Laird Harrison

August 14, 2017

BOSTON — On August 21, the moon will cast its shadow across the United States in a 70-mile-wide path from Salem, Oregon to Charleston, South Carolina. This is the first total solar eclipse visible from the continental United States in almost a century. Anyone in the path will have a chance to see what the National Aeronautics and Space Administration (NASA) is calling "one of nature's most awe-inspiring sights."

Even hundreds of miles away from the path of totality, people who look at the sky will see an impressive partial eclipse. But those who don't take the proper precautions could be left with an unpleasant souvenir: impaired vision related to solar retinopathy.

It happened in Turkey in 1976, in the United Kingdom in 1999, and in Taiwan in 2009. Over and over, during total eclipses of the sun, people have looked up in astonishment — and burned their retinas. And ophthalmologists in the United States fear the same thing will happen here.

There is no known treatment for solar retinopathy, so prevention is very important, said Robert Wong, MD, from Austin Retina Associates in Texas, who is a member of the American Society of Retina Specialists (ASRS) safety committee.

And the main means of prevention is public education, he told Medscape Medical News here at the ASRS Annual Meeting.

Few ophthalmologists in the United States have seen patients whose retinas were damaged during an eclipse, although some have encountered retinal burns caused by lasers, said Geoffrey Emerson, MD, PhD, from the Retina Center in Minneapolis.

"We haven't had very much eclipse-related solar retinopathy reported, because we haven't had any eclipses like this," added Dr Emerson, who is also a member of the ASRS safety committee.

Lack of Public Information

A study of the 2006 eclipse visible in parts of Africa, Asia, Europe, and South America revealed that only 53% of major European newspapers mentioned risk to the eyes, and only 42% described safe measures for viewing the event (Arch Soc Esp Oftalmol. 2007;82:735).

To help inform the public about the risks, the ASRS has posted a fact sheet that describes ways to safely view the eclipse.

People can look directly at the sun only while it is totally obscured by the moon, but that will only last for 2 minutes and 40 seconds in the center of the path of totality, less than that toward the edges of the path, and not at all outside the path, Dr Emerson said.

So most people will need a device to watch the eclipse safely.

Glasses specially made for eclipse viewing that meet International Organization for Standardization (ISO) 12312-2:2015 criteria can be used. But these glasses appear to be rising in price as the eclipse approaches, and it will soon be too late to order them online.

Another option is a pinhole projector. A variety of websites provide instructions on how to make such a projector, and NASA is offering a printable version.

Number 14 welder's glass, which can be purchased at welding supply stores, will also confer adequate protection. But "I'm not recommending that because I don't think people know what number their welding shield is," said Dr Emerson.

Binoculars and telescopes should not be used. The lenses of these devices focus the sun's energy so that it can burn through glasses designed for watching the eclipse, he added.

I worry that people will be trying to take a selfie of it and not realize they're looking at the sun.

Because this will be the first major eclipse in the United States since smartphones became ubiquitous, smartphone cameras might contribute to dangerous viewing. "I worry that people will be trying to take a selfie of it and not realize they're looking at the sun," Dr Emerson pointed out.

Dr Wong said that his practice has been posting warnings on social media and sending them by email to referring physicians and news media organizations.

Solar Retinopathy

To date, cases of solar retinopathy in the United States have been more likely to be the result of mind-altering drugs or occupational hazards, Dr Wong explained.

In fact, one of his patients — a 19-year-old woman — took ecstasy and then lay on her back and stared at the sun a during a music festival in San Francisco's Golden Gate Park. The lens and cornea of her eye focused the sun's energy on her retina, much the same way a magnifying glass focuses energy from the sun to burn a hole in a dry leaf.

"She immediately lost vision," Dr Wong reported. "Fortunately, she did recover, but obviously we talked to her about not doing that in the future. If you're in a drug-induced state, you may be more prone to lack of judgment."

Misinformation can lead to similar errors, he said. Another of his patients had always dreamed of being an Air Force pilot. In a desperate attempt to cure his myopia, he tried a treatment of direct sun exposure described on the internet. The injury to that patient's retina also healed on its own.

That is the natural course of most solar retinopathies. Of 15 patients who damaged their retinas during a solar eclipse in the United Kingdom in 1999, only two had vision below 6/6 at follow-up 8 to 12 months after the event, researchers report (Eye [Lond]. 2002;16:203-206). But in many of the patients, "subtle visual disturbances" persisted, they add.

Another of Dr Wong's patients was less lucky. A fisherman said he had only looked at the sun's reflection off the water through sunglasses. Nevertheless, the harsh rays blistered his fovea, creating a hole that required a vitrectomy to repair, and left a lasting distortion.

But the specialists who raised concerns about eclipse viewing to Medscape Medical News noted that they haven't lost sight of the joy that this rare natural event will bring. Both are planning to watch the eclipse; in fact, Dr Emerson is planning a family vacation to South Carolina specifically for that purpose.

"I want to go to the path of totality because it's going to get dark," he said. "I've heard that animals go to sleep and it gets very quiet. That's going to make it memorable."

Dr Emerson and Dr Wong have disclosed no relevant financial relationships.

Follow Medscape Ophthalmology on Twitter @MedscapeEye and Laird Harrison @LairdH


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