Glaucoma is a condition where your optic nerve is damaged by the pressure of the fluid inside your eye.

It’s one of the leading causes of blindness worldwide and the damage is currently irreversible.

But now scientists in America say the more fit and active you are, the less likely you are to develop glaucoma in the first place.

And the news has been welcomed by leading UK laser eye surgeon David Allamby, who says physical activity can also ward-off other vision diseases, such as age-related macular degeneration and cataracts.

The new research was conducted by experts from Iowa State University and the University of South Carolina.

Lead author Dr. Duck-chul Lee analysed data from more than 9,500 people between ages 40 and 81 enrolled in a long-term study at the Cooper Clinic in Dallas, Texas.

Participants were measured for their aerobic fitness – by way of treadmill tests – and how much exercise they conducted in a typical week.

They were then monitored for glaucoma during a six year follow up period.

In total, 128 cases of glaucoma were reported.

And Dr Lee found that those who were the most active and the fittest had only half the risk of developing glaucoma as the least-active, less-fit group.

And running 10 miles per week, at a 10-minute mile pace, was enough to put participants into the fittest and most-active category.

Writing in the journal Medicine & Science in Sports & Exercise, Dr Lee adds: “A joint analysis of physical activity and fitness showed that meeting physical activity guidelines and being in the high fitness category was associated with the lowest risk for developing glaucoma.”

Dr Lee says glaucoma is down to ‘intraocular pressure’ – ie, a build-up of pressure in the eye when fluid is unable to drain properly.

This increase in pressure then damages the optic nerve.

And leading British vision expert Mr Allamby, medical director of London’s Focus Clinic, says exercise could reduce intraocular pressure – though the precise mechanisms are still not fully understood – and more data is needed.

He explains: “How exercise lowers intraocular pressure is still not known for certain. We know pressure in the eye can rise during exercise and then fall lower afterwards.

“Exercise could help increase blood perfusion to the optic nerve, helping protect the eye even though eye pressure rose during exertion.

“Diet can also play a role in preventing glaucoma.

“Diets that are plentiful in vegetables and fruit seem to be protective against glaucoma, cataracts and age-related macular degeneration, while diets with more meat and nuts may increase the risk of oxidative stress-related eye diseases.

“Also, consumption of food-derived antioxidants like β-carotene, lutein and zeaxanthin appear to be useful for the treatment of macular degeneration and cataracts.

Mr Allamby also says an active lifestyle could be vital to maintaining vision as we age, possibly through a reduction in low-density lipoprotein “bad” cholesterol (LDL-C).

He adds: “Keeping cholesterol levels low doesn’t just prevent heart disease, it may also be important in preventing cataracts.

“A 2018 article in the British Medical Journal highlighted that elevated cholesterol (LDL-C) and triglycerides in the blood were strongly associated with developing age-related cataracts.

“Meanwhile just being outside – and bathed in natural light – during physical activity could help prevent short-sightedness, particularly among the young.

“Dopamine is produced in the eye in response to sunlight, and acts in the retina as a neurotransmitter which helps different cells talk to each other, deciding how the eye develops.

“In particular, dopamine is a vital aspect in how the eye grows, and if it develops a refractive error requiring the use of glasses.

“It affects the size of the eye. And the length of the eye is the important determining factor in how the eye focuses light and what the prescription of the eye will be.”

According to London’s Moorfields Eye Hospital, around two per cent of the population over 40 years old have glaucoma, and around 500,000 Brits overall.

It develops slowly over many years, affects the peripheral vision first, and is often only picked up during routine eye tests.

Symptoms can include blurred vision, or seeing rainbow-coloured circles around bright lights. Both eyes are usually affected, although it may be worse in one eye.

Although it’s not possible to reverse any sight loss caused by glaucoma, further damage can be prevented through eye drops, laser surgery to open up the blocked drainage tubes or reduce the production of fluid in your eyes.

Worryingly, recent research conducted by the National Eye Research Centre estimated that due to an ageing population, glaucoma will affect 3.2 million people in the UK by 2050.

Speaking in March this year, CEO of the National Eye Research Centre, Mike Daw, said: “We’ve found that while detection rates are increasing over time, the symptomless nature of glaucoma in its early stages means that in 2050, almost two million people may be affected, but will probably be completely unaware that they may be heading towards permanent sight loss.”

It’s also not the first time exercise and running has been linked to the prevention of glaucoma.

In 2012 The American Academy of Ophthalmology reported how those who took part in moderate physical activity were 25% less likely to develop the condition compared to those people that were largely inactive.

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