Eye Safety for Eclipse Viewing

Eye Safety for Eclipse Viewing
Sunrise creating lens effect on earth


Eye safety for viewing eclipse

The Path of Totality

As most Oregonians, and certainly those working in the tourism industry, already well-know, there will be a solar eclipse on August 21st, 2017.  And, the “path of totality,” the 60-70 mile band in which the moon will completely cover the sun, darkening the sky and making the solar corona visible, will pass right through Oregon.

Unfortunately, this path of totality will miss Portland, and here, only a partial solar eclipse will be visible.  However, in nearby Salem, Oregon, the eclipse will be total from 10:17AM to 10:19AM that morning.  For those still searching for a place to watch the eclipse, there are great maps of the eclipse path and duration of totality available from both NASA and the American Astronomical Society.  Traffic of course is predicted to be terrible, and campgrounds and hotels within the path of totality have been booked months, and in many cases, years, in advance.

Eclipse Viewing Safety

No matter where you end up watching the eclipse, don’t forget to make sure you are prepared to view it safely.  During the total eclipse, when the moon is completely blocking the sun, the solar corona will be visible and is safe to look at without a filter.  However, at any other time during the eclipse, when the sun is only partially blocked, it is unsafe to look at without approved eye protection (certified to meet ISO 12312-2, the international standard for safety of solar viewing glasses).  Ordinary sunglasses are not safe for solar eclipse viewing. It is also not safe to look at the sun with a camera, a telescope, binoculars, or any other optical device, even while using your eclipse glasses, as these devices can concentrate the sun’s rays and damage your eclipse glasses and your eyes.

The danger in looking at the sun stems not from ultraviolet rays that we commonly associate with sun damage to our skin and eyes, but from visible light rays.  While it is true that ultraviolet light is absorbed by the lens inside the eye and contributes to cataract formation, the primary hazard when staring directly at the sun is from visible light in the blue spectrum rather than invisible, ultra-violet light.  This high-intensity, visible-light exposure overwhelms the rods and cones of the retina causing chemical reactions that can damage or destroy them.  Additionally, light not absorbed by the rods and cones is absorbed by other retinal layers (specifically a layer called the retinal pigment epithelium) and is transformed into heat, literally “cooking” the retina.

Eclipse Viewing Glasses

To avoid this damage to the retina and loss of vision, safety protection is necessary.  The simplest protection is approved eclipse viewing glasses.  It is also possible to create a pinhole projection system to view the eclipse, though this provides only indirect viewing.

When the eclipse is total, and the moon completely covers the sun, it is safe and recommended to remove the eclipse glasses as only the solar corona is visible, and is approximately as bright as the full moon in the night sky, and just as safe to view.  This time is said to be one of nature’s grandest spectacles.  However, as soon as the sun starts to peek out from behind the moon, eye protection must immediately be replaced.

While there are a few steps that need to be taken to protect your eyes and vision, as long as these steps are followed, you will be able to safely enjoy this natural wonder.  Though, if you miss this eclipse, there is still hope.  The next total solar eclipse to visit the continental United States will be April 8th, 2024, though this one will take a very different path through the country.

Update: As of August 14th, 2016 we are sold out of eclipse glasses.  Thank you everyone who purchased your glasses at our office, 100% of proceeds from sales of eclipse viewing glasses were donated to Richmond Elementary School, a total of over $1500.


Optometrist at Portland Eye Care.