On Aug. 21, an event decades in the making will occur across the United States, including portions of far northeast Georgia.

A total eclipse will be viewable along a path from Oregon to South Carolina, and millions are gearing up for it with road trips and events dedicated to viewing the rare phenomenon.

But the excitement of viewing the eclipse could give way to long-term or even permanent eye damage if viewers aren't careful, according to the Georgia Optometric Association.

Dr. Nhung Brandenburg, president of the Georgia Optometric Association, has advice for eye safety during the Aug. 21 eclipse. CONTRIBUTED
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“It doesn’t take long to damage the eyes if you’re not using the proper viewing glasses,” said Dr. Nhung Brandenburg, president of GOA, a statewide association representing doctors of optometry. “The safest course of action is to purchase solar filters or solar viewing glasses that meet International Organization for Standardization (ISO) standards.”

The eclipse will hit the U.S. mainland for the first time since 1979, and 500 million people in North America will see at least a partial blockage.

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For safe viewing, special glasses are required, which block 99 percent of the visible light coming into your eyes in addition to UVA and UVB rays. Leftover 3-D glasses from a movie theater will not work, and neither will multiple pairs of sunglasses stacked on top of each other.

“You’ll need to make sure the glasses are ISO approved,” Brandenburg said. “They’re much, much darker than regular sunglasses. Some are around 3,000 times darker. Don’t put on sunglasses and think it’ll be dark enough. It only takes a few seconds to cause a permanent burn on the retina.”

Luckily, eclipse glasses aren't all that hard to find. Many retail stores and online sources like Amazon sell the glasses for as low as $2 each. Several local libraries are also handing out glasses for free. Brandenburg said to be wary of any online outlets that may be selling unapproved products. If you wear glasses regularly, simply place the solar glasses on top of your regular eyewear. Snapping photos of the sun is not advised either as the unfiltered light can actually damage both the camera and your eyes.

Anyone who looks directly at the sun without the specialized lenses risks burning their retina, which could lead to vision damage in the form of a permanent blind spot. Brandenburg likens it to having a hole punched in the film of a camera.

In metro Atlanta and most of the U.S., glasses will be required for safe viewing at all times. The metro area will get between a 95 percent and 99 percent blockage around 2 p.m., so the light will dim but not completely fade out.

Those who do trek into the path of totality will have a chance to safely — and briefly — look directly at the eclipse without damaging their eyes. During the estimated two minutes and 40 seconds of total eclipse, the sun will sit completely behind the moon with only a white silhouette visible. During that time, it will appear to be nighttime, and viewers can ditch the glasses.

“We will get what they call a partial eclipse here in metro Atlanta,” said Brandenburg, who sees patients at Kaiser Permanente Glenlake Comprehensive Medical Center in Atlanta and at Townpark Comprehensive Medical Center in Kennesaw. “In the path of totality, there will be a black center with a white shadow around it. We won’t get that, but we’ll still get a view of it. It’ll look like someone took a bite out of the circle.”

A few area school systems are taking advantage, including Cherokee County and Cobb County. Both are extending the school day and providing glasses to all students so they can look at the eclipse.

A full map of where the total eclipse will take place can be found at timeanddate.com.

“Remember what your mother always told you: Never look directly at the sun,” Brandenburg said. “That still applies to us in metro Atlanta.”