On August 21, those lucky enough to live in its path will witness the moon completely covering the sun in the first total solar eclipse in more than three decades . The astronomical phenomenon is prompting viewing parties , school closures and visitors from around the country.

But before you feast your eyes on this wonder of nature, you should consider the proper way to protect yourself. Simply staring at the eclipse can cause a lot of harm to your vision, according to Dr. Joel Schuman , professor and chair of the Department of Ophthalmology at NYU Langone Health.

This is one of natures greatest shows but it needs to be observed safely, Schuman told HuffPost. If you dont, you might be paying for it for the rest of your life.

Schuman likens the process to a science experiment many people used to do as kids. Remember trying to hold a magnifying glass against a leaf in the sun to see if something would burn? Thats essentially what youre doing to your eyes should you look directly at the light, Schuman said.

The same burning process happens, except you cant really feel it, he explained. The light from the sun is converted into heat and that can hurt the retina. When you look at the sun, youre looking at the light directly. Youre using that finest, sharpest point of your vision to do that and so thats the part thats damaged or destroyed.

Not only could looking at the eclipse be painful in the moment, it could cause permanent damage to your retina, which takes light received by the eyes lens and converts it to signals that go to the brain. The brain then takes these signals and creates visual recognition of objects.

You may still be able to make out shapes or forms, but you wouldnt be able to, say, read a book like you normally would because there would be a big blind spot in the middle, Schuman said. That concentration of the suns rays cooks the retina, the area thats most sensitive and gives you your best vision.

Of course, none of this means you cant view the eclipse. In order to safely witness science in action, Schuman recommends investing in special glasses if you plan on staring up at the sky. (Sorry, your regular shades wont cut it.)

Retailers like Best Buy and even 7-Eleven are selling the specs so you can safely watch the eclipse. Just be cautious of imposters: Amazon , for example, is already recalling some glasses because they were unable to confirm if they were being sold by a reputable manufacturer. The best thing to do is look for glasses that are labeled with the code ISO 12312-2.

Thats a very specific rating or standard that provides protection for viewing the eclipse, Schuman said. If youre looking at the sun, you would see it safely.

There are also some DIY hacks to view the eclipse without glasses, according to some experts, but do so with caution. Schuman points out that there is also a brief period of time during the phenomenon where you can look to the sky without protective glasses and not risk your eye health: When the eclipse is completely total.

Its only when the disc of the moon is completely covering the sun that its okay to look up without the glasses, he explained. (A total eclipse only lasts a few short minutes , so look quickly.)

But any other time, the slightest sliver of light coming out from one side or the other, you need to be wearing protection in order to avoid that damage, Schuman said.

So grab your friends and queue up Bonnie Tylers Total Eclipse of the Heart just dont forget eye protection as part of those eclipse essentials.

Happy viewing!