Here's what happens when you look at the sun during an eclipse (please don't)

You've likely heard that you shouldn't look at the sun during an eclipse. If you haven't, let us reiterate: Do not look at the sun during the eclipse. Are we all clear on the not looking? Good.

Then let's talk about why it's such a bad idea, what happens if someone does look at the sun and the safest way to watch the eclipse.

To answer these questions, we reached out to Dr. Todd Peabody, a clinical associate professor at the Indiana University School of Optometry.

In case you still weren't clear on whether it's OK to look at an eclipse, let's hear it one more time from an expert: "My recommendation is to not look at the eclipse for any period of time," Peabody said. "The longer you look at it, the more serious the damage. But even in a short period of time, you can do damage, some of which is reversible and some which is irreversible."

► Read: People in Indy are freaking out about the eclipse

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What's important to remember, however, is that the sun isn't super-extra dangerous during an eclipse. It poses the same dangers that it always does — namely, spitting out electromagnetic radiation.

Have no eclipse glasses:Download & print your own eclipse viewer.

The difference is that on a normal day, most people don't stare at the sun. It's just not that interesting and it's uncomfortable. But during an eclipse, the sun is suddenly very interesting.

That's when you run into issues.

Now, you don't need to freak out. But you do need to be careful.

"If you accidentally see it, are you going to be irreversibly blind? Probably not," Peabody said. "But there can be damage in a fraction of seconds."

► Read: Here's what happened to an Oregon man who stared at the sun during the 1962 eclipse

Optical damage from the sun might not be immediately apparent. You don't have pain receptors in your retina, so you likely won't feel anything.

But later, if you or a loved one (be especially watchful of children or those with developmental delays) complain of vision changes, including decreased vision or straight lines seeming wavy, go to your eye care provider — either an optometrist or ophthalmologist will work, Peabody said. 

The eye doctor likely will then use something called optical coherence tomography to scan the eye for damage, which is usually found in the outer retina. If there is damage, it's usually treated with anti-inflammatory, like steroids, which might help and might not help.

► Read: Everything you need to know about watching the eclipse in Indy

While there aren't a ton of studies on how to treat sun damage to the eyes — because again, most people don't stare at the sun — case studies suggest that the longer a person stares at the sun, the worse the damage.

Let's hear it again: "The best strategy is avoidance," said Peabody.

If you want to watch the eclipse, make sure you're doing it safely. If you're using solar eclipse viewing glasses, make sure they are genuine and properly rated.

And whatever you do, don't use sunglasses in place of real eclipse viewing glasses, Peabody warns. 

► Read:Full list of glasses certified as safe by the American Astronomical Society and NASA

"Sunglasses are particularly dangerous because when you wear sunglasses, it limits the amount of light that gets into your eye," Peabody said. "It causes your pupil to dilate, which allows more radiation to get in.

"Sunglasses might actually make (damage) worse."

All that said, Peabody is still going to watch the eclipse. His kids are taking the safe route by watching it indoors with their classmates on TV. But he'll personally be outside — just not looking at the sun.

"What my plan is, is to go outside, observe the way nature reacts — the fact that the birds stop singing, the fact that it's dark ... but I don’t plan on looking directly at the sun because my vision is too important," Peabody said.