A total eclipse of the sun is always fascinating. It was seen by early civilizations as mystical and powerful evidence that there was a God or gods.
Pink Floyd even named a track in its legendary Dark Side of the Moon album after an eclipse – proof positive that it is a surreal event. And yes, hundreds of websites offer the Pink Floyd sound track to add to your eclipse watching experience.
The “where” for the upcoming eclipse is a swath from Oregon to South Carolina (see map) where some areas will experience a total eclipse.
The rest of us will see a partial eclipse, meaning the sun is peeking out from behind the moon. And that is what has ophthalmologists concerned, because looking at a partial eclipse isn’t something your eyes are equipped to handle.
The sun is a giant (109 times the diameter of Earth) nuclear reactor with a surface temperature of over 10,000 degrees (F). For comparison, a nuclear bomb can blind you with a 1 inch sphere of radioactive material. The sun is 400,000 times brighter than the moon. Using the Lux scale, a logarithmic scale of light, moonlight is 0.2, stadium lighting is 200, and the sun is 10,000.
So, the visible part of the sun in a partial eclipse is still sending immense energy in UV light.
How do our eyes work? Light comes into the eye in parallel rays that are focused by the lens onto the retina. Consider the magnifying glass you had as a child, which you used to start small fires or fry a few ants. The lens works like that.
The sun’s UV radiation can burn the retinas in the eyes, leading to permanent damage or even blindness. This can occur even if your eyes are exposed to direct sunlight for even just a few seconds.
You need your retina to see. And to make matters worse, your eye automatically aims its lens at your central vision – your best vision – which you need to see, read, or do almost anything else.
So why not use your sunglasses to look at an eclipse? Because the 10% to 20% of UV radiation not blocked will fry your cornea and retina. Sunglasses dilate (open) your pupil, so more light radiation gets in, which is exactly the opposite of what you want during an eclipse.
If you want to watch the upcoming eclipse, you must wear special eclipse glasses to avoid any permanent damage to your eyes. They are easily found.
I like the American Astronomical Society website at eclipse.aas.org. Click on Eye Safety and you will get a list of approved manufactures of eclipse lenses. These meet the ISO 12312-2 standard for vision protection when looking at the sun.
There is also a list of where you can buy them, including many stores you pass every day. The investment in less than $5, and some vendors are giving them away.
Once you have the eclipse glasses, you just need to get outside and turn on Pink Floyd.
Enjoy this once-in-a-lifetime experience.
Donald Bucklin, MD (Dr. B) is a Regional Medical Director for U.S. HealthWorks and has been practicing clinical occupational medicine for more than 25 years. Dr. B. works in our Scottsdale, Arizona clinic.
Featured and post photos by Igor Zh/Shutterstock. Illustration of solar eclipse path by Bearsky 23/Shutterstock.