Vestibular dysfunction linked to visual impairment falling risk
medwireNews: Vestibular balance contributes to the risk for falls in individuals with visual impairment (VI), say US researchers.
Patients with VI or uncorrected refractory error (URE) found it significantly harder than individuals with normal vision to balance on a foam surface with their eyes closed for 30 seconds without falling over or correcting balance with their arms or legs, report Pradeep Ramulu (The Johns Hopkins University School of Medicine, Baltimore, Maryland) and co-authors.
This test, performed in 4590 patients aged over 40 years, and designed to measure vestibular balance by minimizing visual and perioceptive inputs, was failed by 72.6% of VI participants, 44.4% of URE participants, and 34.0% of controls.
For each 10-line decrease in visual acuity, VI and URE patients were 1.7 times more likely to fail the test, after adjusting for balance-associated factors, such as age, gender, and comorbidity.
Writing in JAMA Ophthalmology, the researchers say this finding was "surprising given that eye closure would be expected to neutralize the effect of decreased vision on balance."
"Our results suggest that balance abilities resulting from individual senses are not necessarily independent of each other. In particular, balance difficulties associated with refractive and nonrefractive vision loss may at least partially be due to vestibular dysfunction, which would continue to manifest itself under eyes-closed conditions," they continue.
In addition, significantly more VI patients self-reported falling difficulties than controls (15.6 vs 3.9%), and there was a trend toward more difficulties in URE patients, although this did not reach significance.
Self-reported falling difficulties were also significantly associated with presenting visual acuity and refractometer visual acuity, with odds ratios of 3.3 and 3.7 per 10-line change in visual acuity, respectively.
By contrast, there was no significant difference in the ability of participants in the three study groups to balance on foam with eyes open for 30 seconds, or on a firm surface with open or closed eyes for 15 seconds. Just 3.3% of VI participants, 2.6% of URE participants, and 0.7% of control participants failed the eyes-open foam test, and 6.5%, 2.5%, and 1.7% failed the firm surface test, respectively.
"Reduced visual inputs may weaken the vestibulo-ocular reflex, an important system that maintains the effectiveness of vestibular balance," the authors hypothesize.
"Alternately, common degenerative pathways or lower physical activity levels may affect balance, particularly among those with VI."
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By Lynda Williams, Senior medwireNews Reporter