In the most polluted areas glaucoma odds run up to 70 percent higher, across 41 pooled studies
A meta-analysis of 41 observational studies from East Asia and the United Kingdom, presented by Ahmed Alnabihi of Riyadh's King Khaled Eye Specialist Hospital at the ESCRS congress in London, finds glaucoma and cataract more common where air pollution is higher. The clearest link is with fine particles: each step up in exposure went with around 8 percent more glaucoma risk and 4 percent more cataract risk, and the most polluted areas had up to 70 percent higher glaucoma odds. The data show an association, not causation.
Science··Morning
41 observational studies, six pollutants, three eye diseases
Ahmed Alnabihi of the King Khaled Eye Specialist Hospital and Research Center in Riyadh presented the analysis at the 44th Congress of the European Society of Cataract and Refractive Surgeons, ESCRS, in London. It is a systematic review and meta-analysis, a study that gathers the existing research on one question and pools the data: 41 observational studies from East Asia and the United Kingdom, drawing on millions of people and some of the largest eye-health databases in the world. The researchers set levels of six pollutants, fine and coarse particulate matter (PM2.5 and PM10), nitrogen dioxide, sulphur dioxide, ozone and carbon monoxide, against how many people were diagnosed with glaucoma, cataract or age-related macular degeneration. Alnabihi said the harm polluted air does to the lungs and heart has been known for years, while evidence on the eyes, which are directly exposed to outdoor air, had been scattered and inconclusive; he added that glaucoma and cataract are labelled age-related as though ageing were the only culprit, and that an environmental factor accelerating them would change how clinicians think about prevention.[1], [2]
Fine particles carried the clearest signal: about 8 percent more glaucoma and 4 percent more cataract per step
The strongest association was with PM2.5, the fine particles in smoke, vehicle exhaust and industrial emissions that are small enough to reach deep into the body. The higher the fine-particle level, the higher the glaucoma risk, and people in the most polluted areas had up to 70 percent higher odds of glaucoma than those in the least polluted. Cataract risk also rose consistently with pollution. Alnabihi put the gradient at around 8 percent more glaucoma risk and around 4 percent more cataract risk for every meaningful step up in exposure. Evidence for age-related macular degeneration was less consistent, though some studies supported a link, and nitrogen dioxide and ozone showed weaker or more mixed associations. Since all the pooled studies are observational, they establish an association rather than showing that pollution brings on either disease. The researchers' working explanation is that fine particles are thought to set off inflammation and oxidative stress, which over years of exposure may harm the optic nerve, the tissue that fails in glaucoma, or the lens, which clouds in cataract; the eye, they note, is open to the environment in a way most organs are not, with no barrier between the tear film, conjunctiva and cornea and outdoor air.[1], [2]
The authors want tighter air rules; 94 million people live with cataract, 7.7 million with glaucoma
Alnabihi said the findings add weight to the case for tighter air-quality standards and for measures such as green spaces and traffic reduction in cities, arguing that every major clean-air policy has so far been justified mainly by heart and lung health and that vision, a sense people are particularly afraid of losing, gives policymakers one more evidence-based reason to invest in emission controls. The researchers call for further work, including studies of eye health in heavily polluted regions. Filomena Ribeiro, head of ophthalmology at Hospital da Luz in Lisbon and the immediate past-president of ESCRS, who was not involved in the research, noted that cataract, a clouding of the eye's lens, is the commonest reason for impaired vision worldwide and affects around 94 million people, while glaucoma, damage to the main nerve linking eye and brain, affects around 7.7 million; both grow more common with age, and in her reading the study adds eye health to the reasons to care about air quality. The findings were announced as a congress presentation, so the sample and method details sit in the congress abstract rather than in a published paper.[1], [2]
