Mars appearance?

Discussion in 'Optometry Archives' started by Repeating Decimal, Aug 13, 2003.

  1. I do not have good central retinal vision in one eye. My other eye has good
    central retinal vision but is developing a cataract. It is also about 5 or 6
    diopter myopic.

    About two nights ago while I was in bed, I happened to spot, with my good
    central vision eye, what I believe was mars. It was close to the moon. The
    next night it was even closer to the moon.

    As one would expect mars did not appear clear. The surprise, however, was it
    appeared to be made up of widely separated colored speckles. Although it was
    hard to tell, it seemed that the speckles did not change over periods of ten
    seconds or so. The appearance was that of speckle from a white laser aimed
    at a diffuse wall. Putting on my glasses, the speckles coalesced into a
    single image of mars.

    The best explanation I can give, and it certainly is not iron-clad, is that
    different portions of the mars disk interfered with one another to produce
    speckle in different colors. I don't think my cataract, had much to do with
    it.

    A similar fine colored speckle can be seen in scattered light from the
    patina of a coin viewed in direct sunlight.

    If someone has a definitive explanation of the phenomenon, I would be
    pleased to learn of it.

    Bill
     
    Repeating Decimal, Aug 13, 2003
    #1
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  2. Repeating Decimal

    mg Guest

    Taking pictures might separate the "instrumental function" from the
    phenomenon in question. Posting the pictures on this board would be of
    interest to many, I am sure.
     
    mg, Aug 13, 2003
    #2
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  3. I started writing this when I had the thought to go out again to observe
    again. The moon and mars both had not risen, at least not in the part of the
    sky I could see.

    I now realize that mars was a red herring rather than merely a red planet. I
    normally wear glasses when I go out at night. Taking my glasses off, I got
    the same effect from the lights on a passing airplane as I did watching mars
    from my bed.

    If you have ever watched a fireworks show, you will probably have seen star
    bursts. The fire work explodes and there is a shower of bright burning stars
    as they are called. Picture one of these frozen in time as in stop action.
    Instead of appearing like a nebulous blob, there is a series of spots. They
    are similar in appearance to that of laser speckle. They do not seem as
    closely packed as with laser speckle. They can be colored. The question is,
    why spots rather than the blob of a defocused image?

    I just went out again for some more observation. If I look at a broad
    source, such as light from a window diffused by a window shade, there are no
    speckles. Looking at other sources, such as tail lights, the speckles become
    more distinct. They get be smaller at large distances. Can these speckles
    arise from a cataract?

    A white laser can be obtained from a mix of gases or from a gas that lases
    at several wavelengths simultaneously. IIRC a mix of Xe and Kr gases in an
    ion laser can do that.

    Bill
     
    Repeating Decimal, Aug 14, 2003
    #3
  4. I am beginning to form a model of what is happening. Comments are welcome.

    The cataract is forming little lenselets on or in the crystalline lens.
    Without my negative lenses each of these forms a relatively sharp image on
    my retina but in different spots. After all, the diameters of these
    lenselets is small so that individually they a large depth of focus. Putting
    on my glasses tilts light in such a way as to have all of these less than
    perfect image focus on the retina in the same place.

    Looking a a distance point source without my glasses results in a series of
    spots on the retina. This looks something like the speckle from lasers, but
    is stationary. Sometime, as the cataract progresses, I expect my glasses
    will no longer be good enough to overlap these images, and that sharp spots
    will no longer be visble.

    This morning, as the moon was setting, I observed it through my cataract. I
    got multiple images of the moon. Even though some of them overlapped, it was
    easy to see that they were decent images. As I squinted to cover up some of
    the cataract's aperture, the number of images decreased. I could get the
    same effect by making a variable aperture using my fingers. Images
    disappeared as different portions of the cataract were covered.

    I think I have explained the phenomenon as far as I am concerned.

    Bill
     
    Repeating Decimal, Aug 14, 2003
    #4
  5. Repeating Decimal

    Han Sibot Guest

    FWIW, I get the same effect looking at the red LEDs on my HiFi
    without my
    Maybe I see what you see, although I don't have cataract. When looking
    without glasses (I'm myopic too, -6) at a small distant light source,
    it does not appear like a uniform blurred disk. Instead it appears
    like a mesh of curved lines ('caustic lines'; not the isolated dots
    from a speckle pattern) . I reminds me of sunlight falling on the
    bottom of a swimming pool: due to the waves on the water surface the
    light is concentrated in curved lines. As a model of a myopic eye
    somebody could hold a lens above the water to focus the sunlight on a
    focal spot above the bottom of the pool. Depending on the waves, a
    mesh of caustic lines would appear again on the bottom of the pool.
    Due to the lens the mesh would be confined to a circular area. This
    explanation is basically the same as yours, I think.

    You seem to consider the irregular lens surface ('little lenselets')
    as an abnormality related to cataract. I don't have cataract so I
    assume this irregularity is present on many human lenses or corneas;
    just its visual effect is more obvious in unaided myopic eyes.

    BTW, in contrast to you I don't see color dispersion.
     
    Han Sibot, Aug 15, 2003
    #5
  6. Repeating Decimal

    Han Sibot Guest

    People who are not so badly myopic, please try this: take a look at
    Mars (or another small light source) through binoculars, first in
    focus, and then gradually defocus the ocular in either direction as
    far as it goes. Defocussed Mars is not a smoothly blurred disk, it is
    a kind of speckle pattern, isn't it?
     
    Han Sibot, Aug 15, 2003
    #6
  7. Even if you do not have cataracts. it is unlikely that your lens will not
    have aberrations. Depending upon the form of the aberrations, I would expect
    multiple or distorted images to form if you are myopic or look through
    positive lenses.

    The lines you are talking about may be floaters.

    I now think that I would not get the spots without the cataract. That is,
    instead of multiple images of a small object, they would be smeared out.

    Bill
     
    Repeating Decimal, Aug 15, 2003
    #7
  8. Repeating Decimal

    Han Sibot Guest

    It is hard to miss that vitreous floaters float in a typical manner in
    response to eye movement. The line pattern doesn't respond to eye
    motion.
    out.

    I don't get multiple images from a small object, so in that respect we
    are seeing different things.
     
    Han Sibot, Aug 15, 2003
    #8
  9. Repeating Decimal

    Han Sibot Guest

    At first I didn't get why you mentioned floaters. On second thought,
    my description of caustic lines as the light lines on the bottom of a
    swimming pool may have suggested my line pattern is dynamic. However,
    it is static; I should have said it looks like a snapshot of those
    lines.
     
    Han Sibot, Aug 15, 2003
    #9
  10. I may be seeing pinhole shadows (images) from "holes" in the cataract. To
    the extent that the holes themselves are lensed, the images will be sharper
    and clearer. I have no doubt that while looking at the moon without glasses,
    I see a superposition of clear moon images. The images are far enough apart
    so that I can tell they are moon images. If the images were larger with more
    overlap, there is no doubt that I would have one blurry mess.

    Bill
     
    Repeating Decimal, Aug 15, 2003
    #10
  11. If that is the case, you may be seeing the network formed by blood vessels
    associated with the retina. It is usually difficult to see that net except
    against a fairly uniform light background.

    Bill
     
    Repeating Decimal, Aug 15, 2003
    #11
  12. Repeating Decimal

    Han Sibot Guest

    At first I didn't get why you mentioned floaters. On

    I'm still trying to localize the optical inhomogeneities my eye
    that causes the speckle/line pattern.

    This cloudless night I looked with a single eye without
    glasses at Mars, and saw the expected circular area filled with
    the speckle pattern. Nothing in that pattern changed when my
    fixation point moved a few degrees away from Mars. This confirms
    that the inhomogeneity is not located in the retina or in the
    vitreous.

    The speckle area has a distinct boundary: outside the
    circular area it is immediately dark. It turned out that this
    boundary corresponds to the pupil of the eye. When the pupil
    contracted (due to shining light in the other eye), the boundary
    of the speckle area contracted as well. During the pupil
    contraction the speckle pattern didn't change (except for the
    disappearance of the outer ring).

    Again moving my fixation point away from Mars, I noticed
    that the circular boundary did not move with respect to the
    speckle pattern. I think that means my optical inhomogeneities
    are close to the plane of the pupil, hence in the lens and/or
    the cornea.

    Blinking sometimes introduced a few new speckles that
    disappeared again within a 1 second, probably disturbances in
    the tear film.

    (BTW just a check using basic geometry: without my glasses I
    saw Mars blurred with a diameter of 2 degrees, and my myopia is
    -6, so my uncontracted pupil must be 6 mm. That's fair.)
     
    Han Sibot, Aug 16, 2003
    #12
  13. Repeating Decimal

    Otis Brown Guest

    The eye has a power of about 60 diopters. The largest
    amount I have heard of is -30 diopters.

    I think he means -5.00 diopters myopic.

    I have also 500 DEGREES of myopia. Where did
    that come from?

    Best,

    Otis
     
    Otis Brown, Aug 16, 2003
    #13
  14. This is another example of improved communication by the use of jargon. :=(
    On another newsgroup, I found to my astonishment that *mcg* was a microgram
    and not a milli-centigram as I would have intuited because of what I know of
    other abbreviations I know.

    Bill
     
    Repeating Decimal, Aug 16, 2003
    #14
  15. Mike, I presume you do not have a cataract forming. In contrast to your
    conclusion, I no longer think that interference is involve in a major way.
    Here are some clues, not using glasses.

    I looked at LEDs on my telephone in a dark room. I got multiple images that
    I presume are caused by the equivalent pinholes with or without lensing (fly
    eye lens). As I rotated my head, the images rotated as my head did. To me
    this indicated that the cause of the effect was attached to my eye and not
    to something exterior.

    I looked at the moon. I again get multiple images. they are separated in
    angle sufficiently so that I can tell that they are mostly separate images.
    Something much larger than the moon would form overlapping images so that it
    would not be possible to tell that the combined images were a sum of
    individual ones. Again, these images rotate with my head.

    Bill
     
    Repeating Decimal, Aug 16, 2003
    #15
  16. I have frequently noticed that blinking brings out features that are
    otherwise missed. Retinal fatigue often causes fixed images to be lost.
    Blinking causes them to show up again. Sometimes it is very difficult for me
    to tell which I am seeing something with both eyes or which eye. This was
    particularly true of ocular migraine which is a neurological phenomenon, not
    a eye phenomenon.

    One interesting thing I noticed is how this shows up to distinguish cone
    (photopic) vision from rod (scoto0pic) vision. Toward dawn, just about when
    there is enough light for photopic vision, I look at a uniform wall. By
    blinking, I can see a hole in my central vision. I attribute that to a lack
    of rods there. It is like the photopsia described by Oliver Sacks in a book
    on some South Sea island natives. Later in the day when there is sufficient
    light to energize cones, this hole disappears.

    Bill
     
    Repeating Decimal, Aug 16, 2003
    #16
  17. Repeating Decimal

    Han Sibot Guest

    I don't doubt your multiple led images and moon images. However, I am
    missing something in your description. It sounds as if those multiple
    images are roughly speaking equally bright and equally sized. In
    contrast, I imagine there should be one main image very similar to my
    image (bright circular disk with speckle, diameter 2 degrees, and a
    sharp boundary that contracts when the pupil contracts). The images
    induced by the small(?) cataract bodies within the lens should be very
    different (a lot less bright, different size, no distinct boundary,
    not responding to pupil contraction). Is that what you see?

    If those secondary images would be weak, I wonder if they are needed
    to explain the speckle pattern.
     
    Han Sibot, Aug 17, 2003
    #17
  18. Repeating Decimal

    Han Sibot Guest


    It sounds as if your eye sees pinhole images only, and the
    normal image has been blocked. I think your cataract model is a
    black screen with a few pinholes, internally in your lens. That
    might be dark, but why not. Now I am curious about the diameter
    of the multiple LED images, not the moon images. Discussing the
    LED images is simpler because then we can forget about the
    angular subtense of the object.

    As you were looking at Mars, you probably know about star
    magnitudes. With a little experience the eye is able to assess
    that two stars are of the same magnitude. If that is possible
    with stars, then it might be possible with LED images too.
     
    Han Sibot, Aug 17, 2003
    #18
  19. Repeating Decimal

    Han Sibot Guest

    That was quite a puzzle! I am not sure what a window screen
    is, so I took a strip of 35mm negative film. My target was a
    small index number at the edge of the strip.

    I held this target between my eye and the red LED, and took
    off my glasses. I was able to read the number at a distance of
    16cm, which is natural for a myopic eye of -6. Due to the
    parallel rays from the remote LED I could read that number just
    as well at any other object distance, from 1 mm before my cornea
    to 1 meter. For any object distance the number appeared sharp,
    and its size remained the same (1 degree of visual angle). It is
    a real image on the retina, but I would like to call it a ghost
    image here because it is different from the conventional image.

    Then I switched on the light in the room, not too bright.
    Bright enough create a conventional image of the number on my
    retina, without outshining the ghost image. The conventional
    image coincided with the ghost image when the object distance
    was 16cm. When the object distance was doubled to 32cm, the
    convential image was 2x smaller than the ghost image. When
    moving my head sideways, the ghost image moved 2x faster than
    the conventional image, and in the same direction as my head.

    I should admit that, at an object distance of 32cm, the
    conventional image was blurred so much to my unaided eye that I
    could not read the number. However, using the entire film strip
    as a target led to the same conclusion.

    The ghost image speed is not nessecarily twice the
    conventional image speed. For example, the ratio would be -1/2
    for an object distance of 8 cm.
     
    Han Sibot, Aug 17, 2003
    #19
  20. The effect of the screen, I believe, is to introduce moire fringes. That can
    give a speed illusion. Try changing the distance between your eye and the
    screen.

    Bill
     
    Repeating Decimal, Aug 18, 2003
    #20
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