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Instead of wearing sunglasses, wear opaque contact lenses with just a tiny pinhole in the centre. You'd get images just as dim as with sunglasses, but with the advantage of near-infinite depth of field (translation: everything, from a few inches away to infinity would be in perfect focus) and colours
would be unaffected.
[link]
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Nice idea. Trouble is, if you got on a bus or the sun went in, they'd be a lot more difficult to take off than sunglasses. You would also really need to take them off, because your pupils dilating wouldn't have any effect - you'd effectively be blinded. They would only work when light levels were constant. |
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Except they would cause people to go blind. Sunglasses are good for your eyes because they reduce the quantity of light, and because they either contain, or are made from materials that block UV-A and UV-B light. The UV component of sunlight is what is actually causing the damage. Pinhole contacts, by their nature, can't protect from UV light. They would make your pupils expand, letting in even more damaging uv rays than if you were weren't wearing sun protection at all and the pupils contracted naturally to reduce the amount of light entering the eye. |
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Contact lens materials filter out a fair amount of UV by themselves. The small aperture of the lens would further reduce UV tranmission. The argument that pupil expansion would let it more UV is not valid, because the opaque part of the contacts would not let through any UV. Total UV exposure of the cornea would be far reduced, perhaps more then with sunglasses. |
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As aj wrote, they would reduce your ability to adjust to different light conditions. In bright sunlight this disadvantage may be outweighed by the benefits of the contacts. |
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I'd like to try them out. Wish I could buy some, but perhaps they can be homemade from cosmetic contact lenses. Anyone know of a safe way to coat these with a dark material? |
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Contact lens materials filter out a fair amount of UV by themselves. The small aperture of the lens would further reduce UV tranmission. The argument that pupil expansion would let it more UV is not valid, because the opaque part of the contacts would not let through any UV. Total UV exposure of the would be far reduced, perhaps more then with sunglasses. |
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As aj wrote, they would reduce your ability to adjust to different light conditions. In bright sunlight this disadvantage may be outweighed by the benefits of the contacts. |
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I'd like to try them out. Wish I could buy some, but perhaps they can be homemade from cosmetic contact lenses. Anyone know of a safe way to coat these with a dark material? |
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It seems that there is an international patent covering pinhole contacts, dating from 2007. |
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I think the point about infinite depth of field is excellent!! |
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To overcome the adaptability problem, how about lenses
with concentric circles of light-reactive pigment,
progressively less sensitive. In bright light, all the
pigment rings would darken, giving you the full benefit of
the pinhole. |
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As the light dimmed, progressively wider rings would
become transparent, creating a sort of solid-state iris
effect. |
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//Anyone know of a safe way to coat these with a dark
material?// |
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If you have rigid lenses, you can use ordinary aerosol paint;
just mask off the central area and spray very lightly on the
*outside* surface until you build up the opacity. Then leave
at least overnight to dry thoroughly. I made a pair of gold
contacts this way. |
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And don't get any dust on them while the paint's drying. |
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