Local doctors are warning Rogue Valley residents to take safety precautions when viewing the solar eclipse that will occur the morning of Aug. 21.

"The sun's rays carry a tremendous amount of photochemical energy. People who look at the sun without protection can suffer vision loss," said Dr. John Welling of the Medical Eye Center in Medford. "It can be permanent or temporary. There can be some improvement three to six months after the initial event, but it's often permanent."

If a person looks at the sun, energy is focused on the retina and causes damage to the rods, cones and retinal pigment of the eye, he said.

Medical Eye Center, 1333 E. Barnett Road, is offering certified solar-viewing glasses for $1 per pair, with a limit of two pairs per person. The lenses of the glasses screen out the damaging rays of the sun, allowing people to safely view the sky as the moon gradually covers up the face of the sun.

Other places to pick up eclipse-viewing glasses include Northwest Outdoor Store, 980 Biddle Road, Medford, and Northwest Nature Shop, 154 Oak St., Ashland. Both stores are selling glasses for $1.95 per pair. They're also available at stores such as Fred Meyer.

Welling warned that regular sunglasses will not protect the eyes from the sun's rays, some of which fall outside the visible spectrum of light.

The moon won't completely block out the sun in the Rogue Valley, which is outside the 70-mile-wide path of totality. Oregon cities that will see a total eclipse include Lincoln City on the coast, Salem in the Willamette Valley and Madras in Central Oregon. The path of totality stretches in an arc across the nation from Oregon to South Carolina.

In the Willamette Valley, the moon will start its path across the sun's face at about 9:05 a.m. The total eclipse phase will start at about 10:17 a.m. and last almost two minutes.

For people in the path of totality, the only safe time to look at the sun is during the approximately two-minute window when the moon completely covers the sun, Welling said.

There will never be a safe time to view the eclipse with the naked eye in the Rogue Valley, he said.

People watching the eclipse should use protection, such as eclipse glasses that meet ISO 12312-2 standards. Glasses should bear wording that they meet the requirement.

"There is no safe amount of time a person can look at the sun without approved solar filters," Welling said. "The damage can be instantaneous."

Doctors at Medical Eye Center warn people to never look through unfiltered cameras, binoculars or telescopes — even while wearing certified eclipse glasses. The magnified lenses intensify the rays of the sun, which can lead to serious eye damage.

People should inspect their eclipse glasses before using them to make sure they are not scratched or damaged. Children should always be supervised when using the glasses.

To use the glasses, put them on while turned away from the sun. Remove the glasses while turned away from the sun as well, doctors recommend.

Other safe viewing methods include indirectly viewing the eclipse through a homemade pinhole projector. Detailed instructions are available online, Welling said.

To make a simple pinhole projector, take a sheet of paper and make a hole in the middle of it using a pin or a thumbtack. Make sure the hole is round and smooth.

With your back toward the sun, hold the piece of paper with a pinhole up and allow the sun's rays to shine through onto a second piece of paper. An image of the eclipse will appear on the second paper.

More elaborate pinhole projectors can be made using a box.

The leaves of a tree can also act as pinhole projectors as light shines through holes and gaps in the leaves. Face away from the sun and look at the shadows cast by a tree, preferably on a smooth, light surface like a white wall. The shadows will appear as multiple images of the eclipse.

— Reach staff reporter Vickie Aldous at 541-776-4486 or valdous@mailtribune.com. Follow her at www.twitter.com/VickieAldous.