By Kathryn Doyle
NEW YORK (Reuters Heath) - Older Americans with macular degeneration tend not to travel as far from home as others with normal vision, according to a new study.
However, that was not the case among people with glaucoma, even though both conditions cause vision loss which could make traveling more difficult, researchers said.
Previous studies established that people with age-related macular degeneration (AMD) stop or restrict their driving, but not necessarily that they travel less, according to lead author Frank Curriero of the Johns Hopkins Bloomberg School of Public Health in Baltimore.
"This study uses global positioning systems to demonstrate that when AMD patients do go outside their home, that they don't go as far away from home as compared to individuals with normal vision," and tend to live a more constricted life, Curriero told Reuters Health.
"We didn't think AMD and glaucoma would have different outcomes, so that was unexpected," he said.
About two million people in the U.S. have age-related macular degeneration, which damages sharp and central vision, important for reading and driving, according to the Centers for Disease Control and Prevention.
The diseases collectively known as glaucoma damage the eye's optic nerve and often lead to the slow loss of peripheral vision. Glaucoma also affects about two million U.S. adults, but only about one million people know they have it, according to the Glaucoma Research Foundation. Neither glaucoma nor macular degeneration is reversible.
For the new study, the researchers used cellular tracking devices to record the movements of 65 older adults with age-related macular degeneration and vision loss, 84 with glaucoma and vision loss and 61 with normal vision. They tracked participants between 7 am and 11 pm for seven days, noting both their maximum distance from home each day and the total distance they traveled.
The average daily excursion, or maximum distance from home, was 5.6 miles for people with macular degeneration, 6.3 miles for people with glaucoma and 6.9 miles for those without vision loss.
For people with macular degeneration, every line they had to move up on an eye chart due to vision loss was tied to a quarter-mile decrease in the farthest distanced traveled from home.
However, that association was not as clear among people with glaucoma or in the comparison group, according to results published in JAMA Ophthalmology.
"It is very interesting that movement tracking revealed these differences as a questionnaire-based study would probably not have found them," said Usha Chakravarthy of The Institute for Ophthalmology and Vision Science at The Queen's University of Belfast in Northern Ireland, who was not involved in the study.
"Having AMD probably dents the confidence even more than glaucomatous field loss," she told Reuters Health.
A quarter-mile decrease in travel per line on an eye chart adds up quickly, Curriero said.
Vision loss can affect quality of life in many ways, though the current study only examines travel distance, he noted.
"With regards to this one metric, our AMD patients were more affected than our glaucoma patients," he said - but people with more severe glaucoma might be affected enough to reduce their travel distances as well.
It's impossible to say at this point if people with macular degeneration were taking appropriate travel precautions, consciously or subconsciously, since vision loss may logically lead to more accidents, or if they were putting unnecessary restrictions on themselves, Curriero said.
The researchers also didn't know how participants traveled - whether they drove themselves, took public transportation or got a ride from a friend or family member, for instance.
"There is always a balance between safety and independence," Curriero said. "A primary concern of ours is if their normal travel radius becomes smaller, they are less able to access care and other necessities outside of the home."
Older people with vision loss need to be proactive in thinking about how they are going to access the services they need, in choosing where and with whom they live and in learning to use public transportation, he said.
"Services directed towards individuals with AMD may have to be based in the home, or include transportation, to properly ensure that they are accessing the services they need," he said.
SOURCE: http://bit.ly/1em976O JAMA Ophthalmology, online September 12, 2013.