(Reuters Health) – In people who already have genetic vulnerability, air pollution of small particles known as carbon black can increase the risk of developing glaucoma, a new study shows.
The researchers found that in older men with genetic variations that made them very vulnerable to oxidative stress, long-term exposure to carbon black, pollutants associated with vehicle emissions and other combustion products, were associated with higher pressure in the eye, according to the study which was published in JAMA Ophthalmology.
"Often, when we think of glaucoma, we think of risk factors such as age and genetic predisposition and we don't think about the environment," said the study's lead author, Jamaji Nwanaji-Enwerem, MD / PhD candidate at Harvard Medical School. in Boston. "But one thing that we are beginning to appreciate is how the environment impacts health outcomes."
One area where there has not been much research is the environmental impact of eye diseases, said Nwanaji-Enwerem. So, he and his colleagues decided to look at the effects of small particles of carbon black, which are smaller than 2.5 microns in diameter and can penetrate deep into the lungs, and from there, into the bloodstream.
The researchers analyzed data from 419 older men from the Boston area who had participated since the 1960s in the larger aging study of the US Department of Veterans Affairs. They come for health examinations every three to five years after joining the study and as part of the exam intraocular pressure is measured.
Glaucoma, which can eventually cause blindness if left untreated, most often caused by high intraocular pressure, or high fluid pressure inside the eye.
"When eye pressure is too high, it causes damage to the optic nerve, the cable that connects our eyes to the brain and the visual pathway," explained Dr. Christopher Starr, an ophthalmologist at New York-Presbyterian / Weill Cornell Medicine in New York City. , who were not involved in new research. "If you lose cells in the nerve, you lose vision. Usually it starts with loss of peripheral vision and as time goes by you lose more."
For this study, Nwanaji-Enwerem's team determined pollution of men using a modeling program that included the level of carbon black collected from 83 monitoring sites and weather data.
The researchers then analyzed the pollution results along with eye pressure readings for each man and a number of other health and lifestyle factors, including BMI, smoking status, heart disease, blood pressure and diabetes.
Overall, they did not find a connection between pollution and eye pressure. But when they looked only at men who had certain gene versions that made them vulnerable to oxidative stress, the researchers found a relationship between higher levels of pollution and a slight increase in eye pressure.
While interesting, the findings of the new study need to be duplicated, Starr noted, adding that even if proven, the effects seen in this study are small. "They may not even be clinically significant in the context of glaucoma," he said.
Differences in intraocular pressure may be even more surprising if the men in the study live in places that have high levels of carbon black pollution, Starr said.
While it's clear that family history can increase your risk for glaucoma, studies of other variables that might have been mixed, said Dr. Julia Polat, assistant professor of ophthalmology at the University of Pittsburgh Medical Center in Pennsylvania, who was not involved in the new research. research.
"When patients ask, & # 39; what can I do to change my risk? & # 39; unfortunately I don't have a lot of sure information to give them," said Polat. "I told them to eat healthy, exercise and quit smoking, not necessarily because it would help with glaucoma, but because these changes can make them healthier overall."
Glaucoma is very dangerous because it generally develops without symptoms, said Starr. That is why people have to get their pressure checked regularly, he added.
"One of the ironic things, if you look at global surveys in almost all societies and cultures, the vision so far is what people value and value," Starr said. "However, people see their doctors for annual examinations, but don't see an ophthalmologist regularly."
SOURCE: https://bit.ly/2JNqelK and https://bit.ly/2FlnQnE JAMA Ophthalmology, online November 8, 2018.