Blurring and distortion of peripheral vision — particularly the type produced by bifocals, trifocals or progressive lenses — may cause errors in foot position that can contribute to the risk of tripping and falling, especially among older adults, suggests a recent study published in the journal Optometry and Vision Science.
Such blurring typically occurs when a person looks down through the lower “reading” portion of bifocals, trifocals or progressive lenses.
“I caution patients to make sure they are looking through the top (distance) portion of these lenses while walking, especially when going down stairs,” says Dr. Meiya Liao, Coastal Eye optometrist. “Our opticians also try to call this to patients’ attention.”
Dr. Liao advises patients to use particular caution when they are wearing progressives, bifocals or trifocals for the first time. “There is sometimes an adjustment period of a few weeks as patients get used to the fact that there are essentially three different focal distances in a pair of progressives or trifocals and two different focal distances in a bifocal.”
She recommends single vision distance glasses for patients who spend a good deal of time hiking, walking or driving. This gives them a large distance viewing area for those activities.
The researchers found that participants in the study made larger foot placement errors and varied more in step position when they were looking ahead of the stepping target, instead of where they were placing their feet. Although the errors were small, they could be significant in situations where precise foot placement was critical, such as on stairs or uneven pavement.
Given the potential for serious consequences from falls, Dr. Liao noted, it is important for all patients, but especially seniors, to take time to get adjusted to a new prescription, and to look directly at where they are placing their feet when walking, especially on tricky surfaces.