When Ralph Chou was about 12 years old, he took all the right precautions to watch his first solar eclipse.
"I did other stupid things, but when it came to looking at that eclipse, I was being very careful," says Chou, a professor emeritus of optometry and vision science at the University of Waterloo, who's a leading authority on eye damage from eclipse viewing.
The upcoming total solar eclipse will be the 19th one he has seen after a lifetime of eclipse chasing. And Chou is worried about first-timers and other folks who might look up at the spectacle without much forethought.
Tens of millions of people are expected to view the first total solar eclipse visible from the contiguous United States in nearly 40 years.
"Unfortunately, I think it is probably true that during every solar eclipse, there's bound to be somebody who does get hurt," says Chou.