-96 diopters then -104 diopters(same guy got -8 worse in a year)

Discussion in 'Optometry Archives' started by acemanvx, Dec 30, 2005.

  1. acemanvx

    acemanvx Guest

    Originally Posted by Lewy
    I remember attending a seminar by Norvilles several years ago. One of
    the questions asked at the time was "What is the highest minus lens you
    have dispensed". Personally I have dispensed a -33.00 as a bonded
    lenticular. In the audience the highest quoted was -42.00.............
    Norvilles topped it by a large margin, they had had an order for
    -96.00, YES you read it correctly, -96.00. To make the lenses thay had
    to cement 2 lenses back to back and each had an aperture of approx
    12mm. A year later they had another order for the same client for
    -104.00, they physically couldn't make it.

    Consensus of opinion was a guide dog or white stick would have been a
    better bet.


    minus 96 diopters? holy is this even possible? I saw one website that
    says they once made a -70 glasses and they said it was a world record
    too! His eyes got worse by -8 in one year? Wow whats his corrected
    vision? something like 20/2000? His uncorrected vision would be
    LP(light perception)
    How much myopia is physically possible? Wouldnt your eyeballs be more
    than twice as long as normal, your corneas extremely steep, your lenses
    like three times thicker?
    acemanvx, Dec 30, 2005
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  2. acemanvx

    otisbrown Guest

    Dear Ace,

    Here are the basic equations of physiological
    optics. If you assume that the eye
    is a "box camera" (Gullistrand model)
    the calculations are quite simple.

    (From Chapter 3 my book)



    In order to understand the design and behavior of the normal eye it is
    necessary to understand its basic optical properties.

    When a light ray enters water it is refracted (bent). The equation that
    describes this bending is shown below. Water has an Index-of-Refraction
    of 1.33. The normal eye has 1.38 as an over-all Index-of-Refraction.
    (Figure 1)


    Figure 1.

    When light travels through a curved surface, the light rays converge on
    a single point. Since an image is made up of a large number of points
    of light, an image will form where the light rays converge. (Figure 2)


    Figure 2 (from Gullstrand's schematic eye, Reference 1).

    The distance between the surface of the lens and the point of image
    formation is called the focal length.

    Focal Power = (Refractive Index) / (Focal Length)

    By using this equation it is possible to analyze the basic optical
    properties of the eye. The approximate dimensions of the eye have been
    established. The radius of the cornea is 0.66 centimeters, the index of
    refraction is 1.38, and the length of the eye is 2.4 centimeters. By
    using these numbers we can calculate the focal power of the normal eye.
    (For reasons of clarity, I have not included the effect of the internal
    lens. A more detailed analysis can be found in Reference 1.)

    Focal Power = 1.38 / .024 Meters

    Focal Power = 57 Diopters


    You can continue with these
    calculations. DrG and the
    other ODs can confirm you
    the formula and your math for you.


    otisbrown, Dec 30, 2005
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  3. acemanvx

    acemanvx Guest

    understood but does this make it possible to have myopia in the triple
    digits? How far can myopia progress? -120? -150? -200? -1000?
    acemanvx, Dec 31, 2005
  4. acemanvx

    otisbrown Guest

    Dear Ace,

    Very difficult to say. In my opinion, the tissues would
    be torn apart by they time you got this much change.

    My "pruspose" is to prevent -- before this process
    even starts.

    But then I am "out numbered" on that point.


    otisbrown, Dec 31, 2005
  5. acemanvx

    Neil Brooks Guest

    Prus-pose. Noun. An explanation for early-onset alzheimers
    characterised by delusions of grandeur, antisocial behaviors, and
    narcissistic personality disorder.
    Neil Brooks, Dec 31, 2005
  6. acemanvx

    acemanvx Guest

    Thats true some people become blind from retina detachments before they
    reach insane levels of myopia but supposedly this guy reached -104
    diopters and while legally and nearly blind, he could still "see" a
    little with two pairs of lenses cemented to each other! As long as the
    patient has some vision left, myopia is measured and glasses fitted.

    Myopia in the -20 to -30 range sometimes leaves the retina intact
    enough to provide the patient with acceptable vision with myodisc
    glasses, usually better than 20/200 corrected.
    acemanvx, Dec 31, 2005
  7. acemanvx

    p.clarkii Guest

    these two are idiots. just let them continue this laughable dialogue
    and see how far it goes. this is about as good as Otis and his myopia
    expert buddy discussing the strengths and weaknesses of the Shotwell
    study. "-96 diopter myopia". "tissues torn apart". "pruspose". give
    me a break.
    p.clarkii, Dec 31, 2005
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