Science: Depth of Field for the Primate Eye

Discussion in 'Eye-Care' started by otisbrown, Sep 27, 2007.

  1. otisbrown

    otisbrown Guest

    Dear Sci.med.vision members,

    One poster raised the issue of optical dead-band,
    and then told some one to F. O. when he
    asked questions about it -- if you are a professional.

    That is NOT the way you deal with scientific
    questions. And it is NOT the way you talk
    to the public about this scientific issue.

    So here is the correct response:

    ===============

    Subject: Depth-of-focus, and range of values.

    Re: Range of "travel" of accommodation.

    I think you know this concept as "depth of field",
    or optical dead-band.

    In engineering it is called dead-band, or DSO, or
    Dead Space Operator.

    What is means is that a signal is blocked,
    and must exceed the dead-band -- for effective
    refractive control to exist. Or for that matter
    for an image to be blurred on the retina.

    Here is the accurate reference:

    "Accommodative Oscillation Can Enhance
    Average Accommodative Response:
    A Simulation Study"

    George K. Hung, John L. Semmlow ang
    Kenneth J. Ciuffreda

    IEEE Transactions on Systems, Man and Cybernetics,
    Vol. SMC-12, No. 4, July/August 1982

    Statement:

    The deadspace operator reflects the optical depth of field, and is
    normally a function of pupil diameter, ranging from +/- 0.15 D
    for a 8-mm diameter pupil to +/- 0.85 D for a 1-mm pupil [15].

    15. F. W. Campbel, "Depth of Field of the Human Eye", Optica Acta,
    Vol. 4 pp 157-164, 1957

    For a sun-light pupil of 2.5 mm, the depth-of-field would be about 1.2
    diopters, as I suggested. (+/- 0.6 diopters).

    That is the source I am using.

    Thus the eye could have a theoretical positive STATE,
    of +1/2 diopter and still have a clear image on the retina,
    because of the eye's depth-of-focus.

    This explains why you can have no "accommodation",
    and good far an near vision.

    Otis
     
    otisbrown, Sep 27, 2007
    #1
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  2. otisbrown

    Neil Brooks Guest

    Sorry. Rishi Giovanni Gatti (Zetsu), Lena102938, and Otis Brown are
    trolls who haunt s.m.v.

    Rishi has published, and is trying to sell worthless books.

    Otis is pathologically dishonest and actually hurts people.
    Following his advice can induce double vision in those
    not working closely with an eye doctor.

    Lena102938 uses anti-eye doctor rhetoric as a substitute for ANY
    actual information. It seems she now has to wear glasses and has
    developed a pathological (and ILLOGICAL) resentment toward the
    industry that "foisted these glasses upon her."

    You'd do well to ignore them and wait for responses from the
    caring, compassionate eye doctors who DO also participate in this
    site.

    Incidentally, Otis: HAVE you spoken to Dave Granet about the Delayed
    Adjustable Suture technique yet?

    I mean ... you wouldn't want to keep lying, now would you?
     
    Neil Brooks, Sep 27, 2007
    #2
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  3. otisbrown

    serebel Guest

    Now if Otis were as smart as an ape, he might have some credibility.
     
    serebel, Sep 28, 2007
    #3
  4. otisbrown

    lena102938 Guest

    Otis, it is true.
    real precision of autorefractor measurements in dynamic eye.
    We should consider:

    1. Step of autorefractor (as a rule) 0.25 D
    2.Pupil size
    3.Chromatic aberration
    4.Distance to eye from light source.
    5.Eye movement
    6.Accomodation
    7.Cornea is not spherical

    Does not sounds like it will give too precise refraction.

    Then second step:
    Glasses prescription (i mean when refraction error low)
    1. Light is dim - pupil is wide
    2.Person is a little nervous,
    3.OD asks fast. No time for accomodation or relaxation.
    4.Main thing: OD asks "which better "
    Person will chose the higher power:

    Miopic:
    -1 lens gives extremely crisp vision even for person with 20/20
    Hiperopic :
    Even if person needs only +1 for reading , reading in +2 even more
    comfortable.

    That is widely advertised scientific approach.

    Lena
     
    lena102938, Sep 28, 2007
    #4
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