|Don's Home Health Eyes Viewing the Sun|
Permanent eye damage can occur in as little as a minute and a half from looking at the disk of the Sun directly, or through a camera viewfinder, or with binoculars or a telescope even when only a thin crescent of the Sun or Baily's Beads remain during a solar eclipse.
In one study when people who stared directly at the sun for several minutes during the 1999 eclipse went to see their doctor, about half had permanent damage.
The moment you begin looking at the sun, you start to develop a sunburn on your cornea (eyeball), known as photokeratitis. The cells of the cornea, the transparent outer layer of the eye, will blister and crack when overexposed to UV light.
Most of the damage is caused by ultraviolet (UV) light. During sunsets, when the intensity of ultraviolet light is lower due to scattering you can look at the sun, but avoid looking directly at it for more than a few minutes at a time.
Looking at the sun steadily during midday for longer periods can cause damage to the retina, the collection of light-sensitive cells located at the back of the eye. Solar retinopathy, as the damage is known, may not be painful like photokeratitis--but the results can be permanent. It is like macular degeneration, resulting in blindness in the center of your field of vision. Basically, that black dot you see after a photo flash that would just never go away.
Viewing a total eclipse:
There are several ways to observe an eclipse safely;
During the short time when the moon completely obscures the sun - known as the period of totality - it is safe to look directly at the star, but it's crucial that you know when to take off and put back on your solar glasses.
Look for crescent shaped images of the eclipsed sun in the shadows below a tree. The leaves create the effect of a pinhole camera.
See Reputable Vendors of Solar Filters & Viewers | American Astronomical Society (AAS)
Paper ISO 12312-2 certified glasses (block out 100% of harmful UV and infrared as well as 99.999% of intense visible light) can be found for $1.00 *.
How long does it take before your eyes get damaged when looking at the sun? | UCSB Science Line
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