People living in and around cities such as Chicago and New York City were three to four times more likely to be diagnosed with dry eye syndrome than those in urban areas with lower levels of air pollution.
Dry eye syndrome – a deficiency in tear production – can severely hamper someone's quality of life and productivity. The condition affects up to 4 million Americans aged 50 and older. Its symptoms include excessive tearing, discomfort wearing contact lenses, and stinging and burning in the eyes.
In this new study, researchers analysed the medical records of more than 600 000 US veterans who were treated for dry eye syndrome in nearly 400 VA eye clinics between July 2006 and July 2011. The records were compared to air-pollution data collected during the same time.
While the study wasn't designed to prove cause-and-effect, the researchers said most major cities had high levels of air pollution and high rates of dry eye syndrome – 17% to 21%. Those cities included Chicago, Los Angeles, Miami and New York City.
The researchers also found that the risk of dry eye syndrome was 13% higher in cities at high altitudes.
The findings suggest that doctors need to be aware of the link between environmental conditions and dry eye, the researchers said. They recommended that doctors get an environmental history when assessing patients with the condition.
"Undoubtedly, many people living in arid and polluted cities would readily attest to the irritating effect air pollution has on dry eye," study author Dr Anat Galor, an assistant professor of clinical ophthalmology at the Bascom Palmer Eye Institute in Miami, said in a news release from the American Academy of Ophthalmology.
"Our research suggests that simple actions, such as maintaining the appropriate humidity indoors and using a high-quality air filter, should be considered as part of the overall management of patients suffering from dry eye syndrome," Galor said.
The study was presented at the American Academy of Ophthalmology's annual meeting in New Orleans.
The US National Library of Medicine has more about dry eye syndrome.