In 2014, the singer Bono announced he'd been dealing with glaucoma for 20 years, and that's why he wears sunglasses all the time.

Glaucoma is a condition that occurs when fluid pressure within the eye increases, damaging the optic nerve.

It affects more than 3 million people in the U.S., half of whom haven't been diagnosed, and it accounts for up to 12% of all cases of blindness, according to the Glaucoma Research Foundation.

The most common form, primary open-angle glaucoma, happens gradually as fluid backs up in the eye. Reducing the mounting pressure can preserve eyesight, but a new survey from the Glaucoma Research Foundation reveals that only 53% of patients say they've achieved their intraocular pressure goal.

Surgery to reduce pressure can be very effective, but there are risks, so doctors may prescribe eye drops and put off surgery.

But patients may have trouble using the drops or resist surgery. That's why it's exciting that a study published in JAMA Ophthalmology found that people who use statins for five-plus years can reduce their risk of primary open-angle glaucoma by 21%.

In addition, the research found that every 20 mg/dL increase in total cholesterol is associated with a 7% increase in the risk of primary open-angle glaucoma.

It's too early to know if statins can reduce glaucoma progression, but clearly, protecting your circulatory system from excess LDL cholesterol helps protect your vision.

So aim for seven servings of produce daily, and eliminate red and processed meats and highly processed foods from your diet.