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Thread: Chromatic aberration (consumer)

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    Chromatic aberration (consumer)

    I recently ordered a pair of glasses (-2.00) with polycarbonate lenses and sent them back because chromatic aberration was causing red and blue fringes on high-contrast edges and in general everything looked less than clear, even if I couldn't discern the colored fringes. Kind of like a bad color print or a misconverging color monitor. So I sent them back and they redid them in high-index plastic (1.67, I think), and I found the problem to be as bad or worse. The people I was dealing with didn't appear to understand my complaint (they suggested trying polycarbonate again) and said that it was not a common one among their patients.

    Today I went to another optician and was told that if I could see chromatic aberration through high-index plastic, I was unusually sensitive. I find that hard to believe and asked whether it could be due to poor craftsmanship instead, and they said no. They also guessed that my current glasses (-1.00) are polycarbonate, and I have no problem with chromatic aberration. (Now that I am aware of it, I can see it very slightly at the very edges, but it's completely not a problem.)

    So, I'm puzzled about why both pairs of new glasses were so bad for me and whether I can trust the same optician to make CR39 lenses for me, or should I go somewhere else?

    Thanks in advance!

    David

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    It's your problem and your decision. You could even concider glass with a low precription like this.

    Chip

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    sub specie aeternitatis Pete Hanlin's Avatar
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    If you can discern color fringing with a -2.00 polycarbonate lens, it would seem you are- indeed- rather sensitive to chromatic aberration (I used to wear poly lenses with a power of -4.75, and could only sporadically sense minimal chromatic effects). However, the fact that you continued to notice the fringes while wearing high index lenses is not surprising and would seem to bear out that you are actually noticing chromatic aberration. 1.67 lenses have approximately the same abbe value (i.e., tendency to break light into colors) as polycarbonate.

    Chromatic aberration occurs as a result of prism, and your -2.00 lenses create more peripheral prism than your former Rx, which would explain the fact that you have not noticed the fringing in the past.

    Return to the optician, and insist on CR-39 lenses. Unless you are wearing exceptionally large frames, I cannot imagine thickness will be an issue. The abbe value of CR-39 is roughly twice that of poly and high index lenses. If you notice chromatic aberration in CR-39 you should 1.) apply for work as some sort of visual inspector, and 2.) consider contact lenses, which will not cause the effect you are noticing in your spectacles.

    Good luck,
    Pete
    Pete Hanlin, ABOM
    Sr. Director Professional Solutions
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    Thanks

    Thanks very much for your quick replies! The people I have been dealing with (Kaiser Permanente) have been kind enough to replace my lenses once and are prepared to replace them a second time, but maybe not the third time (I'm not sure). But if I understand you correctly, I should not be worried about getting a bad pair of CR39 lenses from them?

    Since the consensus seems to be that I'm the aberration :P maybe I can ask a completely tangential question which may or may not be appropriate for this forum. I work on a computer all day and I find that unlike most people, I get more eyestrain from LCD monitors than CRT monitors, provided the CRT's refresh rate is above 75 Hz or so. (The exception was my old PowerBook's LCD, which I never had any problem with...maybe it was dimmer.) I especially can't look at sharp black text against a white background; antialiasing (which uses gray pixels to increase effective resolution at the expense of sharpness) is much easier to look at, although subpixel addressing (which manipulates the individual red, green, and blue elements of an LCD to increase the actual resolution) is often not desirable because of...colored fringes.

    So, now I'm wondering what, physiologically, is different about a person that would make him/her more sensitive to chromatic aberration, and whether that would also explain why I get eyestrain in situations where other people don't. Or am I just crazy :)

    Thanks again!

    David

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    Banned Jim Stone's Avatar
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    Quote Originally Posted by David C
    So, now I'm wondering what, physiologically, is different about a person that would make him/her more sensitive to chromatic aberration, and whether that would also explain why I get eyestrain in situations where other people don't. Or am I just crazy :)

    Thanks again!

    David
    "physiologically" close but more,"am I just crazy ". It is actually really nice to be able to say this. Sorry Dave, but this is probly the case. Try some A/R though. Just might be help enough for you to get through your problem.

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    Thumbs down So, I'm puzzled about why both pairs of new glasses.................

    Quote Originally Posted by David C
    I
    So, I'm puzzled about why both pairs of new glasses were so bad for me and whether I can trust the same optician to make CR39 lenses for me, or should I go somewhere else?
    For your Rx which is a not a complicated job, actually one the simplest jobs in the optical wearing high index in either Poly or other is pushing the buck to far.

    Whatever optician sold you either one, should be ashamed and banned from selling glasses...........he is full of greed and has NO ethics. Poly and other high index have lower base curves and give you a different feel of vision.

    Just get a pair of lenses and mention that they give and charge you for stock lenses in regular CR39 which the closest to glass in the way of visual results and forget the high index you dont even need.
    Chris Ryser
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    http://optochemicals.com............................. http://arcoatings.com

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    Banned Jim Stone's Avatar
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    Quote Originally Posted by Chris Ryser
    Whatever optician sold you either one, should be ashamed and banned from selling glasses...........he is full of greed and has NO ethics.
    Dang dude! There are people on this optiboard that are expected to automatically sell "the package". If they don't so many they lose thier jobs. (It was not the ignorant street people trainees that came up with these policies.) Also this fellow probly came in and ask for thin lenses. Now, with your advice, he's going to go to the local authorities to close this place down! Maybe print this thread out and file a malpractice claim. WOW!

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    1.) A nice pair of glass lenses. Nice and clear with a Anti-Reflective coating
    2.) A nice pair of CR-39/plastic lenses with a A-R coating
    3.) A nice pair of Phoenix/Trivex lenses with A-R coating


    Good Luck.


    Fezz
    :cheers:

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    Quote Originally Posted by Jim Stone
    Try some A/R though.
    Yes, both pairs already had the A/R coating, don't know what kind.

    Also this fellow probly came in and ask for thin lenses.
    No sir, I did not.

    Thanks again for your replies all!

    David

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    Chromatic Abberation?

    recently ordered a pair of glasses (-2.00) with polycarbonate lenses and sent them back because chromatic aberration was causing red and blue fringes on high-contrast edges and in general everything looked less than clear, even if I couldn't discern the colored fringes.
    You state that you have identified the problem as chromatic aberration. I would like to know how you came to this conclusion. The fact that you can see red and blue in the fringes of the lens could also be due to the mismatched index of the lens and the hard coating used. Since most opticians have no conclusive way to identify cromatic abberation problems and I doubt that many consumers do either, I would not pass judgement so quickly as to identifying your problem as chromatic abberation. The index of polycarbonate is 1.58 and most hard coatings are 1.50 to 1.52. With poly there is also a primer used which is also a 1.50 index. Depending on hard coating and primer thickness this maybe causing some very slight chomatic fringe issue. This would not cause everything to look less clear.

    It could even be reflections in the fringes of the lens from the frame depending on the frame material and color.

    If you put a non coated CR-39 lens in the same frame and can see perfectly then you would know that the frame was not a factor.

    The lack of lens clairity is not a part of chromatic abberation. It sounds to me like there is probably another issue and the chromatic abberation was a guess based on no factual analysis.

    There are so many possiblities that I skilled optician should be able to go through the process of elemination and determine a solution. (The Rx could even be wrong for example).

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    Quote Originally Posted by AWTECH
    You state that you have identified the problem as chromatic aberration. I would like to know how you came to this conclusion.
    Nope, I don't know for sure. It sounds like I may have used an overspecific term to describe what I was seeing. All I know is that if, for example, I looked at a white object against a black background, then the left edge would appear red and the right edge would appear blue, if I looked at it to one side, and the colors would reverse if I looked at it to the other side. To a much lesser extent, the same would happen if I looked at it above or below. If I looked at it dead-center, I didn't see anything, but it often didn't have to be that far off-center (hard to estimate -- 15 degrees?) to become noticable. I wish that my optician would try to determine the problem in the way that you describe, but that doesn't really seem to be happening.

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    This is once again an example of the Optician at hand using non-adapt, chromatic abberation as an excuse for this pt's troubles. With this low rx, I too doubt that chromatic abberation is the problem here. But we all know how it's used as an excuse when some opticians cannot find out what the actual problem is.

    And regards to Chris's comment abut the material being sold, I believe you jumped the gun on blaming this Optician and other opticians for selling poly over plastic. There's nothing wrong with that. Plus, we don't know a thing about this patients history, visual acuity, frame type or anything. We weren't there at the sale. So quick to blame opticians again and accuse them for being out for a buck. Give me a break-your accusations are ridiculous ad very very tiresome.

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    Quote Originally Posted by shellrob
    This is once again an example of the Optician at hand using non-adapt, chromatic abberation as an excuse for this pt's troubles.
    No, my optician did not blame it on chromatic aberration (I don't think). That was my doing -- apologies. I should simply have described the problem I was having. What would be the best way for me to go about finding the definite cause? Thanks!

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    Thumbs down And regards to Chris's comment about ................

    Quote Originally Posted by shellrob
    And regards to Chris's comment abut the material being sold, I believe you jumped the gun on blaming this Optician and other opticians for selling poly over plastic.

    ..................Give me a break-your accusations are ridiculous ad very very tiresome.
    We all know that poly is optically not a good as, what you call plastic, CR39 still the best lens after glass. Unless you want to provide eaxtra safety, there is no reason to sell poly except that you can get more money for it. Even if you think it's tiresome it is a fact. :finger:
    Chris Ryser
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    http://optochemicals.com............................. http://arcoatings.com

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    Quote Originally Posted by Chris Ryser
    We all know that poly is optically not a good as, what you call plastic, CR39 still the best lens after glass. Unless you want to provide eaxtra safety, there is no reason to sell poly except that you can get more money for it. Even if you think it's tiresome it is a fact. :finger:
    My point is that you are so quick to blame the optician and say that they only sold it for a a buck when you don't know anything about the patient, his/her needs, visual acuity, activities they do,etc. Don't be so quick to assume the worst.

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    Lets come back to topic. Both of you shall admit, your points are valid. There are opticians who will sell poly over plastic to make money and shellrob, thats a fact. But, having said that, not every optician is doing same. Not all fingers are same, and not all opticians are to be blamed here. Generally, opticians wouldn't like to indulge in such cheap tricks because they may make money by selling poly to a patient and patient when can not get relief still, will approach different opticians. So, just to make few bucks, no one will like to loose a valuable customer. Again, thats my 2 cents. Exceptions are everywhere. lol

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    Master OptiBoarder mike.elmes's Avatar
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    Recently I updated my stock lenses to include Airwear Alize, in the powers +/- 3 and up. This was done to enable us to offer thinner lenses and so we could accomodate the silhouette's, and other drill mounts. I have had some negative feedback regarding chromatic abberation from a few of my customers. We do reccomend airwear in any drill mount as breakeage is MUCH less. However, their are issues. Edge polish is highly reccomended for this material, but is somewhat annoying in terms of adding reflections. Some customers love the weight and don't seem to have a problem with the chromatic abberations, or edge polish. Others are highly annoyed.
    What alteratives exist for drill mounts that have low chr. abbe? Is the Trivex material all it's cracked up to so to speak?

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    sub specie aeternitatis Pete Hanlin's Avatar
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    David,

    Your description of what you are seeing (white objects on black background having a blue or red color fringe- and the fact that you don't notice the effect through the dead center- or optical center of the lens) is a classic description of chromatic aberration. In fact, were you to perform an image search for "chromatic aberration" on a search engine, I have no doubt you would find a picture showing an image very similar to what you are describing (the image would probably be from a site that discusses problems encountered in photography).

    Birefringence- which occurs when the lens coating index of refraction differs from that of the substrate- will show up when looking at reflections on the lens (but only under fluorescent lighting), and does not cause visual symptoms.

    Switching to CR-39 should/will resolve the issue. Also, unlike some of my colleagues here, I don't think your optician did anything other than common practice by suggesting polycarbonate for your lenses. Polycarbonate is thinner, lighter, and provides- for 90%+ of the folks out there- perfectly acceptable vision. BTW, I did not mean to imply that there is anything wrong with your noticing chromatic aberration- my father has very sensitive vision and is able to notice aberrations in windshields and such that take me several minutes to find- even when he points them out.

    You mentioned your occupation involving a computer terminal. There are several things you can do to improve the comfort of your vision:
    1.) ensure the monitor is positioned slightly below a point directly in front of your eyes- your eyes prefer to be positioned down 5 degrees or so (which is typically their position when you are walking).
    2.) some people find it helps to lower the lighting in the room- thus increasing the contrast on the screen
    3.) consider using the monitor settings to provide white text on black (there is usually a setting in the control panel for this)... it is easier to read white text on black on a computer monitor than it is to see black on white
    4.) depending on your age, consider single vision lenses for computer use... your Optometrist can provide such a refraction

    Basically, your eyes may not focus on a terminal the same way they do on a printed page. First, the lighting is different- on a printed page, you are using light reflected from the page- a monitor provides light from its own source. Also, the pixels are not evenly shaded across the entire surface of the pixel- which creates an image that is more difficult to resolve compared to a printed letter. Finally, the blues and reds of the screen will trigger different accommodative responses. If you've ever checked www.weather.com and look at the blue cold front lines and the red warm front lines, you may notice they actually appear to be at slightly different distances from your eye.

    All in all, I would expect your old -1.00 lenses may actually work pretty well for you when using a computer screen.

    If you would like further information on visual effects created by computer monitors, I would suggest a book written by a Dr. Sheedy on the subject entitled: Diagnosing and Treating Computer-Related Vision Problems.

    In the meantime, I suggest you have CR-39 lenses ordered for you with AR and thank the nice folks at Kaiser-Permentae (sp?) for working with you to resolve your visual needs.

    Best regards,
    Pete
    Pete Hanlin, ABOM
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    I feel the need to defend us moral opticians...Chris your acting like a horses behind! I was a fan of yours but I tell you what, you sure jump to conclusions faster then anyone I know. See here is the deal, if an optician is doing his/her job then they educate the pt on all of the lens availabilities, there pros and cons and allow the pt to select what is best for them. So that means we dont push poly or hi index in fact we may tell them to save a buck and in turn earn the trust of them, or we may say hey considering your activities, work or whatever maybe this would be best for you. DOnt just assume we are all money hungry mongers....after all you sure push your product at any given point. Sheeesh you have my blood boiling right now, go take a rest I think your legs must hurt after all that jumping!

    Cindy

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    Way to go, Cindy.

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    sub specie aeternitatis Pete Hanlin's Avatar
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    We all know that poly is optically not a good as, what you call plastic, CR39 still the best lens after glass. Unless you want to provide eaxtra safety, there is no reason to sell poly except that you can get more money for it. Even if you think it's tiresome it is a fact.

    At the time I had LASIK performed (over four years ago, and still thrilled with the results), I had 8 pair of lenses- 7 were polycarbonate, and my Rx was -4.75.

    Why polycarbonate?
    They were lighter than CR-39
    They were thinner than CR-39
    They were safer than CR-39 (or any other lens material, for that matter)
    They were relatively inexpensive (compared to high-index)
    and- finally- my vision with them was perfectly acceptable!

    If optics were the only consideration- and cost, weight, safety, meant nothing to me, of course I would choose clear crown glass- which is clearer than any other current ophthalmic material by far. All things considered (to borrow a phrase from NPR), I happen to believe polycarbonate is the best all around ophthalmic material available. In some cases, perhaps another material may be superior (e.g., if my script was -9.00, I'd probably look for a high index glass lens), but all-in-all, its hard to beat polycarbonate for weight, thinness, safety, and cost (and the optics- contrary to the opinions of some- are quite on par with other high index materials).

    Were this particular patient to have walked into my dispensary, I would have recommended polycarbonate. Once he displayed the symptoms of being unusually sensitive to chromatic aberration, I would have switched him to CR-39, not high index- which has approximately the same abbe value and therefore would be expected to cause the same symptoms (which in this case, actually occurred).

    The patient mentioned getting his lenses at Kaiser- which is a really good integrated insurer/health provider. I sincerely doubt there was any sort of sales motivation behind the original suggestion of polycarbonate.
    Pete Hanlin, ABOM
    Sr. Director Professional Solutions
    Essilor of America

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    I agree with Pete. Polycarb is widely used and rarely do we see a problem with it. My own rx is just a little stronger then yours and I wear poly with no problems. I have also worn cr 39, 1.54, 1.60, 1.67, and 1.70. I see fine out of all of them.

    I think you can trust your optician to redo them in standard plastic. I don't really know why they went with 1.67 unless it is a rimless frame, but I don't see any reason not to trust them. You are just more sensitive then most people.

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    I feel its more of caffeteria approach when it comes to opticians. They should inform patients about types they have and features, restrictions besides benefits and problems. Now once patient has been informed about all types you have got, let him make a choice. If he needs assitance, then make such a recommendation based on what you think is best for patient. Few bucks will not help you , if patient is not satisfied and it shall only affect your poularity. So, just roll out types you got and explain it to patient, let him make a choice. That would be better approach and many do practise on same lines. Not all are money hongers.

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    DOnt just assume we are all money hungry mongers....

    Quote Originally Posted by cinders831
    DOnt just assume we are all money hungry mongers....after all you sure push your product at any given point. Sheeesh you have my blood boiling right now, go take a rest I think your legs must hurt after all that jumping!
    Cindy
    I actually woke up this morning with my whole body hurting, all mechanical, looked at this original post again which is right here below:


    Quote Originally Posted by David C
    I recently ordered a pair of glasses (-2.00) with polycarbonate lenses and sent them back because chromatic aberration was causing red and blue fringes on high-contrast edges and in general everything looked less than clear, even if I couldn't discern the colored fringes.
    Having seen all the screaming against me on this thread I discovered what I should have seen at the start.

    David says he ordered...............which means he made a purchase knowingly of what he wanted.

    This translates into me being wrong, and all of you who have been bashing me, ...........being right.

    I must have blown a mental fuse and as I am trying to be fair most of the time.....................I have to apologize to all you guy's for actually jumping the gun as you say.

    :o
    Chris Ryser
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    http://optochemicals.com............................. http://arcoatings.com

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    Very noble of you Chris. Thank you.

    Cindy

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