by Caroline Cauchi, OD
On August 21, 2017 a total solar eclipse will occur over parts of North America. Dr. Peters, one of the experienced optometrists here at Vision Solutions, discusses when is the best time to see the eclipse and the proper safety procedures you should take to protect your vision.
A 70-mile-wide path of total solar eclipse (where the sun will be fully blocked by the moon) will occur from Oregon to South Carolina. The rest of the country will experience a partial solar eclipse where the sun is only partially blocking the moon. The total eclipse will last for approximately 2 minutes and 40 seconds. In these regions of total eclipse the day will turn into night and other parts of the solar system and surrounding stars will be visible. The rest of our continent will be able to see a partial eclipse for 2 to 3 hours. Our maximum viewing here in San Diego should be around 10:23am. This will be the first total solar eclipse visible in the Continental United States in 38 years. The next total solar eclipse will be April 8, 2024 tracking northeast from Texas to Maine.
Viewing this solar eclipse will be a moment of wonder but safety precautions need to be followed to protect the eyes from harmful radiation. For those people lucky enough to be in the path of total eclipse or “totality”, they will be able to remove their special filtered glasses and view the eclipse without the need of eye protection for those 2 minutes and 40 seconds. But for us in San Diego, special filtered glasses will need to be worn at all times since the magnitude of the radiation emitted from the sun is so great that it will damage the retina inside the eye permanently with extended viewing. This damage initially causes a yellow spot and blurry vision and eventually a permanent “blind spot” in the vision centrally which will last a lifetime. The term for this is solar retinopathy. Unfortunately there are no pain receptors in the retina to let you know when it is being damaged. The pain comes later after the exposure.
The safest way to view the uneclipsed or partially eclipsed sun is by wearing special-purpose solar filters which are worn like sunglasses. Don’t be fooled, they are filters even more powerful than those safety lenses worn by welders to prevent welders burn. These lenses need to meet the international safety standards ISO 12312-2 to qualify. Ordinary sunglasses, no matter how dark they are, are not safe to look at the sun. Similarly, viewing the eclipse through a camera lens, telescope, or binoculars is also not safe unless the above filter is also applied to the viewing device. If you wear eyeglasses for better vision, just put these filtered glasses over top of your original eyewear. There are five manufacturers are making eclipse glasses and handheld solar viewers that meet the ISO 12312-2 international standard for such products: American Paper Optics, Baader Planetarium (AstroSolar Silver/Gold film only), Rainbow Symphony, Thousand Oaks Optical, and TSE 17.
Another method to view this eclipse is to create a pinhole projection on the ground below you where you see the shadow of the event. With the sun behind your back, create an opening in your outstretched hands by placing one hand over the fingers of the other hand making a small pinhole. The little spaces between your fingers will project small images on the ground showing the sun as a crescent.
We have a limited supply of the Rainbow Symphony ISO solar filter glasses at the office. Stop by or call before August 21st to get your safety wear! However you safely view the eclipse, make sure you get outside on August 21 to catch a glimpse of this amazing natural phenomenon!