Air pollution may raise the risk of glaucoma and cataracts

For years, strong scientific evidence has shown that exposure to polluted air can cause irreversible damage to the human heart and lungs. However, despite the eyes being a vital sensory organ that remains constantly and directly exposed to the outside environment and ambient air, far less evidence has been available on the harmful effects of air pollution on eye health.

The need for further research stems from the long-standing view that conditions such as glaucoma and cataracts are primarily age-related diseases, as though aging were their only cause. This perspective, however, may be incomplete. If environmental factors such as air pollution accelerate the progression of these diseases, prevention strategies would need to change, highlighting the need for stronger measures to reduce environmental risks.

Against this background, Dr. Ahmed Alnabeehi of King Khaled Eye Specialist Hospital and Research Center in Riyadh, Saudi Arabia, and his colleagues conducted a comprehensive study to investigate whether different levels of air pollution are associated with an increased risk of common eye diseases, including glaucoma and cataracts.

The researchers conducted a systematic review and meta-analysis, combining data from 41 separate observational studies. The datasets covered the health of millions of people across East Asia and the United Kingdom and included some of the world's largest eye-health databases. They compared exposure to various air pollutants—including fine and coarse particulate matter, nitrogen dioxide, sulfur dioxide, ozone and carbon monoxide—with the incidence of glaucoma, cataracts and age-related macular degeneration.

The findings showed that higher exposure to fine particulate matter was strongly associated with an increased risk of glaucoma. People living in the most polluted areas faced up to a 70% higher risk of developing glaucoma than those living in the least polluted areas. The study also found a consistent association between greater exposure to air pollution and a higher risk of cataracts, with the risk increasing as pollution levels rose.

According to the findings, each significant increase in exposure to air pollution was associated with an approximately 8% increase in the risk of glaucoma and a 4% increase in the risk of cataracts. Very fine particles originating from vehicle exhaust and industrial emissions showed the clearest associations with these diseases, while evidence for other pollutants, including nitrogen dioxide and ozone, was weaker and less consistent.

The researchers suggested that ultrafine airborne particles can penetrate deep into the body and trigger inflammation and oxidative stress, potentially causing cumulative damage over the years to the optic nerve in glaucoma or the eye's lens in cataracts. The external surface of the eye—including the tear film, conjunctiva and cornea—has no substantial protective barrier against ambient air and is directly exposed to these pollutants.

Cataracts, which cause clouding of the eye's lens and blurred vision, are the leading cause of visual impairment worldwide and affect an estimated 94 million people. Glaucoma, which damages the optic nerve, is responsible for vision loss in approximately 7.7 million people globally.

The findings, presented and published at the 44th Congress of the European Society of Cataract and Refractive Surgeons (ESCRS), further highlight the importance of expanding urban green spaces and implementing traffic-reduction policies to help protect vision.