Wellness Wednesday: Eye Safety During a Total Eclipse

A couple weeks ago, in our Wellness Wednesday post called UV Safety and Eyesight, we shared information about how the sun can cause damage to your eyes if you do not protect them. Hopefully, by now, your mom has recovered from your telling her she was right about not looking directly at the sun.

Total Eclipse 2009 in China
Total Solar Eclipse seen in China, 2009

This post is all the more timely because next Monday, the U.S. will experience its first total eclipse of the sun in over 38 years. I’m sure by now you’ve heard all about it. Maybe you’re even tired of hearing about it … or you figure it doesn’t affect you.

Maybe it won’t. If you are not the least bit curious and have no desire to watch one of the coolest natural phenomena in the universe, then that’s fine … you can stop reading now.

Still there?

Good. This means you’re either a little curious or you have nothing else to do at the moment. Whichever one is fine. We are not judging. And hopefully while you’re reading you will even learn something in the process.

What is a Total Solar Eclipse?

infographic-solar-eclipse-facebook.pngSo, we know the Earth spins on an axis, like a top—giving us night and day. It also revolves around the sun in an elliptical orbit once per year—giving us seasons (with a few exceptions). The moon orbits the earth once every 27.323 days, giving us the different phases from new moon to full moon.

During a Total Solar Eclipse, the moon’s orbit crosses paths directly in front of the sun in such a way that from specific areas of the planet, it blocks the sun from view either partially or completely, causing a brief period of darkness in the middle of the afternoon.

total-solar-eclipse-process
Copyright: NASA/Phil Hart

On this occasion, the ‘path of totality’—where viewers will experience a total solar eclipse—cuts diagonally across the U.S. through several states from Oregon down to South Carolina. This means, from those areas, the sun will become completely ‘eclipsed’ by the moon for a brief period on Monday afternoon.

For those of us who are above or below those areas, we will experience a partial eclipse of the sun by the moon. So part of the sun will continue to be visible. But much like the phases of the moon, we will see a waxing and waning effect.

So what’s the big deal?

Well, hopefully, you at least find that a tiny bit fascinating!

Totality2010-S&T-DennisDiCicco
Totality as seen from Easter Island on July 11, 2010. Credit: Dennis di Cicco / Sky & Telescope

But even if you’re not yet sold, if you plan to watch this phenomenon take place or anticipate that your friends might drag you with them to watch … you need to be prepared.

There are many superstitions around total eclipses. But the concern isn’t with the eclipse itself. It doesn’t make people go mad. The sun doesn’t suddenly emit any special rays that are extra harmful. Pregnant women have nothing to fear. You may feel the temperature drop a little for that short time, but it will be brief and no different than just after dusk.

The issue comes when your relaxed eyes are gazing at a covered sun and suddenly it begins to peek back out from behind the moon.

You know what it’s like when you turn on the bathroom light in the morning after your eyes have been in the dark all night long? Ouch! It takes a while to adjust, right? Your dilated eyes need time to constrict and not take in so much light at once.

In an eclipse, this is a similar effect but multiplied by like a million and dangerous because of the UV radiation! When you are typically outside on a sunny day, even without sunglasses (though that isn’t recommended), your eyes adjust, you squint, you look away from the sun … because it is uncomfortable! It’s a reflex. So you are never getting that full on effect of looking at the sun.

During a total solar eclipse, people are purposefully gazing in the direction of the sun and as it begins to peak out from behind the moon, even for a few seconds, that can cause catastrophic damage to your eyes. In the partial phase, visible light is reduced enough that it’s no longer painful or uncomfortable to look at, so people assume it’s safe. And one of the problems is you may not even realize you have done damage until the next day.

WomanShades-MarkMargolis
Credit: Michael Bakich

Exposing your eyes to the sun without proper eye protection during a solar eclipse can cause ‘eclipse blindness’ or retinal burns, also known as solar retinopathy.

You must wear protective eyewear (or you can make a pinhole projector) if you are going to watch any part of a solar eclipse! Sunglasses are not protective. You shouldn’t be able to see anything through a safe solar filter (ISO 12312-2 compliant) except the sun itself.

At this late stage, finding eclipse glasses is getting harder but it’s not impossible. Some libraries are giving them away, or you may still find them at local Best Buy or Lowes stores. You can also try online, but make sure you order from a reputable company and they specify they are ISO 12312-2 compliant.

Witnessing the Total Solar Eclipse

If you are in the path of totality, the moon will begin to cover the sun. Your eyes must be protected. Once the sun is completely blocked by the moon, you can take them off to view this amazing phenomenon. But be brief. This will only last minutes. Be ready to put your glasses back on because as soon as the sunlight begins to appear again, you will need to put them back on.

NASA_map_508.jpgIf you are not in the path of totality, you will only be seeing a partial eclipse. Therefore, you will need to keep your eclipse glasses on for the duration of the event.

When and Where to Watch the Total Solar Eclipse

The actual timing of the eclipse is determined by where you are in the U.S. It can be anywhere between 10:20 a.m. on the West Coast and 2:40 p.m. on the East Coast. Check the NASA website or your local news stations for exact times.

PhilaEclipse
Timing of the Total Solar Eclipse in the Philadelphia, Pa., viewing area.

If you cannot get outside to experience the solar eclipse or you do not have the protective eyewear to do so, many networks are live broadcasting the event, and there will be live streams from NASA as well.

Sources:

American Academy of Opthalmology, American Optometric Association, American Astronomical Society, NASA and Space.com.


More Information:

NASA Eclipse Live Stream [August 21, 12-4 p.m.]

How to safely watch a solar eclipse

Eclipse Across America

How Sunlight Damages the Eyes

WHO: The known health effects of UV

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