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If the past is any indication, emergency departments and doctor's offices are likely to see an influx of patients complaining of sensitive eyes, blurry vision, and blind spots in the hours and days after next month's North American solar eclipse.

Ophthalmologists say it's crucial to perform thorough ocular examinations -- even if sun-exposure damage seems obvious -- and look deeply into the eye with specialized equipment.

"Vigilant patients are coming in, and you always want to make sure it's not anything else," Avnish Deobhakta, MD, of New York Eye and Ear Infirmary of Mount Sinai in New York City, told MedPage Today.

Sun-related injuries, of course, are the first thing to look for in the wake of the , which will be visible over much of the U.S. and Canada. from near San Antonio to Buffalo, will see a full eclipse.

People have long known about the risks of sungazing. In a lecture about looking at things indirectly, ancient Greek philosopher Socrates that "people may injure their bodily eye by observing and gazing on the sun during an eclipse." Socrates declared that viewing an eclipse through a reflection on water is a safer alternative, a strategy that .

The Retina Is Especially Vulnerable to Sun Exposure

Modern technology has given us better ways to protect our eyes via specially designed eclipse glasses known as solar filters. We've also gained understanding of the optical damage that exposure to the sun can cause.

"Watching the eclipse without proper eye protection, even for a short amount of time, can permanently damage the retina, a very important light-detecting part of the eye," Christina Y. Weng, MD, MBA, of Cullen Eye Institute at Baylor College of Medicine in Houston, told MedPage Today. "This damage is referred to as solar retinopathy and often affects the macula -- a critical part of the retina responsible for central vision. On a cellular level, the potent rays from the sun create a photochemical burn in the retinal tissue that can lead to a 'scotoma' where a piece of the vision is missing."

The damage can be similar to the injuries that people suffer from eye exposure to laser pointers, Deobhakta said. In those cases, though, there are pinpoint burns, not the crescents that can be seen from eclipse burns, he explained.

It's also possible for patients to suffer mild corneal abrasions from eclipses, he added. "Things like that are rare but certainly treatable." A provided more detail and noted that "radiation burns result in ultraviolet keratitis from tanning beds, high-altitude environments, welding arcs, and the occasional solar eclipse."

As for the examination, Weng recommended examining any possible cases of solar retinopathy via optical coherence tomography (OCT) imaging and dilated fundus examination, which allows viewing of the back of the eye.

According to Deobhakta, OCT imaging machines are found in some general ophthalmologist offices and every retinal specialist's office. "It's a way to look at the retina in cross section and see whether the center part of the retina, which is called the fovea, is disrupted or not. If that's the case, patients tend to have that kind of damage forever."

Eye Damage Can Be Long-Lasting or Even Permanent

Indeed, multiple reports in the medical literature about eclipse-related eye injuries suggest that visual damage can persist in certain patients.

Deobhakta and colleagues wrote a about a young woman who viewed the 2017 eclipse and suffered solar retinopathy in both eyes. Deobhakta described damage from an eclipse-related burn to the retina this way: "If you're reading a sentence like 'the cat jumped over the moon,' the word 'over' might be blacked out with a crescent. It's like a floating blank, but you can read the rest of the sentence and the page."

The woman had lasting eye damage. Other reports in the medical literature tell similar stories:

• After a 1948 eclipse, 32 children in Los Angeles . Sight problems persisted in 30 of them.
• After a 1999 eclipse, British researchers and found "there have been no reported cases of continued visual loss or symptoms at 6 months." However, found four of 45 patients with eclipse burns were still suffering from symptoms 7 months after the eclipse.
• In Pakistan, researchers from 1995-2002 with eclipse-related eye damage. "Complete recovery was seen in 26 patients, 7 made a partial recovery, while in three patients the visual acuity remained poor."
• A 34-year-old man went to a Northern California ophthalmologist after he watched the 2017 eclipse and developed a blind spot. His vision returned, but the eye doctor said there " that resembles the image of the 80 percent eclipse pattern seen in Sacramento."

As for treatment, there's none for solar retinopathy, although "entities such as steroids have been tried without consistent evidence of effectiveness," according to the . Corneal injuries can be treated with supportive care via lubrication, Deobhakta said. "I always say don't wear contact lenses for a week. Make sure that the patient follows up so we can make sure there's no sign of infection and scan for other things that would be relevant. You don't want to miss them."

Why Do Only Some Eclipse Viewers Get Eye Damage?

Of course, countless people look at eclipses and don't suffer apparent eye damage. Most famously, former President Donald Trump was from a White House balcony without eye protection and apparently didn't suffer any ill effects.

Some groups, however, appear to be more susceptible to these injuries, Weng said. Vulnerable groups include children and younger adults with a clear lens, those taking photosensitizing drugs such as tetracycline, and people with mental impairment/psychiatric disease or under the influence of illicit drugs.

"In many cases, people just live with the damage, and they don't come to see an eye doctor," Deobhakta said. "People just say, 'Well, I can live with it because I have both of my eyes.'" This may sound surprising, but he noted that "in our country, people will live and walk around with dense cataracts where they're barely able to see upon evaluation, but they've never come into an eye doctor until they're in their 80s."

Some people may have genetic vulnerability to sun-related eye injuries, he added, although it's not yet clear who they are.

Astronomer Andrew T. Young, PhD, of San Diego State University, who has , told MedPage Today that timing also matters. "The danger is during the partial-eclipse phases just before and just after totality, or partial phases near mid-eclipse for an observer who is near -- but just outside of -- the path of totality," he said. "The low general light level when more than half of the sun is hidden by the moon allows the pupil to expand," allowing in more light -- and rays from the sun.

On the prevention front, JAMA has offering guidance on safe viewing of eclipses, and the American Astronomical Society offers tips about .

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