Eye Health

Eclipse 2017: How to view safely

David Mitchell - Monday, August 14, 2017

 

We have had quite a few questions recently regarding the upcoming solar eclipse.  The first, best (and simplest) piece of advice I can give you is this:  Do not look directly at the sun.

Here is why:  Solar retinopathy.  That’s the technical name for when you burn a hole through a layer of the back of your eye. 

 Looking directly at the sun without the correct eye protection - even for a short time - can cause permanent damage to your retina,  the light-sensitive part of the eye that transmits what you see to your brain.

Have you ever focused the sun’s rays through a magnifying glass to start a fire (or to burn ants)?   Well, there is a system of lenses in our eyes that focuses light to a fine point, just like the magnifying glass does.  This creates massive amount of energy at the focal point, which can amount to basically burning a hole through the retina.

Normally (during non-eclipse conditions), we have a natural aversion reflex to look away from the sun due to its extreme brightness.  Under eclipse conditions, the light may be less bright, and the aversion reflex not as strong, which may make individuals feel they can stare at the sun for a longer period of time.  However, the intensity of the sunlight is just as strong and damaging.  Do not look directly at the sun.

Damage can occur without pain, and it can take a few hours or even a few days after viewing the eclipse to have symptoms of damage, which may include not being able to see colors as well and loss of central vision, with only side vision remaining.  Do not look directly at the sun.

Now, all that being said, there is only one safe way to look directly at the sun (Do not look directly at the sun), whether during an eclipse or not: through special-purpose solar filters, used in “eclipse glasses” or in hand-held solar viewers. They must meet a very specific worldwide standard known as ISO 12312-2.

Ordinary sunglasses, even very dark ones, or homemade filters, are not safe for looking at the sun--  they transmit thousands of times too much sunlight.

 Refer to NASA’S website or to the American Astronomical Society (AAS) Reputable Vendors of Solar Filters & Viewers (link is external) page for a list of manufacturers and authorized dealers of eclipse glasses and handheld solar viewers verified to be compliant with the ISO 12312-2 international safety standard for such products.

Steps to follow for safely watching a solar eclipse:

  • Always inspect your solar filter before use; if scratched, wrinkled, or damaged in any way, discard it.
  • Always read and follow all directions that come with the solar filter or eclipse glasses. 
  • Always supervise children during an eclipse, and when using solar filters.  Help children to be sure they use handheld solar viewers and eclipse glasses correctly.
  • Before looking up at the bright sun, stand still and cover your eyes with your eclipse glasses or solar viewer. After glancing at the sun, turn away and remove your filter—do not remove it while looking at the sun.
  • Never look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other similar devices. This is important even if you are wearing eclipse glasses or holding a solar viewer at the same time. The intense concentrated solar rays coming through these devices will damage the solar filter and your eyes.
  • Seek expert advice from an astronomer before using a solar filter with a camera, a telescope, binoculars, or any other optical device. Note that solar filters must be attached to the front of any telescope, binoculars, camera lens, or other optics.
  • Outside the path of totality (we in Louisiana are outside this path this year), you must always use a safe solar filter to view the sun directly.
  • If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.
  • Resist the urge to sing Bonnie Tyler out loud.

Eclipse 2017: How to view safely