no depth perception??

Discussion in 'Optometry Archives' started by Liz Day, Nov 17, 2006.

  1. Liz Day

    Liz Day Guest

    A colleague tells me that he has no depth perception. He is in his
    sixties and apparently this has been the case his entire life. He has
    always been nearsighted, but not drastically so, and wears glasses to
    correct this anyway.

    How is this possible? If someone has two eyes both with (corrected to)
    20/20 vision, how could they not also have depth perception?
    Especially if they have been successfully driving a car their whole
    life. Possible? I would have thought that wasn't very safe.

    cheers,
    LD
     
    Liz Day, Nov 17, 2006
    #1
    1. Advertisements

  2. Liz Day

    Salmon Egg Guest

    Haven't you ever met someone who appears to have excellent hearing but
    comprehends almost nothing?

    Bill
    -- Fermez le Bush
     
    Salmon Egg, Nov 18, 2006
    #2
    1. Advertisements

  3. Liz Day

    Mark A Guest


    Maybe he has amblyopia (lazy eye) and only has peripheral vision in his bad
    eye.

    Even if each eye is individually corrected to 20/20, there may be a muscle
    imbalance that does not allow the eyes to work together with binocular
    vision.
     
    Mark A, Nov 18, 2006
    #3
  4. Liz Day

    Liz Day Guest

    Well, we all have "depth perception" using relative motion, relative size
    and atmospheric cues. This is plenty for normal skills like driving.

    I dunno - if I shut or cover one eye while I drive, the feeling of
    disorientation is immediate and disturbing. It's scary to imagine
    driving without stereo vision. YIKES!! I suppose you could move your
    head back and forth like a mongoose.
    <8-(
    delicate neurological discrimination of the differences between two
    images
    perceived from slightly different positions in space.

    Right.
    during a "critical period" in early childhood

    Makes sense.
    Hmmm. I have no reason to think my friend had anything wrong with his
    eyes at that time. Maybe I should ask. I'm having trouble imagining
    how someone could not develop this "natural" ability, or what things
    would look like if your eyes didn't work in synch.

    Yet I believe him, as I've watched him use a camera and be unable to
    tell whether the object to be photographed is present in the viewfinder
    or not. The pictures come out randomly - some with the object in the
    center of the picture as intended, some with it half cut off on the
    edge, and some with it completely absent (because the camera wasn't
    pointing at it). Could this be a dominant-eye thing? Perhaps the
    non-dominant eye is looking through the viewfinder? Neither of us
    could ever figure out what happened.
    Small-angle esotropia?
    Even if each eye is individually corrected to 20/20, there may be a
    muscle
    imbalance that does not allow the eyes to work together with binocular
    vision.

    Can you say more? How would you tell if that was happening?

    thanks,
    LD
     
    Liz Day, Nov 18, 2006
    #4
  5. Liz Day

    jerzger Guest

    Interesting question. I'm in the same boat as your neighbor. As a teen
    I was warned by my eye doctor to be very careful driving due to having
    no depth perception. To be honest, I never knew the different. I'm 55
    now and have an accident free driving record, so somehow, we are able
    to drive safely. Hope this helps to reassure you about your neighbors
    driving :) You'd probably have more to worry about if I was your
    neighbor because now I'm also driving with cataracts! :)
     
    jerzger, Nov 18, 2006
    #5
  6. Liz Day

    jerzger Guest

    Wondering if this might apply to me. Is testing stereo vision something
    you can test on your own, something you ask your eye doctor to do,
    something they automatically do during an eye exam? If you don't have
    stereo vision, are you more likely to do well in correcting cataracts
    with one iol for distance and the other for close up or doesn't it
    matter.

    Mike Tyner wrote:
     
    jerzger, Nov 18, 2006
    #6
  7. Liz Day

    Dan Abel Guest

    and atmospheric cues. This is plenty for normal skills like driving.

    I dunno - if I shut or cover one eye while I drive, the feeling of
    disorientation is immediate and disturbing. It's scary to imagine
    driving without stereo vision.[/QUOTE]

    Now you're getting scary.

    :-(

    Both my wife and I see out of only one eye. We can drive just fine.
    The kind of depth perception that requires two eyes doesn't work well at
    longer distances, so doesn't affect driving that much.

    But we can both use a camera just fine. Your colleague's inability to
    take a picture is something different, and I wonder how it affects his
    driving. Besides, don't most people just use one eye to look through a
    viewfinder?
     
    Dan Abel, Nov 18, 2006
    #7
  8. If they use a viewfinder, they must use their "good" eye, or close their
    good eye if viewing with the amblyopic eye (why would they do that? I
    don't have a clue). I've run into this more with shooters of guns than
    shooters of pictures, and it is a real problem for those who are, e.g.
    right handed and left "eyed". You could get a tooth knocked out trying
    to aim a rifle or shotgun trying to "cross over". They even make
    expensive left handed guns for such people.
     
    William Stacy, Nov 18, 2006
    #8
  9. Liz Day

    Dan Abel Guest

    I've given up shooting. With cataract in both eyes, besides the retinal
    detachments, my dominant eye has shifted sides way too many times, and I
    am now "left eyed" and right handed.
     
    Dan Abel, Nov 18, 2006
    #9
  10. Liz Day

    A Lieberma Guest

    Like Mike Tyner says, you don't miss what you don't have.

    I don't have stereoscopic vision and miserably flunk the eye test that
    has the objects placed in a different position when looked out of both
    eyes vs one eye when looking through the view finder.

    I drive, fly a plane (FAA requires a vision test every two years for my
    class of license), climb ladders and all sorts of good stuff like that.

    I don't have any problems with peripheral vision, just that I don't see
    simultaneously out of both eyes.

    Like you, if I close one eye, I do feel something is amiss, but not to
    the point of disorientation. This happens whether I use my dominant or
    non dominant eye.

    My eyes were crossed when growing up, and I had that surgically
    corrected, but that did not change the stereoscopic vision issues I have.

    Allen
     
    A Lieberma, Nov 19, 2006
    #10
  11. You can call them contrived, but they are legitimate measures of
    stereopsis, unless you've learned how to get around them without
    binocular fusion. This trick can be done for some tests, but not others
    (the ones that are truly random dot style). And just getting around the
    test does not mean you "learned stereopsis".

    Stereopsis is unique to binocular fusion, and ACCURATE stereo (down to
    the level of 30 seconds of arc) is not possible without "normal"
    bifoveal fixation (coupled with normal or non-anomalous retinal
    correspondence, and roughly normal acuity in both eyes).

    And stereopsis is only "learned" in the sense that it develops along
    with normal retinal correspondence. It is not something you can "teach"
    to someone who doesn't possess binocularity unless you can correct the
    underlying defect, and it is certainly not something you can "unlearn"
    without depriving the person of a normal binocularity he/she once had.
    This is not making sense to me. For one thing, exactly how did you
    "lose" binocular fusion? Did you lose an eye, or develop a constant
    strabismus, or what?
    How are you getting it back, and has it been measured clinically?

    w.stacy, o.d.
     
    William Stacy, O.D., Nov 19, 2006
    #11
  12. Liz Day

    Liz Day Guest

    ... I've watched him use a camera and be unable to tell whether the object to be photographed is present in the viewfinder or not. The pictures come out randomly - some with the object in the center of the picture as intended, some with it half cut off on the edge, and some with it completely absent (because the camera wasn't pointing at it).
    Well.... If you're a person who lacks stereo depth perception, but who
    does have two functioning eyes.... what DO you see??

    Allen? You say you don't see simultaneously out of both eyes. Tell me
    more what this is like.
    When I move my eyes so that they are not both focused on the same
    point, I see double images. Do you see double images of everything?
    If so, don't you have to tune one of them out at any given time?

    [But]
    So do I!!! I wonder if there is some test he can take to be sure it's
    OK to drive. Often his behavior suggests to me that he doesn't see
    very well, or is in some way confused, but I don't know *what* it is
    that he isn't seeing. It worries me.
    If someone has enough strabismus to have prevented their acquiring
    stereopsis (i.e., it was never corrected), can you see this by looking
    at them? That their eyes are pointing in slightly different
    directions? Or could it be going on, but be invisible to the outside
    observer?

    Thanks,
    Liz
     
    Liz Day, Nov 20, 2006
    #12
  13. Liz Day

    Neil Brooks Guest

    I'll speak from personal experience here ... having had three
    strabismus surgeries AND vision therapy, but becoming more EXotropic
    now.

    It depends. They could well maintain alignment via their fusion
    mechanism and look like they have straight eyes until something breaks
    down their alignment (fatigue, alcohol, a "cover test" used to elicit
    alignment issues in an exam setting, etc.). They could also be
    perfectly straight when looking in ONE direction, but all over the
    proverbial map when looking in another.

    I look at photos of me and my eyes look pretty darned straight, but ...
    especially in my case ... it takes a huge amount of autonomic
    (involuntary) effort to keep them this way. This, alone, can cause
    symptoms....

    By the way, I drive fine, just took something like 1,500 beautiful
    pictures in about nine different countries, on vacation, and can even
    parallel park reasonably well. Don't throw the ball my way, though.
    Please.
     
    Neil Brooks, Nov 20, 2006
    #13
  14. Liz Day

    A Lieberma Guest

    Can't resist.... the same thing you do????
    Pretty much seeing out of one eye, but lesser peripheral vision should I
    close one eye. If I switch the focus of attention in the way I look, the
    image will jump a little to the right or left, other then that nothing
    different I'd suspect then what you see????
    I don't get the benefits of double vision as you describe above. My eyes
    truly don't work together vision wise. If I look right and left, they
    both move simultaneously, but if I look right, I end up looking out of
    the right eye, and if I look left, I look out of the left eye. I notice
    a slight jump in perception as what I see jumps from one eye to the other
    eye as I shift my eyes to the right or left.

    Other then seeing "simulated double vision" via the computer, when I look
    outside the monitor, it's only one of a kind, no double anything.
    Driving (or flying in my case) is NOT affected by lack of stereo vision.
    Just like any other shall we call it "handicap" the brain adjusts
    accordingly. Again, what I don't have, I don't miss.

    If the car in front of me is getting larger, it's a no brainer I'd better
    be working the brakes. Flying does add a third dimension in which people
    seemed surprise I am able to master. Not only you have to gauge right
    and left, but up and down too! This obviously becomes more critical in
    the landing stage so to compensate for my lack of stereoscopic vision, I
    pick a spot on the windshield and aim that spot for the runway numbers.
    If the spot moves up from the numbers, that means my plane is dropping
    faster then I need to be. If the spot moves down from the numbers of the
    runway, that means I am staying aloft longer then I need to and have to
    adjust the plane accordingly.

    I don't have the ability to look out those 3D glasses, my eyes don't join
    what ever is suppose to join together, either I see out of the right or
    left, but the two images though shall not meet in the middle.
    In my case, after surgical correction, you would never know I didn't have
    binocular vision. The alignment issue is seperate especially after
    surgery.

    Allen
     
    A Lieberma, Nov 20, 2006
    #14
  15. Liz Day

    A Lieberma Guest

    Why is this Neil? If you can drive / parallel park a car, you don't have
    eye hand coordination to catch a ball?

    I don't have problems catching a ball or even hitting one myself.

    A Babe Ruth or Nolan Ryan I am not, but for your basic pick up games, I am
    able to hold my own.

    Allen
     
    A Lieberma, Nov 20, 2006
    #15
  16. Liz Day

    Liz Day Guest

    If someone has enough strabismus... can you see this by looking at them?
    mechanism and look like they have straight eyes until something breaks
    down their alignment (fatigue, alcohol, a "cover test" used to elicit
    alignment issues in an exam setting, etc.). They could also be
    perfectly straight when looking in ONE direction, but all over the
    proverbial map when looking in another.

    OK, thanks.
    ACK! How would I know?! I'm realizing now not to be too sure of
    anything. I had thought everything I saw was so "normal"...... hah.
    What a confusing mess.
    :-( :-(

    Pretty much seeing out of one eye, but lesser peripheral vision should
    I
    close one eye. If I switch the focus of attention in the way I look,
    the
    image will jump a little to the right or left....
    I don't get the benefits of double vision as you describe above. My
    eyes
    truly don't work together vision wise. If I look right and left, they
    both move simultaneously, but if I look right, I end up looking out of
    the right eye, and if I look left, I look out of the left eye. I
    notice
    a slight jump in perception as what I see jumps from one eye to the
    other
    eye as I shift my eyes to the right or left.

    It sounds as though you can somehow switch your brain "off" off the
    view through the eye you're not using. As though you can shift from
    one eye being totally dominant to the other totally dominant. True?
    I understand this now. See my next post. :-(

    LD
     
    Liz Day, Nov 21, 2006
    #16
  17. There are a ton of cues for distance listed at
    http://www.cns.nyu.edu/~msl/courses/2223/notes.8.pdf.

    Stereopsis becomes less useful at distances above about three feet, which
    is surprisingly close.

    For the one-eyed individual, the bigger problem is the lack of visual
    field. I suspect that two-eyed people without stereopsis often don't know
    of their problem-- possibly there are more in ignorant bliss than there are
    those in the know.
     
    Scott Seidman, Nov 21, 2006
    #17
  18. Liz Day

    A Lieberma Guest

    Hey Liz,

    Just messing with you. We both SEE the same thing.

    What we don't see is the quality difference *smile*. You see the same tree
    as I would. However our brains may interpret the tree in a different
    image. But we both see the same tree. Make more sense?
    Yes, one eye is "always dominant" though may not be my dominant eye at all
    times. For example.

    If I look straight ahead, my right eye is the dominant eye and my left eye
    is along for the ride.

    If I look right, I see no image jump.
    If I look to the left, guestimating about 45 degrees or so, I will see a
    slight image jump to the left. You can see this by pointing your finger
    out, and close your left eye. Then open your left eye and your finger will
    be pointed slightly to a different point. This is what my brain interprets
    during this "transition" that is not so seamless I guess.
    Has not hit my newserver server just yet....

    Allen
     
    A Lieberma, Nov 21, 2006
    #18
  19. Liz Day

    Neil Brooks Guest

    No simple answer, but best characterized as this: something tossed to
    me, with a decent amount of arc and minimal velocity: good chance of
    catching it;

    A line drive: I'm getting beaned ... a virtual certainty.
    One of the issues that may come heavily into play: your alignment may
    have been =stable= since just post-operative. In my case, the
    strabismus is nonconcomitant (varying in every direction in which I
    look) AND has been altered with the three surgeries that I've had, with
    vision therapy interventions, AND with age. So ... the neurologic
    whatever-it-is that handles these issues probably never had enough
    stable data to develop the right algorithm.

    I seem to recall that you could say--with some certainty--that a person
    whose eyes turned OUT nearly always threw the ball (say: basketball)
    short of the hoop, while a person whose eyes turned IN nearly always
    over-threw the ball.

    Something like that....

    As I'm going exo- now, AND working my way into presbyopia ... with my
    accommodative issues .... I'm looking into VT once again to try to
    stabilize the angles.
     
    Neil Brooks, Nov 21, 2006
    #19
  20. Liz Day

    Neil Brooks Guest

    This is actually really encouraging, Mike. I've been wondering
    whether--when accommodative amplitudes fade--accommodative
    _convergence_ would remain relatively unaffected.

    I _assumed_ so based on knowing that 80 year olds can still converge.

    Thanks.
     
    Neil Brooks, Nov 21, 2006
    #20
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.