Autorefractor

Discussion in 'Optometry Archives' started by Justin, May 23, 2004.

  1. Justin

    Justin Guest

    I went to my ophthalmologist this week only to find that my BCVA has
    decreased to below the minimum for driving (although I'm "close").
    The retinas in both eyes checked out fine and my ophthalmologist told
    me that she's confident she can correct my vision (even though she was
    not able to do so in her office). She wants to use the autorefractor
    during my next appointment ...she commented that because my Rx is so
    high, small changes can make a huge difference. But I'm a bit
    skeptical. There haven't been any huge changes in my Rx for a couple
    of years now, and I can't really understand why it would be difficult
    to correct my vision using just a snellen chart. Would an
    autorefractor really be helpful in this case?? Last year my VA also
    went below the minimum, but she was able to correct it easily by
    adding -0.50 D. I would greatly appreciate *any* input. Thanks.
     
    Justin, May 23, 2004
    #1
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  2. Justin

    Dr. Leukoma Guest

    (Justin) wrote in
    When you say that your BCVA is below the minimum, I take that to mean that
    with your best current prescription, the vision is at or less than 20/40.
    That's pretty significant. The only possible explanations are: The
    ophthalmologist did a lousy job of refraction, or you have an opacity in
    the media, such as a cataract, or you have a problem with the retina, i.e.
    specifically the macula. I would never use an autorefractor for the end-
    point of an eye examination for anybody other than small children and non-
    verbal adults. Anyway, in 20 years of practice I have never owned an
    autorefractor, preferring instead a simple hand held instrument called a
    retinoscope. Not using an autorefractor has not affected the accuracy of
    my refractions, because we also sell eyeglasses and I rarely have to redo a
    prescription.

    Also, for anybody interested in getting some meaningful commentary, it is
    always useful to state your age, your prescription, and your visual acuity,
    if known.

    DrG
     
    Dr. Leukoma, May 23, 2004
    #2
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  3. Justin

    Otis Brown Guest

    (Justin) wrote in message
    Dear Silver Blue,

    I would be careful with the "auto-refractor".

    One OD said his secretary when to another OD and
    had a prescription made up on the measurement
    made with an auto-refractor.

    When the woman returned she had a -7 diopter
    prescription. After the original OD check
    her vision on the Snellen, he found her
    vision reamined at -3 diopters (if I remember
    correctly. (Was it Mike, DrG, DrJudy?)

    My suggestion would be to use the Snellen
    for these measurements. Opinions vary
    on this point.

    Best,

    Otis
    Engineer
     
    Otis Brown, May 23, 2004
    #3
  4. Justin

    Jan Guest

    You do not get it Mike, Otis is enlarging the number of his famous homemade
    rubber definitions with a new one.

    NATURAL VISION

    The only instruments to use are a plus lens and a Snellen chart.

    O, I almost forget, only flying intelligent engineers are capable to
    understand, so do not try

    Jan (normally Dutch spoken)
     
    Jan, May 23, 2004
    #4
  5. Justin

    Justin Guest

    Well I had a couple of retinal detachments (one in each eye) about
    four years ago, so my visual acuity decreased as a result. I haven't
    had any problems since and, as I mentioned, my retinas look fine right
    now. She never mentioned anything about the development of cataracts
    so I assume that's not the reason for the decrease. As for her doing
    a lousy job ...well ...I've been seeing her for 9 years now and she's
    always been right on the ball in terms of refraction ...so I'm
    inclined to say that that's not the problem either ...but I guess it
    could be possible.

    I would never use an autorefractor for the end-
    Well she used the autorefractor after my RDs to determine how much my
    Rx had changed, however I understood why she needed to do that. I
    can't say I really understand the reasoning this time ...
    Age: 20
    Rx:
    OD: Sphere -15.75 Cylinder: 4.25 x 170
    OS: Sphere -13.75 Cylinder: 2.25 x 175

    Well, she gave me a sheet of paper on which she wrote 20/50, 20/60 and
    told me to bring it with me to my appointment ...I'm not sure what
    each value is for (i.e., which eye ...both eyes ...or whatever)
    because the letters beside the values look like little scribbles.
     
    Justin, May 23, 2004
    #5
  6. Justin

    Justin Guest

    Well I live in Ontario, Canada. I don't know what the requirements
    are over here ...I should have asked but there were just too many
    things on my mind. On one website I found that the weaker eye must be
    at least 20/50, while the stronger 20/30 ...but then on another site I
    found that the stronger eye must be 20/40 with no specifications about
    the weaker ...I don't know which site is correct ...perhaps both are
    incorrect ...it's quite confusing.
    My retinas aren't exactly healthy (see response to Dr. Judy).
    Yes, but how in the world could she be lost?! The way I see it, any
    new Rx *has* to be close to my current one! I'm 20, how much could my
    eyes possibly change in one year???
    Exactly ...so that leads back to my original question ...why use an
    autorefractor?
    The problem is that I could barely make out any of the letters that
    she was showing me, first with my current glasses, and then when she
    tried the "1 or 2" method. What it came down to was that none of the
    lenses she put in front of my eyes made any difference ...all the
    letters were ...blobs ...I ended up just guessing ..and not doing a
    very good job at it.
    I already know that I have astigmatism (4.25 D, 2.25 D), but it hasn't
    changed for the past three years or so.
     
    Justin, May 23, 2004
    #6
  7. Justin

    Justin Guest

    Perhaps the woman didn't follow the instructions?
     
    Justin, May 23, 2004
    #7
  8. Justin

    Justin Guest

    Okay, I finally got the requirements cleared up. "In the case of a
    person whose vision in one eye is better than in the other, visual
    acuity in the better eye that is no poorer than 20/40 as measured by
    Snellen Rating [is required]". The 20/30 better eye 20/50 weaker eye
    rule is only for ppl driving trucks, ambulances, buses etc.
    (http://www.lat.gov.on.ca/english/brochures/pdf/DownLcc.pdf)
     
    Justin, May 24, 2004
    #8
  9. Justin

    Neil_Brooks Guest

    Here goes the convoluted answer of a lay-person...

    1) Vertex Distance. This measures the distance between your eye and
    the lens they put in front of your eye. In high powers (nearsighted
    or farsighted), a few millimeters can make a big difference in what
    should be prescribed. There is a significatn amount of variability in
    vertex distance from patient to patient, from exam to exam, and
    between phoropter (the refraction gizmo with all the lenses) and trial
    frames. There is a material difference--when using trial
    frames--between putting the (high power) cylinder lens in the slot
    _closest_ to the eye and putting that lens in the slot _furthest_ from
    the eye. These issues are all vertex distance and can all affect how
    well you see through your eventual glasses or contacts.

    Vertex distance _may not be_ your issue unless you have glasses or
    contact lenses _made_ from the doctor's prescription. If they're
    having trouble even _getting you to 20/20_ behind the phoropter--or
    with trial frames--then vertex distance isn't likely to be the
    culprit.

    If you're highly near- or farsighted, though . . . vertex distance
    will be something for your eye doctors to consider. In my personal
    experience . . . none of them ever has. Only when I learned about it,
    and brought it to their attention, did we then address it . . . and
    improved my bcva significantly (sigh).

    2) Are they dilating your eyes (cycloplegia) for these evaluations?
    Should they be?? (I'm guessing yes, but I defer to your doctor or any
    of the quite helpful and knowledgeable doc's on this group)

    3) Here's what _I'd_ do (again, Doc's: help me out here):
    a) Ask about cycloplegia. Maybe your accommodative mechanism (think
    of an auto-focus camera) is trying to hard too focus, and the
    doctor/device is having trouble chasing you down;
    b) Ask for wavefront aberrometry. That's a 'mapping' of the eye
    that's supposed to give a darned accurate prescription. It also
    mitigates the 'vertex distance' effects (if used properly) when
    converting that prescription to contacts or glasses. The wavefront
    prescription gave me another line of visual acuity;
    c) Ask for a refraction using trial frames (being mindful of vertex
    distance if this prescription is to be converted into glasses or
    contacts);
    d) Ask for a refraction using the phoropter (likely, this has been
    done);
    e) Ask for a refraction using the auto-refractor,

    . . . then . . . to the best of your ability . . . decide which one
    _you like best_. This is another "art, not science" area. Many
    doctors are taught to prescribe "what the patient likes" than "what
    the gizmo says." Again, though, once they get you to 20/20 in the
    office, they need to record the vertex distance -- and work closely
    with the optician (or contact lens company) to ensure that your lenses
    are correctly made with respect to vertex distance.

    Best of luck. I _know_ how challenging this must be....

    Neil
     
    Neil_Brooks, May 24, 2004
    #9
  10. Justin

    Dr. Leukoma Guest

    (Justin) wrote in
    By convention, the right eye always precedes the left in written notation.

    I don't mean to suggest that your MD was a bad refractionist, but only to
    include it as one of the logical possibilities. The admission of a retinal
    detachment is very revealing. My comments about the autorefractor still
    stand. I would not use one as the "end point" of the refraction, unless
    the patient was non-verbal. Sorry.

    Your prescription is indeed quite severe, severely myopic and severely
    astigmatic(at least in the right eye). Indeed, a minor offset in the axis
    of the astigmatism could indeed produce an undesirable result.

    I would certainly trust the doctor with whom you have established a 9 year
    relationship, but some questions seem indeed to be in order.

    DrG
     
    Dr. Leukoma, May 24, 2004
    #10
  11. Justin

    Justin Guest

    Oops ...I meant Dr. Leukoma, not Dr. Judy ...sorry.
     
    Justin, May 24, 2004
    #11
  12. Justin

    Justin Guest

    If by "end point" you mean that the Rx obtained from the autorefractor
    is automatically prescribed to the patient, then I can't argue with
    that. It has never been done in my case ...it's always been followed
    up by the "1 or 2" procedure, which refined the Rx.
     
    Justin, May 24, 2004
    #12
  13. Justin

    Justin Guest

    (Neil_Brooks) wrote in message
    I'm not sure what you mean by this line ...what other Rx would the
    glasses be made from???
    Well 20/20 isn't a possibility for me, but she wasn't able to correct
    me to my "normal" visual acuity using the phoropter so ...
    Hmmm ...well she did ask me to push up my glasses (if that's what you
    mean) ...but it made little to no difference ...
    No they are not. Nor have they ever. My eyes have *always* been
    dialated after the refraction has been done ...
    Thanks for the input, Neil. =)
     
    Justin, May 24, 2004
    #13
  14. While not an eye care professional, if I oersonally had a correction like
    that I'd probably try to be seen by a low-vision specialist every once in a
    while. Is that out of order?

    Scott
     
    Scott Seidman, May 24, 2004
    #14
  15. Justin

    Dr. Leukoma Guest

    (Justin) wrote in
    snip

    What I mean by the endpoint is indeed the objective
    refraction(autorefractor) without subjective refinement.

    In reply to your first post, I stated that there were only three likely
    possibilities: bad refraction, retinal problem, media problem. I guess we
    can also include a fourth, but more remote "optic nerve" problem, although
    I do not suspect it. From what I gather, your doctor must be thinking
    along the lines of a bad refraction, which is why you are going back for
    another refraction using an autorefractor. However, the additional
    information you subsequently provided does suggest a rather complicated
    picture, involving high myopia, high astigmatism, and a history of retinal
    detachments.

    It sounds like your doctor is working hard on resolving the problem, and I
    wish you good luck.

    DrG
     
    Dr. Leukoma, May 24, 2004
    #15
  16. Justin

    Dr. Leukoma Guest

    Did that come out right?

    What I "really" meant to say was that whenever possible, a subjective
    refinement should be attempted as the "endpoint" of the refraction. There
    are indeed situations where this is not possible, i.e. young children and
    others who are unable to respond to questions.

    DrG
     
    Dr. Leukoma, May 24, 2004
    #16
  17. Justin

    Dr. Leukoma Guest

    Interesting thought, although I would not have thought that the level of
    disability was sufficiently severe in Justin's case(although I don't seem
    to know what it is).

    Perhaps I have a tendency to underutilize the specialty.

    DrG
     
    Dr. Leukoma, May 24, 2004
    #17
  18. Justin

    Jan Guest

    An optometrist should be more than capable to prescribe low-vision aids IF
    necessary.
    At least in my country (The Netherlands, the most beautiful country in the
    world)
    A retina specialist would be more to the point in the case of Justin.

    Jan (normally Dutch spoken)
     
    Jan, May 24, 2004
    #18

  19. !!!
     
    Rishi Giovanni Gatti, May 24, 2004
    #19

  20. I would NOT.

    This idiotic doctor simply destroied this poor girl's eyesight, in 9
    years, causing her TWO RETINAL DETACHMENTS and the poor girl talks
    about that just like having fun with such difficult diseaes...

    This is the point to which your DIRTY profession has brought us.

    Now the girl was 11 years old when she went to this criminal doctor.

    Should be interesting to know what was her problem at that age, if she
    was so severely myopic and astigmatic.

    In any other fieald of human endeavour this doctrou should have been
    fired and removed from the list of licenced practicioners.

    In the field of ophthalmology, any such bum like that continues to
    work and to destroy the eyesight of people.

    This is not a sane world, indeed!
     
    Rishi Giovanni Gatti, May 24, 2004
    #20
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