My Eyeglasses May Have Wrong Base Curve! Need Advice!

Discussion in 'Glasses' started by midwest_46, Aug 17, 2007.

  1. midwest_46

    midwest_46 Guest

    Hi. I am a 33-year-old male.

    Prior to 1997, I wore glasses that were -4.25 in the left eye and -4
    in the right eye. These glasses had a base curve of 3.5 in each lens.
    Also, the lenses were very big in size. Also, the lens material was
    glass (I believe).
    use my -4.25, -4 glasses as reading glasses - for reading, computer
    use, etc. The -5 glasses also had big lenses (about the same size as
    the lenses in the -4.25, -4 glasses). Unfortunately, I never had the
    base curve of these glasses measured, and I lost them in 2006. Also, I
    am uncertain as to the lens material of the -5 glasses.
    driving. I continued to use the -4.25, -4 glasses for reading,
    computers, etc. The base curve of the -5.25 glasses is 2.5 in each
    lens. However, the -5.25 glasses have lenses that are significantly
    smaller than the lenses in my -4.25, -4 glasses. Also, the -5.25
    glasses have lenses made of photo flextint plastic.

    By the way, the base curve of the -4.25, -4 glasses and the base curve
    of the -5.25 glasses were measured at my eye doctor's office.

    Recently, I decided to get some reading glasses with small lenses. So,
    I ordered a pair of glasses that had the following characteristics:

    prescription: -4.25, -4.25 (approximately the same as the prescription
    of my previous reading glasses)

    base curve: 3.5 in each lens

    size of lenses: slightly smaller than the -5.25 lenses (significantly
    smaller than the lenses in the -4.25, -4 glasses)

    lens material: photo flextint plastic

    The new reading glasses have approximately the same prescription as my
    old reading glasses. The new glasses have the same base curve as my
    old glasses.

    However, the new glasses are made of photo flextint plastic, and the
    old glasses are made of glass.

    Also, the new glasses have significantly smaller lenses than the old

    Well, the new glasses give me headaches, while the old glasses do not
    give me headaches. So, what is causing these headaches?

    I bought my new glasses at Lenscrafters. Is it possible that my doctor
    and Lenscrafters measure the base curve in two different ways?
    My doctor measured the base curve of the old glasses at 3.5. When I
    asked Lenscrafters for a base curve of 3.5, perhaps Lenscrafters
    produced lenses that Lenscrafters measured at 3.5 but that my doctor
    would measure as something else?

    Or, since the lenses of the old glasses are big and have a base curve
    of 3.5, perhaps the base curve of smaller lenses of approximately the
    same prescription should be a different base curve?

    Or is the difference in lens material causing the headaches? These new
    glasses are the first glasses I've had that have a prescription in the
    -4.25 range and that are made of photo flextint plastic. Prior to now,
    the glasses that I had in the -4.25 range were made of glass.

    So, please give me some advice. Thanks for any information.
    midwest_46, Aug 17, 2007
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  2. frame fit, optical centers may play a role. base curve may have
    nothing to do with it - have an optician at lens crafters compare both
    michael toulch, Aug 18, 2007
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  3. midwest_46

    midwest_46 Guest

    On Aug 17, 8:02?pm, michael toulch >

    I went to Lenscrafters and had the optical centers checked out.

    The optical centers on the new reading glasses are almost at the
    centers of my eyes. So, the new reading glasses are OK as far as the
    optical centers are concerned. However, the old reading glasses'
    optical centers are below the centers of the eyes (by approximately 4
    to 5 mm).

    The optician also said that the new lenses are smaller than the old
    lenses and that I'm noticing the bottom of the new lenses whereas I
    had not noticed the bottom of the old lenses. In other words, I would
    have to get used to the new glasses.

    However, I then had the optician measure the base curve of all three
    pairs of glasses (-5.25 glasses, old reading glasses, and new reading
    glasses). The optician measured the base curve using something called
    a lens clock.

    Anyway, he measured the base curve of the -5.25 glasses at 2.5, which
    confirms my doctor's measurement. The optician measured the base curve
    of the new reading glasses at 3.5, which is what I had ordered.
    However, the optician measured the base curve of the old reading
    glasses at 3.0, while my doctor's measurement is at 3.5. So, either my
    doctor or the optician made an incorrect measurement.

    Since the new glasses give me a headache and the old ones don't, I'm
    guessing that the 3.0 measurement on the old ones is correct and that
    I should exchange the new glasses for glasses that have a base curve
    of 3.0.
    midwest_46, Aug 19, 2007

  4. **right there - that is a significant difference -the o.c. height.

    **panto tilt and face form of both frames should be compared.
    michael toulch, Aug 21, 2007
  5. midwest_46

    midwest_46 Guest

    So, are you saying that the optical centers in the new glasses are
    SUPPOSED to be 4 - 5 mm below the centers of the pupils?

    So, when the optician is measuring the OC height, is he supposed to
    measure from the top of the frame to about 4 - 5 mm below the center
    of the pupil?

    Also, can you please explain panto tilt, optical axis of the lens,
    center of rotation of the eye, and astigmatic error? You're throwing a
    lot of jargon at me, and I'm having trouble understanding it. :)

    I'm not sure that I understand. Are you saying that the frame must be
    huge for the glasses to feel comfortable? My old reading glasses
    (-4.25, -4) have a huge frame, and they are comfortable. However, this
    frame is very huge and ugly. I was hoping to get a pair of glasses
    with almost the same prescription (-4.25, -4.25), but with a small
    frame (to match the modern style).

    By the way, my -5.25, -5.25 distance glasses have a small frame, and
    they are comfortable. And, if I recall correctly, the optical centers
    of the -5.25 glasses are right at the centers of my pupils. The
    centers are not 5 mm below the pupils.

    An optician at the store where I bought the -4.25, -4.25 glasses
    showed me that the lens clock was calibrated by putting the lens clock
    onto a flat table at the store. The lens clock read "0". So, according
    to the optician, the lens clock was calibrated because the clock
    properly measured the base curve of a flat surface.

    I do not know whether any optician who measured the base curves of my
    pairs of glasses, adjusted the measurements because the glasses were
    not crown glass.

    Well, I am already avoiding polycarbonate lenses. :)

    Thanks for your reply.
    midwest_46, Aug 25, 2007
  6. midwest_46

    midwest_46 Guest

    What are panto tilt and face form?
    midwest_46, Aug 25, 2007
  7. midwest_46

    midwest_46 Guest

    I went into a Lenscrafters store and had all three of my glasses
    measured for 1) panto tilt and 2) the distance between optical center
    and center of my eye.

    -4.25, -4 glasses (old reading glasses) :

    panto tilt: 8 degrees
    optical center: 6 mm below center of eye

    -4.25, -4.25 glasses (new reading glasses) :

    panto tilt: 15 degrees
    optical center: 2 mm below center of eye

    An optician at the Lenscrafters where I bought the new reading glasses
    tried to give them the same panto tilt that my old reading glasses
    have. He ended up giving the new glasses twice the panto tilt of the
    old glasses.
    At my request, the Lenscrafters employee who was measuring the panto
    tilt adjusted the panto tilt to 10 - 11 degrees. The optical center
    remained 2 mm below the center of the eye. This adjustment resulted in
    some alleviation of the discomfort I was feeling. However, I will have
    new lenses made with the optical center being 5 mm below the center of
    my eye (to match the 10 - 11 degree tilt).

    -5.25, -5.25 glasses (driving glasses) :

    panto tilt: 8 degrees
    optical center: 5 mm below center of eye

    How do I know whether my lenses are sperical or aspehrical?

    How can I tell the difference?
    midwest_46, Aug 31, 2007
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