# Optical Forums > General Optics and Eyecare Discussion Forum >  Essilor's Prevencia vs Hoya's Bluecontrol

## fixide

Hello,  I am highly interested in new lenses that filter blue light. Although nothing is scientifically proven regarding the reduction of risk type AMD, there are returns that show less fatigue and blindness behind screens.

   On optiboard, the most important criticism is the yellow coloration of these glasses. I tested the Prevencia and indeed the white walls become slightly yellow. 

 I do not know if those glasses can be recommended for someone who will bring this pair every day or only for a second pair. 

   Essilor says its lenses filter 20% of blue light. Hoya says that BlueControl (also called "Remark") filter 10%. 

By filtering more, is that Prevencia have a yellow tint most?    Has anyone had the opportunity to test both glass?

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## Megab7176

I will tell you that I have Prevencia on my lenses. It does have a slight yellowish brown tint but I have to say in my 20 years as an optician i haven't found a better AR! If you have a blue light you can shine it threw your lenses and see how much blue light it really blocks. The slight tint I have found to be soothing on my eyes. Its pretty much all I sell at my practice. Everyone I have sold it to loves it! I have had a few guys that aren't to keen on the purple hue but the girls love the color!

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## fixide

Have you been able to compare with Hoya's BlueControl? Essilor lenses filter says his best. However I would have liked to know if the customer return on yellow tint is marked in Hoya.

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## becc971

I have seen both, I feel like Hoya's lens gets dirtier faster and I don't have a lot of faith in their coatings in general from past experience.  I love my prevencia, I haven't personally tried the Hoya coat but i've seen them on a few people and they always look gross!!

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## becc971

yellowish tint seems to be about the same for both i feel

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## colem84

The only thing I don't like on my Prevencia lenses is how it reflects a purple color, compared to blue/green with Avance or Sapphire. In terms of glare reduction, they are great. I also have Transitions, so I'm used to a slightly altered color and it does not bother me. I also have a pair with Hoya Recharge A/R and I like its glare reduction as well, and it reflects a blue color, which is nice.

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## colem84

> I have had a few guys that aren't to keen on the purple hue but the girls love the color!


I'm not too thrilled with the purple color, but I live in East Carolina University territory and the majority of colors around here are purple and gold, so it works out!  :Cool:

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## fixide

So  - a yellow tint somewhat similar on both glass. - A glass that hoya faster dirty - And a hoya glass less efficient: 10% HEV filtered against 20% for Prevencia.  ?  I think the "recharge" is the same as the BlueControl. This AR have plenty of names with hoya. In Japan I think it's named venus guard lapis...

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## Dr. Bill Stacy

The yellow is not a tint at all on these lenses, it's the result of the reflection of blue light away from the front surface.  When you remove most of the blue from in front of you, all the other wavelengths take over, the brightest of which is yellow.  Unfortunately, reflection from the back surface is very bad on all these lenses, reflecting not only visible blue but also UV radiation into and on and around the eyes.  See www.noviolens.com

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## fixide

> The yellow is not a tint at all on these lenses, it's the result of the reflection of blue light away from the front surface.  When you remove most of the blue from in front of you, all the other wavelengths take over, the brightest of which is yellow.  Unfortunately, reflection from the back surface is very bad on all these lenses, reflecting not only visible blue but also UV radiation into and on and around the eyes.  See www.noviolens.com


   But Essilor states that Prevencia filter UV outside and inside... http://www.essilor.com/en/Press/News...a_28022013.pdf  Marketing?

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## Dr. Bill Stacy

Here's a direct link to the video if you want to see the proof:  https://youtu.be/KCiTMOd7iEw

The Prevencia is not really an AR coating, it's a blue mirror coating which they but on both surfaces.  Sure, blue coming from in front of the wearer is reflected back towards the source from BOTH surfaces.  But blue coming from behind the wearer is reflected AND CONCENTRATED (because of the concavity of both surfaces from the back side) from BOTH surfaces back on and into the eyes and adnexa.  Unintended consequences...

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## MikeAurelius

I have to disagree. This same "issue" was brought up during the development of laser protective eyewear. There was a fear that the curve of the inside of lens would act as a reflector into the eye of an off-axis "behind and to the side" laser beam exposure. Multiple beam traces were done and not one single ray ever impinged on the eye.

If the UV/Blue light is absorbed/reflected by the lens to any major extent, there is not enough left to "reflect" back into the eye. The very theory is nonsense. If there's nothing passing through the lens, what is it going to reflect off of? Is the eye all of a sudden a mirror? 

You might be able to sell this snake oil to a consumer, but it won't fly with professional opticians who understand filters and optics.

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## fixide

The internal surface "issue" has been taken into account by Hoya, but not on the bluecontrol :  http://www.hoya.eu/index.php?SID=55b...&page_id=28573      To return to the subject (vs. Prevencia BlueControl), I need more feedbacks. It is also difficult to have prevencia lenses in essilor stock. Most corrections need to be manufactured. There is also more choice on the BlueControl. The yellow tint is very well supported by some and less for the other. Can be a matter of color perception (white wall...). It also may be necessary to leave 5 days of adaptation.    Perhaps these lenses  would be more advisable as a second pair for work or for inside? But given the price of the glasses for a high correction, I can not offer both, despite the gain in comfort.

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## Dr. Bill Stacy

I can post a ray tracing if you like, but as to my snake oil, if UV/blue light is reflected by the BACK surface coating of the lens by definition such reflected radiation never enters the lens substrate itself. That's pretty basic optics.   Apparently you didn't watch the 8 min video that conclusively demonstrates that TONS of UV coming from behind the wearer can be concentrated on the eye.  Here it is again:  https://youtu.be/KCiTMOd7iEw

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## Dr. Bill Stacy

The above post was an answer to Mike's post 3 above.  As to fixide's post 2nd above, it's real interesting to me that Hoya.eu (europe) is advertising stuff we apparently cant't even get in the US, like the "UV Control" and the BlueControl, while their "Recharge" available to us isn't even mentioned in the Hoya.eu sites.

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## MikeAurelius

Sorry, I don't watch snake oil videos.

The Department of Defense studied this in detail during the 1980's and 1990's using ray tracing with lasers. *There. Is. No. Way. What. You. Are. Claiming. Is. True.
*
Please stop.

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## Dr. Bill Stacy

Ok then I'm guessing you've never seen a pair of Prevencias or Recharges or BlueProtects or TechShields, am I correct?  
These are the 4 big "blue protective" coatings marketed in the US.  If you ever get a chance to see a pair, try them on and face away from the sun.  Then tell me if you don't see dramatic blue reflections coming off the back surfaces as you turn your head from right to left or left to right.   But don't look too long, because you'll also be getting a hefty dose of UV along with the blue.  All 4 brands reflect UV strongly off the back.  It's not exactly rocket science. Easily proven as I did in the video which clearly shows the reflected UV strongly darkening a photochromatic test lens. Snake oil indeed.

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## Megab7176

If you rub Prevencia on a snake with they become an anti reflective purple snake? I really do love my prevencia. Like I said. I have seen most of them. I love this one the best!!

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## morinput

Dr. Stacy, 
Thanks for the video. One question, in the AR test lens on the right, did you use one of the newer UV protective AR's like Avance' UV or just a standard AR coated lens?

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## Dr. Bill Stacy

In the test glasses, the right lens was a Hoya Recharge, the left was a Hoya Super Hi Vision EX3, their best AR

Looking at Gilda from the front she is  wearing those glasses, so the right lens is on your left and vice-versa.

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## Dr. Bill Stacy

Anyway, I don't think the EX3 is advertised as a uv blocker.  And that's a good thing, since uv coming from behind is allowed to harmlessly pass into the lens substrate where it's mostly if not totally absorbed. I don't use "uv protected" ARs because I'm pretty sure they reflect UV  like the blue reflectors do because uv wavelengths are right next to indigo in the spectrum.  Not as much of course, but why pay extra for a coating that reflects ANY uv?

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## morinput

Actually UV protective AR's are designed to allow the UV to pass through to the lens substrate to be absorbed rather than being reflected back into the eye which lens manufacturers are fond of telling us is a major drawback to AR lenses without this enhancement.

Your video clearly shows that non-uv protected AR coatings do not reflect an appreciable amount of UV back into the eye at least at the specific wavelength that activates the photochromatic lens. Interesting...

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## Dr. Bill Stacy

Exactly, and an astute observation.  I think Essilor and friends found a way to charge for something you already had.

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## lensgrinder

Full disclosure:  I work for Zeiss.
I am not going to speak for Essilor or Hoya, but I will discuss Zeiss DuraVision Blue Protect.

We put DuraVision Platinum(Our most advanced AR coating) on the back surface of our Blue Protect lens, not a blue protect coating on the back side as you suggested in your article.  This AR coating on the back surface has about <0.1% reflectance.  With that amount of reflectance and a small target area(i.e.3-5mm pupil) I think this  is a non-issue. 

Blue Protect lenses are not meant to be worn outside or at night time.  It is not an AR coating as it blocks a portion of the visible spectrum.  Their intended purpose is for indoor use.

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## Lee H

> I can post a ray tracing if you like, but as to my snake oil, if UV/blue light is reflected by the BACK surface coating of the lens by definition such reflected radiation never enters the lens substrate itself. That's pretty basic optics.   Apparently you didn't watch the 8 min video that conclusively demonstrates that TONS of UV coming from behind the wearer can be concentrated on the eye.  Here it is again:  https://youtu.be/KCiTMOd7iEw



Dr. Stacy, thank you for sharing this video. I find it very interesting. I have tried the several of the blue "AR's" that protect (20-25%) against blue light and I found them uncomfortable due to the backside blue reflections. I have also had several clients with the same experience. I have also had others that these reflections do not bother but the UV exposure off the back surface is reason for concern. As far as someone saying these lenses should not be worn outside, I find this interesting because of the HEV from the sun we are exposed to. I feel like we are going to hear more about this subject very soon and we will see an excellent solution. Thanks again for sharing.

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## Dr. Bill Stacy

Someone mentioned ray tracings.  Here's one for you:  https://youtu.be/DFWxL8bXSFU

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## fixide

It's really a problem if the blue filter lenses reflect more UV light than standard AR.

    Essilor and Hoya but do not specify that these lenses are for indoor ! Instead, they say that it lenses for life... Zeiss too : https://www.zeiss.com/vision-care/en...ueprotect.html "ZEISS offers a comprehensive blue-violet light blocking portfolio that meets different consumer requirements for indoor and outdoor activities, filtering different amounts of blue-violet light depending on the activity." 

  I have many clients (and also me) who do a lot of computer but it does not mean they will not drive at night or going outdoors in bright sunlight.    This answers one of my initial questions was: Do these glasses are more advisable as a second pair ?    

The trouble is that for strong corrections, everyone can not afford to have several pairs! The objective would be to enjoy the comfort of filtering blue light but without taking risks with a reflection of the back surface.

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## Dr. Bill Stacy

> Full disclosure:  I work for Zeiss.
> I am not going to speak for Essilor or Hoya, but I will discuss Zeiss DuraVision Blue Protect.
> 
> We put DuraVision Platinum(Our most advanced AR coating) on the back surface of our Blue Protect lens, not a blue protect coating on the back side as you suggested in your article.  This AR coating on the back surface has about <0.1% reflectance.  With that amount of reflectance and a small target area(i.e.3-5mm pupil) I think this  is a non-issue. 
> 
> Blue Protect lenses are not meant to be worn outside or at night time.  It is not an AR coating as it blocks a portion of the visible spectrum.  Their intended purpose is for indoor use.



Well that's news to me.  I had a pair made for myself and they definitely had a strong blue reflectance off the back side.  Is this something new for Zeiss?

I ordered mine from ziess california about a month ago.  I asked Zeiss if they could do a blue reflector on the front and and AR on the back, and they said no, it would ruin their machine.  Maybe my complaining had an effect.

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## Dr. Bill Stacy

In fact, it turns out that 2 minutes into my 8 minute vid:  https://youtu.be/KCiTMOd7iEw  the pair lenses in that part of the clip are my Zeiss BlueProtect lenses in my own computer Rx made, ok maybe 2 months ago!  The clip plainly shows more than 1% coming off that back surface.  In all fairness, I LOVE them for working early in the morning before the sun comes up.  It's curious that Zeiss says they are "not meant to be worn outside or at night", if they are safe.  Of course my main worry is the UV you catch wearing them in direct sunlight.  But yeah, the bright blue reflections you can catch driving at night from the intense LED headlights are distracting to say the least.

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## Dr. Bill Stacy

Just talked to a guy at Carl Zeiss California lab who now tells me that they are now putting the AR on both surfaces and adding the blue reflctor to the front surface only.  My pair will be going back for a remake, but I got this sneaky suspicion that it's still gonna be a problem for light coming from behind. Why?  Well it turns out that unless the lens substrate is also well UV protective (by absorption), the UV will hit that front surface and bounce it back to the back where any unabsorbed UV will simply pass through the AR to the eye and adnexa.

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## lensgrinder

> As far as someone saying these lenses should not be worn outside, I find this interesting because of the HEV from the sun we are exposed to.


That was me and I did not mean to say you cannot wear them outside, it is not the intended use.  It is a pair of glasses that should be worn when viewing digital devices.  Wear a pair of sunglasses for full protection from the UV and blue light.




> Well that's news to me.  I had a pair made for myself and they definitely had a strong blue reflectance off the back side.  Is this something new for Zeiss?
> 
> I ordered mine from ziess california about a month ago.  I asked Zeiss if they could do a blue reflector on the front and and AR on the back, and they said no, it would ruin their machine.  Maybe my complaining had an effect.


I am not sure why they said that, but we have had an AR coating since we launched the product.  Our reflectance from DuraVision is blue.




> In fact, it turns out that 2 minutes into my 8 minute vid:  https://youtu.be/KCiTMOd7iEw  the pair lenses in that part of the clip are my Zeiss BlueProtect lenses in my own computer Rx made, ok maybe 2 months ago!  The clip plainly shows more than 1% coming off that back surface.


I have attached an image from your video which shows the amount of reflectance from the lens.  Look at the blue light on the wall.  Your hand is blocking transmission of the light which is striking your photchormatic lens.  






> In all fairness, I LOVE them for working early in the morning before the sun comes up.  It's curious that Zeiss says they are "not meant to be worn outside or at night", if they are safe.  Of course my main worry is the UV you catch wearing them in direct sunlight.  But yeah, the bright blue reflections you can catch driving at night from the intense LED headlights are distracting to say the least.


Zeiss does not say this, I say this as an Optician.  Why would you wear a pair of clear or almost clear lenses in direct sunlight or outside at all.  I say they are not good at night because they do reduce the amount of visible light transmission which is needed in lower light situations.

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## Dr. Bill Stacy

I have attached an image from your video which shows the amount of reflectance from the lens.  Look at the blue light on the wall.  Your hand is blocking transmission of the light which is striking your photchormatic lens.  



I think the frame you show plainly shows that my UV emitting flashlight is directed at the inside surface of the  Hoya Recharge sample lens which I was holding in my left hand.  Most of the blue light passed through the clear Trivex material forming a bright spot on my palm; I was aiming the lens so that the reflections off the inside (back) surface of that lens would be directed at the photochromic lens I had taped to the wall. Some of that reflection did hit my right hand, but most of it clearly hit the photochromic lens on the wall which immediately darkened in the spot so irradiated. 

A few seconds later I showed front and back surfaces of my new Zeiss BlueProtect lenses I had put in that P3 metal frame; that's the one I was showing the very bright reflection off the back as well as the front sides, the one I say has BlueProtect mirrors on both sides. I think my ranting may have affected Zeiss, and also VSP which seems to be changing its TechShield product (they are going to release their fix to this problem shortly, or so I hear).

Zeiss does not say this, I say this as an Optician.  Why would you wear a pair of clear or almost clear lenses in direct sunlight or outside at all.  I say they are not good at night because they do reduce the amount of visible light transmission which is needed in lower light situations.[/QUOTE]

Actually I do wear clear trivex lenses with ar coatings in direct sun.  The clear  trivex protects me from the UV.  Clear trivex is fine at night too, and you get minimum distracting images off the back side with ordinary AR coatings.  The darkness of sunglasses is not additional UV protection, just relief from the brightness of visible light which only bothers some people and is not particularly harmful to the eyes.   Of course there's also a cosmetic value for some people to the dark and/or mirrored lenses. I do use polarized lenses while sailing in daylight...

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## Pete Hanlin

Just wanted to clarify a few things regarding Crizal Prevencia.

1.) The "purple color" is a result of the lens doing its job.  The front side AR stack is designed such that the residual reflection is concentrated around blue-violet light.  You will notice the color most in a room lit with CFLs (compact fluorescent lights- the bulbs that have the squiggly coil that are replacing a lot of the incandescent lights in your house and workplace), because a large component of the light produced by these bulbs is in the blue violet range of the visible spectrum.  If you go outside, the purple will not be as pronounced- because sunlight has a much more evenly distributed color spectrum.
2.) All Crizal lenses are designed to reduce UV reflections from the back surface.  Typically, AR stacks are designed to reduce visible reflections using destructive interference (much as Bose headphones are designed to reduce droning noises).  However, a stack which destructively interferes with visible wavelengths will often tend to amplify UV wavelengths.  A couple years ago, the entire range of Crizal products was optimized to destructively interfere with both visible AND UV wavelengths (that's what the E-SPF messaging is all about).
3.) The AR stack on the front and back of Crizal Prevencia lenses is different (this is not true of all blue attenuating lenses on the market).  The front surface reflects away a percentage of blue-violet light (while allowing most blue-turquoise light to pass through).  The back surface stack is optimized to destructively interfere with visible and UV reflections.  If you put the same blue reflecting stack on both sides, you are reflecting blue light back into the eye from the back surface (which would be counterproductive).
4.) As mentioned above, the lens material itself is not yellow- any time you filter part of the blue end of the spectrum (by either absorption or reflection) you will introduce some yellow tinging.
5.) The product intended for outside use is Xperio UV (which has a back surface stack which is designed to interfere with visible and UV reflections).  From personal use (here in sunny Texas), I can attest to the reduction in UV exposure.  I've measured the UV reflections from Xperio UV lenses and numerous name brand sunlenses, and Xperio UV reduces exposure from backside reflections much more efficiently than most sunlenses (my favorite brand name pair was reflecting 40-50% of UV from the back surface- which had an AR... when I would wear these sunglasses to go outside in the summer, I would notice a slight case of photokeratitis at the end of the day.  With my Xperio UV lenses, my eyes feel absolutely fine at the end of the day (you usually notice the effects of UV exposure to the eye about 6 hours or so after exposure).

Best regards,
Pete

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## Dr. Bill Stacy

> Just wanted to clarify a few things regarding Crizal Prevencia.
> 
> 1.) The "purple color" is a result of the lens doing its job.  The front side AR stack is designed such that the residual reflection is concentrated around blue-violet light. 
> 
> You are calling it an AR stack which I don't think is true.  I think it may indeed have an AR layer somewhere buried in the stack, but that is far over-ridden by the violet mirror coating.  Do you deny that near the top of that stack there exists a partial mirror coating?  Otherwise, how do you account for the dramatic violet reflections?
> 
>  You will notice the color most in a room lit with CFLs (compact fluorescent lights- the bulbs that have the squiggly coil that are replacing a lot of the incandescent lights in your house and workplace), because a large component of the light produced by these bulbs is in the blue violet range of the visible spectrum.  If you go outside, the purple will not be as pronounced- because sunlight has a much more evenly distributed color spectrum.
> 
> Old information.  Most CFLs are being and should be replaced with LEDs, preferably LEDs that emit outside the UV/Blue range.  
> ...



Thanks

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## sharpstick777

Why settle for a pathetic 10% to 20% reduction in Short Wave Blue?  

Blue Tech filters 85% to 90% and Mitsui's new MR95/UV++ filters 95% of Blue light.   Mitsui's new product is material based, its not a coating or add on.  Its also AR independent so you don't have to suffer from a flash mirror like AR.  Its also relatively inexpensive.  and relatively clear, its residual color is about 1% in 1.56, 1.5% in 1.60, and 2% in 1.67.

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## Pete Hanlin

_You are calling it an AR stack which I don't think is true. I think it may indeed have an AR layer somewhere buried in the stack, but that is far over-ridden by the violet mirror coating. Do you deny that near the top of that stack there exists a partial mirror coating? Otherwise, how do you account for the dramatic violet reflections?_
Anti-reflective and mirror surfaces use the same components (i.e., metallic oxides of higher and lower index are stacked to produce reflections).  To attenuate reflection you create reflections which destructively interfere (AR stack).  To enhance reflections, you create reflections which compound (mirror stack).  Its the same basic process.  In Crizal Prevencia, the residual (purplish) color is created because the rest of the visible spectrum is being destructively interfered at a greater level than the blue-violet wavelength.  Therefore, it is an AR stack (there is no compounding of blue-violet light to create a mirror- the color you see is because all the other colors have been reduced).

_Old information. Most CFLs are being and should be replaced with LEDs, preferably LEDs that emit outside the UV/Blue range._ 
The strongest wavelength of light cast by a CFL is around 435nm (blue violet).  The strongest wavelength of light cast by many LEDs is around 455 (still on the violet side of blue).  My understanding is OLED lights have less of a blue component, and may be a better illumination option.  I agree with you regarding CFLs- I certainly don't allow them in my house (since I don't like their appearance and don't care to bring mercury into my home).  Personally, I've stockpiled enough incandescent bulbs to keep me CFL/LED free for a few years (I just prefer the light they produce).

_Has Essilor tested UV reflections from radiation first striking the back surface of their lenses (coming from behind and to the side of the wearer? If not, why not? If so, where's the data?_
The paper at this link should address questions about back surface reflections.
http://www.crizalusa.com/content/dam...z_E-SPF_nb.pdf

_I appreciate the work Essilor has done on this subject, and agree that the Prevencia may be the best of the big 4 on the market today. But I think Essilor is ignoring the backside light sources to its peril. It has tuned the back side to further reduce front side radiation to the detriment of the patient in real world situations._ 
This link leads to numerous papers on the subject of back side reflections and attenuation of blue light.
http://www.crizalusa.com/ecp-tools-i...ompendium.html 

_You'll have to excuse me if I don't think much of your n=1 personal keratitis testimonial._
I do not care for n=1 testing either.  A part of my role here at Essilor is the writing of clinical protocols to ensure we reach p values which are sufficient to substantiate claims).  That is why I referenced the observation as being based on personal experience.  That said, I do have access to quite a few measurement devices not available to the average practitioner- so I'd like to think I'm able to evaluate the characteristics of lens performance fairly well (at least well enough to hold up in court :^).  There is far, far too much n=1 evaluation of products in this industry- so thanks for calling me out on that point.

Best regards,
Pete

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## Dr. Bill Stacy

Thanks for the civility of your post, and your scientific bent is also appreciated.  I do like the soft white LEDs, but am unsure as to how much UV is coming off those.  They are getting pretty close to incandescents (my fav too, except for the energy usage).

I will be reviewing your links.

Thanks again

Bill

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## Pete Hanlin

Likewise, it is nice to see an Optometrist who understands and applies ophthalmic knowledge!

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## Joe Zewe

It would be helpful if the manufacturers of these lenses offered a graph that shows the transmission percentages from 380nm through 500nm.  When numbers are thrown around like "blocks 25% of blue light", without seeing either the raw transmission data or a plotting of the data, it is very difficult to assess the effectiveness of the lenses.  In fact, transmission data above 500nm is also helpful as some of these lenses (especially tinted lenses) impact transmission above the blue light sprectrum.

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## Dr. Bill Stacy

My wish list includes quick, easy and affordable instrumentation for in office spectrophotometry of lenses, and the same for determining index of refraction.  
If a $100 little scope can tell what the brix of grape juice is, why can't we have something like that?  And they even have the nerve of calling it a refractometer!

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## Chris Ryser

Real and total Blue light and UV absorption you can never fully reflect with an AR coating. Maybe with a full mirror.

However lenses can still be tinted with a 100% working Blue-Blocker dye to also get 100% protection.

See at ==============>
http://optochemicals.com/products/info_blueblocker.htm

Furthermore and most important:

*Dangers of blue light with macular degeneration!*

 I am strongly recommending that all patients with macular degeneration, especially those that have had cataract surgery, invest in a pair of real blue blocking glasses and not partial reflectance.

For a complete article of the impact of blue light in macular degeneration

*Blue Light and Macular Degeneration:  * 
http://www.healingtheeye.com/Article...ight_ARMD.html

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## Chris Ryser

> *My wish list includes quick, easy and affordable instrumentation for in office spectrophotometry of lenses, and the same for determining index of refraction.  
> If a $100 little scope can tell what the brix of grape juice is, why can't we have something like that?  And they even have the nerve of calling it a refractometer!
> *


It was also on my wish list a few years back and then I invested some close to $ 20,000.00 in one.



At least I can back up any statements I make.

*Super Aurius Series*
The Super Aurius instruments are unique for their very high performance scanning, with derivatives, overlay, extended analytical power and multi-cell Kinetics. They cover the full 190-1100nm wavelength range with a narrow 1.8nm optical bandwidth. With straylight of 0.01%, wavelength precision of 0.1nm and baseline stability of better than ±0.001A/hr, the most demanding analytical work may be undertaken.

See all of it: =============>
http://www.cecilinstruments.com/aurius-1.html

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## lensgrinder

> Actually I do wear clear trivex lenses with ar coatings in direct sun.  The clear  trivex protects me from the UV.  Clear trivex is fine at night too, and you get minimum distracting images off the back side with ordinary AR coatings.  The darkness of sunglasses is not additional UV protection, just relief from the brightness of visible light which only bothers some people and is not particularly harmful to the eyes.   Of course there's also a cosmetic value for some people to the dark and/or mirrored lenses. I do use polarized lenses while sailing in daylight...


The premise of this thread is blue light, a clear Trivex lens transmits roughly 85-90% of the blue light.  Since blue light is about 33 times worse outdoors than it is indoors it should be of concern for outdoors just as it is indoors.  
A grey lens will transmit roughly 10% of the blue light and a brown lens roughly transmits <8%.





> It would be helpful if the manufacturers of these lenses offered a graph that shows the transmission percentages from 380nm through 500nm.  When numbers are thrown around like "blocks 25% of blue light", without seeing either the raw transmission data or a plotting of the data, it is very difficult to assess the effectiveness of the lenses.  In fact, transmission data above 500nm is also helpful as some of these lenses (especially tinted lenses) impact transmission above the blue light sprectrum.



The middle of the page show a transmission chart of DuraVision Blue Protect.

http://www.zeiss.com/vision-care/en_...ueprotect.html

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## Dr. Bill Stacy

OK I've always been a little more scared by UV than by visible blue, but I get that there is a potential threat there too.  However, my points on backside UV reflections off these lenses is just as true for backside blue reflections, which are being CONCENTRATED on the eye by the concave back surfaces of these lenses. It's the very thing that I find distracting about them, and may cause more harm than the front surface is preventing.  The solution seems obvious to me.  Put a blue AR coating on the front surface, a blue blocking tint in the substrate, and a red reflective AR on the back side. I've been trying to get such a lens made, but there is great reluctance to do this by the labs I use (hoya, zeiss, VSP, CSC).

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## Happylady

What about some of the new thinking that blue light in sunlight slows and perhaps prevents myopia? Maybe blocking blue light isn't always a good thing.

Honestly, I hate the way these lenses look with the purple reflection.

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## Dr. Bill Stacy

> What about some of the new thinking that blue light in sunlight slows and perhaps prevents myopia? Maybe blocking blue light isn't always a good thing.
> 
> Honestly, I hate the way these lenses look with the purple reflection.


The longer wavelengths of blue (azure, aqua, cyan) don't seem to mess with your circadian rhythm and may have other benefits, but I'm always suspicious of any myopia prevention claims.  

But your complaint raises another issue, might the strong purple reflection be a hazard to someone facing you?  I'm envisioning blue light wars...

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## Happylady

I just think the reflection is very in your face and ugly.

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## Dr. Bill Stacy

> I just think the reflection is very in your face and ugly.


There's that.  If a 1 time lab redo or dr. redo is available, you might want them to take advantage of that and have them remade in a standard AR with or without a very light peach or apricot tint (#1 or #1.5) which would make them cosmetically pleasant and people will be able to see your eyes way better.

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## fixide

So, at this time, it is not recommended to advise these lenses as main pair for people who have to go outdoors or driving with? Even if these people are mainly indoor and work on computer under fluorescent bulbs ?

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## Dr. Bill Stacy

At this time, I only recommend them for people who can completely control all light sources located behind them that can potentially harm their vision or their eyes.  This includes people with very large hair that blocks their glasses from all backside light sources, people who don't mind wearing a large protective hat to block the same, or people who somehow only face all the ambient light in all their environments.  I'm refraining from Rxing them at  until a better solution comes (soon).

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## sharpstick777

> It would be helpful if the manufacturers of these lenses offered a graph that shows the transmission percentages from 380nm through 500nm.  When numbers are thrown around like "blocks 25% of blue light", without seeing either the raw transmission data or a plotting of the data, it is very difficult to assess the effectiveness of the lenses.  In fact, transmission data above 500nm is also helpful as some of these lenses (especially tinted lenses) impact transmission above the blue light sprectrum.


Absolutely!

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## sharpstick777

Great info Mike




> I have to disagree. This same "issue" was brought up during the development of laser protective eyewear. There was a fear that the curve of the inside of lens would act as a reflector into the eye of an off-axis "behind and to the side" laser beam exposure. Multiple beam traces were done and not one single ray ever impinged on the eye.
> 
> If the UV/Blue light is absorbed/reflected by the lens to any major extent, there is not enough left to "reflect" back into the eye. The very theory is nonsense. If there's nothing passing through the lens, what is it going to reflect off of? Is the eye all of a sudden a mirror? 
> 
> You might be able to sell this snake oil to a consumer, but it won't fly with professional opticians who understand filters and optics.

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## sharpstick777

> ...  Since blue light is about 33 times worse outdoors than it is indoors it should be of concern for outdoors just as it is indoors.  
> A grey lens will transmit roughly 10% of the blue light and a brown lens roughly transmits <8%.


One of the ironies of all this marketing hype is that potentially if you are using tablet, and not going outside, it would reduce your SWB exposure over all.

Sunwear is the most important product to reducing SWB.

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## Dr. Bill Stacy

I'd sure like to see the data where the following was done and the methodology.   The only way that the statement below could be  true is if they had used full wrap protective frames as are in common use today in laser work.  With ordinary spectacles, there is no way laser rays would NOT get into the eye, and it wouldn't be "through the lens", for sure.

_I have to disagree. This same "issue" was brought up during the development of laser protective eyewear. There was a fear that the curve of the inside of lens would act as a reflector into the eye of an off-axis "behind and to the side" laser beam exposure. Multiple beam traces were done and not one single ray ever impinged on the eye._

_If the UV/Blue light is absorbed/reflected by the lens to any major extent, there is not enough left to "reflect" back into the eye. The very theory is nonsense. If there's nothing passing through the lens, what is it going to reflect off of? Is the eye all of a sudden a mirror?_ 

_You might be able to sell this snake oil to a consumer, but it won't fly with professional opticians who understand filters and optics.


_

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## MikeAurelius

Department of Defense. 

Aberdeen Test Center (US Army)

Further testing was done at Los Alamos Nat'l Laboratory, Fort Hood, and Fort Hunter Ligget. Some of the test data and procedure is still classified, but the open source I've seen and know about was all done with Nd:YAG 1064 nm lasers, which is what most of the target acquisition lasers are. They run fairly high wattage due to the requirements for targeting, so a stray flash is very dangerous.

My company was involved with the laser eyewear programs for both the Army and the Navy in the late 1980's through the 1990's. We manufactured lens blanks from Schott KG-3 and KG-5 for the optical laboratory in Yorktown NWS, and Fitzsimmons Army Medical in Denver. My company also manufactured completed laser safety spectacles for the AH-64 Apache and A-10 Warthog programs.

All testing was done with 80th percentile head size/shape models to simulate normal wearing positions. Head models were fitted with laser receptors in place of (simulated) eyes. Lasers were arm-mounted and ray tracing was done from 180 degrees side exposure to approximately 250 degrees back and side exposure. A variety of vertical heights was used in conjunction with horizontal displacement. Helmets were not used, as these tests were to simulate hazardous exposure in a laboratory or test facility.

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## Dr. Bill Stacy

> Department of Defense. 
> 
> Aberdeen Test Center (US Army)
> 
> Further testing was done at Los Alamos Nat'l Laboratory, Fort Hood, and Fort Hunter Ligget. Some of the test data and procedure is still classified, but the open source I've seen and know about was all done with Nd:YAG 1064 nm lasers, which is what most of the target acquisition lasers are. They run fairly high wattage due to the requirements for targeting, so a stray flash is very dangerous.
> 
> My company was involved with the laser eyewear programs for both the Army and the Navy in the late 1980's through the 1990's. We manufactured lens blanks from Schott KG-3 and KG-5 for the optical laboratory in Yorktown NWS, and Fitzsimmons Army Medical in Denver. My company also manufactured completed laser safety spectacles for the AH-64 Apache and A-10 Warthog programs.
> 
> All testing was done with 80th percentile head size/shape models to simulate normal wearing positions. Head models were fitted with laser receptors in place of (simulated) eyes. Lasers were arm-mounted and ray tracing was done from 180 degrees side exposure to approximately 250 degrees back and side exposure. A variety of vertical heights was used in conjunction with horizontal displacement. Helmets were not used, as these tests were to simulate hazardous exposure in a laboratory or test facility.



And they were all tested with wrap around, fully protective frames, right?  Certainly not ordinary dress frames, right?

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## MikeAurelius

Nope. Randolph Engineering Aviators.

http://shop.randolphusa.com/aviator-p5044.aspx

6 base uncoated KG-3/KG-5 filter glass lenses.

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## opty4062

I wear prevencia with transistions 7. I have never noticed any blue reflections, not one iota, inside, outside, upside down, I do not see them Sam I am.

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## Dr. Bill Stacy

> Nope. Randolph Engineering Aviators.
> 
> http://shop.randolphusa.com/aviator-p5044.aspx
> 
> 6 base uncoated KG-3/KG-5 filter glass lenses.


A yes the old Air Force pilot style.  Fit many of them when I was in the USAF, before lasers were used or encountered in the cockpit for sure.  

Because they would offer precious little protection from lasers bouncing off the various items in the cockpit.  

And you guys can't see how a laser beam could hit the eye and/or the back surfaces of those lenses while wearing that frame?  

Don't try using those in an operating room where laser beams are bouncing off the walls. Use the side protected ones they always have on hand, or you could get burned.

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## Dr. Bill Stacy

> I wear prevencia with transistions 7. I have never noticed any blue reflections, not one iota, inside, outside, upside down, I do not see them Sam I am.


It's either a full wrap frame or you have a very large bushy hair style,  or you wear a big sombrero, or you only wear them in the dark.  I can think of one other reason.  But I try to avoid going ad hominem. 

OK there's always the possibility they forgot to put those blue mirrors on there...

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## King.Matthew

Blu-Tech, second pair, for computer and digital devices.

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## MikeAurelius

> A yes the old Air Force pilot style.  Fit many of them when I was in the USAF, before lasers were used or encountered in the cockpit for sure.  
> 
> Because they would offer precious little protection from lasers bouncing off the various items in the cockpit.  
> 
> And you guys can't see how a laser beam could hit the eye and/or the back surfaces of those lenses while wearing that frame?  
> 
> Don't try using those in an operating room where laser beams are bouncing off the walls. Use the side protected ones they always have on hand, or you could get burned.


And now you are an expert on laser eyewear???

Look, bud, give it a rest. You've said your bit, I'm not buying it, and all you are doing now is embarrassing yourself.

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## opty4062

"It's either a full wrap frame or you have a very large bushy hair style, or you wear a big sombrero, or you only wear them in the dark. I can think of one other reason. But I try to avoid going ad hominem. 

OK there's always the possibility they forgot to put those blue mirrors on there..."


 None of the above. Just sharing my personal experience,  sorry it conflicts with yours.

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## Dr. Bill Stacy

> "It's either a full wrap frame or you have a very large bushy hair style, or you wear a big sombrero, or you only wear them in the dark. I can think of one other reason. But I try to avoid going ad hominem. 
> 
> OK there's always the possibility they forgot to put those blue mirrors on there..."
> 
> 
>  None of the above. Just sharing my personal experience,  sorry it conflicts with yours.


If this is a pic of you wearing your prevencia lenses, I can see why you are not getting any reflections off the back surfaces.  Your hair do is blocking pretty much all backside radiation.  If you were to pull the hair back, tight to your head, face away from the sun, and rotate your head so that the sunlight can reach the back surface of one lens or the other, you will see a bright blue reflection.  But don't stare at that reflection for long, it's loaded with UV as my video clearly shows.  If you don't get a blue reflection off the back side, they are not Prevencia coated.

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## Dr. Bill Stacy

> And now you are an expert on laser eyewear???
> 
> Look, bud, give it a rest. You've said your bit, I'm not buying it, and all you are doing now is embarrassing yourself.


Actually I AM an expert on LASER eyewear.  I know that one of the major requirements of LASER protective eyewear is that it protect the eyes from stray LASER beams from all angles, including front, back, side, all 360 degrees.  This is why all decent LASER protective eyewear have full wrap frames and/or side shields.  

But it doesn't take and expert to see that that old pilot style frame you showed doesn't provide any side or back protection at all.  Even a layman could see and appreciate that.  

And no, I'll not "give it a rest" as I consider eye protection from LASER and UV to be a very important subject, one that I'll be actively engaged in for some time.

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## MikeAurelius

So, mr. snake oil salesman, exactly what are your qualifications to be an "expert" on laser eye protection? Have you been certified by the LIA? Are you up to date on all your CE's? Do you have the most current copies of the ANSI Standards for laser safety in your office?

Because here's the thing, mr. snake oil salesman: lasers penetrate into filter substrates and are absorbed, they do not reflect, which, if you truly were an "expert" on "laser eyewear", you'd know that. You'd also know that 


> "they would offer precious little protection from lasers bouncing off the various items in the cockpit.


 isn't even possible because "various items in the cockpit" don't have reflective surfaces, they have matte finish surfaces to dispurse and diffuse any possible beam impingement.

If you are an EXPERT, you would know these things. 

As an aside, what is the registration number for your "noviolens" that you claim has a patent pending. As soon as you make the claim of "patent pending" on any public document, you are required to make the number available so that others can look to see that 1) it is an actual patent pending and 2) it does not violate someone else's existing patent.

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## MikeAurelius

Mr. Laser Protection Expert, what is the required protection level for a Class IV 100 Watt CO2 laser with a collimated 5 mm beam at 10.6 um? You should be able to answer that one real fast, it's an easy low and slow ball.

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## opty4062

> If this is a pic of you wearing your prevencia lenses, I can see why you are not getting any reflections off the back surfaces.  Your hair do is blocking pretty much all backside radiation.  If you were to pull the hair back, tight to your head, face away from the sun, and rotate your head so that the sunlight can reach the back surface of one lens or the other, you will see a bright blue reflection.  But don't stare at that reflection for long, it's loaded with UV as my video clearly shows.  If you don't get a blue reflection off the back side, they are not Prevencia coated.


Sure and if I close one eye and stand on one foot in traffic on a Saturday after 4pm in July I might get hit by a car. Dude, my simple point is, average user, average wear NORMAL circumstances equals NO blue reflections, in my personal experience. Your horse is dead sir, have some compassion.

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## Dr. Bill Stacy

I'm not sure why you take such offence at my attempts to alert the public about a potential hazard of UV radiation that is presented by makers of "blue protective" spectacle lens coatings.  That said, I'm off to work in a few minutes and will do the best I can to take up your challenges above in the short time I have.

My credentials are that I'm a graduate of U.C. Berkeley (class of '67, B.S., M.Opt.) where I first studied the physics of LASERs which at the time were only theoretical, since the first one was patented 3 years after I graduated.  But the physics dept. at UC is where much of the early work was being done, and I took several classes in that very physics dept.  We optometry students were shown that one of the valuable results of that work would be in eye surgery.

I am not LIA certified, because I'm not directly engaged in LASER work, only routine eye care as a general optometrist and have no need for such an industrial certification.  I know of no practicing optometrists who do, although no doubt at least one or two in the country do. 

Shortly after my graduation, I was elected to fellowship in the American Academy of Optometry.

After that, I served 2 years as an optometrist in the USAF Biomedical Science Corps. and became familiar with the visual needs and demands of military aviation.  

After returning to CA I was appointed to 2 terms on the California Board of Optometry by the Governor.  During my second term,  I developed the first computerize examination for licensure for optometrists in California, and I think in the world.  After my 2nd term I worked for the board as a consultant for disciplinary actions and examinations for licensure.

Since then, I've been in private practice and am involved in fitting safety eyewear for several governmental agencies. 

Yes my CE is up to date, you can check with the Board in Sacramento, my CA license is # 5233 T. 

And yes, I have a copy of the latest ANSI standards in my office.  What was it, about $200?  I can prove it is not a pirated copy with my receipt of the purchase of about 4 months ago.  

Regarding your comment that

 "lasers penetrate into filter substrates and are absorbed, they do not reflect, which, if you truly were an "expert" on "laser eyewear"
 you'd know that."  

I know that your statement is completely wrong.  I think most people with any scientific knowledge in this field know that LASERs reflect off any solid material.  Sure, they can penetrate a substance, but no material I can think of is COMPLETELY transparent to LASER radiation.  
Yes, part of the radiation penetrating a substance can be absorbed by that substance, even causing damage to it (such as human tissue), and some can pass through (such as in an optical lens)  but some is always reflected off according to all the laws of physics and math.  

As for your comment that

 "You'd also know that ... isn't even possible because "various items in the cockpit" don't have reflective surfaces, they have matte finish surfaces to dispurse and diffuse any possible beam impingement."

another impossibly wrong statement.  Just take a handheld laser pointer and shine it at any matte surface of your choosing.  Just don't look at the reflection that comes off it.  

As for Noviolens, I was cautioned not to post anything that might be of a personal financial interest to me here, but you asked, so here it is:

Application # 62/179,975 filed on 05/25/2015, USPTO confirmation # 7423 mailed to me on 06/12/2015.  

I'd be happy to fax a copy of that to anyone, including you.

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## Dr. Bill Stacy

I'm off to work, but will tackle your next post(s) when I get a chance.

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## MikeAurelius

> Application # 62/179,975 filed on 05/25/2015, USPTO confirmation # 7423 mailed to me on 06/12/2015.




No such number in the USPTO search, which contains all confirmed filed applications through 8/4/2015.

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## MikeAurelius

All right, you've proven you're NOT an expert in Laser Safety Eyewear .

Now as for the rest...




> I know that your statement is completely wrong. I think most people with any scientific knowledge in this field know that LASERs reflect off any solid material. Sure, they can penetrate a substance, but no material I can think of is COMPLETELY transparent to LASER radiation. 
> Yes, part of the radiation penetrating a substance can be absorbed by that substance, even causing damage to it (such as human tissue), and some can pass through (such as in an optical lens) but some is always reflected off according to all the laws of physics and math.


You have no idea how absorbers work, do you? Laser light does not reflect off an absorber, it enters the material, and the light is absorbed. The filter absorbers are specifically made to allow very small 10 to the minus 5th or less photon energy to pass through the material. Not reflected, absorbed. Again, if you were any kind of "expert" you would know this.

I'll futher codify that IR absorbers will take on part of the energy they are being exposed to. The lens surface will bubble, pit, the lens will even crack, and if the beam is strong enough, it will eventually burn through (eventually can be .5 seconds or 5 minutes depending on a whole bunch of factors).

Is there "some" reflection, yes, perhaps 10 to the minus 5th, and that meager amount will certainly be absorbed by another laser filter.
Next:




> another impossibly wrong statement. Just take a handheld laser pointer and shine it at any matte surface of your choosing. Just don't look at the reflection that comes off it.


Matte surfaces do not reflect. They absorb. What you are seeing is the impact point of the laser beam, not a reflection. Once again, **IF** you knew anything about lasers, you would know this.

A basic primer on absorption (again, something that even as an OD you should know):

*Visible Light Absorption*

Atoms and molecules contain electrons. It is often useful to think of these electrons as being attached to the atoms by springs. The electrons and their attached springs have a tendency to vibrate at specific frequencies. Similar to a tuning fork or even a musical instrument, the electrons of atoms have a natural frequency at which they tend to vibrate. When a light wave with that same natural frequency impinges upon an atom, then the electrons of that atom will be set into vibrational motion. (This is merely another example of the resonance principle introduced in Unit 11 of The Physics Classroom Tutorial.) _If a light wave of a given frequency strikes a material with electrons having the same vibrational frequencies, then those electrons will absorb the energy of the light wave and transform it into vibrational motion. During its vibration, the electrons interact with neighboring atoms in such a manner as to convert its vibrational energy into thermal energy. Subsequently, the light wave with that given frequency is absorbed by the object, never again to be released in the form of light._ So the selective absorption of light by a particular material occurs because the selected frequency of the light wave matches the frequency at which electrons in the atoms of that material vibrate. Since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies of visible light.

(emphasis mine)

Here's the link for the above material: http://www.physicsclassroom.com/clas...d-Transmission

Here's some more information about materials that are transparent to laser wavelengths:

In several industries, an increasing need exists to cut, drill and mark glass, sapphire and diamond  materials that are difficult to machine using traditional mechanical methods due to their brittleness and hardness. _Their transparency at visible and near-infrared wavelengths has also made them a challenge to process using lasers._ Now, industrial solid-state lasers with pulse widths in the subnanosecond domain can perform a variety of operations on these materials. 

http://www.photonics.com/Article.aspx?AID=56800

The Air Force uses FLIR target designators on their fighter bombers. The unit is encased in a hemisphere of fused artifical sapphire. And at 5 mm (approximately) thick is totally transparent to the Nd:YAG 1064 nm lasers the military uses for target acquisition.

----------


## Robert Martellaro

I haven't seen the ANSI Z136.8 recommendations, but I wouldn't risk wearing laser safety eyewear that doesn't provide an adequate amount of peripheral protection.

Old, but relevant.

http://www.mdsr.ecri.org/summary/det...px?doc_id=8201

----------


## MikeAurelius

> I haven't seen the ANSI Z136.8 recommendations, but I wouldn't risk wearing laser safety eyewear that doesn't provide an adequate amount of peripheral protection.
> 
> Old, but relevant.
> 
> http://www.mdsr.ecri.org/summary/det...px?doc_id=8201


You are absolutely correct, Robert, peripheral protection is a must, and in many cases, a requirement. However, it isn't for "reflected exposure from the back surface of the lens", it is for off-axis direct impingement on the eye itself, where the LSE doesn't cover correctly or properly.

The test I described above was performed to put to rest questions about reflected laser energy from the backside of the LSE into the eye. Off-axis impingement was already a known quantity and the reason why peripheral protection was written into the standard.

----------


## Chris Ryser

Here are Hoyas Claims :

*BlueControl Benefits*

HOYA BlueControl lenses help:



Neutralise blue light, preventing eye strain and fatigueReduce glare for a more comfortable and relaxed vision
Enhance contrast perception offering a more natural colour experience
Protect your lenses against water, dirt, grease and dust, keeping them clean for longer



see at : ==============>

http://www.bluecontrol.eu/en/benefits

----------


## Steve Machol

> So, mr. snake oil salesman, exactly what are your qualifications to be an "expert" on laser eye protection? Have you been certified by the LIA? Are you up to date on all your CE's? Do you have the most current copies of the ANSI Standards for laser safety in your office?


This thread has degenerated into accusations and name-calling. Thread closed.

----------

