Solar
Eclipse
Can a Solar Eclipse Really Blind You?
By Stephanie
Pappas, Live Science Contributor
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. Even so, if
they're with you during your eclipse outing, your furry friends should wear
protective glasses as well
Damaged eyes
Early observers of astronomy
sometimes found out about solar retinopathy the hard way.
Thomas Harriot, who observed sunspots in 1610 but
did not publish his discovery, wrote in 1612 that after viewing the sun his "sight was dim for an hour."
Oxford astronomer John Greaves was once quoted as
saying that after sun observations, he saw afterimages that looked like a flock
of crows in his vision.
In the most famous case of all, Isaac Newton tried
looking at the sun in a mirror, essentially blinding himself for three days and
experiencing afterimages for months.
Scientists don't have a good bead on the prevalence
of eye damage after a solar eclipse.
In one study, conducted in 1999 after a solar
eclipse visible in Europe, 45 patients with possible solar retinopathy showed
up at an eye clinic in Leicester in the United Kingdom after viewing the
eclipse.
Forty were confirmed to have some sort of damage or
symptoms of damage; five of those had visible changes in their retina.
Twenty of the patients reported eye pain, while
another 20 reported problems with vision. Of the latter group, 12 reported that
their sight had returned to normal seven months later, but four could still see
the ghosts of the damage in their visual field, such as a crescent-shaped spot
visible in dim light.
"Our
series demonstrates that, contrary to popular belief, the majority of people
with eclipse retinopathy are not totally blinded," the researchers wrote in 2001 in the journal The
Lancet.
However, they warned, earlier post-eclipse studies
had turned up more severe problems in patients, suggesting that widespread
media warnings not to look at the eclipsing sun may have prevented more damage
during recent eclipses.
Safe
eclipse viewing
Research also suggests that
while a lot of the damage may heal, some may be permanent.
One 1995 study followed 58 patients who sustained
eye damage after viewing a 1976 eclipse in Turkey.
Healing occurred during the first month after the
eclipse, the researchers reported in the journal Graefe's Archive for Clinical
and Experimental Ophthalmology, but by 18 months, whatever damage remained was
permanent up to 15 years later.
So, while it might be tough to go totally blind by
looking at an eclipse, doing so without proper protection could leave a
long-lasting stain on your vision.
The only safe way to view an eclipse, according to
NASA, is to use specially designed sun filters, often available at telescope
stores, or to wear No. 14 welder's glasses, available at welding specialty
stores essentially a hole in a piece of cardboard or paper — can also be used
to view the eclipse indirectly by casting a shadow of the sun on the ground or
on a screen.
REMEMBER not to stare directly at the sun without protective eyewear during the
Aug. 21 total solar eclipse.
If you don't have certified eclipse viewers, you
can also make a pinhole camera viewer that will allow you to see the
eclipse without looking at the sun directly.
Editor's
Note: This
article was first published in 2012 and updated for the Great American Solar
Eclipse in 2017.
Originally published on Live Science.
Stephanie Pappas is a contributing writer for Live
Science. She covers the world of human and animal behavior, as well as
paleontology and other science topics. Stephanie has a Bachelor of Arts in
psychology from the University of South Carolina and a graduate certificate in
science communication from the University of California, Santa Cruz. She has
ducked under a glacier in Switzerland and poked hot lava with a stick in
Hawaii. Stephanie hails from East Tennessee, the global center for salamander
diversity. Follow Stephanie on Google+.
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