Ditch the bifocals when outside & reduce falls
Researchers find single lens distance glasses lower the number of falls in active older people
26th May 2010 - Providing single lens distance glasses to older people who wear multifocal glasses and who regularly take part in outdoor activities is a simple and effective way of preventing falls, concludes a study published today on bmj.com.
However, the researchers, from Australia, warn that this strategy may not be appropriate for frailer people who spend more time indoors.
Presbyopia (a progressively diminished ability to focus on near objects) is the most common form of impaired vision in older people. To correct this condition, people are either prescribed separate single lens glasses for distant and near vision or, for convenience, a single pair of multifocal glasses, usually called bifocal, trifocal or varifocal (sometimes called progressive lens) glasses.
Multifocal glasses have benefits for tasks that require changes in focal length, such as driving, shopping and cooking, where the wearer has to change quickly from focussing on distant to near objects. However, they also have optical defects which can impair balance and increase the risk of falls in older people.
The lower lenses of all types of multifocal glasses blur distant objects in the lower visual field, and this factor in particular may represent an important problem for older people. Multifocal glasses have also been shown to impair depth perception and reduce contrast. Three recent studies in older people have found they also impair step negotiation and accuracy of foot placement when stepping on to a raised surface.
The researchers in Sydney set out 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.
The study involved 606 people who were at high risk of falling (either aged over 80 or over 65 with a history of falls). All participants used multifocal glasses at least three times a week when walking outdoors and did not use single lens distance glasses.
Participants were randomly split into an intervention and a control group. After an initial examination by an optometrist, 305 intervention participants were prescribed a pair of single lens distance glasses for wearing outdoors and in unfamiliar settings, and were instructed in their use.
The optometrist told participants to use their new single lens glasses for most walking and standing activities. In particular they were instructed to use them when walking up or down stairs outside the home, walking in the street and at shopping centres, walking or standing in other people’s homes and unfamiliar buildings, negotiating rough or uneven ground and getting off public transport.
The intervention group participants were also provided with a booklet and reminder cards (with instructions on appropriate use of glasses) and a glasses cord or cloth glasses holder that could be worn around the neck or placed in the participant’s pocket to help the swapping of glasses.
They were also shown how multifocal glasses can increase the risk of falls.
The remaining control participants had the same optometrist examination as the intervention group, but were not provided with single lens glasses and received no falls prevention advice.
No other fall prevention interventions, including strength and balance training, were offered to either the intervention or control participants.