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Thread: Putting blue light to bed!

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    Eyes eastward... Uilleann's Avatar
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    Putting blue light to bed!

    OK.

    It's well past time to clear the air. This thread isn't the place for gross hyperbole shouting the horrible new dangers of "blue light". It's a place for rational, science based discussion about the facts of indeed what - if any - direct scientific proof exists today, showing damage to human eyes from blue light emitting devices. Further, the exact nature of what devices are tested, the nature of their display technology, ambient lighting factors, and of course lifetime environmental, social, and lifestyle factors that can alter conclusions must be presented as well.

    In particular, with the new glut in expensive "dangerous blue light blocking" lenses - none of which block the same frequencies of visible light, or at the same level - a fact based discussion on the exposure level, and what frequency or frequencies, and at what life stages is shown to be scientifically / clinically significant is prudent.

    If labs and lens makers are going to throw out the scary Danger! card to the public, it incumbent on us, as fact based eye care professionals to do no less than cut through the fluff, eliminate the smoke and mirrors, and present fact based solutions. But only if/when truly harmful scenarios are proven, and can be mitigated with ophthalmic technology.

    In particular, the questions I am personally left with are:


    • What very precisely are the wavelengths deemed to be harmful?
    • What very precisely is the exposure of those wavelengths required to be harmful?
    • Is such exposure an immediate risk, or cumulative over time?
    • What very precisely are the devices and/or displays currently thought to be most harmful?
    • What screen/power settings were tested with each device?
    • Can each device's display be easily modified by a user without the need for an added lens to achieve the same (or better) attenuation of earlier defined frequency or frequencies?
    • How do variables such as genetics, age, lifestyle and location impact study results?
    • Can study results be peer replicated, with clearly defined similarity proving damage or danger?
    • HAVE study results been replicated?
    • How specifically does sun exposure factor into potential or real damage to the eye from the same frequency or frequencies? And at what level is it hazardous?


    I look forward to an interesting, fact based discourse. With so many ready to cash in on the "dangers" of this "new" light, I and the healthy scientific skeptics on this board (and of course off) are very interested in the discussion due to both the potential health and financial implications.

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    Wow. We started two threads at the same time on the same topic!

    Must be the blue light effect.

    For most of your technical questions, Essilor did some great videos on their research protocols. But one thing I can say is that if there is ANY harmful effect, as most harmful things, increasing exposure increases harm, unless there are other beneficial/protective mechanisms, known or unknown.

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    Eyes eastward... Uilleann's Avatar
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    Thanks for opening things up Doc. I'm aware of Essilor's angle, and have read a number of their papers and conclusions. I've spent my time with more than a couple other manufacturers marketing department slicks, varied studies referenced from recent to decades old, and spoken with a number of dispensers and doctors. But the instant terms such as: "might", "possibly", "may", "seem to indicate" and such creep into the discussion, my BS needle pegs. My aim in this thread is to cut through the crap. Let's get down to the actual science, and see what - if any - issue there may or may not be with the scary and terrifying new blue light that is apparently coming for our jobs, our precious children, and most likely going to take over the world in the next three months! ;)

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    One eye sees, the other feels OptiBoard Silver Supporter
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    A nice roundtable discussion for Optiboarders.

    http://www.eyeworld.org/article.php?...=&morphologic=

    For the general public.

    Macular degeneration
    https://nei.nih.gov/health/maculardegen/armd_facts

    Cataracts
    https://nei.nih.gov/health/cataract/cataract_facts
    Science is a way of trying not to fool yourself. - Richard P. Feynman

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    Redhot Jumper Blue Light blocking came up in the 1980's

    Blue Light blocking came up in the 1980's. Not because there was any harm done to the eye, there was no studies nor any warning about any danger, but out of 2 reasons:

    1) A full blue light filter also blocked all UV from 280 nm to over the 400 nm mark. That was a valid reason specially for dental work which started just then to use UV curing of their UV curable fillings.

    2) It also filtered out visible blue light, which is known to be diffused light.
    By absorbing the blue light, the vision becomes a lot clearer on snow and on water as well as on the road and in fog. So it got widely sold as sunglass lenses because of producing better and clearer and sharper vision by cutting fully out the blue, which after a while of wearing them, you can see it again.

    At that time, as 30 years ago, there was no other reason than the above ones, to sell blue blocking lenses and all the other studies and or opinions slowly started to make the circuit, if valid or not.

    That was how I started to get into it.

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    Quote Originally Posted by Robert Martellaro View Post
    A nice roundtable discussion for Optiboarders.

    http://www.eyeworld.org/article.php?...=&morphologic=
    So much information! So much passive-aggression! What a fascinating read.

    Cionni: I think you need to change that from blocks to filters; it doesn't block all the blue light, Dr. Mainster. It blocks a normal amount of blue light, what a normal lens would block. I think we have to be very careful about what we say blocks. 'Block' means none gets through and that's absolutely not true.

    Mainster:
    Dr. Cionni, a sacked quarterback lying on the ground and staring up at the sky had blocking. It just wasn't complete blocking.
    I'm Andrew Hamm and I approve this message.

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    Quote Originally Posted by Uilleann View Post
    Thanks for opening things up Doc. I'm aware of Essilor's angle, and have read a number of their papers and conclusions. I've spent my time with more than a couple other manufacturers marketing department slicks, varied studies referenced from recent to decades old, and spoken with a number of dispensers and doctors. But the instant terms such as: "might", "possibly", "may", "seem to indicate" and such creep into the discussion, my BS needle pegs. My aim in this thread is to cut through the crap. Let's get down to the actual science, and see what - if any - issue there may or may not be with the scary and terrifying new blue light that is apparently coming for our jobs, our precious children, and most likely going to take over the world in the next three months! ;)
    As far as the precise wavelengths of concern, Essilor's study on rat retina cells pretty conclusively nailed that down to those in the deep blue/violet or indigo. I can't recall the precise wave length, but they tuned their Prevencia to reflect maximally at that wavelength. The problem with all biology and physiology is that we are dealing with living, moving things and the precision you might be interested in is not possible, everything is + or - a probability factor or factors. Not much in science is as black and white as you'd like. If it were, there would be little or no controversy at all.

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    Eyes eastward... Uilleann's Avatar
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    Quote Originally Posted by Dr. Bill Stacy View Post
    As far as the precise wavelengths of concern, Essilor's study on rat retina cells pretty conclusively nailed that down to those in the deep blue/violet or indigo. I can't recall the precise wave length, but they tuned their Prevencia to reflect maximally at that wavelength. The problem with all biology and physiology is that we are dealing with living, moving things and the precision you might be interested in is not possible, everything is + or - a probability factor or factors. Not much in science is as black and white as you'd like. If it were, there would be little or no controversy at all.
    Yet the marketing departments and labs making bank certainly have each decided on their own "proprietary" frequency(ies), and levels of attenuation. If not based on science - as they're all different - how can they be "correct"? What is their proven function? To bleed money from an easily scared and duped public? UV wavelengths are easily categorized, and widely studied, scientifically agreed upon and understood. Yet we cannot do the same with the new flavor of lenses?

    What's more, the battle cry that all these new fangled e-devices are killing our kids eyes! rings from coast to coast. WHY??? WHAT devices cause so much damage??? WHAT is SPECIFICALLY so dangerous about THEIR PARTICULAR screens? Will our faces spontaneously melt from overexposure to visible light from them? HOW MUCH does it take then? If we're told to sell these lenses, due to this magical new health benefit...I need to know a LOT more than ANY of these marketing yahoos is putting out.

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    Actually, they are remarkably similar. The thin film versions of the big 4 all look very similar. Reflecting the same or very nearly the same wavelengths. The indoor blue absorptive lenses all look various shades of yellow, while the sun versions are all orangish brown. But you're right, it would be nice if they all used some spectrophometric standard so we could compare apples with apples.

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    Eyes eastward... Uilleann's Avatar
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    More to my original point - even if they could agree on some form of standard - a standard of what? It certainly appears they would be pulling such a standard out of nowhere but their posterior orifice. Yes?

    And I'm still highly interested to know which of the "dangerous" blue light devices are the worst for us, which are not, and what are all the varied shades in between. It doesn't seem that ANY scientist has been able to unlock that chestnut to date. Which only further smacks of charlatanism and pure quackery. This is step one if we are to sell any of these lenses in the name of "safety" to any patient. Yet no one can do it.

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    At the risk of being so labeled, I'll venture that what I've gleaned so far and what I'm telling my patients is this:

    1. Deeper shades of blue (indigo) and any visible violet are the worst offenders.

    2. Lighter shades of blue (sky, baby), are safe and may even be helpful.

    3. The device doesn't matter as much as the distance (cells and gameboys are the worst because they are held so close to the eyes, esp. by kids).

    4. The worst time of day for blue/violet stimulation is the 2 hours before sleep time, unless you want to remain wired half the night.

    5. All white light coming off of any digital screen is loaded with blue wavelengths. Ditch the blue and white where you can in favor of black, yellows, greens and pinks.

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Please include a debunking of the blu light demonstration laser pens.

    intensity counts too, people!

    B

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    Eyes eastward... Uilleann's Avatar
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    Cool. OK, so let's play with the last three in particular to begin with. You see no scientifically useful distinction Doc between an LCD (TN vs VA vs IPS), LED, OLED (& AMOLED of course) or CCFL screens and the often wildly differing brightness, color gamuts, and general differences in the human eye's perception of each? Further, are you assuming that each and every display has the same level of light output, in all scenarios, for every user - and further that ANY blue flavored light is somehow bad? Would we be better off all switching back to the monochromic amber screens on black backgrounds from the 70's?

    It's a silly premise here sure - but this seems to be the angle taken by the labs and marketers to date. To that end, why have we seen absolutely NO studies on the effects of digital movie screens, which are now more reflective, and illuminated with hyper bright (and white...which we all know means more of that horrific blue again!) lamps such as the newest Barco lamp trend. And of course, we can't forget the HID headlight and now the LED headlight shift since the early 90's. You can purchase those things all the way into the 9000K range - which is full on purple. You'd think there would be a public health outcry and nationwide legislation passed banning all such devices yeah? Their blue intensity far outclasses any tiny screen, particularly for the drivers of such vehicles constantly being subjected to all that light reflected back at them off the road surface, and avid lovers of the cinema.

    As for the first two points, one man's Indigo may be another's royal blue. Who's to say which is more "dangerous"? With UV, we know that the three common ranges (A, B, & C) are associated with rather clearly defined frequency parameters. We also understand the increase in energy, and potential for penetration in the human body, both in relation to the skin and the eye, with decrease of frequency. Yet this is simply and suddenly not possible for the newest scourge on the optical frontier? We seem to be all too quick to circle the wagons against a complete unknown. Would you agree?

    Thanks for the dialogue Doc. I hope we cal all find some science and fact based consensus somewhere along this thread.

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    Essilor in conjunction with the Vision Institute of Paris, found the most harmful band wave to be the 430-440 nm. Prevencia is designed to reflect 20% or so of this band wave from the eye.
    Computer fatigue/stress is real. Disruption of the circadian rhythm and it's affect on the human condition is real. How much does smoking contribute. Would a proper diet with exercise result in better sleeping patterns for folks who work in an office and are in front of a computer hours on end, day after day, and year after year.
    I have found conflicting information, at best, when it comes to HEV and the effect it has on AMD. I do not engage my patients with the blue light and how it may increase AMD discussion. My personal experience with Bluetech are, greater relaxation when working at the computer.
    I am here to help my patients any way that I can.
    We can't force someone to change their diet, exercise regularly, and take more breaks, but if I can offer a product that takes away fatigue and provides them with a greater sense of security, is that not what we are here to do.
    I do not employ scare tactics that appear to be initiated by lens companies to sell product. During the interview process we discuss with the client how they want to use their Rx, expectations they might have, and if the conversation of HEV comes up, I try to provide them with both sides of the argument and let them decide what would be best for them. I will be providing them with a sample of the Bluetech lens with a corresponding coating.
    Last edited by Paul Smith LDO; 10-10-2015 at 12:33 PM.
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    Master OptiBoarder DanLiv's Avatar
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    We are in a clinically nebulous era about blue light where there is good evidence there is some reason for concern, but no good evidence about how much we should be concerned. Despite the heavy handed marketing every manufacturer is embracing I'm taking a conservative stepped approach to blue light control.

    In my opinion the primary targets for UV protection are heavy digital device users (I mean heavy as in 8+ hour per day professionals, not check-your-snapchat-every-two-minutes teens) and children.

    I believe anyone or any age who uses digital devices for prolonged periods of time can benefit from "digital eyewear", essentially mild plus rxs (I use finished +0.25 to +0.75 for emmetropes and for Rxs typically Anti-Fatigue/Relax at +0.50 over DV). I was fitting such eyewear before the blue light frenzy, so now all I do is include the blue light protection gratis (slightly more expensive to me, but not much), offer an explanation of the potential harmful effects of blue light, and inform my customers that my they are protected at no charge. Worst case scenario in 10 years this all turns out to be bunk, but it cost them nothing anyway. More likely scenario in 10 years at least some of the evidence is thoroughly substantiated, and my customers have already been protected all that time.

    Children are becoming de facto heavy digital device users, especially at school. Plus their eyes have not accumulated the natural blue light filtering pigment. They are significantly exposed and have increased susceptibility. I offer it to parents at no additional charge. Most opt for it, a few don't just because of the reflectance.

    Judging the exact harm blue light causes in various scenarios is necessary for doing a cost-benefit analysis for your customers. I won't ignore the potential harm of blue light, but I'm not 100% certain of how much of a concern it should be. Since I don't have the info to accurately calculate the benefit, and cost to my customer is just guesswork on my part, the cost-benefit to the customer is simply based on their trust in me. I won't risk that trust so I give it to them gratis. When the cost is zero, the value is infinite.

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    Quote Originally Posted by Uilleann View Post
    Cool. OK, so let's play with the last three in particular to begin with. You see no scientifically useful distinction Doc between an LCD (TN vs VA vs IPS), LED, OLED (& AMOLED of course) or CCFL screens and the often wildly differing brightness, color gamuts, and general differences in the human eye's perception of each? Further, are you assuming that each and every display has the same level of light output, in all scenarios, for every user - and further that ANY blue flavored light is somehow bad? Would we be better off all switching back to the monochromic amber screens on black backgrounds from the 70's?

    It's a silly premise here sure - but this seems to be the angle taken by the labs and marketers to date. To that end, why have we seen absolutely NO studies on the effects of digital movie screens, which are now more reflective, and illuminated with hyper bright (and white...which we all know means more of that horrific blue again!) lamps such as the newest Barco lamp trend. And of course, we can't forget the HID headlight and now the LED headlight shift since the early 90's. You can purchase those things all the way into the 9000K range - which is full on purple. You'd think there would be a public health outcry and nationwide legislation passed banning all such devices yeah? Their blue intensity far outclasses any tiny screen, particularly for the drivers of such vehicles constantly being subjected to all that light reflected back at them off the road surface, and avid lovers of the cinema.

    As for the first two points, one man's Indigo may be another's royal blue. Who's to say which is more "dangerous"? With UV, we know that the three common ranges (A, B, & C) are associated with rather clearly defined frequency parameters. We also understand the increase in energy, and potential for penetration in the human body, both in relation to the skin and the eye, with decrease of frequency. Yet this is simply and suddenly not possible for the newest scourge on the optical frontier? We seem to be all too quick to circle the wagons against a complete unknown. Would you agree?

    Thanks for the dialogue Doc. I hope we cal all find some science and fact based consensus somewhere along this thread.
    ok the precise wavelengths is 430-440 according to Paul's note. Sounds right. Strong nearby sources of those wavelenths were lethal to rat retina cells. That's good enough for me to take it seriously for NEARBY light sources. All those others you mention, including the violet headlights are far enough away to not be a big concern, however annoying they might be. Same for LEDs, Fluorescent fixtures, if they are several feet away, no big deal, again however annoying they might be. Even a large screen computer monitor at 20 inches is not all that big a deal, but it costs little or nothing to tune those down a bit. The huge gorilla in the room is the hand held devices which kids tend to hold a few inches from the eyes for God knows how many hours under the covers and elsewhere. They are getting a dose that approaches that of the Essilor experimental setup.

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    Eyes eastward... Uilleann's Avatar
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    Some valid points raised. As we're trying to intelligently navigate the now shark infested waters of the blue light chum feeding frenzy, a question related to the benefits to children in particular: Indeed developing media are extremely clear, and UV exposure is a measured concern particularly from birth through the late teens / early 20's. But the effect is two-fold. Yes the media is clear, but in addition, our tendency to be outdoors is much greater in our youth. Due to the number of hours outdoors, it would seem the far far greater danger would be from the intense UV (and who knows about blue sunlight) exposure.

    Yet the focus is only on the 'evil' digital screens and their devil blue light! ;) It absolutely screams of a problem seeking an expensive solution - one all too readily pushed by lab and lens makers today. Unfortunately, the cost isn't truly zero, though it can obviously be lower for some providers than others. So where is the outcry and rabid paranoid fear based marketing for children's sun protection? A logical conclusion can be made that it should be even more pressing, due to proven risk. But, we're left with crickets...

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    Quote Originally Posted by Uilleann View Post
    Some valid points raised. As we're trying to intelligently navigate the now shark infested waters of the blue light chum feeding frenzy, a question related to the benefits to children in particular: Indeed developing media are extremely clear, and UV exposure is a measured concern particularly from birth through the late teens / early 20's. But the effect is two-fold. Yes the media is clear, but in addition, our tendency to be outdoors is much greater in our youth. Due to the number of hours outdoors, it would seem the far far greater danger would be from the intense UV (and who knows about blue sunlight) exposure.

    Yet the focus is only on the 'evil' digital screens and their devil blue light! ;) It absolutely screams of a problem seeking an expensive solution - one all too readily pushed by lab and lens makers today. Unfortunately, the cost isn't truly zero, though it can obviously be lower for some providers than others. So where is the outcry and rabid paranoid fear based marketing for children's sun protection? A logical conclusion can be made that it should be even more pressing, due to proven risk. But, we're left with crickets...
    Most eyecare providers recommend hats, sunglasses or both for kids who spend more than a few minutes in direct sunlight. And remember, the blue sky during daytime is predominantly the longer wavelength "sky blue" which has been found to be beneficial. "Rabid paranoid fear" is a bit strong for a genuine and logical scientific concern over what is truly a huge change in radiant energy reaching kids' eyes these days.

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    Eyes eastward... Uilleann's Avatar
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    Dr S - does it not seem strange, that the human eye has evolved with specific photo receptors most sensitive to those exact frequencies (420–440 nm)? And that those same eyes have functioned for centuries in un-attenuated sunlight with those same photo receptor cells intact and functioning well...so far as we can tell. Is it rational to believe 1/3 of our natural human color perception cells have become completely overloaded in the space of 5-10 years because of some small screens? As for the brightness of these screens, our eyes can still manage a staggering amount of visible light intensity (estimates place that ability at something more than a 10-billion fold capability). If the only object in a dark environment is a bright screen, the eye can (and does - unless somehow prohibited) adjust to that intensity. Doubly so if that little screen is held close to the eye, filling more of the visual field of the observer. And of course, none of this begins to touch on the fact that many (most?) screens and devices include auto dimming features to attenuate in darkened scenarios even further yes?

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    True, but those receptors (S-cone cells) are densely packed in the tiny little macula, fairly sparse in the vast peripheral retina where most of the direct sun and overhead sky light is concentrated, except for a few whacked out people who like to look directly at the sun. So over the millions of years, our rods have taken the beating and taken it well, because they are relatively insensitive to the blue end of the spectrum. At no time in history before the current era have human maculas been subjected to such intense nearby blue emitters. No time. Ever. Period.

    I haven't done the math, but I think staring at handheld video blue or white screen from 5 inches away is possibly higher in blue flux than one would get from staring directly at the sun. Amazingly those sun starer cult people seem to fare pretty well visually. Maybe it's because there is so little deep blue from the sun that actually makes it through 93 million miles of space and several miles of atmosphere...

    Oh and the eye adjusting, yes it can by some pupil constriction and by light adaptation, but these are not particularly protective of the macula. And autodimming, a very commonly and easily over-ridden feature. 10 billion fold capability? Not sure where that number comes from or what it represents.

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    Simply put Uilleann, a hand-held device simply does not have the energy budget to put out harmful radiation in the visible (or invisible) energy spectrum. I consider it the height of absurdity to think that people will "someday" be blinded by looking at a cell phone or pad. There's other words, but absurdity is the most kind and least likely to get flagged.

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    Quote Originally Posted by MikeAurelius View Post
    Simply put Uilleann, a hand-held device simply does not have the energy budget to put out harmful radiation in the visible (or invisible) energy spectrum. I consider it the height of absurdity to think that people will "someday" be blinded by looking at a cell phone or pad. There's other words, but absurdity is the most kind and least likely to get flagged.
    What about the thousands of glass blowers who got blinded by just looking at hot glass for hours on end. I'm sure there were naysayers back then until it was discovered that cumulative damage was indeed being caused by nearby hot glass radiant sources. The exact same type of radiant energy that for millions of years everyone seems to have tolerated pretty well.

    Because the source was 93 million miles away plus around 300 miles of radiation reflecting and absorbing atmosphere, not the 30 inches or so in an ozone free air environment in the case of glass blowers. Fortunately some clear thinking scientists figured it out and came up with the scientific answer you are very familiar with. Fortunately the naysayers were wrong as they have often been throughout the history of science.

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    Quote Originally Posted by Dr. Bill Stacy View Post
    What about the thousands of glass blowers who got blinded by just looking at hot glass for hours on end. I'm sure there were naysayers back then until it was discovered that cumulative damage was indeed being caused by nearby hot glass radiant sources. The exact same type of radiant energy that for millions of years everyone seems to have tolerated pretty well.

    Because the source was 93 million miles away plus around 300 miles of radiation reflecting and absorbing atmosphere, not the 30 inches or so in an ozone free air environment in the case of glass blowers. Fortunately some clear thinking scientists figured it out and came up with the scientific answer you are very familiar with. Fortunately the naysayers were wrong as they have often been throughout the history of science.
    If you are going to throw out baloney, at least educate yourself enough about what the hazard actually *IS* instead of what it isn't.

    There weren't and aren't "thousands of glassblowers who got blinded by just looking at hot glass for hours on end". FACT.

    The well-known "glassblowers cataract" is caused by heat energy, not UV or blue light. It generally affected only those of northern european heritage due to the lack of melanin in their bodies. Typically only one eye was affected, usually the opposite eye from the hand-dominant side of the body, as that was closest to the glass furnace. And, btw, that's nowhere near "the exact same type of radiant energy that for millions of years everyone seems to have tolerated pretty well." Look up "black body radiation". A glass furnace is not equivalent to the sun, not even when the sun is 93 million miles away. Didymium is not the solution for "glass blowers cataract", and if you had done even 15 minutes of research, you'd know that. Didymium *DOES NOT* block IR/heat energy. Only sodium flare. Again, if you would have bothered doing some research, you'd know that too.

    But since you seem to know everything without even bothering to study it, go on spewing your baloney. Just be sure when you deal with *MY* industry, you get your facts right.

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    I hate to correct such an expert in his field, but I did not mention UV or blue light in my post that you quote above. Maybe I'm wrong and there weren't thousands, but it's a very old profession and was certainly plagued at one time by the very well understood occupational cataract that was even named after the profession. So unless you have access to some very old medical statistics that show otherwise, I'm comfy in assuming that it's in the thousands of souls that were prematurely retired due to such unprotected blowing.

    And of course I was referring to the infrared part of the solar spectrum that is the culprit in glass blowing. You are quite right that I did not know that your lenses did not protect at all from the infrared, I only assumed that, and have to wonder if any infrared spectroscopy has been done on various protective lenses. Therminon and Unisol glass comes to mind. I did not mention Didymium at all.

    I'm entirely familiar with black body radiation which has nothing to do with this discussion. The sun puts out exactly the same kind of infrared radiation as any other radiant heat source puts out, and certianly there are thousands of blacksmiths and foundry workers who have also been blinded by "glass blowers cataract" over history from nearby sources of heat and IR. Fortunately for earthlings, most of that powerful energy dissipates over 93 million miles of space and is reflected/absorbed by our 300 miles of atmosphere, or we'd all be crispy critters.

    Oh, and maybe didymium itself doesn't absorb or reflect IR, but I'll bet the glass substrate itself reflects quite a bit of it which is one reason all those workers have to wear eye protection on the job.

  25. #25
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    Quote Originally Posted by Dr. Bill Stacy View Post
    I hate to correct such an expert in his field, but I did not mention UV or blue light in my post that you quote above. Maybe I'm wrong and there weren't thousands, but it's a very old profession and was certainly plagued at one time by the very well understood occupational cataract that was even named after the profession. So unless you have access to some very old medical statistics that show otherwise, I'm comfy in assuming that it's in the thousands of souls that were prematurely retired due to such unprotected blowing.
    There is data on the so-called 'glass blowers cataract' going back to at least the mid-1700's. I downloaded it off the internet, I'm sure it's still there if you do a modicum of searching for it.

    And of course I was referring to the infrared part of the solar spectrum that is the culprit in glass blowing. You are quite right that I did not know that your lenses did not protect at all from the infrared, I only assumed that, and have to wonder if any infrared spectroscopy has been done on various protective lenses. Therminon and Unisol glass comes to mind. I did not mention Didymium at all.
    No, you didn't mention didymium, but you trolled the bait. Direct quote: " Fortunately some clear thinking scientists figured it out and came up with the scientific answer you are very familiar with. "

    There is infrared transmission charts available, and if you take a few minutes, you'll find them on my website, along with UV/VIS transmission charts of all my filters. Done on a CARY 5 UV/VIS/NIR spectrophotometer, from 200 nm to 3000 nm.

    I'm entirely familiar with black body radiation which has nothing to do with this discussion. The sun puts out exactly the same kind of infrared radiation as any other radiant heat source puts out, and certianly there are thousands of blacksmiths and foundry workers who have also been blinded by "glass blowers cataract" over history from nearby sources of heat and IR. Fortunately for earthlings, most of that powerful energy dissipates over 93 million miles of space and is reflected/absorbed by our 300 miles of atmosphere, or we'd all be crispy critters.
    Black body radiation has everything to do with this discussion. Where do you think the energy calculations for various wavelengths come from?

    Oh, and maybe didymium itself doesn't absorb or reflect IR, but I'll bet the glass substrate itself reflects quite a bit of it which is one reason all those workers have to wear eye protection on the job.
    No, actually, they wear specialized eye protection to filter out the harmful IR. Sodium flare is just a nuisance. The glass substrate doesn't reflect, it transmits. This isn't the first time you've made this assumption about reflection vs absorption vs transmission. Glass workers, unless they are working outside, aren't exposed to UV, because the temperatures aren't hot enough (black body calculations again).

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