anti reflective coating?

Ever noticed how many older folks have brown patches burned into their
upper cheekbone? It is immediately below the glasses and exactly where
a downward reflecting sun hits.

So I wonder if anti reflective coating on outside of lenses is a good
idea for a preventative. It seems comparable to the times I walk along
a waterway when the water is riffled by wind vs calm - sun reflecting
off the calm can be brutal.

But I distrust coatings, which may make cleaning a problem and may not
age gracefully. Opinions?

On Jan 14, 4:10*pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> With or without a coating, the sun would have to be at a precise angle,
> almost directly overhead, to reflect off lenses at the proper angle to burn
> the cheeks. Striking the cheeks obliquely like that, you limit the reflected

Interesting, but since most glasses are curved inward and are (or
should be) canted a bit downward... I think the bounce is from a lower
sun angle that hits the lense so low that it doesn't have to much
distance (and thus divergence) to the skin spot in question. And I
don't think it comes from sunburn, so may not strictly be UV but
rather some long term response to a slight differential of light.
Maybe somewhere on web there are portraits of the problem from a
dermatology point of view that sheds some (ahem) light, maybe of
sunblasted faces of Australian blondes or redheads.

"dumbstruck" <(E-Mail Removed)> wrote in message
news:5b9333fb-43b9-43b3-98f5-(E-Mail Removed)...
> Ever noticed how many older folks have brown patches burned into their
> upper cheekbone? It is immediately below the glasses and exactly where
> a downward reflecting sun hits.

No, never noticed it.

> So I wonder if anti reflective coating on outside of lenses is a good
> idea for a preventative. It seems comparable to the times I walk along
> a waterway when the water is riffled by wind vs calm - sun reflecting
> off the calm can be brutal.

If the lens already reflects UV, I doubt an AR coating would add much
aditional protection.

> But I distrust coatings, which may make cleaning a problem and may not
> age gracefully. Opinions?

If you get one of the factory coatings like Zeiss Caret Advantage, Essilor's
Crizal, etc, then they are quite durable if you don't abuse them. Quality AR
coatings are also available from other lens manufacturers.

The coatings applied by local optical shops are much more fragile and cost
more in the long run because you often will have to replace your lenses
before your Rx changes.

On Jan 14, 4:10*pm, "Mike Tyner" <mty...@mindspring.com> wrote:

> People's cheeks get burnt because they don't wear sunblock. Coating their
> glasses wouldn't make any difference.

I'm not talking about the traditional areas that are dabbed with
glacier cream due to sun exposure... such as nose and the whole span
of the upper cheek. Just some small oval spots that mimic glasses yet
sit immediately below them. Can't find good pictures of this on the
internet though.

Some snooping on internet suggests they may be melasma, which isn't
just from sun but a combination of sun and unusual hormone activity
(such as from birth control pills or pregnancy). But this still
doesn't seem to match what I see among the public. Guess the evidence
doesn't support a class action lawsuit against the opto world though -
thanks.

On Jan 15, 4:57*am, "Mark A" <no...@nowhere.com> wrote:
> If the lens already reflects UV, I doubt an AR coating would add much
> aditional protection.
>
> > But I distrust coatings, which may make cleaning a problem and may not
> > age gracefully. Opinions?
>
> If you get one of the factory coatings like Zeiss Caret Advantage, Essilor's
> Crizal, etc, then they are quite durable if you don't abuse them. QualityAR
> coatings are also available from other lens manufacturers.

Thanks, sounds like an expense with questionable payoff, unless I
expect to face TV lights or something. If it is a melasma issue,
wikip* sez the upper cheek would be an issue mainly for "men and women
of German/Russian and Jewish descent" with out of tune hormones,
thyroid, or...

> "dumbstruck" <(E-Mail Removed)> wrote in message
> news:e3bd5328-62b2-4e04-88b9-(E-Mail Removed)...
> Thanks, sounds like an expense with questionable payoff, unless I
> expect to face TV lights or something. If it is a melasma issue,
> wikip* sez the upper cheek would be an issue mainly for "men and women
> of German/Russian and Jewish descent" with out of tune hormones,
> thyroid, or...

Your conclusion is invalid. AR coating will improve your vision in almost
all lighting situations. AR coating was invented by Zeiss for camera lenses
many years to improve the quality and resolution of photographs (cameras
don't get sunburn).

On Jan 16, 7:15*am, "Mark A" <no...@nowhere.com> wrote:
> Your conclusion is invalid. AR coating will improve your vision in almost
> all lighting situations. AR coating was invented by Zeiss for camera lenses
> many years to improve the quality and resolution of photographs (cameras
> don't get sunburn).

Wow, I think I will give it a try next time. Although I think eyeglass
glare coatings aren't functionally the same as, say, telescope anti
glare: http://en.wikipedia.org/wiki/Anti-re...Ophthalmic_use
..

And I will get the cheap stuff, which probably won't have the crud
repellant layer they talk about. I had a terrible time with an anti
scratch coating long ago which wouldn't clean well and came off in
patches.

But a good experiment to check the claimed anti glare properties for
nighttime, etc.

On Jan 15, 6:44 pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> "dumbstruck" <dumbst...@gmail.com> wrote
>
> > Interesting, but since most glasses are curved inward
>
> I don't get that.

Look at the lowermost part of the lense - it curves in toward the
skin. Look at the skin below which it is almost touching. This faces
upward, giving something in the rough vicinity of a right angle for
the sunlight to bounce.
\ =lense
/ =cheek
Just talking about a third of an inch bounce to a browned hotspot just
below lowest part of lense. The physics seem similar to a solar oven.

On Jan 15, 6:51*pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> "dumbstruck" <dumbst...@gmail.com> wrote
>
> > Can't find good pictures of this on the
> > internet though.
>
> Doesn't sound very common.

My observations are for light skinned community living considerably
closer to the equator than say Key West. Clouds are rare, and with the
sun like a year round xray machine, you become aware of ravages of
even reflected sun. A concave angle on a light colored building can
create a solar hotbox - not sure if it is IR, UV or what. Old folks
get "age" spots like crazy, but it seems more than coincidence how
many line up just below eyeglasses.

> "dumbstruck" <(E-Mail Removed)> wrote in message
> news:5bfe9be3-1b76-4f4c-90c8-(E-Mail Removed)...
> Wow, I think I will give it a try next time. Although I think eyeglass
> glare coatings aren't functionally the same as, say, telescope anti
> glare: http://en.wikipedia.org/wiki/Anti-re...Ophthalmic_use
..
No, that is not correct. They ARE functionally the same. To quote the
Wikipedia article link you posted regarding AR coating for glasses
(ophthalmic use):

"Allowing more light to pass through the lens also increases contrast and
therefore increases visual acuity."

This is exactly the same reason why AR was originally invented for camera
and telescope lenses.

> And I will get the cheap stuff, which probably won't have the crud
> repellant layer they talk about. I had a terrible time with an anti
> scratch coating long ago which wouldn't clean well and came off in
> patches.

I would classify AR coatings as 3 "levels"

- Cheap stuff - will not last long, and will scratch, peel, or discolor
easily
- Good Stuff applied at manufacturer lab - much more durable than the cheap
stuff
- Good Stuff and easy to clean (often with Teflon, etc) - durable and easy
to clean (these are two different attributes)

So if you get the cheap stuff, don't expect it to last. I would recommend at
least "the good stuff," even if you don't get the "easy to clean" variety.