A new study, published “online first” on June 6, 2013 in JAMA Ophthalmology (formerly Archives of Ophthalmology), concludes that visually impaired individuals have a significantly greater risk of balance problems. The authors also offer suggestions to develop more effective fall prevention strategies for individuals with visual impairment or reduced visual acuity.
JAMA Ophthalmology is an international peer-reviewed journal published monthly by the American Medical Association (AMA), and is part of the JAMA Network of journals.
About the Research
The study, entitled Visual Impairment, Uncorrected Refractive Error, and Objectively Measured Balance in the United States, was authored by Jeffrey R. Willis, MD, PhD; Susan E. Vitale, PhD, MHS; Yuri Agrawal, MD; and Pradeep Y. Ramulu, MD, PhD, who represent the following institutions: Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD; the National Eye Institute, National Institutes of Health, Bethesda, MD; and the University of California/Davis Health System Eye Center.
Here is more information about the study, excerpted from the article abstract:
Importance: Further research is crucial to better understand the reason for falls in individuals with visual impairment and to develop appropriate fall prevention strategies.
Objective: To compare balance measures in individuals with normal vision, visual impairment, and uncorrected refractive error [i.e., persons who could benefit from glasses to achieve normal vision but who don’t wear glasses].
Design and Setting: Cross-sectional study based on a national survey sample.
Participants: A total of 4,590 adults, 40 years or older, participating in the 2001 through 2004 National Health and Nutrition Examination Survey.
Main Outcome Measures: Participants completed tests of standing balance with eyes open or eyes closed on a firm or [foam] surface. The main outcome measure was [the time it took to lose balance] on firm and foam testing surfaces.
Results: In eyes-closed foam surface balance testing, [there was a higher rate] of balance loss with visual impairment and uncorrected refractive error. [Loss of balance] during eyes-open or eyes-closed balance testing on a firm surface was not more common among participants with visual impairment and uncorrected refractive error.
Conclusions and Relevance: [Balance with eyes closed] on a foam surface was worse for individuals with visual impairment or uncorrected refractive error. Reduced visual inputs may weaken the vestibulo-ocular reflex, an important system that maintains balance.
More about the Study
From a study summary in The Medical News, entitled Research shows visually impaired individuals have greater risk of diminished balance:
The research … suggests that vision may play an important role in calibrating the vestibular system, which includes the bones and soft tissue of the inner ear, to help optimize physical balance. The work provides direction for more targeted studies on how poor vision impacts vestibular balance, and how to better develop fall prevention strategies for those with poor vision.
“We know that vision and balance are highly integrated in the brain, but we don’t fully understand the relative contributions of the visual, proprioceptive [i.e., the ability to sense the position and location of the body], and vestibular systems in maintaining balance and preventing falls, especially among the visually impaired,” said Jeffrey R. Willis, lead author of the study. “These results have important implications for improving balance and mobility in the U.S. population and preventing falls.”
“Future research should focus on better understanding how poor vision may affect the vestibular-ocular reflex, and thus vestibular balance,” said Willis. “Studies should also address how poor vision may lead to lower levels of physical and balance activities, as well as on how vision-related fall prevention strategies can be integrated with other fall prevention strategies to more effectively limit falls in our society.”
Information about the Study Participants and Study Limitations
From Poor Vision Tied to Poor Balance by Michael Smith at MedPage Today:
“One putative link between vision and falls is poor balance,” [the researchers] noted, but studies evaluating the issue have largely been done in clinic-based samples, where a bias exists because participants have already sought care.
To overcome that issue, they turned to the National Health and Nutrition Examination Surveys (NHNES) for 2001-2002 and 2003-2004, which reflect a representative sample of the U.S. civilian, non-institutionalized population.
In those years, participants underwent visual acuity testing, objective balance testing, and assessment of peripheral neuropathy, the researchers noted, while interviews yielded self-reported medical history and demographic data.
Of the 6,785 participants who were 40 or older, 4,590 had complete data on vision, balance, and peripheral neuropathy, including 4,201 with normal vision, 248 with an uncorrected refractive error, and 141 with visual impairment.
The finding that worse balance was associated with poor vision during the eyes-closed foam test was “surprising given that eye closure would be expected to neutralize the effect of decreased vision on balance,” Ramulu and colleagues commented.
One possible explanation, they noted, is that reduced input from the eyes weakens the vestibulo-ocular reflex, which maintains the effectiveness of vestibular balance. On the other hand, they added, common degenerative pathways or lower physical activity levels might affect balance and be especially severe among those with visual impairment.
They cautioned that about a third of the NHANES participants did not complete the tests in the study and in general those who did not complete balance testing were older and sicker than those who did, which might underestimate the effects.
VisionAware will continue to provide updates for ongoing safety and mobility research as they become available.