People across the United States will have the chance to see a total solar eclipse on Aug. 21, the first time the spectacle was viewable from the continental U.S. since 1979. While it may be tempting to brush off warnings about looking up at this eclipse bare-eyed, don't: The light of an eclipse really can damage your eyes — though warnings of total blindness may be overstated.



The condition is called solar retinopathy, and it occurs when bright light from the sun floods the retina on the back of the eyeball. The retina is home to the light-sensing cells that make vision possible. When they're over-stimulated by sunlight, they release a flood of communication chemicals that can damage the retina. This damage is often painless, so people don't realize what they're doing to their vision.
Solar retinopathy can be caused by staring at the sun (regardless of its phase), but few people can stand to look directly at our nearest star for very long without pain.


It does happen occasionally — medical journals record cases in which people high on drugs have stared at the sun for long periods of time, causing serious damage. Adherents of sun-worshipping religious sects are also victims. In 1988, for example, Italian ophthalmologists treated 66 people for solar retinopathy after a sun-staring ritual.



But during a solar eclipse , more people are at risk. With the sun almost covered, it's comfortable to stare, and protective reflexes like blinking and pupil contraction are a lot less likely to kick in than on a normal day. Even pets are vulnerable to eye damage from looking at an eclipse, though they don't tend to look directly at the sun.




https://www.livescience.com/20433-solar-eclipse-blind.html