Researchers in Australia say they've found a simple and effective way to cut the risk of falls in elderly people who wear bifocals or other "multifocus" lens glasses: Have them wear single-lens distance glasses when they go outdoors.
Multifocus glasses correct both close and distant vision. While such glasses are convenient, studies have shown that their wearers have a high risk of falls when outside their homes and walking up or down stairs. The reason? These types of glasses impair distant depth-perception, which could impair an older person's balance.
This led researchers in Sydney, Australia, to test whether giving older people an additional pair of single-lens distance glasses for wearing when outdoors or in unfamiliar settings would help to reduce falls. It did, but only for certain older people.
"The intervention works best for older people (those 70 years old and older) who regularly leave their homes each week," Stephen Lord, of the Falls and Balance Research Group, Prince of Wales Medical Research Institute in Sydney, told Reuters Health by e-mail.
"This is the group where we saw the 40 percent reduction in falls over the year. It is less effective — and may even contribute to outside falls —in frail older people who only occasionally go outside," he noted.
"A second pair of glasses is a cost issue," Lord admitted, "but single-lens glasses are less expensive than multifocal glasses."
The study, published in the British Medical Journal, involved 606 elderly people who were 80 years old on average, who wore multifocal glasses, and who were at high risk for falling.
Roughly half of them were prescribed a pair of single-lens distance glasses and were instructed to wear them outdoors and in unfamiliar settings. They also received advice on how to cut their risk of falling. The other half, acting as the control group, continued to wear their multifocal lens and received no falls prevention advice.
Over 13 months, nearly 350 people fell about 950 times. The total number of falls in the single-lens wearers was reduced by 8 percent compared with the control group. For those who regularly went outdoors, all falls, outside falls and falls resulting in injury, fell by a significant 40 percent.
However, for those who spent more time inside, outside falls increased significantly. This, the researchers say, may indicate that more cloistered (perhaps frailer) older people are less likely to benefit from a predominantly outdoor fall-prevention intervention.
There was no indication that falls occurred at the time of switching from multifocal to single-lens glasses.
There were, however, more minor non-fall injuries — such as lacerations, burns, eye injury, collision, or lifting or twisting injuries — in the single-lens wearers than the multifocal-lens wearers (77 versus 51). This finding, which the researchers say they will report on "in detail" in an upcoming paper, "highlights the potential for unintended consequences after any alteration to eyewear in older people."
The authors of a commentary note that the people in the study were encouraged to have transition single-focus lenses, which become darker in bright sunlight. These lenses decrease glare and may have been important in those who were active outside, write John Campbell and colleagues from Dunedin School of Medicine in New Zealand. They caution, however, that while the tints in these lenses lighten when a person goes inside, the transition time can be up to two minutes.
They also note that some people in the study had single-focus lenses with a fixed or graduated tint, which, if worn inside, may have reduced visual acuity and may have increased the risk of falling.
"Older people should be advised against fixed-tint glasses and should be aware of the delayed change with some photochromic lenses," Campbell and colleagues conclude.
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