Experts warn watching solar eclipse without a protective eyewear risk lasting blind spots.
Everyone who plans to look skyward when the solar eclipse occurs on Monday should have proper protective eyewear, or risk lasting blind spots, experts warn.
Regular sunglasses will not do, the US space agency says.
Only eclipse glasses that have a certification of "ISO 12312-2 international standard" are safe for use, according to NASA.
Other options are number 14 welder's glass, or making a pin-hole projector that allows a user to project the image of the sun onto paper or cardboard.
Dangers are real
"The dangers of looking at the sun are real and serious," said Vincent Jerome Giovinazzo, director of ophthalmology at Staten Island University Hospital, Northwell Health.
"The damage can really be permanent and right smack in the centre of their vision."
Many may recall a childhood experiment of using a magnifying glass to focus sunlight on a leaf or a sheet of paper and set it on fire.
"The same thing can happen to your eyes," said Giovinazzo.
Jules Winokur, an ophthalmologist at Lenox Hill Hospital in New York, has seen the damage in patients who stared at the sun.
"They get a kind of macular degeneration where they are burning into their retina and they can lose vision and it can be permanent," he said.
"You can be left with a scar from where you were staring at the sun, and that can be right in the centre of your vision."
Don’t let lack of discomfort fool you
Most people don't want to look at the sun because it hurts. But during an eclipse, the pain and discomfort are not there.
"It is actually not as uncomfortable to stare at the sun but the damaging effects are the same," Winokur explained.
"And what you can do is you can burn your macula the same shape of whatever crescent the sun is showing. You wouldn't necessarily feel uncomfortable."
There is one exception to the rule of not staring directly at an eclipse.
Those in the path of totality, where the sun is completely blocked by the moon, can take off their protective eyewear for the short period of time when the sky is completely dark and no circles of sunlight are visible around the moon.