difficulty of making small corrections for distance vision

Discussion in 'Eye-Care' started by Liz Day, Sep 28, 2006.

  1. Liz Day

    Liz Day Guest

    My vision has finally deteriorated to the point where I need glasses
    for both near and distance. My problems are minor compared to those
    of many people; yet the experience so far has been frustrating.

    I got prescription glasses for distance. But distant objects (such as
    birds) were still a bit blurry. After a month, I went back to my
    regular doc (he'd been on vacation when I got the first exam). He
    rechecked my eyes and found 1/4 diopter of astigmatism in one eye.

    Things are slightly out of focus through my other eye, too, but I don't
    know why.

    He'll check my eyes one last time before I get the scrip filled. I'm
    concerned we may miss something. He said my astigmatism was so minor
    as to hardly exist, and, compared to the serious medical problems of
    his other patients, I'm sure this is true. But *I* can sure see the
    blurriness! It really takes the pleasure out of birdwatching, which
    is my main recreation and stress relief.


    The "distance" part of the eye exam is done at only 20 feet. I'd think
    that if you wanted your focus to be tack-on at 150 feet instead (given
    that you can't have both), you'd test it with something further away.

    Is there such a thing?

    Also, the letters used for the exam are projected from an overhead
    projector. They aren't that sharp to begin with. Most real objects
    have a clearly defined edge, but these don't. Thus, it's hard to tell,
    when looking through the exam machine, whether "this one or that one"
    is better. But you sure can tell outdoors if something's not sharp.
    Does anyone ever test distance vision using real objects - letters on a
    sign, or something?

    Also, it seems the test lenses do mostly gross corrections. If you
    have only a little bit of astigmatism or prism or something, I'm
    thinking maybe the examiners can't always find that, because their
    tiniest correction is still way bigger than what you need.

    I'm pessimistic that we'll be able to correct everything that's wrong.
    I'm also not sure how motivated the doc will be to fix the scrip from
    "good enough" to "as good as possible".

    What can I do at this upcoming exam to get the best results?

    central USA
    Liz Day, Sep 28, 2006
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  2. Liz Day

    Liz Day Guest

    What does it involve? My curiosity is killing me now.
    Is that a visible difference?
    I'd rather the distant stuff be clear, at the expense of the closer
    I dunno how clear it's supposed to be. I got up on a chair and looked
    at them on the wall. They have jagged edges up close; at a distance
    these edges look soft or fuzzy. This is normal for an image projected
    from a xeroxed transparency, but far from the crispness of a piece of
    paper with letters printed on it.
    (Please say more about that...)
    Well.... I guess I'm skeptical because of my experience with it so far.
    The first optometrist to examine my eyes (seen because my regular
    doctor was out of town) did this test. When we got to that point, and
    I said, "A is a little better than B, but both are still out of focus",
    she said, "That's as good as it gets". I suggested there might be
    astigmatism, and she put up a lens that when I looked through it made
    things *totally* out of whack. So she said I didn't have astigmatism
    at all. Since doc #2 says I do and she says I don't, this causes me to
    think that maybe this test is not that precise. It might be the
    person administering it, but I think the test images and/or test lenses
    also make it harder for the patient to give reliable answers.
    Yes, I get this impression too, that many people don't seem to notice
    even rather large haloes, or misalignment, or whatever. Unfortunately,
    I can indeed detect small differences in clarity. When birding, you're
    often trying to spot something very small from quite some distance
    away. Any deterioration of this capacity is noticeable, and
    frustrating. (I'm probably spoiled, also, by having spent so many
    years studying fine detail through very nice binoculars.)
    Yeah, I don't know what 0.12 diopters would even look like. What IS
    the smallest correction they have in that arsenal of test lenses,
    Can you say more about this? I thought that astigmatism was
    manifested by thin lines looking double at one angle and OK at another
    angle. So I would have tried to use E, M, and T. The Os are better?
    What is "JCC"?

    I'm afraid I'm going to go in there, do whatever can be done, and still
    come out with glasses that leave much to be desired.

    Indianapolis central USA
    Home of the dull-colored warbler, the tiny cryptic sparrow, and many
    birders with very expensive binoculars..... *sigh*
    Liz Day, Sep 29, 2006
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  3. Liz Day

    Charles Guest

    I sympathize with your desire to optimize your vision. You should
    certainly shop around for an eye doctor who sympathizes as well. That
    would be my first suggestion. My previous eye doc wanted to blow off
    0.25 diopter of correction, which I found to make an absolutely
    enormous difference. If you are like me, being 0.25 nearsighted
    relative to what you are used to is totally unacceptable.

    Having said that, I doubt going in increments smaller than 0.25 is
    worth the trouble. Remember that your eyes can accomodate to near, so
    you can overshoot the minus power by a smidge and you'll pull it in
    when looking far away. Astigmatism doesn't work that way, but my
    experience is that you simply can't notice errors smaller than 0.25.
    And I've been called picky.

    If you want to be anal and really understand what's going on (like me)
    you can go out on E-bay and get yourself a cheap trial lens kit to
    experiment with. I found it very educational, and you can hold lenses
    up over your glasses or contacts to second guess your Rx in real life
    situtations (like looking at birds?)

    Have you considered RGP contacts? I recently changed, and the vision,
    especially distance, is the best I've ever had. It took a few doctors
    to get it right though, so I'd recommend seeking out someone who has a
    fair number of RGP patients.

    (I'm a patient, not a doctor)
    Charles, Sep 29, 2006
  4. Liz Day

    Dick Adams Guest

    I don't think that contacts are the answer for not being able to get a
    proper script for spectacles. My experience is that approximately one
    out of each three alleged refractometrists are able to get to within
    0.5D of one's actual need for both of two eyes at one sitting. The
    really bad ones may get bristly if challenged, like when you go back
    with your new glasses and claim blur.
    Yes, I agree that anality is the best answer here. I wish I knew more
    about cheap trial lens kits. (I have got some, but they were not particularly
    cheap). Having a test pattern for astigmatism on a wall can be useful also.
    For me, the final test is reading lit signs at night, in the distance. In the
    end, one must master the simple arithmetic of diopters which is sometimes
    known to the phoropter jockeys (who, in my experience, are sometimes,
    if not frequently, on-the-job-trained lackeys).
    Dick Adams, Sep 29, 2006
  5. Liz Day

    callimico66 Guest

    I have oblique axis astigmatism in both eyes, not much--.5 D I think,
    but you're right--only the big "O" reveals it. I asked my optometrist
    why doctors don't use the "fan spokes" image to test, and she said it's
    old fashioned, not used anymore. Why is that? With the big "O" I have
    to look at specific parts of it--the diagonal parts--and try to explain
    which are blurry. My eye doctor had me turn the axis slider on the
    phoropter (?) lenses to try to get the axis correct. This was minimally

    I gave up getting the astigmatism correction in my glasses--there were
    just too many variables--the Rx never seemed right. Partly it's the
    type of lens, the shape of the frame, the accuracy of how the lens is
    placed in the frame, the way the frame sits on my assymetrical nose and

    And then my eyedoctor told me that the cylinder correction in the lens
    only "corrects" about 15 degrees of arc, whereas, I perceive a greater
    arc than that in my blurry astigmatism axis. Is this correct, or have I

    But viewing birds at a distance? For me, without binoculars--only
    glasses, that would be impossible. And with my contacts, forget it.

    callimico66, Sep 29, 2006
  6. Liz Day

    Liz Day Guest

    I sympathize with your desire to optimize your vision. You should
    certainly shop around for an eye doctor who sympathizes as well.

    [Mike Tyner]
    I'd call a few offices and tell them you've had trouble getting a good
    refraction, and ask which of their doctors have the best luck
    satisfying engineers.

    Ah HAH. Thanks for this tip.

    [Dick Adams]
    My experience is that approximately one out of each three alleged
    refractometrists are able to get to within 0.5D of one's actual need
    for both of two eyes at one sitting. The really bad ones may get
    bristly if challenged, like when you go back with your new glasses and
    claim blur.

    Yes, that's what happened with the first one. :-(
    I don't want to be a pain, but I would prefer to nail down the
    refraction during the exam, even if that's tedious - rather than nail
    it down by ordering glasses and looking through them. If the person
    does a good exam, and finds that I have between zero and 1/8 diopter of
    whatever, and there's no realistic way to correct for that, I'll live.
    But I'd like to be confident that we did find out just what's wrong
    with my vision. I'd like to not have to keep wondering whether if we
    tried the exam yet AGAIN it would help.

    The current person is an ophthalmologist, and he examined my eyes for
    disease etc. as well. I think he is reasonably competent and patient,
    but I worry that just by the nature of the test (especially those fuzzy
    letters) and the natural flakiness of vision (it seems you need to look
    back and forth at things a couple of times to be sure you're on
    target), that it might take more than "reasonably". :-(


    [Mike Tyner]
    That's not typical. Mine are smooth, just a little blurring at the
    limits of resolution for projection film.

    Oh dear. I've never seen yours, so I can't tell if those I've seen
    are any worse. Maybe they look find to most people and I'm just picky.
    But the letters have never looked really sharp to me. They're dimly
    lit, too. I feel as though my ability to accurately make fine
    discriminations with them is limited. It's not like the close-up part
    of the exam, where there is little doubt as to whether what you're
    seeing is clear.

    Why use a projector at all? Wouldn't it also work to just put a piece
    of paper on the wall, in the same place, with the letters on it the
    same size as they are projected on the wall? You'd see the same thing
    in the mirror as you do now, and you could put a lot brighter light on
    it too. Right?

    I imagine the doc would have a cow if I brought such a thing in.

    [much info on how astigmatism tests work and what to look for]
    Thank you all, this is very helpful. Phew.

    [Mike Tyner]
    The lens used to test astigmatism _should_ make things a little

    In other words, you make it too blurry - you overshoot - and then work
    backwards to where it looks right?

    My existing glasses correct for one eye being different from the other.

    (Distance correct ion = +1.25 right eye, +1.75 left eye).
    Will it help to wear these glasses before I go in? I'm thinking that
    my eyes will have time to adjust to roughly where they need to be,
    before trying to fine-tune the more difficult things.

    .....RGP contacts can be spectacular.

    Thanks... I read about them (there is a good web site at


    But my initial reaction is EEEEEEEEEEKKK you put something in your
    Even seeing people wearing contacts gives me the crawls. The
    description sounds like they might give really good vision, but I dunno
    if I'm ready for them.

    Viewing birds at a distance?

    It's difficult. You have to locate the bird in the landscape first,
    with just your glasses, before you can put binoculars on it. But the
    birds try to stay invisible. Lately, I've been watching shorebirds,
    because they tend to stand still out in the open, rather than rushing
    behind a leaf. With birds in trees, you have to be fast, or all you
    get is a glimpse of something's tail 2 seconds before it vanishes. I
    can tell you of many fine tail views, or at least partial views, or at
    least leaves that were almost partial views.....
    Liz D.
    Liz Day, Sep 30, 2006
  7. Liz Day

    CatmanX Guest

    One of the problems with being an optometrist is that we do test in
    unnatural surroundings. The peripheral vision is the major component in
    focussing, but we block it out behind a refractor. We assume that 6m is
    infinity, when it clearly isn't.

    As a result, a percentage of people tend to get mildly overplussed,
    resulting in fractional blur at distance. How do we eliminate this?
    Longer rooms, trial frames, finishing off in the waiting room while you
    look across the road, I am about to install a wall sized mirror to
    reduce the effect of a wall 4m away.

    I would recommend you get retested in a trial frame, then finish off
    the final spherical component out of the consulting room.

    dr grant
    CatmanX, Sep 30, 2006
  8. Liz Day

    Liz Day Guest

    One of the problems with being an optometrist is that we do test in
    (It is? I didn't know that.)
    I've not heard of a trial frame, or of any testing being done outside
    the exam room.
    It sounds like a smart idea, but how would you get the exam lenses out
    into the waiting room? (Remember, I don't know what most of this
    stuff looks like.)
    It does seem like it would be a bit more reliable to double-check the
    scrip by looking at real objects that have real edges under good
    outdoor light. I didn't realize you could do that without actually
    having glasses made.

    Liz Day, Oct 1, 2006
  9. Liz Day

    Jan Guest

    CatmanX schreef:
    We assume that 6m is
    Add a - 1/8 dpt and you are done (I take it for granted you did know

    A question related to this, do you use a red/green test?

    Jan (normally Dutch spoken)
    Jan, Oct 1, 2006
  10. Liz Day

    CatmanX Guest

    Adding -.125D can be misleadsing also. What we find in a refraction is
    not necessarily what the eye wants in the real world. As much as most
    (99%) of refractions are fine with what we find in the refractor head,
    there is this small group that are probably active accommodators that
    give funny results with their new specs.

    And no, I don't use red/green, I can't do it (brain wiring probably)
    and don't ask it of my ptients as I can't adequately explain what they
    are supposed to get. I always finish with a frial frame and +/-0.25

    CatmanX, Oct 1, 2006
  11. Liz Day

    Liz Day Guest

    (Sorry for posting to the group, but I can't get through to you via
    private mail.)
    Liz D.
    Liz Day, Oct 16, 2006
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