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Pinhole contacts

Opaque contact lenses with tiny pinholes in them
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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.
hippo, Feb 05 2001

MkI pinhole contact. http://i923.photobu...%20MkI/IMG_5419.jpg
And yes that's a photo of Feynman in the background. [MaxwellBuchanan, Jul 07 2011]

[link]






       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.
aj, Feb 05 2001
  

       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.
eyeguy, Jan 27 2004
  

       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.   

       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.   

       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?
jmvw, Oct 21 2009
  

       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.   

       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.   

       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?   

       It seems that there is an international patent covering pinhole contacts, dating from 2007.
jmvw, Oct 21 2009
  

       I think the point about infinite depth of field is excellent!!   

       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.   

       As the light dimmed, progressively wider rings would become transparent, creating a sort of solid-state iris effect.
MaxwellBuchanan, Oct 21 2009
  

       //Anyone know of a safe way to coat these with a dark material?//   

       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.   

       And don't get any dust on them while the paint's drying.
MaxwellBuchanan, Oct 21 2009
  

       Very odd. I just thought (or thought I'd thought) of this, and Googled "pinhole contacts" before posting it. This page was the top hit.   

       Even odder and more disturbing, I didn't even recognise my annotations from a mere two months ago. I think my short- term memory is going.   

       Even worse, I think my short-term memory is going too.
MaxwellBuchanan, Dec 30 2009
  

       Even odder. Once again, the idea of pinhole contacts popped into my head, because I'm now both short- and far-sighted and want something that will solve all problems. Once again, I found myself back at this page. Once again, I had completely forgotten about it, and about having annotated it.   

       It gets worse. I was about to say something about my memory being lousy when I realized I'd already said that in my last annotation.
MaxwellBuchanan, Jul 02 2011
  

       "Great minds run in the same channel." Or "rut" as the case may be.   

       Try piercing an index card with pinholes -- MULTIPLE pinholes, closely spaced -- and holding that up to one eye, as close as you can get it. It's an old trick for testing visual acuity in people with refractive error who forgot their spectacles. It does what you want, which is to correct myopia and presbyopia simultaneously with a single "lens."   

       Some experimentation with size and spacing of pinholes is required, or you can buy a plastic version from a vendor of medical equipment.
mouseposture, Jul 02 2011
  

       Done that. Also just tried a pinhole in a small piece of foil held against my contact lens. Works fine - focus from about 1 inch to infinity. Next step is to paint up some contacts.
MaxwellBuchanan, Jul 02 2011
  

       The problem of reduced light adaptation is trivially solved by carrying a few-kw floodlight. (Batteries in backpack or handcart).
spidermother, Jul 03 2011
  

       (Max), forgetting and rediscovering your annos is part of the joys we all owe [Jutta] for. I periodically find an idea on [recent] and compose a witty response while reading it, and then go "Oh, I was here a few years ago...never mind."   

       Someday I'll tell you about my plan for my Alzheimers mom and my brother's Alzheimers mother-in-law.   

       Did that make any sense? Leaving the site now, see you next week.
normzone, Jul 03 2011
  

       That's nothing - *I'd* completely forgotten about this idea, and apparently I wrote it.
hippo, Jul 03 2011
  

       // want something that will solve all problems //   

       We can help. Assimilation into the collective will solve all your current problems in one go. We'll even throw in a handy laser pointer on the side of your head.
8th of 7, Jul 03 2011
  

       I read this as Pinhole Contracts.... small print that is even smaller!
xenzag, Jul 03 2011
  

       If you wear contacts for short-sightedness, but are also getting far-sighted (like me), pinhole lenses would seem a good option. With a 1mm pinhole (in a piece of foil, held just touching the front surface of one contact lens) I got sharp focus over the entire visual range.   

       My Googling found "pinhole" contacts, but only for certain eye diseases; and they often had concentric zones of different power, rather than a simple pinhole. Given that pinhole glasses are well-known, there must be some good reason why pinhole contacts aren't common, but I'll have to do the experiment to find out what that reason is.   

       My previous attempts at painting lenses (many years ago) were fine, but a sharp pinhole would involve a sharp edge to the paint (which was on the outer surface). We have a metal evaporator at work, though, so it ought to be possible to deposit a gold film with a pinhole (gold films are opaque even when very thin, avoiding the problem of sharp paint-edges).
MaxwellBuchanan, Jul 03 2011
  

       You're not getting far-sighted - that's hyperopia (which is what I've got). What you've got is (probably) presbyopia - the age-related decline in the flexibility of the eye's lens, which means you can't focus as close as you used to be able to.
hippo, Jul 03 2011
  

       If having presbyopia makes you cry are you then a presbyterian?
xenzag, Jul 03 2011
  

       // What you've got is (probably) presbyopia//   

       That's the one.   

       What utterly amazes me is that presbyopia is seen as a normal and unavoidable degeneration, and there seem to be no drugs being developed to reverse the hardening of the lens. Given that it's a very well-understood process involving essentially a single protein (crystallin, if memory serves), it should not be too difficult a problem to solve.
MaxwellBuchanan, Jul 03 2011
  

       // no drugs being developed to reverse the hardening of the lens //   

       There are drugs to stop you caring about it though. Ethyl alcohol is particulalrly good in this respect.
8th of 7, Jul 03 2011
  

       The MkI pinhole contact lens was not a complete success. For one thing, I only had red acrylic spray-paint. For another thing, the hole wasn't crisp enough and had fadey edges. And for yet another thing, I forgot that contacts are designed to slide around a bit, so the damned hole wouldn't stay central.   

       However, it was painless, and the focus (though not great) was roughly the same from about 8 inches to infinity, I think.   

       Photo in link.
MaxwellBuchanan, Jul 07 2011
  
      
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