How large a zone can orthoK go up to? 7mm? larger?

Discussion in 'Optometry Archives' started by acemanvx, Mar 8, 2006.

  1. acemanvx

    acemanvx Guest

    Due to my huge pupils, I will want the largest zone possible. I know
    6mm is standard but theres also 5.5mm and 5mm as well as larger. I have
    seen 7mm and heard of even larger! I googled it and orthoK is indeed
    available in 7mm. Not sure if larger but 7mm is not bad as my pupil
    probably wont get over 7mm except in near total darkness. I am willing
    to accept mild halos and starbursts or rather, a mild increase over
    what I have. I use my vision in the day much more than night and I dont
    drive anyway so it wouldnt matter. If worse for worse comes, orthoK is
    reversable and I can stop orthoK then resume it anytime.
    acemanvx, Mar 8, 2006
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  2. acemanvx

    p.clarkii Guest

    your pupils wouldn't be so large if you quit eating mushrooms.
    now go discover girls or something-- quit fixating on vision
    p.clarkii, Mar 9, 2006
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  3. acemanvx

    Dr. Leukoma Guest


    In my opinion, 7 mm is out of the question for your prescription. The
    amount of correction is inversely proportional to the diameter of the
    treatment zone. Look up Munnerlyn's formula for the exact
    relationship. One generally has only 50 microns of tissue to play
    with, so figure out the maximum depth is 50 microns, the diameter is 7
    mm. How much correction in diopters can result?

    Dr. Leukoma, Mar 9, 2006
  4. acemanvx

    CatmanX Guest

    Making a 7mm optic does not equate to the optic zone created on the

    Anyway, no-one would touch a douche like you anyway Nancy.

    dr grant
    CatmanX, Mar 9, 2006
  5. acemanvx

    Dr. Leukoma Guest

    This is true. But, since you are the "expert," exactly what
    probability do you give to getting that accomplished, pretending that
    the k's and eccentricity are "average"?

    Dr. Leukoma, Mar 9, 2006
  6. acemanvx

    acemanvx Guest

    "One generally has only 50 microns of tissue to play
    with, so figure out the maximum depth is 50 microns, the diameter is 7
    mm. How much correction in diopters can result?"

    OrthoK can only flatten 1/3 to 1/2 of that. If you have 50-60 microns
    to play with, figure about 25 microns maximum to play with. With 6mm
    orthoK, thats 6 microns per diopter so 4 diopter improvement is about
    the limit. with 7mm zone, its 8 microns per diopter so the limit
    becomes 3 diopters.

    "In my opinion, 7 mm is out of the question for your prescription."

    I wear -3.25 glasses most of the time.

    "Making a 7mm optic does not equate to the optic zone created on the

    itll be about 6.75 mm for a 3 diopter correction. I will see if I can
    get 7.5mm or even 8mm zone orthoK.
    acemanvx, Mar 10, 2006
  7. acemanvx

    Dr. Leukoma Guest

    OK, Ace. You win. Nobody can tell you anything.

    So, run along and get OK and report back to us.

    The OK nomograms are derived from Munnerlyn's formula as any OK expert
    will tell you. Of course the amount of tissue displaced will vary with
    the thickness of the epithelium, and is not the same for everybody.

    Dr. Leukoma, Mar 10, 2006
  8. acemanvx

    CatmanX Guest

    Actually most are derived from Jessen's formula, with the exception of
    BE, which take a different tack.

    However, you are correct in thinking that Nancy is a dickhead. She
    really is. She does not listen, she thinks you are an OK expert, when
    you have publically ridiculed OK (as is your right) and then tells you
    how to prescribe RGP lenses.

    I agree with you Lou, Nancy is one sick puppy.

    Happy refracting brother in lenses.

    dr grant
    CatmanX, Mar 10, 2006
  9. acemanvx

    acemanvx Guest

    His formula says theres a .25 diopter regression after 4 hours and a .5
    diopter after 10 hours. Wont make a difference to me since ill be
    undercorrected anyway.

    He also states a .75 diopter regression after 16 hours for 3 diopter
    correction. Ok so ill just move a couple inches closer to the computer
    monitor, no biggie.

    He also found that when comparing the regression at seven-day, 30-day
    and 90-day intervals, the amount of regression appeared to slightly
    decrease with time

    additionally, orthoK was preferred by a higher percentage of subjects
    than glasses or soft contacts. This means your more likley to be happy
    with orthoK than with glasses!

    Before enrolling in the study, 82 percent of the subjects were soft
    contact lens wearers, and at the conclusion of the study, only 18
    percent of them preferred to continue to wear soft contact lenses. The
    subjects who preferred soft contact lenses or spectacle correction over
    Paragon CRT lenses were the ones who reported the most complaints of
    lens discomfort and glare or flare.

    I cant find much more info, but from what I can see, -6 diopters is the
    limit for 5mm orthoK, -4 for 6mm and -3 for 7mm.

    5mm orthoK displaces 4mm of tissue per diopter(4x6=24)
    6mm orthoK displaces 6mm of tissue per diopter(6x4=24)
    7mm orthoK displaces 8mm of tissue per diopter(8x3=24)

    "Of course the amount of tissue displaced will vary with
    the thickness of the epithelium, and is not the same for everybody."

    The above figures are for a thick epithelium. If mine is average
    thickness, ill expect an improvemen of -2.25 or -2.5 diopters plus a
    reduction or elimination of my astigmastim.

    DrG, you are presbyopic so you know full well the benefits of your -3.5
    pescription in seeing clearly from 11.5 inches. If you sit about 2 feet
    from the computer, a -1.75 undercorrection is needed. If you got OrthoK
    and fully corrected, youd need reading glasses for near and
    intermediate. If your OrthoK undercorrected you, you wont need glasses
    except for reading fine print or for driving and watching movies.
    acemanvx, Mar 10, 2006
  10. acemanvx

    CatmanX Guest

    ****, I laughed so hard I nearly shat.

    Lou Coma knows more about the math of OK than you and he doesn't know
    the start of it as he does not do it. However, he does know math and he
    knows that the bigger the zone, the smaller the change.

    Now to you Nancy. You are stupid. You post crap that is not worthy of
    posting and if I were moderator (Christ I wish I was) you would never
    post here or anywhere again.

    You don't know shit. You don't know the start of shit. You know OK even

    Just PISS OFF and stop annoying the general public with your shit.

    dr grant
    CatmanX, Mar 10, 2006
  11. acemanvx

    acemanvx Guest

    If you think you know so much, why dont you educate me instead of
    spouting off vuglarities? Teach me about OK, o master!
    acemanvx, Mar 10, 2006
  12. Why would I waste my time. You are a parasite. You know noting and
    learn nothing.

    Go away.

    dr grant
    drgranthatesyou, Mar 10, 2006
  13. acemanvx

    Dr. Leukoma Guest

    Your figures are close to mine. When I say thickness, I mean the
    saggital thickness, which is the difference in thickness between the
    center and the edge of the treatment area. OK causes the central
    cornea to thin by pushing epithelium out into the mid-periphery, where
    it piles-up. Helen Swarbrick published an excellent study on this a
    few years back. She found that the average dioptric change was 1.66.
    This was accomplished by an average central thinning of 9.3 microns and
    an average mid-peripheral thickening of 10.9 microns. The effective
    saggital depth is about 20 microns, or 12 microns/diopter for a 6 mm
    zone. With a total of 50 microns to play with (25+25), this works out
    to about 2.75 to 3.00 diopters of change for a 7.0 mm zone, ASSUMING
    the lens mechanics would permit it.

    The above is only theoretical, which is why I asked Dr. Mason to
    comment from his personal experience. Instead, he made some obscure
    reference to the founder and patron saint of orthokeratology, George
    Jessen, and did not answer the question directly.

    With respect to being presbyopic, my preference is for 100% clarity at
    infinity, and 100% clarity at whatever nearpoint distance I am working,
    which means that I prefer to wear progressive lenses over my contact
    lenses. I have zero tolerance for blur, and zero tolerance for
    fluctuating vision. This means that I would not be a good candidate
    for either OK or LASIK.

    Dr. Leukoma, Mar 10, 2006
  14. acemanvx

    Dr. Leukoma Guest

    Virtually all of the OK experts who publish make reference to
    Munnerlyn's formula. For those who don't know, the Jessen to whom
    Grant refers is George Jessen, the co-founder of Wesley-Jessen, and the
    widely acknowledged founder of modern OK, who was still practicing and
    lecturing in Chicago during the time I went to school there.
    I have never publicly ridiculed OK, Grant. We have calmly and
    rationally discussed different sides of the OK issue. Although I am
    certified to do OK, I don't do much of it. For me, and for now,
    overnight OK is not on the table. For me, OK is still a means by which
    patients can extend the refractive effects after their lenses are
    removed for the evening, or for sports and other activities.

    Dr. Leukoma, Mar 10, 2006
  15. acemanvx

    Dan Abel Guest

    No capital "D". No period. Does "dr" stand for Donald Randolph, or
    "don't reply"?
    Dan Abel, Mar 10, 2006
  16. acemanvx

    CatmanX Guest

    The guys who design OK lenses all use Jessens formula, which is
    prescribing a lens that is 4D flatter than flat K. The only exception
    to this is the BE series, which chooses base curve according the the
    required change in script. Munnerlyn's formula is only used in
    publications to discuss corneal curve changes, not in calculation and
    design of lenses.\\

    dr grant
    CatmanX, Mar 10, 2006
  17. acemanvx

    Dr. Leukoma Guest

    Here we go. Of course, that statement didn't sound right, and so I
    called up a lens designer. He calculates the base curve from the
    patients RX and the corneal curvature. He indicated that the method
    you describe is somewhat outdated.

    Dr. Leukoma, Mar 10, 2006
  18. acemanvx

    CatmanX Guest

    Actually, he just used Jessen's formula. Add the script to the flat K
    (in D) and add an extra 0.50. This is the indicated base curve for your
    lens. That is Jessen's formula. Your lens designer used it, CRT uses
    it, Tabb uses it, Euclid uses it, R&R use it. This is why with all
    these designs, you get a +0.50 overrefraction over your trial lens.

    CatmanX, Mar 11, 2006
  19. acemanvx

    Dr. Leukoma Guest

    Sorry, I was confused. In the previous post, you said 4 diopters
    flatter than K. If you said just add 0.50 diopters of minus to the
    script, I would have understood. In fact, I would have understood
    better if you had said 0.75 diopters added to the script.

    Dr. Leukoma, Mar 11, 2006
  20. acemanvx

    Dr. Leukoma Guest

    By the way, for those who don't understand, Grant is making the point
    that shoots for an over-correction of 0.50 to 0.75 diopters in
    orthokeratology to allow for the normal regression during the day.

    So, in essence you wake up a little farsighted and go to bed a little

    Dr. Leukoma, Mar 11, 2006
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