Dos and Don’ts of watching a solar eclipse

On Monday, April 8, a solar eclipse will cross North America, passing over Mexico, the U.S. and Canada. The total eclipse will darken the skies during the middle of the day beginning in Texas and then traveling through Oklahoma, Arkansas. Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine.

While Cape Cod will not be in the path of the total eclipse, the moon’s passing between Earth and the sun will still darken the sky quite a bit, and you may be tempted to look up at it.

But, looking at the eclipse with your eyes unprotected can be very dangerous, said emergency medicine physician Michael Rest, MD, Director of the Falmouth Hospital Emergency Department. Staring at the sun for any length of time can lead to two possible medical issues: Solar retinopathy and solar keratitis.

Both conditions can happen after just a few minutes of looking directly at the sun, he said.

“Solar retinopathy is damage to the retina due to the radiation from the sun,” said Dr. Rest. “The retina is the sensory screen at the back of the eye that converts light into electric nerve signals to the brain. Typically, this condition is painless, and it develops over hours to days after the damage occurs. It may start as purple spots and it can progress to significant loss of vision.”

Unfortunately, there is little treatment once the damage has occurred, he said. He does not expect the hospital emergency departments will see any solar retinopathy cases immediately after the eclipse, as it is slower to develop and painless, but it's important to seek non-emergent ophthalmology care, if you fear you may have damaged your eyes, he said.

Solar keratitis is burning to the cornea (the outer lens of the eye), according to Dr. Rest.

“This is essentially a sunburn, and it can be very painful. The pain usually starts several hours after the injury. It is treated with analgesics (pain meds). It can cause cataracts, which can be fixed later on,” he said.

“We may see the solar keratitis cases (in the EDs), as it is very painful and usually sets in the night following the injury,” he said.

Best Way to View the Eclipse

On Cape Cod, the eclipse will be partial and can be seen between 2:15 and 4:38 p.m. on Monday.

The best way to watch the eclipse is by video, now-retired ophthalmologist Eugene Ciccarelli told Cape Cod Health News before the last lunar eclipse in 2017. NASA is streaming the eclipse live on its website beginning at 1 p.m. EDT.

The problem with looking directly at the eclipse is that you are using your macula, which is the very center part of the retina, according to Dr. Ciccarelli. “That’s the part that’s the most sensitive too, so all you need to do is get a nice little burn right smack in the macula and it can reduce your vision permanently.”

One of the other issues with viewing the eclipse is there are no pain receptors in the retina so there is nothing to warn you that you might be damaging your eyesight. The sliver of light coming from the sun during an eclipse may not be enough to scare you, but it is enough to burn you, he said.

NASA Warnings

If you have invested in approved solar filters to watch the eclipse, NASA offers the following warnings:

• Always inspect your solar filter before use. If it is scratched or damaged in any way, discard it.
• Always supervise children using solar filters.
• Stand still and cover your eyes with the solar filter before looking at the sun and do not remove the filter until you are looking away from the sun.
• Do not look at the partially eclipsed sun through an unfiltered camera, telescope, or binoculars, even if you have filter glasses on.
• The concentrated solar rays will damage the filter and cause serious injury.
• If you are outside the path of totality, you must always use a safe solar filter to view the sun directly.
• If you plan to use welder’s glasses, the only safe ones are those that are Shade 12 or higher, which is much darker than the typical filters that welders use. But be aware that even Shade 12 is considered too bright to ensure perfect safety.
• Ordinary sunglasses do not protect your eyes. Do not use them to view an eclipse.