed, an adjustment of a .0125 alpha was used for a significance threshold.

Conclusion: MfLs appear to not only degrade visual performance, but also degrades key components of gait performance. The results of this study provided evidence that contributes to the validation of MfLs as a possible fall risk.

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