People living in areas with higher levels of air pollution may have an increased risk of developing glaucoma and cataracts, according to a systematic review and meta-analysis presented at the 44th Congress of the European Society of Cataract and Refractive Surgeons (ESCRS). The study has not yet undergone peer review.
The research, presented by Ahmed Alnabihi of the King Khaled Eye Specialist Hospital and Research Center in Saudi Arabia, pooled data from 41 observational studies, involving millions of people, predominantly across East Asia and the United Kingdom. The investigators analyzed exposure to different pollutants, including fine particles (PM2.5 and PM10), nitrogen dioxide, sulfur dioxide, ozone, and carbon monoxide, and compared them with the occurrence of glaucoma, cataracts, and age-related macular degeneration.
Results indicate that the higher the exposure to fine particles PM2.5, the greater the risk of glaucoma. People living in the most polluted areas had up to 70% higher odds of developing the disease than those living in the least polluted areas. A consistent association was also identified between higher pollution levels and an increased risk of cataracts, with the risk rising as exposure increases.
“For years we have known that air pollution damages the lungs and heart, but its effects on the eyes have been far less studied, and the existing evidence was scattered and inconclusive,” says Ahmed Alnabihi.
“Every day we see patients losing their vision due to conditions such as glaucoma and cataracts. These diseases are classified as age-related, as if aging were the sole culprit, but that has always seemed incomplete to me. If something in the environment is accelerating these conditions, it changes how we think and suggests that we can take action to reduce the risks,” he adds.
According to the researchers, for each meaningful increase in pollution exposure, the risk of glaucoma rose by about 8% and the risk of cataracts by about 4%. The association with age-related macular degeneration was less consistent, although some of the studies analyzed indicated a possible link. For other pollutants, such as nitrogen dioxide and ozone, the associations were weaker or produced less uniform results.
“Fine particles are tiny particles found in smoke, vehicle exhaust, and industrial pollution, small enough to penetrate deep into the body. For each substantial increase in pollution exposure, the risk of glaucoma rose by about 8% and that of cataracts by about 4%,” explains Ahmed Alnabihi.
A possible explanation lies in the inflammatory effects and oxidative stress caused by fine particles. According to the researchers, prolonged exposure could damage the optic nerve, associated with glaucoma, or the lens, in the case of cataracts. The eyes also display particular vulnerability because they are directly exposed to the environment.
“The ocular surface — the tear film, the conjunctiva and the cornea — has no barrier between them and the exterior air. This makes the biological plausibility here stronger than for some other organs,” says the researcher.
The authors argue that the results reinforce the need for stricter air quality standards and measures aimed at reducing pollution, including the creation of green spaces and reducing traffic in cities.
“All major clean air policies have been justified primarily by the health benefits to cardiovascular and pulmonary health. Our work adds a new organ system to that discussion. Policymakers who need to justify investments in emission controls now have another evidence-based reason to do so, and it is a reason that affects our vision — a sense that people are particularly afraid to lose,” emphasizes Ahmed Alnabihi.
However, the researchers consider that more studies are needed, particularly on ocular health in regions with very high levels of air pollution.
Filomena Ribeiro, former president of ESCRS and head of the Ophthalmology Department at Hospital da Luz in Lisbon, who did not participate in the study, highlights the dimension of the two diseases.
“Cataracts, in which the eye’s lens becomes cloudy, cause blurred vision and vision loss. They are the leading cause of visual impairment worldwide, affecting about 94 million people. In glaucoma, the main nerve connecting the eye to the brain becomes damaged, leading to vision loss if the disease is not diagnosed and treated early. Globally, glaucoma affects about 7.7 million people,” she says.
“Both diseases become more common as we age, but this study indicates that people exposed to higher levels of air pollution also face an increased risk. This investigation adds eye health to the growing list of reasons to worry about air quality,” she concludes.
