Polycarbonate versus High Index Plastic (1.67) lens help!

Discussion in 'Optometry Archives' started by KC, Sep 4, 2007.

  1. KC

    KC Guest

    Hi all,

    I just picked up a new pair of glasses from Lenscrafters. They
    recommended Polycarbonate because it was apparently shatterproof etc
    etc. My prescription is -5 and -5.25, so I think that's fairly high.
    The frames are a lot smaller, almost a 40% smaller than my old (13 yr
    old) frames. Here are some of the problems I'm seeing:

    1. Keeping my head facing forward if I try to look at something
    slighty to the right or left of me, it's blurry.
    - eg. I can see my computer monitor fine. If look at the phone on
    my desk, a foot away from the monitor, I can't read the brand name or
    the function buttons, they're all blurry

    2. Reading stuff on my desk, all the print (black) has a yellow
    outline/halo. (Chromatic Aberration?)

    Also for #1, when driving if I glance at my driver's side mirror
    (without turning my head), I can't read the license plate info or for
    example the word "TAXI" on a taxicab's hood.

    The Lenscrafters person suggested I get "High Index Plastic", which is
    a $100 upgrade. I don't want to get those and then find that they are
    the same as the polycarbonate.

    Does anyone know if these aberrations that I'm seeing is normal for
    Polycarbonate? And would high index plastic lenses of 1.67 make a
    huge difference? What about 1.74? Although, Lenscrafters doesn't
    carry any lens of 1.74. I think Nikon makes a lens like that but
    they don't carry Nikon lenses.

    Any advice would be greatly appreciated!

    Thanks,

    Kevin
     
    KC, Sep 4, 2007
    #1
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  2. KC

    Zetsu Guest

    Hello,

    It is surely obvious then; that the glasses are never a satisfactory
    substitute for normal vision without glasses, and at best are an
    immense annyoance although they may correct the condition, and at
    worst they are of no value at all, and induce harm.

    Discard the bad and aggravating crutches, learn to see perfectly
    without glasses. This may be accomplished by playing with the rest
    methods and imitating the normal eye.

    http://en.wikisource.org/wiki/Perfect_Sight_Without_Glasses
     
    Zetsu, Sep 4, 2007
    #2
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  3. KC

    Mark A Guest

    Polycarb has the worst optics (lowest abbe value) of any commonly dispensed
    lens material. It has an refraction index of 1.59. The nearest index plastic
    is 1.60 which should be much better optically than polycarb, should be about
    the same cost as polycarb (maybe slightly higher), and should have better
    optics and much cheaper than 1.67. The only disadvantage with 1.60 compared
    to 1.67 is that 1.60 will be a little bit thicker and hence a little bit
    heaver.

    Personally, I would invoke the 30 day money back guarantee and go to
    Wal-Mart Optical (if you are very concerned about price) or a good
    independent optician. Wal-Mart has some fairly good lens materials available
    to them (although I am not sure about SV lenses) 1.74 is probably overkill
    for your Rx, and generally speaking the higher the index, the worse the
    optical quality (except for polycarb, which is the worst at 1.59 index).

    If you must have safety glasses, find someone who dispenses Trivex material
    (Hoya Phoenix material is one brand that is made of Trivex)..
     
    Mark A, Sep 4, 2007
    #3
  4. Hey Mark,

    Thanks for your response. I thought I had it but after reading your
    response, I guess I was wrong. The higher the refractive index the
    worse the optical quality? (Optics in physics was over a decade
    ago). Basically the issue I have with the current set of lenses
    (Polycarbonate) is the fact that I can't even move my eyes 15-20
    degrees off center and it gets blurry. Also looking down at
    black&white documentation, most of it has a yellow halo. Would the
    plastic lens fix those issues at both 1.60 and 1.67 refractive
    indices?

    The price doesn't really matter, I would rather get it done right.
    However, lenscrafters has been kinda disappointing so far. From what
    I've read one typically doesn't use polycarb lenses for prescriptions
    of -5 and greater.... well they should have recommended against it.
    They specifically said "Oh this is the best lens for your prescription
    and it comes with all the protective coatings blah blah". A co-
    worker of mine got his frames from Wal-mart for almost the same price
    I paid for mine at Lenscrafters, so I didn't even look into Wal-mart.

    As for the money back gaurantee, I'm not 100% sure of that. I know
    that they will fix any issues and even replace the frame/lens upto 30
    days, in my case +10 days because the store manager gave me an
    extension so I could research the "plastic" lenses.

    Thanks,

    Kevin
     
    Jennifer.Coutinho, Sep 5, 2007
    #4
  5. KC

    KC Guest

    Mark,

    Thanks for your resposne. I didn't realise that the higher the
    refractive index the worse the optics. I guess I need to go back to
    Grade 12 physics, that was eons ago. :) The issue I have with the
    current lenses is that if I look 15-20 degrees off center it's all
    blurry. Also, if I look down at a black&white document, the black
    print has yellow halos on it. If I got the 1.60 or 1.67 plastic would
    it eliminate the blurriness and halos?

    Cost is not really an issue (within reason), I didn't go to Wal-mart
    because I wanted quality... .but Lenscrafters hasn't proven that they
    know a whole lot more about optics. From everything I've ready they
    should have been pushing plastic lenses for a prescription worse than
    -5, not polycarbonate. A co-worker of mine got a new set of glasses
    from Walmart and he paid about the same as I did at lenscrafters.

    About the "30 day money back guarantee", I'm not sure I can do that.
    I know they will fix whatever is wrong, replace the frames, lenses
    etc. They might not do a moneyback deal though. In my case the
    manager of the store extended the 30 days by 10 so that I could
    research the plastic lenses online.

    Thanks,

    Kevin
     
    KC, Sep 5, 2007
    #5
  6. KC

    Mark A Guest

    Yes, the higher the index, then generally speaking, the worse the optics.
    You don't something (thinner lighter lens) for free (optically speaking).
    The biggest exception is polycarb which at only 1.59 index, it has the worst
    optics of any commonly dispensed lens, but it is a safety lens.

    Unless Lenscrafters has changed its policy recently, they offer an
    unconditional 30 day money back guarantee. Call another LC and ask them.

    You might look at 1.67 VIZIO ATORIC SINGLE VISION with UTMC (Ultra Tough
    Multi Coating, which is an AR coat). Or look at similar lens designs from
    Zeiss or Hoya. Lenscrafters carries mediocre quality lenses. Call around to
    various optical shops in your area to see what lens they carry.
     
    Mark A, Sep 5, 2007
    #6
  7. And while you're at it, toss out those orthotic insoles and the knee brace.
    Next toss out your false teeth and use the rest method to firm up your gums
    to chew food. No need for the heart pacemaker either, so out with that.
    Insulin, who needs it? You can control your blood sugar with your mind.
     
    No One In Particular, Sep 5, 2007
    #7
  8. KC

    Zetsu Guest

    Hello,

    Please, who are you?

    Yes that is right: you are no one in particular!
     
    Zetsu, Sep 5, 2007
    #8
  9. KC

    KC Guest

    Robert,

    Thanks for the information. Do technicians at Lenscrafters even have
    an optical hat? The comment I got before leaving the store the last
    time was "We can switch you to a high index plastic, that should make
    it better if it really bothers you but maybe it's something that you
    need to get used to..... we could change your frame if you want.".

    They're not giving me any details around the options. What they need
    to tell me is why I see blurry outside of the focal area, why the
    chromatic aberration etc.

    When I asked if a bigger frame would make a difference, she said "a
    little but not really".
    Is this for High Index Plastic? Lenscrafters only carries 1.67, so
    I guess its abbe value 32.

    The frames I picked are plastic, full frames. So I don't think the
    thickness matters all that much, not as far as seating it goes
    anyway. Here's a pair very similar..

    http://eyeglasses.go-optic.com/enlarge.asp?id=20312&cat=DFRAMES

    I might have to just do the 100% refund and go elsewhere since these
    techs don't seem to be very knowledgable OR even care about the end
    result. So far it seems like all sales, great fronting but no
    substance.

    Kevin
     
    KC, Sep 5, 2007
    #9
  10. KC

    lena102938 Guest

    Kevin,
    You can find more info about lenses
    In the thread "Surprised by OTC Reading Glasses"
    Read posts by Mark A
    It is very interesting
    Lena
     
    lena102938, Sep 5, 2007
    #10
  11. KC

    Mark A Guest

    At best, there is only one decent optician in each Lenscrafters store, and
    they don't work all the time. That is at best.

    The rest of the sales people were selling shoes or apparel at a different
    store in the mall last month.
     
    Mark A, Sep 6, 2007
    #11
  12. KC

    lena102938 Guest

    Mark
    What about the plus lenses?
    Will Low-index +2D lenses (glass or plastic)
    Look too thick ?
     
    lena102938, Sep 6, 2007
    #12
  13. KC

    Mark A Guest

    A plus 2.00 lens is moderately weak, and will not be too thick for a
    mid-index lens (1.53 - 1.60). Plus lenses are thin at the edges and thicker
    in the middle. Most people who have a problem with thick lenses don't like
    the edge thickness, which is more of problem for a minus Rx (nearsighted).

    If cost is big factor, you could even get 1.50 plastic, which has excellent
    optics, but may not come factory coated (for UV or AR) and is going to be
    heavier than the others. Don't get any coating that is not factory coated by
    the lens manufacturer.

    Glass is really too heavy unless you some special requirement for it. Trivex
    (Hoya Phoenix) or any 1.60 plastic would be good. The Trivex is a safety
    lens like polycarb, but with excellent optics.
     
    Mark A, Sep 6, 2007
    #13
  14. KC

    lena102938 Guest

    Thanks
    Lena
     
    lena102938, Sep 8, 2007
    #14
  15. Hi, your prescription is almost identical to mine. I have worn
    polycarbonate for years because of the durability issue -- I ride
    motorcycles and cannot accept a material for my glasses that may shatter
    in the event of an accident. I do not have any of the issues that you
    discuss and doubt that high-index plastic will make any difference.

    I am not an eye doctor so thus cannot tell you why you're having
    problems, just that it's not inherent in the polycarbonate material with
    your prescription strength.
     
    L. Ron Waddle, Sep 10, 2007
    #15
  16. Kevin,

    I haven't read the lengthy follow-ups to this, but just in case my two
    cents is worthwhile:
    Five or seven years ago Lenscrafters recommended me the "Featherwates"
    polycarbonate lenses, and I could tell something was unusual the
    moment I put them on (this was not the usual sort of adjustment
    issues). My vision is around -7.75 and -8.25. If I was not staring
    directly out of the center of the lenses, everything became blurry,
    and many things split into a variety of colors in my peripheral vision
    (most noticeably at a sharp black line against a white). I can't
    remember if I went back the same day, or the next, but after
    explaining what was going on, the person at Lenscrafters admitted that
    a percentage of the population (I forget how much, but enough to be
    notable, I guess) had this problem with the polycarbonate lenses, and
    they replaced them for free. (Sorry, I forget what material my
    glasses are currently made of, instead.)
    Best of luck solving your problem! To my knowledge the company is, at
    least, aware of the problem and what lenses to offer that will not
    cause it.

    -Sarah
     
    fleecepenguin, Sep 11, 2007
    #16
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