Eating more green leafy vegetables can protect your eyes from a common eye condition called glaucoma, according to latest study.

Researchers from Harvard Medical School have found that increasing intake of green leafy vegetables can reduce the risk of glaucoma by up to 30%.

Glaucoma, also called primary open-angle glaucoma (POAG), is an eye condition that causes an abnormal high pressure in the eye and damages the optic nerve. The condition can gradually lead to losing eye sight.

We found those consuming the most green leafy vegetables had a 20 to 30 percent lower risk of glaucoma. Jae Kang, an assistant professor at Boston's Harvard Medical School and lead author of the study said.

Green leafy vegetables such lettuce, kale, spinach and broccoli are rich in dietary nitrate which can improve the blood flow in the eye.

For the study, researchers have followed up more than 100,000 men and women for over 25 years, nearly 60,000 women from Nurses Health Study (1984-2012) and around 41,000 men from Health Professionals Follow-up Study (1986-2012).All participants were 40 years or older. None of them had glaucoma at the start of the study but 1,483 people developed the eye condition in subsequent years.

Researchers have found that those who ate more green leafy vegetables, a cup and half a day, were 20 to 30% less likely to develop glaucoma than those who consumed the least.

In glaucoma, we think there is an impairment of blood flow to the optic nerve, said Kang. And an important factor that regulates blood flow to the eye is the substance called nitric oxide. When you consume the higher amount of green leafy vegetables, you have greater levels of nitric oxide in your body.

Glaucoma is not curable yet and once a person loses its vision, it cannot be regained. In United States, more than 3 million people have glaucoma which results in blindness in more than 120,000 people, according to Glaucoma Research Foundation.

Glaucoma is the second leading cause of blindness in the world, accounting almost 12% of all causes of blindness.