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In The Journal of the American Medical Association, researchers estimate that approximately 14 million U.S. people aged 12 and older have "visual impairment," and that more than 11 million of them could improve their vision with corrective lenses.
The study defines "visual impairment" as visual acuity of 20/50 or worse in the better-seeing eye. Visual acuity refers to the sharpness of vision at 20 feet from an object. A person with 20/50 vision can clearly see something 20 feet away that a person with normal vision can see clearly from a distance of 50 feet.
Bad distance vision was considered "improved" if corrections boosted visual acuity to 20/40 or better. Glasses, contact lenses, or corrective eye surgery can make such corrections.
The study focused on distance vision problems (nearsightedness, or myopia), not flaws in close-up vision (farsightedness).
How's Your Distance Vision?
The report comes from Susan Vitale, PhD, MHS, and colleagues of the National Eye Institute, a branch of the National Institutes of Health.
They studied data from a series of national health surveys given from 1999 to 2002. More than 13,000 survey participants got their vision checked in a mobile examination center.
"Overall, 1,190 study participants had visual impairment, and of these, 83.3% could achieve good visual acuity with correction," write Vitale and colleagues. The researchers applied those figures to the U.S. population to arrive at their national estimates.
Fuzzy Estimate?
The figures may not be exactly right, but they indicate that many people have poor distance vision that could be corrected.
Data included 765 people (nearly 6% of the group) who forgot to bring their corrective lenses to the eye exam. Excluding those people would mean that about 5%, not 6.4%, of participants had impaired vision.
The researchers write that they "think it is appropriate" to include those participants, though they acknowledge that doing so "may result in an overestimate" of vision impairment prevalence.
On the other hand, 990 survey participants didn't take the eye exam and 938 others didn't have complete visual acuity data.
People without visual acuity data were more likely to be poor, less educated, and not white. Those traits were more common in participants with impaired vision. For that reason, the researchers caution that they may have underestimated the prevalence of visual impairment.
Either way, correcting vision problems is "an important public health endeavor with implications for safety and quality of life," write Vitale and colleagues.
SOURCES: Vitale, S. The Journal of the American Medical Association, May 10, 2006; vol 295: pp 2158-2163. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Basic Information About Vision." News release, JAMA/Archives.