Eye adaptation to lenses?

Discussion in 'Eye-Care' started by Charles, Nov 3, 2005.

  1. Charles

    Charles Guest

    I'm curious to what extent, if any, the eyes will adapt to lenses. For
    example, if you took a person with good vision and made him wear lenses
    with mild cylinder correction, would he just see blurry in one
    dimension forever, or would his eyes somehow adapt over time?

    It seems like when you get your eyes checked for prescription, there
    might always be a bias toward the current prescription if there is any
    adaptation of this sort. If this is the case, maybe there is value in
    biasing towards less power to avoid power "creep" over time.

    I'm thinking about this because in my own case I started wearing
    glasses at about age 25 and it was just a mild prescription to fine
    tune my vision. It wasn't really necessary, but things were a little
    more crisp with the glasses. Over time I seem to have become more and
    more dependent, and now after 10 years I can't stand not having the
    glasses on and the prescription has "grown". I can't help but think
    that maybe if I had never gotten glasses in the first place, I still
    wouldn't have them.

    Is there anything to this? Based on the threads I've read here, I tend
    to think that what I'm saying goes against the generally accepted
    evidence?
    --
     
    Charles, Nov 3, 2005
    #1
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  2. Charles

    otisbrown Guest

    Dear Charles,

    Subject: Does the eye "change" it refractive state
    when you place a minus lens on it.

    In primate (scientific) studies, the answer is
    a clear "yes".

    On sci.med.vision, the majority opinion is no.

    You should evaluate the scientific experiments
    yourself concerning this issue, because
    every time I state simple scientific
    proof and truth, one man posts
    "wanrings" about basic science.

    That speaks of intense scientific bias.

    It depends on how you "word" you question.

    Enjoy,

    Otis
     
    otisbrown, Nov 3, 2005
    #2
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  3. Charles

    otisbrown Guest

    Dear Charles,

    Here is Dr. Guyton's statement of
    the scientific facts concerning
    the effect that a lens has
    on the refractive state of
    the natural eye -- for
    your interest. I sounds
    like your eyes "adapted"
    in this manner.

    Best,

    Otis

    ________

    We asked Dr. David Guyton, the Krieger Professor of
    Pediatric Ophthalmology at Johns Hopkins' Wilmer Eye Institute, to
    discuss how these new findings may change the treatment of myopia
    in children and young adults. -- The Editors


    ***************

    The Physician's Perspective -- David L. Guyton, MD

    According to old-wives' tales, wearing glasses makes the eyes
    worse. Generations of ophthalmologists and optometrists have told
    their patients just the opposite, that the eye's development is
    predetermined by genetics and cannot be affected by glasses. A
    growing body of animal and human research, however, suggests that
    the old wives were right after all.

    The ability of young rhesus monkeys' eyes to gradually change
    shape in response to what they see comes as no surprise to vision
    scientists. Over the past two decades, their studies have
    demonstrated that the eyes of young birds, tree shrews, guinea
    pigs, and marmosets react to unfocused images by altering their
    growth to correct the problem.

    It is highly likely that the eyes of infants and young
    children also adapt to what they see. This adaptation occurs by a
    relative change in eye length that works something like this: As
    the front of the eye grows and becomes less curved, images focus
    deeper and deeper within the eye. If the lengthwise growth
    perfectly matches the change in the eye's other dimensions, then
    images continue to focus on the retina. If there is a mismatch
    and the focus is off by even the thickness of this paper, then
    vision will be blurred. Remarkably, the eye apparently senses
    where images focus and compensates when needed. If light focuses
    in front of the retina, the eye will stop lengthening until the
    images catch up. If the focus is behind the retina, the eye grows
    in length at an accelerated rate until the retina is "pushed back"
    to the correct spot relative to the eye's other dimensions.

    Thanks to this feedback mechanism, the eyes generally
    maintain clearly focused images throughout early life despite
    dramatic changes in size.

    In addition to eye size and shape, the distance between the
    eye and the objects it is viewing also determines where images
    focus. Near objects come to focus behind the retina, but the lens
    changes shape and pulls the images forward until they are clear
    enough to recognize. However, they often remain slightly behind
    the retina. This slight mismatch may be the mechanism by which
    prolonged close work such as reading can signal the eye to grow
    longer. If such a signal occurs frequently and strongly enough in
    early life, the human eye may gradually lengthen and become
    permanently focused for near objects. This produces
    nearsightedness.

    Most of the adaptive changes in eye length occur during
    infancy and youth, while the eye is still growing in its socket.
    When the front of the eye stops growing, around age nine or ten,
    any further adaptive change can occur only in the myopic direction
    -Ä the eye can grow longer, but not shhorter. Activities such as
    prolonged reading at close distances may cause the eyes to
    continue lengthening well into one's 20s.

    If this cycle of incomplete focus and eye lengthening is the
    primary cause of myopia, how can we intervene in this process?
    Some practitioners believe that limiting the amount of close-up
    reading or television watching a child or young adult does each
    day may prevent myopia. These days that is a difficult task. So
    I advise parents to encourage children to hold objects and reading
    materials as far away from their faces as comfortable, and to sit
    at least three feet away from the television screen. (Those who
    insist on holding books close to their eyes, or sitting a foot
    from the television or computer, may already have developed
    significant myopia or some other problem that warrants a
    professional eye examination.)

    For my young patients with simple myopia, I suggest they
    leave their distance glasses off while reading, something I have
    always done myself. A child who cannot see the board at school,
    for example, should wear glasses to see the board, but remove them
    when reading a book or writing.

    <snip>
     
    otisbrown, Nov 3, 2005
    #3
  4. Charles

    Dick Adams Guest

    The folks here, it seems, think that eyeglasses are good for you,
    by and large. Being in the eyeglass business is conducive to that
    view.

    Well, here is some interesting reading, to help prepare you for
    discussions with the O.D.s:

    http://www.myopia-manual.de/index.htm

    Well, I am just guessing that is the right one. Maybe there is a
    hyperopia manual out there, too. There is a lot of stuff out there.
     
    Dick Adams, Nov 3, 2005
    #4
  5. Yes, you have opened an old can of worms here, but I still want to
    throw in my 2 cents worth. It has been established for more than a
    century that we all tend to start with juvenile hyperopia, or literally
    translated "the farsightedness of childhood." We grow out of this
    natural hyperopia in most cases by about age 6 or 7. If we are lucky,
    we stop right around the proper eye length and we don't need corrective
    lenses until we are in our 40s.
    Myopes go through their natural hyperopic years much quicker, and then
    all bets are off as to when the myopic stretching will stop. There are
    general trends in all studies, such as myopic parents tend to have
    myopic kids, and Asians are more myopic than other races. But, through
    all the studies, it seems to come down to the general belief that
    myopia is an inevitable byproduct of mandatory public education and the
    simple fact that we work at near for thousands of hours more than we
    look at distance. If you recognize that we were "originally built" to
    hunt for food on the horizon, kill it and eat it...hyperopia once
    ruled. Then, with indoor plumbing, pennicillan and Playstation
    2...myopia has taken over.
    So, the belief that we can intervene to stop myopia, I feel, is like
    trying to stop the fact that humans have grown progressively taller for
    the past 100 years. Its all about adaptation. If you give young
    myopes plus lenses to cancel their myopia, you might also take them out
    of school and send them hunting with a bow and arrow as well.
     
    doctor_my_eye, Nov 3, 2005
    #5
  6. I have often been asked why there is blatant hostility on one side or
    another when it comes to the battle of "nature vs. nurture" on the
    theories of myopic progression. My answer is that hostility occurs
    when there are other issues that create emotional baggage that create
    that flashpoint over otherwise simple debates.

    In the optometric profession, the "old timers"are more likely to be the
    behavioral optometrists, who suscribe to the OEP (see www.oep.org) and
    believe in the benefits of vision therapy and eye exercises. The "new
    blood" are the generation of optometrists who have been able to
    prescribe drugs and perform medical diagnoses with much more "medical"
    an orientation. This is an "old" vs. "new", it is "Behavioral" vs.
    "medical", it is like "psychology vs. psychiatry". Hence, the baggage.
     
    doctor_my_eye, Nov 3, 2005
    #6
  7. Charles

    Dick Adams Guest

    So, what if you recognize them as their myopia begins to get
    noticeable and put reading glasses on them, for reading only?
    What if their reading glasses correct astigmatic defects as
    well as spherical, and set convergence to virtual infinity, and
    are properly calculated for their actual reading distance?

    Better say, also, for this hypothetical study, that the use
    of said reading glasses for reading is confirmed by observation.

    Well, with all due respect, I can tell you that one source of hostility generates
    when one goes for some hardware to correct one's vision at some distance
    where one wishes to see things with optimum acuity and minimum discomfort,
    but when one gets instead a bunch of gobbledygook followed by some
    pronouncement such as "with your eyes, I can only give you 20|XX" where
    XX can be almost any two digits.
     
    Dick Adams, Nov 3, 2005
    #7
  8. Charles

    Dr. Leukoma Guest

    Yes. What you are thinking goes against the evidence. Whether one
    accepts the evidence is another matter. Otis doesn't accept the
    evidence, and has constructed a very elaborate illogically- constructed
    house of cards to explain it all away.

    DrG
     
    Dr. Leukoma, Nov 3, 2005
    #8
  9. Charles

    otisbrown Guest

    Dear (Majority opinion) Doctor my eye,


    MyEye> So, the belief that we can intervene to stop myopia, I feel, is
    like
    trying to stop the fact that humans have grown progressively taller for

    the past 100 years.

    Otis> The primate studies say nothing about genetics.
    They are very clear. When you place a minus lens
    on the fundamental primate eye -- the refractive
    status FOLLOWS the applied minus lens. This
    is a dynamic process. It always occurs when
    that test is correctly done. Are you suggesting
    that "genetics" monitors that applied minus lens,
    and changes the eye's refractive state, when
    ever "genetics" senses a change in the average
    visual enviroment?

    MyEye> Its all about adaptation. If you give young
    myopes plus lenses to cancel their myopia,

    Otis> I suggest you cultivate their intellect about
    this issue before they are given that first minus lens.
    They might conclude that they have no choice
    but to pay attention to the experimental
    data (above) and do "prevention" under their
    on contorl. It is obvious that you can
    be of no "help" to them.

    MyEye> you might also take them out
    of school and send them hunting with a bow and arrow as well.

    Otis> This is one statement I simply do not understand.
    Yours in the majority opinion. The second opinion
    would offer a discussion to the parents of
    a child who is a zero diopters. The second opinion
    would suggest that the parents review the
    basic scientific facts as the concern the dynamic
    nature of the fundamental eye. If the parents
    turn it down, the the minus lens is the only
    opinion for that child.

    Otis> The purpose of the plus is to "move" that
    "near" environment out to infinity, thus simulating
    living in an out-door world. If the person does
    not with to develop stair-case myopia (refractive
    state "down" at -1/2 diopter per year), then
    keeping your distant vision clear with
    the plus makes a great deal of technical
    and scientific sense.

    Otis> But I do respect the fact that the person must
    himself make this assessment, and make
    habitual use of the plus to preserve his
    distance vision for life. See

    www.chinamyopia.org

    for the OD "second opinion".

    Best,

    Otis
     
    otisbrown, Nov 3, 2005
    #9
  10. Charles

    otisbrown Guest

    Dear Friends,

    The outcome of this type of discussion depends on
    what we are talking about.

    DrG expresses the MAJORITY OPINION, that the
    natural eye is not dynamic, and does not
    control its refractive state to a change
    in its visual environment.

    DrG uses his position of "doctor" to enforce that
    "belief" on himself. But that it belief, not
    the objective, scientific facts.

    If respect the eye as a sophisticated system,
    and check for this behavior of a pures-scientific
    level, then by direct test, you determine
    that a population of eyes, will change their
    refractive status to an applied minus lens.

    But that is a 21st century point-of-view,
    and the minus-lens has been used
    in the manner of a quick-fix (with no
    chage) for the last 400 years.

    That is why there is an argument about
    prevention -- or no-prevention.

    Depends on who is calling the shots.

    Best,

    Otis
     
    otisbrown, Nov 3, 2005
    #10
  11. Charles

    Dr. Leukoma Guest

    Otis just gave a perfect example of evading the argument, as well as
    not knowing what he is talking about.

    DrG
     
    Dr. Leukoma, Nov 3, 2005
    #11
  12. There have been a few very strong OEP studies that have suggested that
    all young myopes who are given bifocals at an early age become less
    myopic than those who are corrected with their full minus correction.
    But, when those studies are performed under controlled conditions, like
    factoring in the race and refractive error of the parents, the studies
    get weaker and harder to replicate.
    The more that scientists attempt to study myopic siblings and replicate
    where they study, how long, what they eat, etc, etc...the more that
    genetics seems to come into play. For example, put an Asian-American
    child in the same rigorous study regimen as an Anglo, the student of
    Asian heritage gets more myopic and at a faster rate. If we can
    theorize that a myopic eye is a softer eye that stretches more readily,
    then we can account for the fact that myopic parents give their kids
    the "double whammy"; they pass down a softer eye and then teach their
    children how to love a good book. If Mom or Dad are of Asian descent,
    you might as well put minus lenses in the kid's diaper bag when you
    send him home from the hospital. ;)
     
    doctor_my_eye, Nov 3, 2005
    #12
  13. Charles

    ryoung8918 Guest

    but when one gets instead a bunch of gobbledygook followed by some
    I don't know why, but here's my story...

    I'm a hyperope who until fairly recently could accomidate my way to
    passing the DMV test. Once I realized a couple of years ago (headaches
    and blurriness) I needed glasses/contacts I went to an optometrist who
    told me among other things:

    "You can only see 20/20 in perfect conditions. Because you didn't have
    your vision corrected when you were younger, you really can't be
    corrected to 20/20."

    "I'd never put a man over 40 as a first time contact wearer into RGP
    contacts. (with laughter)"

    "I wouldn't bother filling the glasses perscription. You'll be back in
    6 months wanting bi-focals."

    She spent 10 minutes trying to refract me, put me in Acuvue Advance and
    sent me on my way. It was certainly better than my vision had been, so
    I considered it an improvement.

    This year, I changed my medical insurance to Kaiser Permanente which
    had vision care as part of the plan. Saw the doc there, and what a
    difference! She spent about an hour with me, taking time to make sure
    the refraction was the best it could be. I ended up not only seeing
    20/20, but read three letters off the 20/15 line. Checked my close
    vision too and said she thought it I'd need bifocals in a couple of
    years, but that for now I could manage with the distance correction.
    She did an excellent job listening to my experience with my vision and
    working with me. I'm not endorsing a medical plan, just the particular
    doc I ran into.

    And to say that I've heard the, "you can only be corrected to 20/XX..."
    line.
     
    ryoung8918, Nov 3, 2005
    #13
  14. Charles

    Dr. Leukoma Guest

    Myopes have softer, more elastic eyes?

    DrG
     
    Dr. Leukoma, Nov 3, 2005
    #14
  15. A bit of a "stretch", eh? If it is a given that the sclera of an Asian
    eye appears more translucent because it is thinner, can we deduce
    logically that thinner is therefore more elastic? Here's a great
    article that summarizes a lot of myopic progression studies.

    http://www.iovs.org/cgi/content/full/40/9/1936
     
    doctor_my_eye, Nov 3, 2005
    #15
  16. Another bit of a "stretch" in logic, eh? If that Asian eye appears
    more translucent because the sclera is thinner and allows the choroid
    to show through more readily, is that thinner sclera a more elastic
    sclera as well? Here's one of my favorite studies of Asian children.

    http://www.iovs.org/cgi/content/full/43/2/332
     
    doctor_my_eye, Nov 3, 2005
    #16
  17. A bit of a "stretch", eh? If it is a given that the sclera of an Asian
    eye appears more translucent because it is thinner, can we deduce
    logically that thinner is therefore more elastic? Here's a great
    article that summarizes a lot of myopic progression studies.

    http://www.iovs.org/cgi/content/full/40/9/1936
     
    doctor_my_eye, Nov 3, 2005
    #17
  18. A bit of a "stretch", eh? The translucence of the sclera on Asian eyes
    is often attributed to its thinness. Can thin be also more elastic, by
    derivative logic? Here's a great article that touches a lot of bases
    on myopic progression studies.

    http://www.iovs.org/cgi/content/full/40/9/1936
     
    doctor_my_eye, Nov 3, 2005
    #18
  19. Charles

    Dr. Leukoma Guest

    That article was pretty informative in 1999 when it was published.

    DrG
     
    Dr. Leukoma, Nov 3, 2005
    #19
  20. Charles

    Charles Guest

    I was afraid I'd open a can of worms. I specifically didn't use the
    word "myopia" anywhere in my initial question to try and avoid this.
    Is the answer to my astigmatism question:

    "...if you took a person with good vision and made him wear lenses
    with mild cylinder correction, would he just see blurry in one
    dimension forever, or would his eyes somehow adapt over time?"

    is the answer that the person would not adapt at all? A related
    astigmatism question would be: can the muscles of the eyes strain in
    such a way as to overcome astigmatism to some extent? And if so, does
    aiding with glasses allow these muscles to relax and lose strength such
    that unaided vision would be worse after wearing the glasses for a
    while?
    --
     
    Charles, Nov 4, 2005
    #20
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