A total solar eclipse is a phenomenon that could bring millions outside to watch the moon completely cover the sun. However, looking directly at the sun can be dangerous and even lead to blindness.

How can you safely experience this likely once-in-a-lifetime phenomenon?

Dr. Brianne Scanlon, a Marshfield Clinic optometrist, says staring directly at the sun can damage the retina, which is the light-sensitive part of your eye.

“Staring at the sun can cause a condition called solar retinopathy,” Scanlon said. “This is a condition where the harmful UV rays from the sun damage retinal tissue. Essentially, the retinal gets ‘cooked’ from the sun. This damage to the cells within the retinal tissue can cause vision to be lost or distorted, and if the degree of damage is great enough, vision loss could be permanent.”

Other symptoms you may notice are increased sensitivity to light, watering eyes, or general eye discomfort or soreness. No true treatment for solar retinopathy is available at this time other than treating the discomfort. Over time damaged retinal cells may heal, but there’s no guarantee.

Since the brain does not interpret the light as pain, you will not know if you have looked at the sun or eclipse for too long. As a result, staring at the sun can cause blurry vision and temporary or even permanent blindness.

Your brain can’t process if the damage is permanent or not,” Scanlon said. “Even if you stared at the sun for a second, that small glance can lead to blindness. So it’s very important to never stare directly at the sun.”

If you are really interested in viewing the solar eclipse, here are two safe ways:

Wear special eclipse glasses

They are inexpensive and some libraries are even giving them out for free.

“Normal sunglasses do not filter out enough harmful UV rays to make staring directly at the sun safe,” Scanlon said. “These eclipse glasses are created with a safety standard that needs to be followed.”

According to NASA, eclipse glasses should have an ISO 12312-2 international standard and the manufacturer’s name and address printed somewhere on the product. They should not be used if they are older than three years or have scratched lenses.

Use a pinhole projector

Another way to view the eclipse is through a pinhole projector. Sunlight streams through a small hole such as a pencil hole in a piece of paper, or even the space between your fingers onto a makeshift screen such as a piece of paper or the ground.

“Only look at the projected image on the screen,” Scanlon said. “Do not look at the sun through the pin hole since the sun’s rays can still go through the hole.”

If you have questions about protecting your eyes from viewing a solar eclipse, contact your provider.