Epiretinal & Aniseikonia

Discussion in 'Optometry Archives' started by lynn, Jul 21, 2005.

  1. lynn

    lynn Guest

    I have diagnosed with an Epiretinal Membrane in my left eye. I
    addition to blurred vision; objects in my left eye appear to be 10-15 %
    larger than my right eye. My corrective lens compensate for a
    difference of 4%.

    I have chronic tension headaches centered in the forehead. This has
    been a ongoing problem. I get some relief from botox injections, and
    over-the-counter pain medication. My surgeon does not want to perform
    a Membranectomy until my vision is worst than 20/40 corrected in my
    left eye. Any suggestions or help would be appreciated. I live in the
    Dallas, TX area.
     
    lynn, Jul 21, 2005
    #1
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  2. It might be helpful if you'd post your spectacle Rx along with acuities
    with the Rx in place. I would assume the membrane has nothing at all to
    do with the aniseikonia.
    These may or may not be related to aniseikonia; are probably not related
    to the membrane.

    So they are at least partly muscle spasm type headaches, I'd guess.
    Post the acuities. The membrane peel will probably give you better
    vision in the left eye, but may have no effect on your headaches or and
    will not affect the aniseikonia.

    w.stacy, o.d.
     
    William Stacy, Jul 21, 2005
    #2
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  3. lynn

    lynn Guest

    My pre-USAF Vietnam era physical eye exam was Lt. eye 20/10 & Rt. eye
    20/15.

    Before the epitretianl membrane, their was no headaches nor was there
    any difference in image sizes between the two eyes.

    Peeling MAY inprove the eye sight. But there is a good deal of risk
    involved with the peeling.

    IMHO the epiretinal membrance has a changed the optics causing the
    larger image on the Lt. side.
    Wearing an eye patch over the Lt. eye reduces the muscle tension in the
    forhead but makes for poor depth perception.

    Am looking for the best epiretinal surgeon in the country.
     
    lynn, Jul 25, 2005
    #3
  4. OK then since I don't have any Rx data to work with, I'm going to make a
    couple of (large) assumptions. The maculopathy has caused the macula to
    move forward, making the left eye more hyperopic, so when you wear a
    plus spectacle lens to correct that hyperopia, you have induced
    aniseikonia. If this is true, the aniseikonia may be completely fixable
    with a contact lens on that eye.

    We've got some good ones here in the Sacramento area. Where are you?
    Most major metropolitan areas have vitreo-retinal groups. I'd go to one
    of those group practices that only does v/r work.

    w.stacy, o.d.
     
    William Stacy, Jul 26, 2005
    #4
  5. lynn

    lynn Guest

    The aniseikonia occurs with or without glasses. Tried contacts but to
    no avail.

    Will get my prescription this week.

    Live in Dallas, TX. We have the vitreo-retinal groups. I would prefer
    a doctor with loads of experience with ERM removal.
     
    lynn, Jul 26, 2005
    #5
  6. Actually, this is not an uncommon problem. IT IS UNRELATED TO THE MACULA
    MOVING FORWARD. This (central) size shift is not really aniseikonia in the
    usual sense - it is a metamorphopsia.

    What happens is the epiretinal membrane distorts the macula size, making it
    smaller (the usual story) or larger. If the photoreceptors are pulls towards
    thefova, making it smaller, the same image falls on more photoreceptors, so
    the image seems larger than the other eye. However, it is only in the
    center. Periphery is unchanged. This causes a disparity in the central image
    both not the periphery that locks the eye images together.

    This has no optical remedy, since it is not uniform across the image as in
    optical aniseikonia due to anisometropia, which can be helped by contact
    lenses or "size" lenses, as Dr. Stacy describes above.

    The only papers on this describe using Bangerter foils on the lens to blur
    the image just enough that the macula image can be ignored, without losing
    the use of the periphery. An ophthalmologist that I know had this, and he
    also placed a tiny round disk of Scotch Magic tape (the frosted stuff) in
    the optimum spot on the glasses to allow him to block out just the macula of
    that eye.



    David Robins, MD
    Board certified Ophthalmologist
    Pediatric and adult strabismus subspecialty
    Member of AAPOS
    (American Association of Pediatric Ophthalmology and Strabismus)
     
    David Robins, MD, Jul 26, 2005
    #6
  7. Ok then in view of what Dr. Robins posted, you don't actually have
    "regular" aniseikonia, but a special variety of metamorphopsia that the
    maculopathy caused. If I recall correctly, you can't really correct
    that much of an image size difference optically, nor would you want to,
    since it's not affecting the majority of your fields (only the central 5
    degrees or so). I'm afraid your only fix is to find that special
    surgeon for that special, exquisitely delicate procedure. Good luck.

    w.stacy, o.d.
     
    William Stacy, Jul 26, 2005
    #7
  8. lynn

    Gerard Guest

    I agree with Dr. Robins on the explanation of the aniseikonia
    associated with an epiretinal membrane (see also the abstract of a
    paper we wrote on this topic below). As he mentions the aniseikonia
    cannot be fully corrected by introducing a constant optical
    magnification difference, because the amount of aniseikonia changes
    (rather smoothly) with visual field angle. Nevertheless, partial
    relief seems to be possible by searching for and correcting the
    aniseikonia at the visual field angle that seems to bother the patient
    most.

    Gerard de Wit, Ph.D.
    Optical Diagnostics
    http://www.opticaldiagnostics.com

    -----------
    Field dependent aniseikonia associated with an epiretinal membrane: a
    case study

    Gerard C. de Wit, Ph.D. and Cecilia S. Muraki, O.D.

    Purpose: Aniseikonia is a binocular anomaly in which the two eyes
    perceive images of different size and/or shape. It is usually assumed
    to be constant as a function of visual field angle (i.e. angular
    distance from the line of sight). This is correct for optically
    induced aniseikonia, such as the aniseikonia that is associated with
    anisometropia and probably also pseudophakia. The purpose of this
    paper is to show that if the aniseikonia is of retinal origin, then the
    aniseikonia may no longer be constant as a function of visual field
    angle (i.e. field dependent aniseikonia).
    Design: Case report, with the patient having a unilateral epiretinal
    membrane.
    Methods: The aniseikonia was measured in the vertical and horizontal
    direction with a customized version of the Aniseikonia Inspector™
    software. The visual field angle was made variable by changing the
    dimensions of the size-objects in the direct comparison procedure.
    Main outcome measures: Aniseikonia as a function of visual field angle.
    Results: The patient exhibited good repeatable aniseikonia ranging from
    23% to 2.5% for visual field angles ranging from 0.36° to 5.7°. In
    this range higher angles had lower aniseikonia. A control subject did
    not show this field dependent aniseikonia.
    Conclusions: Aniseikonia may vary with visual field angle due to a
    retinal origin such as with an epiretinal membrane. The problem with
    field dependent aniseikonia is that it cannot be fully corrected with
    conventional optics which exhibits an approximately constant
    magnification as a function of visual field angle. Nevertheless, by
    correcting 5-10% aniseikonia which was present in the visual field
    angle measurement range at 2° to 3°, our patient had improved visual
    comfort, especially for reading.
    -----------
     
    Gerard, Aug 2, 2005
    #8
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