> > > The theory is that you can't stand to look at the full sun long enough to damage your eyes. However, with part of the disc blocked by the moon, you can continue to look and the part that is still visible will burn your eyes. That's what they tell us.
> >
> > I had always heard it was something like since there was less light overall, your pupils would be more dilated thus letting the light from the disc (which is just as intense as always) do more damage. I have no idea how true that is.
> >
> > > But I must repeat my question: How many people do you know who have been blinded by a solar eclipse?
> > >
> > > Howard
> >
>
> I hear someone local (ie Roseburg OR) died of the plague recently, though I didn't know him. I imagine looking at the sun for more a few minutes would damage my eyes, but I've never done that. It's pretty featureless from this range. The brightness of the light I think has less to do with that than the contrast, perhaps. For example, it may hurt less for me to look at the bright sky and glance at the really bright sun than it hurt for Dave to look at the completely unlit flash and then the very-much lit flash. :) But then, if that were the case, wouldn't the eclipse provide too much contrast as well?


So this is what I heard about "eclipse blindness" from the optometry sage in the neighbourhood:

"Eye damage due to viewing an eclipse? It's like what happens when you play pyromaniac with a magnifying glass, on a sunny day. The lenses of your eyes act as tiny magnifiers. If you look at a partially eclipsed sun, its rays are focused on the retinas of your eyes, and these can get fried. This is the same sort of thing as using that magnifying glass to focus the sun to a pinpoint and burn a hole in paper or leaves. The only difference is that it'd be your eyes getting burned instead. Part of the danger lies in the fact that the retina is not sensitive to pain; you wouldn't even feel it happening. But a retinal burn is permanent and irreversible, producing a blank spot in your fovea, the most vital part of your field of vision.

"During an eclipse, the sun's photospheric crescent is intensely bright, even though it may seem relatively dim. The UV radiation given out is still more than enough to cook delicate tissue -- that means it can destroy the photo-reactive, light-sensitive rod and cone cells in the retina."

As for statistics, well, public awareness programs have done a pretty good job in preventing more retinal injuries. They say scary things like, "During the March 7, 1970 eclipse in the United States, there were 145 reported cases of people who damaged their eyes by looking at the partially eclipsed sun either directly, or through sunglasses, and also while using homemade devices of exposed colour film, smoked glass, and the like." So you need a filter that is at least a Number 14 welder's glass (dark UV filter) to safely look directly at an eclipse. Come to think of it, that's pretty dark... That kind of glass has a thin layer of aluminum, chromium, or silver deposited on its surface to directly attenuate visible, ultraviolet, and infrared energy. Or you can use that indirect-image, pinhole view-projector thingie. I seem to recall that after last year's August 11 eclipse, British hospitals received 200 calls from people who'd looked at the eclipse without proper protection for their eyes, and only found out a few hours later that they now had eye problems.

I always wondered about this part before, but here's the rub: The sun isn't actually more dangerous during eclipses. People just have more of a tendency to *stare* during a partial eclipse. Damage has occurred with as little as five seconds of direct exposure. Okay, now I'm scaring myself, heh.

Wolfspirit