A rare astronomical event will take place on April 8, 2024, when a total solar eclipse crosses North America, passing over Mexico, the U.S., and Canada. During a total solar eclipse, the moon moves between the sun and the earth blocking the sun from view. This results in the sky darkening, much like what you’d experience at dawn or dusk.

Millions of people will stop to witness this event, and defense health officials emphasize certain precautions and protections for your eye health to maintain operational readiness and quality of life.

“A solar eclipse is a beautiful and unique event to enjoy, and share with family and friends,” said Dr. Mariia Viswanathan, an ophthalmologist and vision care research and readiness section chief at the Defense Health Agency Vision Center of Excellence. “But safety should always be the top priority.”

According to U.S. Navy Capt. Todd Lauby, chief of the DHA VCE, it’s possible to injure your eyes without taking the right kind of safety precautions.

“Exposure to the sun’s intense light radiation can damage the retina leading to conditions called solar retinitis and retinopathy,” said Lauby.

“The sun’s ultraviolet rays can also cause photokeratitis, which is essentially a sunburn on the surface of the eye,” added Viswanathan.

These conditions can result in temporary or permanent vision loss depending on the severity.

“The length of time exposure, cumulative exposures, and even the size of your pupils can determine the severity of vision loss,” said Lauby. “Only a few seconds of exposure or multiple exposures of shorter duration can damage the sensitive cells in the retina.

“The injury to the eye affects the area of the retina called the macula, which is responsible for our central vision, he continued. “Those affected will report symptoms of persistent after-images in their vision, reduced or distorted vision, a black or blind spot in their central vision, or abnormal color vision.”

There are ways to protect your eyes from sun exposure when watching a solar eclipse, but normal sunglasses are not up to the task, said Lauby

“Sunglasses will not protect your eyes from directly viewing a solar eclipse no matter how dark they are,” he said.

Viswanathan and Lauby recommend wearing only approved eclipse glasses labeled ISO 12312-2 purchased from a trusted source.

“Another option is Number 14 welder’s glass,” said Lauby.

“In addition, it is not safe to view a solar eclipse through cameras, binoculars, or telescopes, even with eclipse glasses, since they are not designed for the concentrated rays streaming through these devices,” he said.

Viswanathan agreed, adding, “These devices do not offer sufficient protection or filters against the sun's harmful rays. In fact, looking at the sun through such devices can amplify the light and heat leading to even greater risk of eye damage.”

“There are special-purpose solar filters that must be used over the front of the optics of these devices to protect your eyes,” said Lauby.

“You can make your own eclipse projector using a cardboard box, a white sheet of paper, tape, scissors, and aluminum foil,” said Lauby.

According to NASA’s instructions for creating an eclipse projector, light will stream through a pinhole punched into aluminum foil taped over a hole in one side of the box. During the partial phases of a solar eclipse, this will project a crescent sun onto a white sheet of paper taped to the inside of the box. Look into the box through another hole cut into the box to see the projected image.

“This way, you're not looking directly at the sun, but rather at its projected image, which is a safe way to view an eclipse,” said Viswanathan.

If you think you’ve been injured, Lauby recommends seeing an optometrist or ophthalmologist for a thorough examination.

“This is to ensure an accurate diagnosis and determine the amount of damage, as well as to exclude any treatable eye conditions that may be affecting your vision,” said Lauby. “Your eye care provider can continue to assess your vision and perform retinal imaging scans to monitor for any improvement over time.”

“These injuries occur without pain. Be alert if you suspect you or your child may have suffered an eye injury from viewing a solar eclipse—it’s important to seek medical attention immediately,” said Viswanathan.

Symptoms of injury can include:

• Loss of central vision
• Distorted vision
• Altered Color Vision

“Even if symptoms aren't immediately apparent, damage could still have occurred, so it's best to get checked by a vision care provider,” said Viswanathan.

“Remember, proper protection and education are the keys to preventing an injury,” said Lauby. “It can be fun to watch a solar eclipse if done safely.”

A total solar eclipse won’t be visible again in the U.S. for almost two decades—until 2044—so excitement is building for this uncommon occurrence. The last one occurred in 2017.

To learn more about the solar eclipse and ways to protect your vision, visit NASA’s total solar eclipse safety page.