Introduction

The Rehabilitation Research Design and Disability (R₂D₂) Center, affiliated with the College of Health Sciences (CHS) at UW–Milwaukee, is conducting an integrated set of research activities to address a seriously under-considered factor in falls research: the use of bifocal lenses. The U.S. Department of Education, through the National Institute on Disability and Rehabilitation Research (NIDRR), has awarded $450,000 over three years to fund the project. This project focuses on new users of bifocal glasses, typically individuals in their 4th or 5th decade, and targets a better understanding of falls intervention strategies related to eyeglass wear. Recommendations will be articulated not only for multifocal lens wearers, but also for the producers of lenses and biomedical engineers.

Falls and fall-related injury are a widely documented public health problem causing decreased function, suffering, increased health care costs, and even morbidity and mortality. Reasons for falls can be quite complex and are generally considered to be multifactorial. Specific to middle-aged workers, it is known that a significant number of workplace accidents occur on stairs and uneven surfaces. Common and potentially confounding what is currently known about falls risk factors in older adults, however, is the high incidence of multifocal lenses worn by this population. A seminal study conducted by Lord, Dayhew & Howland (2002) found that multifocal glasses in individuals aged 63-90 impair depth perception and edge-contrast sensitivity and multifocal lenses were observed to double the risk of falling. If we are to adequately address this risk in falls prevention programs it is crucial to understand the process of adaptation to multifocal lenses. Comparison of data from this project to the Lord et al. data will generate new knowledge about the process of adaptation to multifocal lenses with application to falls in the elderly. Additionally, it may contribute to what is known about work-place falls for middle-aged individuals.

Numerous questions prompt this investigation. They revolve around whether the multifocal eyeglass problems identified by Lord et al. develop, or if they have always been there. With the paucity of research available on these visual behaviors in middle-aged adults, it is the clinical expertise of eye care specialists that lead to generalizations about individuals who adapt to bifocal lenses, when they adapt, and those who never adapt.

The BIFOCAL Project will replicate the Lord et al. 2002 study with new bifocal wearers and begin an investigation to examine the effects of bifocals on functional mobility. Additionally, it will observe brain function during bifocal adaptation using state-of-the-science fMRI protocols.

Importance of the Problem

For a number of years, investigations to better understand falling in the elderly have focused on physical and psychosocial attributes of the faller and the physical and psychosocial factors in the environment. In 2002, the Lord et al. study unveiled a variable of potentially enormous effect. Use of bifocal and multifocal eyeglasses associated dramatically with the falls of elders. If a technology like eyeglasses–meant to improve function–has an unintended negative health effect doubling the risk of falling, substantial research to confirm and better understand this phenomenon to identify interventions has quickly launched to significant importance.

With the aging of the American population, the prevention of disability is a major focus. Falls and fall-related injury among elders are a widely documented public health problem. Recent research into falls has identified three broad domains of causal factors: personal factors (e.g. chronic disorders and neurological deficits), environmental factors (e.g. obstacles in a path of travel), and behavioral factors (e.g. activities and choices that can destabilize balance) (Connell & Wolf, 1997). Reasons for falls can be quite complex and are generally considered to be multifactorial. Common and potentially confounding to all of these domains, however, is the high incidence of multifocal lenses worn by this population.

While bifocal glasses are viewed as being convenient, the negative counterpart of bifocals is that they create visual distortions that may cause the user to not see an obstacle on the ground. In general, empirical data on the negative aspects of bifocal use is extremely limited, and literature mentioning multifocal lenses as a risk factor in falling is primarily anecdotal. For example, in Mary Tenetti’s Preventing Falls In Elderly Persons, “avoidance of multifocal glasses while walking” is listed as a management strategy for persons with decreased vision. Furthermore, she states that her recommendation of vision assessment “is based on observational data, the finding is associated with the risk of falling” (2003, p. 45) and cites no references with her recommendation. Clearly, little is known about the actual mechanisms inherent in bifocal use that make their use a risk factor for falls.

The aforementioned study conducted by Lord, Dayhew & Howland (2002) at the Prince of Wales Medical Research Institute, Randwick, University of New South Wales, Australia examined how multifocal lenses affected decreased depth perception (DP) and edge-contrast sensitivity (CS) at critical distances for detecting obstacles in the environment. They then related these variables to the risk of falling. They studied 156 individuals aged 63-90 and found that those who wore multifocal spectacles were more than twice as likely to incur a fall either outside their home or on stairs as those who wore single vision (SV) lenses or no glasses. Joerger (2003) supports these findings, documenting that the new use of bifocals in able-bodied individuals can play a contributing factor in gait with the potential to increase the risk of falling, even in a relatively young set of subjects.

If we are to adequately address these risks in falls prevention programs it is crucial to understand the process of adaptation to multifocal lenses. To this end, the BIFOCAL Project focuses on new users of multifocal glasses. The investigation targets a better understanding of intervention strategies related to eyeglass wear to prevent falls. Not only will this information be of benefit for older adult falls prevention, but it is also specific to middle-aged individuals. It is not unreasonable that the information generated from this project may impact middle-aged workers.

Project Goals & Strategies

The BIFOCAL Project specifically targets a better understanding of intervention strategies related to eyeglass wear to prevent falls. To reach this objective, the BIFOCAL Project identifies five goals, and two strategic phases to accomplish the goals.

Five Goals

1. Measure outcomes of bifocal use.
2. Understand the process of adaptation to new bifocals.
3. Explore brain function as a potential explanatory variable.
4. Draft recommendations for clinical practice and design.
5. Disseminate scientific papers and presentations to inform research, device development, and practice.

Two Strategic Phases

Phase 1: Functional Measures

Phase 1 replicates the Lord et al. dependent measures and adds a measure of functional mobility in a longitudinal design examining new bifocal wearers, typically in their 4th or 5th decade.

Phase 2: Functional Magnetic Resonance Imaging (fMRI)

Phase 2 employs fMRI in new bifocal users over their period of adaptation. While the paradigm is designed, specific parameters for Phase 2 will be revised from analysis of Phase 1 data. This study will be the first to use fMRI to observe adaptation of bifocal usage.

The purpose of Phase 2 revolves around the BIFOCAL Project’s goal to better understand brain function that may mediate the visual information received by an individual, changing how they perform physically, even to the point of falling. Classical studies in psychology demonstrate how the brain adapts to visual stimuli to optimize their functions. We also know that the neural system is designed to inhibit information to optimize functional outcomes. For example, electrical stimulation is used to provide cutaneous sensory stimulation to reduce pain. Fluent motion depends on coordinated stimulation and inhibition of relevant motor neurons.

Evidence suggests that bifocal lenses impair distance vision in the lower visual field. (Lord et al., 2002; Joerger, 2003). We know that new users of bifocal lenses often take time to adapt to bifocal use. They initially encounter an uncomfortable “seasick” feeling that resolves over use. Specifically, the brain may be helping to cause this adjustment by learning to inhibit and functionally ignore the visual data from the lower visual field. Understanding if this is the case will not only reveal key aspects of brain adaptation to the use of technology, but it will help narrow and orient intervention methods. For example, if the brain does seem to initially inhibit the integration of visual information in the lower visual field with bifocals, this information could provide the scientific reason to emphasize the need to require bifocal users to look downward while walking, or to consciously understand that a visual neglect may be occurring in the lower field.

If reduced or altered brain activity exists due to bifocal use, fMRI analysis may be able to distinguish the differences in brain function. Mapping visual cortex responses to visual stimulation has been available for some time. Moreover, our collaborator, Dr. DeYoe, has developed additional methods (Functional Field Maps) for the convenient analysis of fMRI mapping data with respect to different visual field locations.

Evaluation

Both internal and external activities will monitor the formative milestones and document the summative achievements of this project

Personnel & Partners

The BIFOCAL Project personnel and partners are made up of a highly interdisciplinary team from the R₂D₂ Center at UW-Milwaukee, Prism Clinical Imaging/the Medical College of Wisconsin, St. Marys Hospital and Medical Center Rehabilitation Services, Madison, Wisconsin, and others.

Key Personnel

Kathy Longenecker Rust, MS, OT and Roger O. Smith, PhD, OT are co-principal investigators for the project. Each brings multiple perspectives to this project. Ms. Rust has advanced training in issues related to falls in the elderly and in her most recent clinical position at St. Marys Hospital & Medical Center, she served on the two-year Nursing Research Project aimed at reducing falls in the hospital. Dr. Smith’s expertise includes outcomes measurement and interventions for people with disabilities, with specific focus on outcomes measurement methods for assistive technology and universal design.

Additional Personnel and Partners

Additional BIFOCAL Project personnel include highly-respected experts with backgrounds in biophysics and neuroscience, ophthalmology, physical therapy, assistive technology implementations, and test & measurement statistics. Project personnel and partners include:

• Edgar DeYoe, PhD, Medical College of Wisconsin. Dr. DeYoe has performed extensive research in functional neuroimaging (fMRI) of brain systems responsible for sensory perception, especially vision, and brain-related sensory pathology. He will oversee the fMRI component of Phase 2 of the study.
• Michele Stanley, PT, Rehabilitation Services, St. Marys Hospital and Medical Center of Madison, Wisconsin will oversee subject testing for Phase 1 of the study.
• Philip Taugher, MD, Occupational Therapy Department, UWM will serve as ophthalmology consultant.
• Stephen Lord PhD, Principal Research Fellow, Prince of Wales Research Institute and Linda Cieslik, PhD, Program Coordinator for Community Health – Milwaukee County Department on Aging will serve on the Research Advisory Panel.