Here’s how air pollution can cause blindness

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Living in a more polluted area is associated with a greater likelihood of having glaucoma, a debilitating eye condition that can cause blindness, says a new study.

The findings, published in the journal Investigative Ophthalmology & Visual Science, found that people in neighbourhoods with higher amounts of fine particulate matter pollution were at least six per cent more likely to report having glaucoma than those in the least-polluted areas.

“Air pollution may be contributing to glaucoma due to the constriction of blood vessels, which ties into air pollution’s links to an increased risk of heart problems,” said study author Sharon Chua, the University College London, UK.

“Another possibility is that particulates may have a direct toxic effect damaging the nervous system and contributing to inflammation,” Chua said.

Glaucoma is the leading global cause of irreversible blindness and affects over 60 million people worldwide. It most commonly results from a build-up of pressure from fluid in the eye, causing damage to the optic nerve that connects the eye to the brain. Glaucoma is a neurodegenerative disease.

The findings were based on 1,11,370 participants of the UK Biobank study cohort, who underwent eye tests from 2006 to 2010 at sites across Britain.

The participants were asked whether they had glaucoma, and they underwent ocular testing to measure intraocular pressure, and spectral-domain optical coherence tomography imaging (a laser scan of the retina) to measure thickness of their eye’s macula (central area of the retina).

The participants’ data was linked to air pollution measures for their home addresses, from the Small Area Health Statistics Unit, with the researchers focusing on fine particulate matter (equal or less than 2.5 micrometres in diameter, or PM2.5).

The research team found that people in the most-polluted 25 per cent of areas were at least six per cent more likely to report having glaucoma than those in the least-polluted quartile, and they were also significantly more likely to have a thinner retina, one of the changes typical of glaucoma progression.

Eye pressure was not associated with air pollution, which the researchers suggest that air pollution may affect glaucoma risk through a different mechanism.

Particulate matter exposure is one of the strongest predictors of mortality among air pollutants.

This study adds to previous evidence that people in urban areas are 50 per cent more likely to have glaucoma than those in rural areas, suggesting now that air pollution may be a key contributor to that pattern.

“We found a striking correlation between particulate matter exposure and glaucoma. Given that this was in the UK, which has relatively low particulate matter pollution on the global scale, glaucoma may be even more strongly impacted by air pollution elsewhere in the world,” said study lead author Professor Paul Foster.

“And as we did not include indoor air pollution and workplace exposure in our analysis, the real effect may be even greater,” Foster added.