In 1784, Benjamin Franklin created bifocal glasses so he
could see clearly up close and far away using the same lenses.
He suffered from presbyopia, or loss of flexibility
in the eye lenses, as do virtually all people by their 50s.
Despite their obvious convenience, bifocal glasses may be
dangerous for the elderly, based on a study in the Journal
of the American Geriatrics Society.
Falls in seniors are common and can have severe consequences,
such as hip fractures and even death. Researchers examined
a possible link between multifocal glasses (bifocals, trifocals
or progressive lenses) and risk of falling in more than 150
people ages 63-90. Subjects also were examined to assess different
abilities while wearing the lenses.
Seniors who wore multifocal glasses (nearly all wore bifocals)
were more than twice as likely to fall over one year as those
who did not, and even more likely to fall due to tripping,
when negotiating a staircase or when away from home. These
individuals also performed significantly poorer on tests of
depth perception and edge-contrast sensitivity.
As you get older, consider owning two separate pairs of glasses
if you have presbyopia - one pair for near vision, the other
for distance. Although keeping two pairs may be less convenient,
it may save you from a dangerous fall. If you insist on wearing
multifocal lenses, remember to be especially careful when
traveling outside of your home and on uneven surfaces.
Lord SR, Dayhew J, Howland A. Multifocal glasses impair
edge-contrast sensitivity and depth perception and increase
the risk of falls in older people. Journal of the American
Geriatrics Society 2002:50(11), pp. 1760-1766.
To read more on senior health, check out http://www.chiroweb.com/find/archives/senior.