A solar eclipse occurs when the moon blocks all or part of the sun from your view. Solar eclipses can be partial or total. Although there are two solar eclipses yearly, they are only visible in some areas.
A total solar eclipse, where the moon completely blocks the view of the sun, only happens an average of once every 350 years in a specific location. If you're lucky enough to be in the path of a solar eclipse, though, it's important to use solar eclipse glasses to protect your eyes.
Solar Eclipse Eye Protection
Watching a solar eclipse is an awe-inspiring experience, but looking directly at the sun can damage your eyes.
Your retina is located at the back of your eye. It transmits images of what you see to your brain. The light from the sun can damage or destroy the cells on your retina, leading to solar retinopathy, also known as "eclipse blindness".
What Are Solar Eclipse Glasses?
The only way to safely look at the sun during an eclipse is with solar eclipse glasses. Solar eclipse glasses are made with solar filters that conform to a worldwide safety standard known as ISO 12312-2. Regular sunglasses or homemade solar filters are not safe for watching an eclipse because they transmit sunlight at a rate that is thousands of times too high.
Here are some tips for safely watching a solar eclipse:
- Check your solar eclipse glasses before using them. If you see any scratches or damage, don't use them.
- Follow the instructions that come with your solar eclipse glasses or solar viewer.
- Supervise children to make sure they're using solar eclipse glasses correctly.
- Cover your eyes with your solar eclipse glasses before you look at the sun. Look away before you remove your glasses.
- During the totality, the time when it gets dark becomes the sun is completely blocked out, you can take off your glasses and look at the eclipse. As soon as the sun begins to reappear, though, you need to put your glasses back on.
- Never use a camera, binoculars, or telescope to look at a solar eclipse, even if you have your eclipse glasses on. These devices will intensify the sun's rays and damage your solar eclipse glasses and your eyes.
How Do Solar Eclipse Glasses Work? What Are Solar Eclipse Glasses Made Of?
Solar eclipse glasses are made of a black polymer or silvery mylar that blocks 100% of infrared and ultraviolet light. They only transmit about one millionth of the sun's visible light. Black polymer glasses make the sun look orange, and mylar glasses make it appear bluish-white.
The eclipse glasses are so effective at blocking light that you won't be able to see anything but the sun when you're wearing them, so don't walk around.
Although the lenses are durable, they can be damaged, so inspect them before you use them.
Solar Eclipse Eye Damage Symptoms
Even the tiniest sliver of sun emits enough light to seriously damage your eyes. Looking directly at the sun can damage your eyes at any time, but it's not usually an issue. Under normal circumstances, you have an aversion reflex that will prevent you from looking directly at the sun. During an eclipse, though, it's possible to look directly at the sun without feeling any discomfort.
Unfortunately, you may not know you've damaged your eyes until the next day, when you may experience:
- Loss of central vision
- Altered color vision
- Distorted vision
In the case of solar eclipse eye damage, your peripheral vision is usually spared, with most of the damage occurring in the center of your vision.
Eclipse retinopathy can be immediate and permanent, immediate and reversible, or delayed and progressive. Symptoms of eclipse blindness include:
- Bad vision
- Blind spots
- Distortion of shapes
- Change or tinting of color perception
- Light sensitivity
Treatment for Solar Eclipse Eye Damage
Unfortunately, there's no treatment for eclipse retinopathy. If you think you've damaged your eyes by looking at the sun, do the following:
- Stop looking at the sun.
- Go into a dark room and rest your eyes.
- Follow up with your primary care provider in one to three days.
- Follow up with an eye specialist for testing to determine the extent of the damage.
Your vision may recover within a few months after sun damage, but there's no guarantee.
How Can You Tell If Your Solar Eclipse Glasses Are Safe?
You can check to see if your glasses are labeled with the ISO 12312-2 or ISO 12312-2:2015 international safety standard. However, some bad actors simply copy the ISO logo and print it on eclipse glasses that don't meet the standard, and you can't test the glasses yourself because it has to be done with an expensive piece of lab equipment.
The best way to be sure your eclipse glasses are compliant is to buy them from a reputable dealer.
Although there's no other way to be sure your glasses are safe, there are some ways you tell if they're unsafe, including:
- You should only be able to see the sun or something comparably bright through your eclipse glasses.
- If your eclipse glasses are torn, scratched, or punctured, don't use them.
- If your eclipse glasses are coming loose from the cardboard, don't use them.