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Thread: Simple/Basic Contact Lens Question

  1. #1
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    Simple/Basic Contact Lens Question

    I know Optiboard has been around for years and I know this has probably been asked but I couldn't find anything in search. Interested in finding out contact lens fitters opinions; as colleague and I are having a disagreement. We are both opticians (11 years vs 25 years, dual license (glasses/contact lens) vs (2) dual licenses with (2) CCLFs; basic beginner question but.....

    Simple Eyeglass Rx to Contact Lens fit.

    -1.75 -0.50 x 170
    -1.75 -0.25 x 168

    What contact lens powers do you fit in a soft, disposable monthly lens?

    PS
    16 year old girl
    Last edited by CantCU; 10-10-2016 at 12:58 PM. Reason: Additional info

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    One eye sees, the other feels OptiBoard Silver Supporter
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    Quote Originally Posted by CantCU View Post
    Simple Eyeglass Rx to Contact Lens fit.

    -1.75 -0.50 x 170
    -1.75 -0.25 x 168

    What contact lens powers do you fit in a soft, disposable monthly lens?
    Sphere equivalent OD = -2.00, OS = -1.87. Use -2.00 for both, primarily for convenience (same power for both eyes), although -1.75 might be desirable in the left if the client is older (thirtysomething).
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    Eyes eastward... Uilleann's Avatar
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    Not sure what to disagree with - Robert nails it.

    Technically: OD -2.00, OS -1.75. But for a 16 year old girl, stick with -2.00 OU. Pt will appreciate the convenience of the same power OU, and she can easily cope with the very slight over minus OS.

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    Thanks, Yep, exactly what I did -2.00 / -1.75....boss got upset and told me not to "over correct".... Told me the last time I SEd on a -0.50 cyl to not do that anymore (you don't SE until -0.75)....so I started with -1.75 (as he says) va was good 20/20- , but not crisp, slow on reading chart, and she complained ...MOR -0.25, bam, she is happy. I explained the need for SE and was told to not SE on -0.50 cyl anymore!!! Experience and training tells me to SE to start with, but I did it his way and patient wasn't happy. "If they come back in a week complaining, fix then". Note: I am the 25 year + 2 licenses + 2 CL.

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    Optimentor Diane's Avatar
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    Two separate powers, -2.00 and -1.75. I see over minus way too much. Convenience is best correction not one power.

    Diane
    Anything worth doing is worth doing well.

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    One eye sees, the other feels OptiBoard Silver Supporter
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    Quote Originally Posted by CantCU View Post
    Told me the last time I SEd on a -0.50 cyl to not do that anymore (you don't SE until -0.75)....I explained the need for SE and was told to not SE on -0.50 cyl anymore!!!
    Maybe they're confusing sphere equivalent with torics, where .75 DC is usually the starting point when considering their use for astigmatism.

    Quote Originally Posted by Diane View Post
    Two separate powers, -2.00 and -1.75. I see over minus way too much. Convenience is best correction not one power.
    Knowing that there's a fair chance that the lenses will be reversed at some point, resulting in the same degree of overminus in the OS (an insignificant -.12 D for an age 16 CL wearer) and an underminus in the right, and that it's prudent to round the sphere equivilant error up for young myopes, and down for old myopes, I would argue that in this example, it would be best (and more convenient for everyone) to fit the same power for both eyes.
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    Eyes eastward... Uilleann's Avatar
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    Bingo Robert. You understand the difference between 20/20...and 20/happy - just like many successful docs and dispensers do. With a 16 year old girl, keep it simple. The -0.12 over correction is completely negligible for a patient like this. She's far more likely to be concerned with the state of her mascara, or the latest text on her mobile than if she has the right lens in the right eye. Certainly the different powers can be written and dispensed to the patient, though it really is splitting the smallest of tiny hairs with a young myope like this.

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    The k readings might help in this situation. Why? The tear layer.

    If you are not doing topography measurement, to eliminate tear layer influence then the best power is the patient preference power.

    This might be -1.75, or -2.00 or even -1.50. I find that the brand of lens makes a difference, too!
    Eyes wide open

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    What's up? drk's Avatar
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    If the patient can tell a significant difference between a -1.75 and -2.00, give them the -2.00, of course.

    Having said that, I would start with -1.75 OU for a couple of reasons:
    1. Convenience, as stated
    2. I don't EVER use the spherical equivalent, just the sphere. Having said that, I fit torics when the astigmatism hits -0.75, so that only means we're talking about one animal: "the -0.50 DC patient". (Obviously, you cannot do a spherical equivalent on a -0.25 DC patient).

    Why not use the spherical equivalent in 1/2DC cases, as so many fitting guides say (and many people successfully do)?
    a. I've tested it: it almost never improves subjective or objective acuity.
    b. Theoretically, at least, by putting the "circle of least confusion" of the "interval of Sturm" on the retina, you will have accommodative instability...the eye has to choose whether it wants to be a little overminused or a little underminused and the eye can vacillate between the two states, especially considering a distant or near object. It's better to put "the back" of the interval of Sturm on the retina (by eschewing spherical equivalent) and there will be no accommodative stimulus.

    That would be theoretically particularly important in a case like this, where the kid has active accommodation and the other eye has essentially no cyl. Which eye sets the accomodation at distance? At near? Which eye is dominant? Sure, it's minutiae.

    This is really angels on the head of a pin stuff. There's no "right" or "wrong", but the art of prescribing. Your boss should chill.

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    All good answers. Science before art, but art nonetheless.
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    Master OptiBoarder CCGREEN's Avatar
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    Quote Originally Posted by drk View Post

    This is really angels on the head of a pin stuff. There's no "right" or "wrong", but the art of prescribing. Your boss should chill.
    "angels on the head of a pin stuff. There's no "right" or "wrong", but the ART of prescribing........."
    Perfect analogy. Splitting half hairs is stressful.
    Paint your canves with right or left hand. As long as we reach the same goal without over taxing the pt and they leave 20/Happy.
    When we keep putting money in the bank and the business continues to grow and we enjoy coming to work and helping patients that's what is all about. Life creates enough stress. Lets not add to it by being aniel about trivial matters.

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    Thanks everyone. Optiboard is great, so many great comments, opinions, tips. I have missed being on here, glad to be back.

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    OptiBoard Professional Kujiradesu's Avatar
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    Just reading this thread after the fact and had a question for the refractionists and CL fitters in the community:

    Would vertex distance have a bearing on what RX you would prescribe in this instance? With all the talk about not wanting to over-minus the patient, I was just wondering if this consideration could be justification for fitting -1.75 OU instead of -2.00 OU. (Im fully aware of the fact that -2.00 fit 10mm closer to the eye is only effectively -1.95. Just wondering if this should be considered in your determination of RX overall)
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    Optimentor Diane's Avatar
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    Quote Originally Posted by Kujiradesu View Post
    Just reading this thread after the fact and had a question for the refractionists and CL fitters in the community:

    Would vertex distance have a bearing on what RX you would prescribe in this instance? With all the talk about not wanting to over-minus the patient, I was just wondering if this consideration could be justification for fitting -1.75 OU instead of -2.00 OU. (Im fully aware of the fact that -2.00 fit 10mm closer to the eye is only effectively -1.95. Just wondering if this should be considered in your determination of RX overall)
    Because the power is minus, fitting 10 mm closer to the app with affectively make the power stronger rather than weaker. So without doing the math, the effective power would be -2.05D. I would fit on the edge of weaker. Myopes tend to draw up more minus powers and it ultimately affects accommodation.
    Anything worth doing is worth doing well.

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    OptiBoard Professional Kujiradesu's Avatar
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    Because the power is minus, fitting 10 mm closer to the app with affectively make the power stronger rather than weaker.
    Whoops. Thats on me. I shouldve remembered my PLUS AWAY STRONGER- EFF: More Plus; MINUS CLOSER STRONGER; EFF: More Minus.

    Thanks for checking me on that.
    Optical Cross: n. crucifixion apparatus used by the New Jersey State Board.

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    I would start with -1.75 in both eyes. If an additional .25 minus helps, I would give it. With the rule astigmatism is more easily "masked" by the body of the lens itself. Keep in mind, if the patient is an emerging presbyope (which is not the case in your example), you want to keep the minus as low as you can and still make the patient 20/happy.

    I happen to use a lot of Acuvue....the reasons why are not germane to this question, but I find they tend to run a little high on the minus side anyway. And then there is the issue of vertex....yes, even at -1.75, a CL is more "effective" than the same sphere in a spectacle lens.

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