America is preparing for the first total eclipse in a century

As millions of Americans turn their faces to the sky to see the world's first total solar eclipse in a century, many will try to wear sunglasses designed for that purpose, but experts warn the public to stay away from unsafe spectacles.

Approved eyeglass manufacturers, tested to ensure that they are safe to follow up on the event, were quick to meet the increasing demand before the total eclipse on August 21st.

They joined astronomers and ophthalmologists in warning against flawed imitation glasses flooding the US market.

"They are a handful of unscrupulous people who exploit the eclipse to raise money and endanger public safety," said Richard Feinberg, a media officer at the American Astronomical Society.

Experts say staring at the sun without putting on a pair of suitable glasses filters the light. Even if the moon partially obscures the sun during the eclipse, it can damage or destroy photoreceptor cells in the retina, leading to blind spots in the eye.

The use of specially designed glasses with sun filters allows the user to stare safely into the sun at any time for an indefinite period of time.

Although the use of safe glasses to stare at the sun dates back more than three decades, it has not been made available to the masses before on this wide scale this year.

Fainberg says total eclipse may be the largest in terms of the number of observers in human history.

This is largely due to the fact that this eclipse will be the first in 99 years to include the entire United States.

It will also be the first total solar eclipse to be seen from any of the 48 states in North America since 1979.

The lenses of some fake glasses allow light to be diffused from sources that emit relatively weak light, such as fluorescent lamps, while the observer sees through the original eyeglass glasses dark shadows when looking at light sources that are weaker than the sun.