RESNA 28th Annual Conference - Atlanta, Georgia
Abby Brayton B.S., Traceey Joerger, M.S., OTR, Kathy Rust, M.S., OTR, Roger O. Smith, Ph.D., OT, FAOTA
Rehabilitation Research Design & Disability (R2D2) Center, University of Wisconsin – Milwaukee
This literature review focuses on three studies related to the use of multifocal lenses and accidental falls. The implications of this research are discussed. Three implications for future research and design are explored: 1) training in the use of multifocal lenses; 2) awareness of negative outcomes; and 3) future design of multifocal lenses. Future design of multifocal lenses could include new optics for auto focus glasses or flip style designs.
Multifocal lens; accidental falls; bifocal lenses
Accidental falls are a large threat to the health of society. In the year 2000-2001, there were 542,000 falls resulting in visits to a hospital emergency room in people aged 45-64 in the United States [1]. In the year 2001-2002, unintentional falls were responsible for 4,134 deaths in the United States in people aged 45-64 [2]. One major study found multifocal glasses user were twice as likely to fall as nonmultifocal glasses wearers [3]. These wearers were more likely to fall due to a trip, when outside of their homes, and when walking up or down stairs. Joerger [4] investigated the use of multifocal glasses as a contributor to the risk of falling by causing impaired gait speed and quality. Multifocal lens design poses a visual problem. The bottom portions of the glasses are for near vision and blur or distort feet and walking surfaces. The current design of multifocal lenses is for convenience, and may pose problems if worn when walking.
Several key studies pose that the use and design of bifocal lenses may actually cause falling. These are reviewed and discussed as to their implications of interest to the assistive technology field.
Lord et al. [3] examined 156 community dwelling people aged 63-90. Eighty-seven of these subjects were regular wearers of multifocal lenses, meaning they wore them for all activities of daily living (ADL), including walking outside of the home. All subjects were tested on depth perception and edge contrast sensitivity. Each subject completed monthly questionnaires for one year regarding information on the number, cause, and location of any falls suffered each month and the type glasses worn at the time of each fall. When tested on depth perception and distant edge contrast sensitivity, the regular wearers of multifocal glasses performed significantly worse when forced to view test stimuli through the lower segments of their glasses.
One hundred forty-eight subjects were available for follow-up. Multifocal glasses wearers were at an increased risk of falls. The regular multifocal glasses wearers were significantly more likely to fall because of a trip, a trip outside of the home, or when walking up or down stairs. This study indicates that blurring the lower visual field impairs depth perception and edge contrast sensitivity at critical distances for detecting objects in the environment when walking. Therefore, multifocal glasses appear to increase the risk of a tripping fall by reducing the capacity of older adults to perceive obstacles in the environment. To further validate these findings, the subject’s in this study who chose not to wear their multifocal glasses when walking outside, did not have an elevated risk of falls.
Joerger [4] investigated gait speed, using the Get-Up-and-Go Test (GUGT), and quality, using the Timed-Get-Up-and-Go Test (TGUGT) under the conditions of wearing bifocals and not wearing bifocals. Thirty college students were tested on a three metered walking area with a 2x4 obstacle at the halfway point using basic non-prescriptive bifocal lined glasses with clear upper lenses. The mean average score for the TGUGT was 10.84 seconds without bifocals, and an increase of 0.45 seconds occurred with the use of bifocals. However, this was not found to be a statistically significant difference. The total mean average score on the GUGT was 1.29 while not using bifocals, with an increase of 0.34 with the use of bifocals. This difference was found to be statistically significant, suggesting that the use of bifocal glasses affect the quality of gait, which in turn, can increase the user’s risk of falling.
A third study, focusing on the behavioral factors contributing to falls [5] found eyesight behaviors to be a behavioral theme contributing to falls. Eyesight behaviors is defined as “the manner in which they compensate for, misjudge, or fail to notice details in their environment due to problems with their eyesight (p. 110).” This can include the use or nonuse of multifocal glasses. One subject in the study believes that problems with her multifocal glasses contributed to her misjudging the height of the drain on which she caught her foot and then tripped. She now tends to walk without her glasses because she feels that they restrict her vision in many ways.
Based on the limited research on the use of multifocal glasses and falling, it appears that a potential enormous health problem may be caused by the use of a very common technology used as an assistive device. A large amount of research has been reported on visual impairments and risk of falling. However, the link between eyeglasses and falling has only begun to addressed.
There are three main implications for assistive technology providers and rehabilitation specialists. 1) Rehabilitation specialists may need to train their patients in the proper use of their multifocal lenses. For example, multifocal lenses can be purchased at a drug store without any accompanying information on use or possible risks. Multifocal lenses were designed for the purpose of convenience, and are not intended to be worn when walking, yet many consumers of multifocal lenses are not provided with this information.
2) Rehabilitation specialists and assistive technology providers need to be aware of the negative aspects of assistive technology, and complete more research in the field of negative outcomes of assistive technology, including multifocal lens use. Not only do we need to be aware of the possible negative aspects of assistive technology, we also need to be prepared to deal with those negative aspects, either through consumer education or alternative choices. Educational material regarding the use of multifocal lenses may need to be developed and distributed to new users of multifocal lenses.
3) This problem has implications in the future design of multifocal lenses. To make multifocal lenses safer for users, new designs should be considered. This includes new optics for auto focus glasses, flip style designs, or glasses that signal when someone stands o walks with them.
The ATOMS Project and this work are supported in part by the National Institute on Disability and Rehabilitation Research (NIDRR), grant number H133A010403. The opinions contained in this publication are those of the grantee and do not necessarily reflect those of the NIDRR and the U.S. Department of Education.
Roger O. Smith, Ph.D., OT, FAOTA
Occupational Therapy Department, College of Health Sciences
Rehabilitation Research Design & Disability (R2D2) Center
University of Wisconsin-Milwaukee
P.O. Box 413
Milwaukee, WI 53201-0413