The much anticipated once-in-a-lifetime celestial event - where the moon and sun have the same apparent size - will take place nationwide on Monday, August 21, 2017.

Dr. Mark Ewald, ophthalmologist at TriStar Centennial Medical Center in Nashville, Tenn. - the largest city within the totality's path (when the moon completely blocks the sun) - has a passion for both the cornea and the cosmos.

Eye protection is a must for the upcoming eclipse and Dr. Ewald addresses key questions about seeing one of nature's rarest wonders:

Why is it recommended to wear specialized glasses during the eclipse?

Solar eclipse glasses are absolutely needed in order to safely view the sun as the moon passes in front of the sunlight. The sunlight from the eclipse is actually no more dangerous than regular sunlight. However, the temptation to stare at the eclipse is greater than looking at the sun on a normal day.

Will regular sunglasses work?

Eclipse glasses block about 99.9 percent of sunlight, while regular sunglasses do not. Sunglasses are used for viewing indirect sunlight only. Under no circumstance should sunglasses, telescopes or binoculars be used to view the eclipse.

So, what happens to your eyes if you watch the eclipse with the naked eye?

If someone stares too long at the sun - either during the eclipse or on any given day - the retina of the eye can suffer solar retinopathy.

What is solar retinopathy?

Solar retinopathy is a photochemical reaction in your retina, the light-sensitive tissue that lines the back of your eye that sends singles to your brain about what is being seen. Symptoms of solar retinopathy include pain, tearing and redness. But, most dangerously, you would experience blurry vision or loss of central vision.

Is damage reparable or permanent?

Depending on the severity of retinopathy, damage can be temporary or permanent. However, temporary vision loss can last months before recovery occurs. If the damage is permanent, there is not a restorative medication or surgery for the retina.

What should someone do if he or she thinks they have an eye injury as a result of watching the eclipse?

If you are experiencing symptoms, immediately stop looking at the sun. Please seek medical attention for an examination to confirm a diagnosis by scheduling an appointment with an eye care professional.

Dr. Ewald notes that when the sun is completely blocked by the moon, it is safe to look directly at the eclipse; however, this only applies to those who are in the path of totality. If you aren't in the path of totality, you should keep your glasses on throughout the entire event.

Once the totality is over and the sun's rays start shining again, eclipse glasses should be replaced immediately.

Through working with his patients, Dr. Ewald sees how important and essential vision is to communicating, reading, driving - basically most day-to-day functions. He stresses the importance to take preventative measures by wearing approved solar eclipse glasses since there are not treatment modalities for solar retinopathy.

For him, the reason to take care of eyesight is personal.

"During medical school, I found the physiology of the eye interesting, further peaking my interest to become an ophthalmologist," said Dr. Ewald. "My grandmother had dry macular degeneration, which limited her sight and independence, so I have seen first-hand how important eyesight is for a person's daily life."

If you plan on watching the eclipse, practice safety! Be sure to wear your solar eclipse glasses and ensure that the lenses are not tampered with or scratched.

Dr. Mark Ewald practices ophthalmology at TriStar Centennial Medical Center in Nashville, Tennessee. TriStar Centennial is part of TriStar Health, a division of HCA Healthcare.