The only time it's safe to view the sun without eye protection is during the totality of a total solar eclipse, or the brief period when the moon completely blocks the light of the sun, according to NASA.
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"The visible light, that normally would be blinding to us, temporarily isn't there. It's blocked by the moon," Dr. Joel Schuman, an ophthalmologist at Wills Eye Hospital in Philadelphia, told Action News leading up to the eclipse. "So, that allows us to stare at the sun without feeling that we're actually getting harmed."
Now, in the wake of the solar eclipse, there may be a spike in people wondering if they've done some damage to their eyes from gazing up without the proper protection.
But how do you know if you have eye damage from the eclipse?
While the clouds did hamper some viewing efforts in parts of the U.S., many eventually caught a glimpse of at least the partial eclipse.
After experiencing the rare celestial moment, some might find their eyes are bothering them or feeling a little funny, even if they were wearing the protective glasses -- but don't panic. Your eyes are probably fine.
Leading up to the eclipse, experts stressed that it was absolutely necessary to wear certified eclipse glasses or use handheld solar viewers that meet a specific safety standard, known as ISO 12312-2, when watching all other phases of a total or partial solar eclipse. The safety standard means that the lenses meet international requirements for direct solar viewing, according to the American Astronomical Society, or AAS.
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Philadelphia doctors explain importance of protecting your eyes during upcoming solar eclipse
When asked about what could happen if you don't protect your eyes, Dr. Schuman said, "You would burn the part of the retina that has the most sensitive, sharpest vision because you're looking directly at the sun."
The lenses of solar eclipse glasses are made of black polymer, or resin infused with carbon particles, that blocks nearly all visible, infrared and ultraviolet light, according to The Planetary Society. And sunglasses don't work in place of eclipse glasses or solar viewers.
Dr. Schuman said those who don't protect their eyes could experience what is called "solar retinopathy," which occurs when intense light energy injures or damages the retina and causes permanent damage.
While the highly specialized cells inside our eyes don't feel any pain, the rods and cones and photochemical reactors become inflamed and damaged when looking at the sun, said Ronald Benner, an optometrist and president of the American Optometric Association.
It's a bit like the effect that occurs when we see a camera flash go off, which can distort our vision for a few minutes before it goes away. But the intensity of solar retinopathy causes permanent damage that won't be immediately apparent. Overnight, the cells can die, and they won't be replaced. There is no treatment for solar retinopathy. It can improve or worsen, but it is a permanent condition.
The changes in a person's vision depend on the type of damage that is done, and these can occur in one or both eyes.
"It can take somebody a very short time, even seconds, from seeing 20/20 to seeing 20/200," Dr. Schuman added.
"The retina is an extension of the brain, so it's actually neurological tissue, and when you damage that, it doesn't always come back," Benner said. "If you damage one cell, that cell may never be the same. But if you damage a group of cells, then you're going to end up with blotchy vision, like having someone dab oil on your windshield. If you just kind of damage them and they don't completely die, then color vision is going to be altered. What can you do about it? Absolutely nothing other than prevent it."
If the damage occurs in the center of someone's vision, it can affect the ability to read or recognize faces, Benner said.
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However, in the unlikely chance of more serious damage, you would have likely already started to experience the symptoms, including blurriness, light sensitivity, or dark spots.
If you experience vision issues or eye discomfort after viewing the eclipse, Benner recommends booking an appointment immediately using the American Optometric Association's doctor locator. Symptoms may take hours to a few days to manifest, and they include loss of central vision, altered color vision or distorted vision.
"For most people, it's an alteration of color vision," Benner said. "The next morning, colors just don't look right, or it may be bleached out it or just kind of hazy all the time. For others, it may be that they actually have holes in their vision."
Benner also said to talk to your kids.
"If your child experiences eye damage, they have to live with it the rest of their life. And they may not be able to tell you, 'I'm not seeing clearly out of one eye," he said.
Where to recycle and donate your eclipse glasses
If you have special glasses that helped you watch the rare celestial event, here's what to do with them now that the eclipse is over.
Astronomers Without Borders has been accepting donations for over 15 years. They partner with organizations where you can drop off or send your used glasses.
You can also send them to Eclipse Glasses USA, which takes in used but undamaged eclipse glasses and then repurpose them for other eclipse events.
You could also recycle them by removing the lenses and recycling the cardboard.
When is the next solar eclipse in America?
The next major total solar eclipse will not return to North America for another 20 years -- on March 30, 2033 -- and only includes Alaska, with a partial solar eclipse over most of the country.
In 2044's U.S. eclipse, totality will only occur over North Dakota and Montana. Another with a broader U.S. path will occur in August 2045.
CNN contributed to this post.