Expert Health Articles

Ensuring Eye Safety During a Solar Eclipse

Stephen Orr, MD

Ophthalmology
Medical Staff Member - Blanchard Valley Health System

The residents of Hancock County will have a front-row seat for the total eclipse of the sun on Monday, April 8, 2024. For many, this will be a once-in-a-lifetime opportunity. With proper preparation and precautions, it is possible to safely observe the eclipse without damaging your eyes.

Eclipse Blindness

“Eclipse blindness” is caused by the exposure of the retina (the back part of the eye) to high-intensity visible light. The rods and cones (the cells responsible for vision) can be permanently damaged by prolonged exposure to direct sunlight during an event like an eclipse, even when there does not appear to be much light from the sun. This damage can cause permanent, irreversible visual loss by two different mechanisms. First, the light itself causes chemical reactions within the cells that cause them to stop functioning. Second, the actual heat from the sun burns and destroys certain layers of the retina. The end result is visual loss that can be permanent, and for which there is no current treatment. 

Unsafe Methods

There are unsafe and safe ways to view the eclipse. Unsafe ways include no eye protection, standard sunglasses (layering several pairs is not safe either), food wrappers such as Pop-Tarts or potato chip wrappers, CDs or DVDs, “space blankets,” polarizing filters, the plastic used in gardening, exposed color photography film, and exposed film negatives. The eclipse should never be viewed through an unfiltered telescope, camera, or binoculars. Using any of these methods alone or in combination will put you at risk of “eclipse blindness” and permanent visual loss.

Safe Eclipse Viewing

Safe ways of viewing the eclipse include the use of specially designed eclipse glasses. These devices have a lens that is layered with a chromium alloy and/or aluminum. All authorized eclipse glasses will indicate that they comply with the requirements of ISO 12312-2. If your eclipse glasses do not have that designation, they are not considered safe. Eclipse glasses are designed for viewing the eclipse without a telescope, camera, or binoculars and should not be used with any of these devices. Eclipse glasses should also never be used as a filter in front of a camera, telescope, or binoculars. An aluminized polyester known as “black polymer” can be used in front of a telescope, camera, or binoculars as long as it has been fitted in an appropriate holder. Welding filters with shade numbers 12 to 14 that are used for electric arc welding are also considered safe. Filters with lower numbers are not safe. Arc welding filters should also not be used in front of a telescope. 

With some preparation and appropriate precautions, you can safely enjoy the solar eclipse.