On August 21, a total solar eclipse will touch the U.S. mainland for the first time since 1979, following a path that crosses the country from Salem, Oregon to Charleston, South Carolina.

Tens of millions of people who live within a 70-mile radius of its cross-country track will witness the eclipse in totality (the sun completely blocked by the moon) while millions of others outside of it will enjoy a partial eclipse.

The American Optometric Association (AOA), America’s family eye doctors, is urging Americans to view the eclipse with proper eye protection to avoid any temporary or permanent eye damage from the sun.

“The eclipse is a rare moment that the whole country is able to share,” said Dr. Gary Upchurch of Associates in Eye Care in Albany. “As America’s primary eye health and vision care experts, doctors of optometry are excited to help everyone enjoy it safely by protecting their eyes.”

To ensure spectators won’t miss the remarkable sight, the AOA is sharing a few tips for safe viewing:

• Get centered and enjoy the view. Within the path of totality, you can safely witness the two or more minutes when the moon completely covers the sun with the naked eye. Otherwise, your eyes should always be protected by verified viewing tools. Never look directly at the sun without eye protection, even briefly. Visit eclipse.aas.org to access eclipse duration charts.

• Know your duration. Outside of the path of totality, always use solar filters. O.D.s want to reinforce that the only safe way to look directly at the uneclipsed or partially eclipsed sun is through special-purpose solar filters or other ISO-certified filters, such as “eclipse glasses” or handheld solar viewers. The AOA encourages ordering solar eclipse glasses in advance and recommends referring to the American Astronomical Society’s (AAS) site for a list of manufacturers.

• Be aware of harmful solar exposure. If you stare at the sun without protection, you may experience damage to your retina (the tissue at the back of your eye) called “solar retinopathy.” This damage can occur without any sensation of pain, since the retina does not have pain receptors. The injury can be temporary or permanent. Visit your local doctor of optometry immediately if an accident occurs.

To access additional information and educational materials on the solar eclipse, visit aoa.org/2017eclipse.