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aparker22@gmail.com
medicine forum beginner
Joined: 03 Jul 2006
Posts: 1
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 Posted: Mon Jul 03, 2006 4:04 pm Post subject:
Polarized contact lenses?
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I've been reading here quite a bit lately, and thought some of you
would
have something to say about this.
With all the advancements in contact lenses, especially the recent
""nike sport tint"" stuff, I think it would be possible
to create a polarized filter on contact lenses.
Basically, you'd need a toric lens with the toric weighting, but +0.0
cylinder (unless, of course, it's needed for correction). I suppose
there's some difficulty that would be involved in actually applying the
filtration: you'd either need to apply some kind of coating, or
somehow figure out how to align things when the lenses are cast..
It seems that polarized lenses are good for cutting down on glare, and
might be comfortable enough for all-around use..
Anyone think this would be a good idea? |
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LarryDoc
medicine forum Guru Wannabe
Joined: 29 Apr 2005
Posts: 262
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| Posted: Mon Jul 03, 2006 5:56 pm Post subject:
Re: Polarized contact lenses?
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In article <1151942642.787866.129340@m73g2000cwd.googlegroups.com>,
aparker22@gmail.com wrote:
| Quote: | I've been reading here quite a bit lately, and thought some of you
would
have something to say about this.
With all the advancements in contact lenses, especially the recent
""nike sport tint"" stuff, I think it would be possible
to create a polarized filter on contact lenses.
Basically, you'd need a toric lens with the toric weighting, but +0.0
cylinder (unless, of course, it's needed for correction). I suppose
there's some difficulty that would be involved in actually applying the
filtration: you'd either need to apply some kind of coating, or
somehow figure out how to align things when the lenses are cast..
It seems that polarized lenses are good for cutting down on glare, and
might be comfortable enough for all-around use..
Anyone think this would be a good idea?
|
A nice idea but not at all practical to do. Nearly impossible, actually
as you would need to fuse a polarizing layer to the existing lens and
then, as you mentioned, stabilize the rotation.
A much better and easily accomplished solution is to wear polarized
sunglasses over regular contact lenses.
FYI, we do have tinted lenses in any shade or density and even
photochromic RGP lenses that get darker outside and clearer inside.
LB, O.D. |
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Mike Tyner
medicine forum Guru
Joined: 24 Mar 2005
Posts: 1299
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| Posted: Mon Jul 03, 2006 6:23 pm Post subject:
Re: Polarized contact lenses?
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<aparker22@gmail.com> wrote
| Quote: | It seems that polarized lenses are good for cutting down on glare, and
might be comfortable enough for all-around use..
Anyone think this would be a good idea?
|
Yes, but unworkable for a couple of reasons.
"Polarized" lenses are a sandwich - two layers of plastic surrounding an
acetate film that is very similar to a photo negative. The acetate film
supports a layer of emulsion, a gel where silver halide crystals are formed
by preciptitation under an electric field.
The gel is probably permeable to oxygen when wet, but the acetate base film
would virtually block all oxygen from percolating through the contact into
the eye. A completely different carrier system would have to be developed.
The gel might be sandwiched into soft lens materials, but it would surely
swell and loosen when wet. It would be so fragile that rubbing and even
blinking would probably rearrange the gel, not to mention shaking up the
polarizing crystals. Then there are toxicity concerns since the materials
must be pretty incompatible with the eye, and would have to be sealed
between layers of (wet) contact lens material.
Toric contacts aren't 100% stable. It would be normal for the polarizing
axis to rotate a little, sometimes a lot.
All this for the limited benefit of polarizing, with the obvious drawback of
50% filter after sundown and screwey LCD instrument panels.
And the market is pretty limited, in part because those who really benefit
(fishermen, drivers) are arguably better off with spectacle lenses. Contacts
offer no impact protection, nor UV protection for the lids and adnexa, nor
can they be removed quickly.
-MT |
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Quick
medicine forum Guru
Joined: 19 Jun 2005
Posts: 343
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| Posted: Mon Jul 03, 2006 6:29 pm Post subject:
Re: Polarized contact lenses?
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LarryDoc wrote:
| Quote: | In article
1151942642.787866.129340@m73g2000cwd.googlegroups.com>,
aparker22@gmail.com wrote:
I've been reading here quite a bit lately, and thought
some of you would
have something to say about this.
With all the advancements in contact lenses, especially
the recent ""nike sport tint"" stuff, I think it would
be possible
to create a polarized filter on contact lenses.
Basically, you'd need a toric lens with the toric
weighting, but +0.0 cylinder (unless, of course, it's
needed for correction). I suppose there's some
difficulty that would be involved in actually applying
the filtration: you'd either need to apply some kind of
coating, or somehow figure out how to align things when
the lenses are cast..
It seems that polarized lenses are good for cutting down
on glare, and might be comfortable enough for all-around
use..
Anyone think this would be a good idea?
A nice idea but not at all practical to do. Nearly
impossible, actually as you would need to fuse a
polarizing layer to the existing lens and then, as you
mentioned, stabilize the rotation.
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Ummm, just how thick does a polarizing layer need to
be to work?
-Quick |
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Mike Tyner
medicine forum Guru
Joined: 24 Mar 2005
Posts: 1299
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| Posted: Mon Jul 03, 2006 6:37 pm Post subject:
Re: Polarized contact lenses?
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"Quick" <quick7135-news@NOSPAMyahoo.com> wrote
| Quote: | Ummm, just how thick does a polarizing layer need to
be to work?
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Good question. Most (minus) contacts are less than 0.1 mm at the center.
The raw polarizing film I bought from Edmund was thicker than that, probably
0.3 mm dry and about double when wet.
-MT |
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biscuit
medicine forum Guru Wannabe
Joined: 24 Apr 2005
Posts: 296
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| Posted: Mon Jul 03, 2006 7:17 pm Post subject:
Re: Polarized contact lenses?
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LarryDoc wrote:
| Quote: |
FYI, we do have tinted lenses in any shade or density and even
photochromic RGP lenses that get darker outside and clearer inside.
LB, O.D.
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Whoa. Is this widely available, or only in specific applications? In
other words, what are the odds of a lens like I currently have being
available in "transitions"?
Do they look weird/creepy when dark?
-- |
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Repeating Rifle
medicine forum Guru Wannabe
Joined: 04 May 2005
Posts: 141
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| Posted: Mon Jul 03, 2006 9:07 pm Post subject:
Re: Polarized contact lenses?
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On 7/3/06 11:29 AM, in article
Amdqg.79642$4L1.40045@newssvr11.news.prodigy.com, "Quick"
<quick7135-news@NOSPAMyahoo.com> wrote:
| Quote: | Ummm, just how thick does a polarizing layer need to
be to work?
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Polaroid film is much thinner than the sandwich used to protect the flimsy
film. Technically, what is needed is a birefringent (preferably uniaxial)
material that is highly absorbing along one crystal axis but clear in the
other. Tourmaline is such a material. Other materials might be something
like the needle like crystals of some dyes. The original work by Land used
such crystals. See: http://en.wikipedia.org/wiki/Polaroid. Dyes tend to have
very strong absorption so that little thickness is required.
Bill
-- Ferme le Bush |
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