Someone mentioned ray tracings. Here's one for you: https://youtu.be/DFWxL8bXSFU
Someone mentioned ray tracings. Here's one for you: https://youtu.be/DFWxL8bXSFU
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.
Last edited by fixide; 07-29-2015 at 11:03 AM.
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.
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.
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.
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.
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.
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.
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.
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...
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
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.
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
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
Likewise, it is nice to see an Optometrist who understands and applies ophthalmic knowledge!
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.
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!
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
Last edited by Chris Ryser; 07-31-2015 at 01:06 AM.
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
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%.
The middle of the page show a transmission chart of DuraVision Blue Protect.
http://www.zeiss.com/vision-care/en_...ueprotect.html
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).
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...
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.
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 ?
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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