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Jerry Avins jya at ieee.org
Thu Dec 12 08:43:54 EST 2002

jmdrake wrote:
>   ...  The extra layers
> of non-sensitive cells that the light must pass through before reaching
> the sensitive cells acts like a "filter" to protect from UV radiation.
> That's such a concern that human "engineers" have devised UV blocking
> sunglasses to further block potentially damaging rays.  

Those special UV-blocking lenses were invented not by engineers, but by
advertising copywriters. Uncoated glass lenses block harmful UV.
Coatings are needed only on plastic to bring them up to the standards
set by glass.

UV is also blocked from the retina by the vitreous humor. The greatest
danger UV poses to unprotected eyes is to the lens. Inverting the retina
can't help that. All the chordata have inverted retinas, including fish.

A specious argument diminishes even the best founded position. We need
to take great care with the facts in order to convince in the long run.

Engineering is the art of making what you want from things you can get.

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