Air Pollution May Increase the Risk of Glaucoma and Cataracts, Study Finds

Aging is one of the biggest risk factors for glaucoma and cataracts. However, a review of 41 studies suggests that long-term exposure to air pollution—particularly fine particulate matter known as PM2.5—may also be associated with a higher risk of developing these common eye diseases.

The findings were presented in September at the 44th European Association of Cataract and Refractive Surgeons Congress in London. The studies collectively included millions of people in East Asia and the United Kingdom.

How Glaucoma and Cataracts Affect Vision

Glaucoma is a group of eye diseases that damage the optic nerve, which carries visual information from the eyes to the brain. The condition can cause permanent vision loss, often affecting peripheral vision before central vision.

Cataracts are even more common. They develop when the eye’s lens becomes cloudy, causing blurred vision and, in severe cases, blindness.

Age increases the risk of both conditions, as do certain medical conditions, including diabetes. The new review suggests that where people live and the air they breathe may also influence their risk.

PM2.5 Shows the Strongest Link to Eye Disease

The researchers examined exposure to several air pollutants, including particulate matter of different sizes, nitrogen dioxide, sulfur dioxide, ozone and carbon monoxide.

Most of the studies estimated long-term exposure using pollution levels around participants’ homes and communities. Researchers used government monitoring systems, satellite data and computer models to estimate exposure. Some studies also examined short-term exposure and sudden eye problems, such as acute angle-closure glaucoma, a medical emergency that can rapidly cause vision loss.

The review compared pollution exposure with the incidence of glaucoma, cataracts and age-related macular degeneration (AMD), another common eye disease that affects the retina and can impair clear, detailed vision.

PM2.5—particles smaller than 2.5 micrometers—showed the clearest association with glaucoma and cataracts.

• People with the highest PM2.5 exposure were 70% more likely to develop glaucoma than those with the lowest exposure.
• An increase in PM2.5 exposure corresponding to the difference between the 25th and 75th percentiles within each study was associated with 8% higher odds of glaucoma.
• The same exposure difference was associated with a 4% higher risk of cataracts.

The evidence linking air pollution with AMD was less consistent. Other pollutants also showed weaker or inconsistent associations with eye disease. Nitrogen dioxide was not significantly associated with AMD, ozone was not associated with cataracts, and neither pollutant was associated with glaucoma. Sulfur dioxide and PM10 were not significantly associated with any of the three conditions.

Researchers Warn That the Findings Do Not Prove Cause and Effect

The study was observational, meaning it can identify an association but cannot prove that air pollution directly causes glaucoma or cataracts.

The review’s findings on PM2.5 and glaucoma were relatively consistent across the studies, according to Nidhi Singh, an environmental epidemiologist at Germany’s IUF Leibniz Institute for Environmental Medicine, who was not involved in the research. The evidence linking PM2.5 with cataracts was more variable but still moderately consistent.

Singh cautioned that the results do not establish a causal role for PM2.5 in glaucoma or cataracts on its own. Instead, they support a possible relationship that requires further research.

How Air Pollution Could Damage the Eyes

The biological mechanisms behind the association remain unclear. However, researchers suggest that fine particles may be absorbed into the body and trigger oxidative stress, a condition in which harmful molecules overwhelm the body’s natural defenses.

Air pollution may also contribute to chronic, low-grade inflammation, in which the immune system remains mildly activated for an extended period.

In the eye’s lens, oxidative stress and inflammation could damage crystallin proteins that help keep the lens transparent. This damage may cause the lens to become cloudy, leading to cataracts.

In the optic nerve, similar processes may damage retinal ganglion cells, specialized neurons that transmit information from the retina to the brain. This could contribute to glaucoma independently of eye pressure, which is already a major glaucoma risk factor.

Because the eye’s surface is in direct and continuous contact with outdoor air, pollutants may have a potentially direct route to affect eye tissues.

Previous Research Also Links PM2.5 With Eye Damage

Other studies have provided clues that may support a connection between PM2.5 exposure and eye disease.

In one animal study, mice exposed to ambient PM2.5 for nine months developed increased pressure inside the eye, a known risk factor for glaucoma. Researchers also observed oxidative and nitrogen stress in tissues involved in draining fluid from the eye, which may help explain the rise in pressure.

Research involving people and human cells has shown similar patterns. Data from more than 480,000 participants in the UK Biobank suggested that people exposed to higher PM2.5 levels were more likely to develop glaucoma over time.

In another study, scientists exposed laboratory-grown human retinal tissue made from stem cells to PM2.5 particles. The exposure was associated with disrupted retinal cell development, including increased cell death among retinal ganglion cells.

These findings offer possible explanations for how air pollution could affect the eyes. However, researchers say it remains unclear exactly how these mechanisms combine in the human body.

This article is for informational purposes only and does not provide medical advice.