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Thread: Meridional anesiokonia, vertical imbalance, irregular astigmatism, and progressives

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    Question Meridional anesiokonia, vertical imbalance, irregular astigmatism, and progressives

    I am new to the OptiBoard and would like to seek any suggestions on the following case:

    The patient had RK about 20 years ago and was left with irregular astigmatism, poor contrast sensitivity and for now asymptomatic meridional anesiokonia. On top of this, he also had muscle surgery 12 years ago for a long standing forth nerve palsy and now is beginning to show a vertical imbalance again. He has worn Varilux Comfort lenses for about 10 years and has tolerated progressive lenses better than one might have thought. His last Rx was OD +1.12 -1.50 x 148, OS +3.50 -2.00 x 082, with +2.50 add OU in the 1.67 index material with +5.50 BC OU.

    My five-fold goal for this patient is to design new progressive lenses that will enhance contrast sensitivity, not push him over the edge on the anesiokonia, to correct his vertical imbalance, maintain comfortable vision at near, with glasses that are cosmetically pleasing.

    RX: OD +1.25 -1.50 x 130 with 2 prism diopters base up, OS +4.00 -2.25 x 087, +250 Add OU. Monocular PD is OD 33.5, OS 34.5.

    Goal #1: Enhance overall vision and contrast sensitivity by switching to an uncoated Autograph II variable (free-form), 1.60 Index, and applying Zeiss Carat Advantage AR with Foundation A.

    Goal#2: Try to maintain or slightly improve the current meridional anesiokonia in the vertical meridian by using equal BC OU (either +5.00 or +6.00), minimum center thickness on the OS and matching it on the OD. Vertex distance is probably stuck at 13mm because of deep set eyes. I am not sure what BCs the manufacture recommends, but I suspect it is probably a +6 on the OD and +7 on the OS which would only make the anesiokonia worse.

    Goal#3: Fully correct the vertical phoria with 2 prism diopters base up on the OD (not split). Normally, I would cut the prism, but I am leaning on giving it all because not correcting it would only increase the induced vertical prism in the reading portion of the lens.

    Goal#4: Although I measured 20 high to center of pupil on each eye, I plan to set the OD at 19.5mm and the OS at 20mm to account for image displacement secondary to the vertical correction. The one thing I have considered, but not sure I want to do is to slab-off the OD. It is my understanding that on a free-form lens they can nearly make the line invisible by blending it. I am just not sure it is needed since I am adding back the vertical correction. I guess the other thing I could consider is using a shorter fixed corridor length, but since his former lens is such a soft design, I’m not sure that is a good idea. I would really like to hear some input on the slab-off and between variable and fixed corridor length.

    Goal#5: I guess in addition to the above, the frame choice would be the only other key decision. The Frame being considered is a Charmant AR6020 (Eye 53, DBL 19, B 38, ED 57), Pantoscopic Tilt is 10 degrees, Panoramic Angle is 5 degrees, and as stated Vertex distance of 13mm. The only difference from his current frame is that the B is 34 and the ED is 54 in his old glasses.

    I would love to hear any suggestions or recommendations.

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    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    That's a thoughtful and well organized post. Welcome to Optiboard!:cheers:

    My thoughts are:
    Good call on the 1.60 index - they're thin enough and ABBE is very important.
    The Autograph II should work, I have not used any yet. I have had very good luck with the Hoya ID.
    Don't slab it - even a blended slab will have a large unuseable division line.
    I would maybe find a frame with a bit smaller B, but don't get too rectangular or your thickness will suffer.
    Avoid a short-corridor if possible on this guy.

    I think you've covered the bases well, and I'm sure people a lot smarter than me will also lend some advice.
    DragonlensmanWV N.A.O.L.
    "There is nothing patriotic about hating your government or pretending you can hate your government but love your country."

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    Thanks for your thoughts. It sounds like we are thinking along the same lines. I have been traveling all day and have just gotten back home.

    I am never easy giving an Rx that induces 3.25 prism diopter vertical imbalance 10mm below center with magnification difference over 4.5% in the same meridian. However, the patient’s meridional anesiokonia is long standing, he has obviously functioned with it, and he is currently fusing at near through the induced vertical even with the uncorrected vertical phoria. The patient does have mild asthenopia along with his blurred vision. Simply clearing the vision could make this worse. I sense that it won’t take much to turn the patient into a wrist-drop patient. However, poor visual acuity remains the chief complaint.

    Of course, the total vertical imbalance will be 2 prism diopters less at distance and near and the anesiokonia should be no worse. My thinking currently is that the new glasses most likely will be a nice improvement over his past. The VA in the OD improves from a very poor 20/30 to 20/20 and in the OS from 20/30 to a poor 20/20 minus. His being under corrected in the OS probably has served him well from an asthenopia point of view, but certainly has impaired his binocular vision at distance to some degree.

    Would anyone ever consider over correcting the vertical phoria slightly to reduce the vertical while reading. Certainly reducing the corridor length would reduce the vertical at reading, but would certainly harden the design over what the patient is use to. I plan to make a final decision and order the glasses either tomorrow or Friday. I am actually more concerned about the vertical than the anesiokonia.


    As they say, prescribing glasses is part science and part art!
    Last edited by kymaverick; 10-22-2008 at 04:29 PM. Reason: remove quote

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    Master OptiBoarder OptiBoard Gold Supporter DragonLensmanWV's Avatar
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    Quote Originally Posted by kymaverick View Post
    Thanks for your thoughts. It sounds like we are thinking along the same lines. I have been traveling all day and have just gotten back home.

    I am never easy giving an Rx that induces 3.25 prism diopter vertical imbalance 10mm below center with magnification difference over 4.5% in the same meridian. However, the patient’s meridional anesiokonia is long standing, he has obviously functioned with it, and he is currently fusing at near through the induced vertical even with the uncorrected vertical phoria. The patient does have mild asthenopia along with his blurred vision. Simply clearing the vision could make this worse. I sense that it won’t take much to turn the patient into a wrist-drop patient. However, poor visual acuity remains the chief complaint.

    Of course, the total vertical imbalance will be 2 prism diopters less at distance and near and the anesiokonia should be no worse. My thinking currently is that the new glasses most likely will be a nice improvement over his past. The VA in the OD improves from a very poor 20/30 to 20/20 and in the OS from 20/30 to a poor 20/20 minus. His being under corrected in the OS probably has served him well from an asthenopia point of view, but certainly has impaired his binocular vision at distance to some degree.

    Would anyone ever consider over correcting the vertical phoria slightly to reduce the vertical while reading. Certainly reducing the corridor length would reduce the vertical at reading, but would certainly harden the design over what the patient is use to. I plan to make a final decision and order the glasses either tomorrow or Friday. I am actually more concerned about the vertical than the anesiokonia.


    As they say, prescribing glasses is part science and part art!
    I'm personally having to deal with just a tad of imbalance myself.
    OS -1.50 -1.50 X25
    OD -15.00-2.00 X164
    3.00 add OU.:cheers:

    But only until Nov 11, then my cataract will be removed OD and I should be close to the same reality in both eyes.

    AHHHH, binocular vision again! Can't wait.:D
    DragonlensmanWV N.A.O.L.
    "There is nothing patriotic about hating your government or pretending you can hate your government but love your country."

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    >>AHHHH, binocular vision again! Can't wait.<<

    Binocularity is definitely a double-edge sword. Drs. Rubin and Milder wrote, we wonder how much more symptom-free and happy the huge majority of patients would be if they did not have to strive to attain those wonderful “benefits” of binocularity and fusion? Some would call this a heretical statement. They may be correct, but often it is true!<g>

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    What's up? drk's Avatar
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    I didn't get which eye had the 4th N?

    You have optimized progressives, you have segmented MFs with slabs and iseikonic designs, you have post-RK reverse-geometry RGPs. I'd start with simple and work up from there.

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    Quote Originally Posted by drk View Post
    I didn't get which eye had the 4th N?

    You have optimized progressives, you have segmented MFs with slabs and iseikonic designs, you have post-RK reverse-geometry RGPs. I'd start with simple and work up from there.
    Prior to surgery, it was a right hypertropia from a paresis of the right superior oblique along with the overaction of the antagonist, right inferior oblique. The patient hasn't worn any prism since the surgery in late 1996, but you will note that when he did, it was in the opposite direction from what it is now.

    BTW, in 1997 I fitted the patient with a pair of Conforma’s RK Bridge RGP. The fit and vision was good; however, the patient discounted wearing the lenses because of complications secondary to a dry eye. He continued to prefer glasses with progressive lenses.

    If the patient wasn’t myself, I would probably be more reluctant to fix that which isn’t broken.<g> However, there is noticeably a crack. Personally, I don’t plan to go to conventional slab MFs unless I don’t have another choice. I took an early retirement at age 45 for health reasons, so good binocularity for slit lamp and retinal evaluations is no longer an issue.

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    What's up? drk's Avatar
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    Ok, then what can you do? You must work with optimized progressives, and there's not much you can do other than what you've suggested.

    As to vertical imbalance, I'd go short corridor for the everyday pair, and a separate Rx for computer and near work. It's up to you whether you can tolerate splitting the vertical imbalance between distance and near.

    Curious: Is your vertical imbalance comitant, vis a vis, downgaze?

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    Quote Originally Posted by drk View Post
    Ok, then what can you do? You must work with optimized progressives, and there's not much you can do other than what you've suggested.

    As to vertical imbalance, I'd go short corridor for the everyday pair, and a separate Rx for computer and near work. It's up to you whether you can tolerate splitting the vertical imbalance between distance and near.

    Curious: Is your vertical imbalance comitant, vis a vis, downgaze?
    I am glad you asked me that question. Just goes to show you what happens when you have been out of the exam room for 8 years. You forget to ask yourself perhaps the most important question: is the vertical imbalance comitant. Of course it isn’t. Gee, that makes me feel dumb! I knew there was something I was missing because I didn’t have a significant fixation disparity in primary gaze or in reading gaze. I pulled out my Maddox rod and quickly checked myself with and without correction at distance and near. Without correction, the amount of prism decreases as I gaze down and actually changes direction. Considering this along with the fact that the distance correction itself would induce some net Base up prism OD as one gazes up, I will be greatly reducing the amount of prism prescribed if I don’t cut it out completely. In fact, that is probably what I will do. I will also move the ht back to 20 high OU.

    Thanks again for your input. I knew there wasn’t something correct with what I was considering, but I couldn’t put my finger on it.

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