Don't Look Now

A total eclipse is due next week, and U.S. medical authorities are as alarmed as a tribe of ignorant savages when the sun is blacked out by the moon. The experts' worry has nothing to do with superstition. They know that after every total eclipse there are thousands of cases of severe damage to the eyes, and some cases of blindness, from careless gazing. Last week such disparate organizations as the American Medical Association, Manhattan's Hayden Planetarium and New York State's Department of Education were busily spreading identical warnings: "Don't look directly at the eclipse." What makes an eclipse so dangerous is that it works insidiously. As the twilight deepens, the viewer can look at the sun without squinting. Meanwhile, the pupils of his eyes are opening wider --just in time to receive the shattering bombardment of infra-red rays that continue after most of the visible radiation is gone. There is no warning pain as the radiation passes through the viewer's dilated pupil and is focused onto the center of the retina, even when the concentrated rays burn a hole in this sensitive, irreplaceable screen. Slight damage to this part of the retina causes incurable blurring of vision. Damage of medium severity destroys all but peripheral vision. More burning of the retina means blindness.

Children's eyes are especially sensitive to damage; for them, as for adults, no sunglasses--not even welders' goggles--are dense enough for safe, direct observation of the eclipse. Neither is a piece of smoked glass. At least two thicknesses of photographic film, fully exposed in daylight and overdeveloped, are needed to make a safe filter. The wiser witness will view the eclipse indirectly, with his back to the sun. This can be done by punching a hole with a pin or sharp pencil in a sheet of cardboard (which serves as a primitive camera) and observing the moon's progress on another sheet of white card a few feet away. The Illinois Society for the Prevention of Blindness recommends a sunscope built from a large cardboard box with a pinhole at one end, a paper reflector inside the opposite end, and a hole in the side big enough for the viewer to stick his head through. (He has to be careful not to block the rays from the pinhole.) To those who find this too cumbersome, the experts suggest the safest plan of all: stay indoors and watch the eclipse on TV.

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