When older people have their vision tested in a doctor’s office, the results might not reflect how well they actually see at home, according to a new study. Researchers suggest the difference could be due to poor lighting in people’s homes.

That could explain why people often complain of vision problems doctors wouldn’t expect based on their eye test results, the study’s authors write in JAMA Ophthalmology.

“A simple awareness of this discrepancy between vision in the clinic and home may alert the clinician to recommend increased lighting or refer these patients for an in-home evaluation by an occupational therapist or low vision rehabilitation specialist,” Dr. Anjali M. Bhorade said.

Bhorade led the study at the department of ophthalmology and visual sciences at Washington University School of Medicine in St. Louis, Missouri.

Between 2005 and 2009, she and her colleagues studied 175 people age 55 and older, 126 of whom had glaucoma, an eye condition that leads to damage of the optic nerve.

Participants went to a clinic for eye exams and were visited at home, where the researchers tested their vision and recorded light levels.

More than half of them scored better on eye tests in the doctor’s office compared to at home. The difference seemed to be greater for people with more severe glaucoma.

The researchers tested participants’ ability to read traditional eye charts from a distance and within arm’s length, and to distinguish between light and dark areas. All results were better in the office, on average.

It makes sense there would be variation between the clinic and home, Bhorade said. But she and her team did not expect the differences to be so great.

Lighting during office tests tended to be two to four times brighter than in homes.

More than three-quarters of homes had light levels below recommendations set by the Illuminating Engineering Society of North America.

Vision testing isn’t the only area in which people perform differently at home and in the office. Blood pressure readings and mental acuity tests tend to differ by location as well. For those tests, increased anxiety in the doctor’s office and more distractions at home might play a role, Bhorade told Reuters Health in an email.

Though the new findings come primarily from a group of patients with glaucoma, they have implications for older adults with and without the condition, she said.

“One danger is that a clinician may disregard a patient’s complaints of not being able to see well in their home,” Bhorade said.

Another concern could be that patients with cataracts who complain that too much glare makes it difficult to see may not qualify for cataract surgery if their vision is tested in the office, but would qualify if tested at home, she added.

“This is a significant potential problem, both under and overestimating vision problems. The former can leave patients undertreated, the latter overtreated,” Dr. Jeffrey L. Goldberg, an ophthalmologist who wrote an editorial accompanying the study, told Reuters Health.

“Thankfully I think this probably happens to such extremes only rarely,” Goldberg said. He studies glaucoma and other optic nerve diseases at the Shiley Eye Center of the University of California, San Diego.

There are many other possible explanations for differing test results between home and office, but lighting is likely a key issue and can be easily addressed, he said.

Light meters for testing levels at home or an in-home evaluation by an occupational therapist might not be options for everyone. But there is a quick and easy alternative, Goldberg said: “Try better lighting and see if it helps.”

SOURCE: JAMA Ophthalmology, online November 21, 2013.

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