Reputable Scientists say that myopia is genetic - surely it must be true?

Discussion in 'Optometry Archives' started by andrew Judd, Mar 15, 2005.

  1. andrew Judd

    andrew Judd Guest

    Dear Readers

    No less an organ than the british medical Journal tells us that

    http://bmj.bmjjournals.com/cgi/content/full/324/7347/1195#B9

    "Two well conducted and well controlled studies show that refractive
    errors are much more strongly correlated in monozygotic twins than in
    dizygotic twins - ref 9 , 10"

    And helpfully allows a link to References to 9 and 10. (Ref 9
    Provides more detail but 10 appears to be a similar study using MZ and
    DZ twins)

    Ref 9 shows its a 'Classical twin study' using the 'Equal environment
    assumption'.

    http://www.iovs.org/cgi/content/full/42/6/1232?ijkey=b10cc18d7c1f9187636c25d8f16c93ebacbc7e2d

    "Conclusions

    We have demonstrated that genetic effects are important in the
    development of refractive error, with heritability of 84% to 86% for
    myopia/hyperopia. The heritability of astigmatism is 50% to 65% and
    predominantly involves dominant genetic effects"

    And here is that environment assumption confirmed in Figure 1.

    "C is correlated by a factor of 1.0 for both MZ and DZ twins (the
    equal environment assumption)."

    So it has to be proven that myopia is strongly genetic? Surely? This
    was all peer reviewed, right? These guys are all trained scientists,
    right?

    But if we care to investigate that 'Equal Environment Assumption'


    http://www.net4dem.org/cyrev/archive/Misc. Articles/IQ/IQandGenetics1.htm1.

    For those who have only so much time to find out the facts i have
    extracted 3 sections of the page.

    1."Comparing monozygotic and dizygotic twins

    Another area where increasing recognition of complexity is confounding
    issues in IQ research is the study of twins that are raised within
    their biological families. Many of the conclusions concerning
    inheritance of intelligence come from comparisons between these
    monozygotic and dizygotic twins. A fundamental simplifying assumption
    underlying these studies is that the environment in which each member
    of a twin pair develops and grows up, from conception on, is
    essentially identical (Scan & Carter-Saitzman, 1979). The degree to
    which twins are considered to experience the same environments is
    thought to be the same for either monozygotic or dizygotic pairs.
    Thus, according to the argument, the difference in concordance for any
    trait between the two classes of twins can be ascribed to genetics.
    This "equal environment assumption" is based on the fact that such
    twins develop in the same womb and are raised together by their
    biological parents a t the same time in the history o f the family an
    d in the history of their society. This assumption did not encounter
    serious criticism until the early 1960's (Joseph, 19 98).

    One of the major problems with this assumption is that the physically
    identical nature of monozygotic twins could contribute to making their
    environments much more similar than that of dizygotic twins (Billings
    et al., 1992). This consequence of genetic identity could result from
    the ways in which both family and the larger society treat or deal
    with individuals who are known to be identical and physically present
    as identical. In addition, the known closer bonds between monozygotic
    twins as compared to dizygotic twins can contribute to greater
    behavioral similarity. Studies designed to respond to these criticisms
    have yielded conflicting results. The research suffers from the same
    problems of defining quantitatively those factors that could be
    considered to influence behavioral development in a family and social
    setting. Furthermore, contrary to the original simplifying
    assumptions, the studies have revealed that there are differences in
    the shared environments between the two classes of twins (Joseph,
    1998). In a review of these studies, Joseph claims that, in the case
    of studies of inheritance of schizophrenia, "the evidence suggests
    that the classical twin method ... is [based] on the fallacy of the
    equal environment assumption" (Joseph, 1998).

    2.Several recent papers cast further doubt on the equal environment
    assumption as it relates to early stages of development. Dr. Bernie
    Devlin and co workers showed that conditions with in the womb may have
    substantial effects on the concordance of subsequent scores on IQ
    tests for identical twins (Devlin et al.,1997).

    3."Given the examples I have provided here, Capron et al.‘s statement
    that, in such studies, "... not all environmental factors may be
    known..." appears a gentle understatement of the extent of the
    problem"


    Andrew:)
     
    andrew Judd, Mar 15, 2005
    #1
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  2. andrew Judd

    RM Guest

    Andrew,
    I guess I am one of those who has "only so much time" to become involved in
    newsgroup discussions. Can you please just cut to the core of what your
    point is in this post? I doubt that you only want to say that myopia
    development has a genetic basis. That is well known and accepted by almost
    everyone (except Otis). Do I detect a note of sarcasm?
     
    RM, Mar 15, 2005
    #2
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  3. andrew Judd

    andrew Judd Guest

    I had not intended to be unclear about this post but wanted the reader
    to draw their own conclusions.

    For those who understandably dont have time to read all that I wrote
    here is a summary.

    1. Myopia is claimed to be strongly genetically inherited based on for
    example Classical twin studies done at a reputable london hospital
    which were widely aired in the media last year.

    2. These 'Classical' type twin studies are claimed to be
    scientifically valid at resolving the issue of 'Nature versus
    Nurture'. Ie which is more important for myopia:

    A) Our genetic nature? or

    B) Our environment?

    3. These Classical studies use the 'Equal Environment Assuption' to
    resolve the 'Nature versus Nature' argument.

    4. The Equal Environment assumption has been shown to be an erroneous
    assumption.

    I should add there is no valid data available that supports the idea
    that myopia is genetically related.

    Andrew
     
    andrew Judd, Mar 15, 2005
    #3
  4. andrew Judd

    andrew Judd Guest

    Rm

    Can you provide a reference to your belief that myopia has a genetic basis?

    Thanks

    Andrew
     
    andrew Judd, Mar 15, 2005
    #4
  5. (andrew Judd) wrote in
    When phrased this way, the question, at least, makes sense (less your
    last addition). What gets in the way is what you consider to be "our
    environment". Most would say the relevant variables are things like how
    much near work a person does, while you say it has to do with the persons
    relationship to their parents.

    Scott
     
    Scott Seidman, Mar 15, 2005
    #5
  6. andrew Judd

    andrew Judd Guest

    andrew Judd, Mar 15, 2005
    #6
  7. andrew Judd

    RM Guest

    The genetic basis of myopia is known. What is also known is that genetics
    is not everything. I offer the following starting information for you.
    You can "Google" and "PubMed" yourself for lots more details.

    1. A well known genetic basis is evident by comparing myopia incidence in
    persons of Asian descent versus persons of European descent. The difference
    is something like 70% vs. 30%. This is true regardless of "environment"
    since Asians living in the US or Europe still have the same high rates of
    myopia versus the native population and vice versa.

    2. The studies of Young et al. which have identified the locations of
    specific genes on human chromosomes that relate to myopia development. See
    these two references:
    Young, T.L., Ronan, S.M., Drahozal, L.A., Wildenberg, S.C., Alvear,
    A.B., Oetting, W.S., Atwood, L.D., Wilkin, D.J., & King, R.A. (1998).
    Evidence that a locus for familial high myopia maps to chromosome 18p.
    American Journal of Human Genetics, 63, 109-119.

    Young, T.L., Ronan, S.M., Alvear, A.B., Wildenberg, S.C., Oetting, W.S.,
    Atwood, L.D., Wilkin, D.J., & King, R.A. (1998). Second locus for familial
    high myopia maps to chromosome 12q. American Journal of Human Genetics, 63,
    1419-1424

    3. Finally, there are population studies that show that myopia
    development correlates best with parents who have myopia, and/or siblings
    that have myopia. This correlation is much stronger than prolonged
    near-work, and other factors. See the following two web references:

    http://www.optometryonline.net/news/article.cfm?ID=504
    http://researchnews.osu.edu/archive/myokid.htm

    Finally, I will refer you to several review articles which summarize the
    current state of understanding of myopia development. From there you can
    find much more specifics if you are really interested.
    http://annals.edu.sg/pdf200401/V33N1p4.pdf
    http://www.revoptom.com/index.asp?ArticleType=SiteSpec&page=osc/apr01/lesson_0401.htm
    http://dels.nas.edu/ilar/jour_online/40_2/V40_2NortonAnimalModels.asp
    http://www.optometrists.asn.au/gui/files/ceo865276.pdf
     
    RM, Mar 16, 2005
    #7
  8. andrew Judd

    andrew Judd Guest

    Scott

    If anybody knows of any studies that suggest myopia is linked to
    genetics and which demonstrate good science then I am very interested
    to read them.

    Similarly if there are any studies that prove myopia is caused by near
    work I am sure Otis would be delighted to hear from you.

    Fundamentally my argument is that myopia is related to anxiety - at
    least one of your own quoted studies supports that view.

    So even more reason for me to be confused as to why you are now
    wanting to support the Otis answer to myopia.

    Andrew
     
    andrew Judd, Mar 16, 2005
    #8
  9. andrew Judd

    RM Guest

    So even more reason for me to be confused as to why you are now
    The Otis "answer" to myopia is to use plus lenses. Why people oppose it in
    this forum is because it has been tried before in scientific studies and
    proven to be ineffective.

    I don't think any of us oppose the idea that a near environment has
    something to do with myopia development. There are studies that show this
    quite clearly just as they show that genetics has a role as well, an even
    clearer role. The question is how do you counter the environmental
    influence(s) to reduce myopia progression. With the exception of some
    experimental pharmacologic treatments, nothing has been shown to work so
    far.

    The clinicials and vision scientists who post here are all about proof and
    fact. Call that "mental masturbation" if you like. I wouldn't. "Mental
    masturbation" to me is more like what you are doing. Coming around here
    pontificating about all kinds of causes of visual disorders that have no
    basis in science whatsoever. If seems to make you feel good to make these
    kind of statements which you know seem quite outrageous to the eyedocs here.
    I liken it to self-gratification through "mental flashing". Personally I'm
    not interested especially since I've taken the time to read a little into
    Kaplan's beliefs.
     
    RM, Mar 16, 2005
    #9
  10. andrew Judd

    andrew Judd Guest

    quite clearly just as they show that genetics has a role as well, an
    even
    clearer role.

    Oh really? Genetics has an even clearer role? Please give a citation
    and text that we can all share to check you are not making it up.

    vision scientists who post here are all about proof and
    Come on! Dont be coy! Lets have a name. Just a single name.
     
    andrew Judd, Mar 17, 2005
    #10
  11. andrew Judd

    Rich Guest

    My soon-to-be-published book, "Myopia for Dummies", gives the
    definitive answer to this question: LIFESTYLE causes myopia, not genes.

    Contrary to popular belief, people in east Asia are no more genetically
    susceptible to short-sightedness than any other population group.

    The epidemics of myopia in countries such as Singapore and Japan are
    due solely to changes in lifestyle, and similar levels could soon be
    seen in many western countries as lifestyles there continue to change.

    As kids spend more time indoors, on computers or watching television,
    Westerners are going to become just as myopic.

    Myopia is on the increase in most places, but in countries such as
    Singapore it has reached extraordinary levels. There, 80 per cent of
    18-year-old male army recruits are myopic, up from 25 per cent just 30
    years ago.

    Employers such as the police are having problems finding people who
    meet their requirements. There is also an increasing incidence of
    extreme myopia, which can lead to blindness.
    ---------------------------
    --Rich

    Just kidding about "Myopia for Dummies"! Actually, the above was
    paraphrased from a report by Dr Ian Morgan of the Visual Sciences
    Group, Research School of Biological Sciences, Australian National
    University
    The complete article is available on this site:

    http://www.newscientist.com/article.ns?id=dn6117
     
    Rich, Mar 17, 2005
    #11
  12. andrew Judd

    RM Guest

    Andrew, your foolishness continues to amaze me. Why not look at the post
    that I sent you on 3/15 per your request that contains the references you
    are asking for!

    Now go wack-off somewhere privately so we don't all have to watch you.
     
    RM, Mar 17, 2005
    #12
  13. andrew Judd

    Dr Judy Guest

    Since you don't believe the twin study that you yourself posted,
    (genetically identical twins have very similar amounts of myopia, non
    genetically identical twins are not as similar), I don't know what kind of
    "proof" you are looking for. A PubMed search using Myopia and Genetic as
    keywords yields over 750 citations.

    I think most vision scientists would say that myopia is multifactorial, it
    depends upon a number of genetic factors, environmental factors and their
    interaction -- it is neither 100% due to genetics nor is it 100% due to
    environment.
    To rephrase your question:
    " If anybody knows of any studies that suggest myopia is linked to anxiety
    and which demonstrate good science then I am very interested to read them"

    Dr Judy
     
    Dr Judy, Mar 17, 2005
    #13
  14. andrew Judd

    andrew Judd Guest

    Dear Dr Judy

    I dont know how much up to speed you are on what else i have said on
    these twin studies.

    It is simple to get facts that Identical twins have statistically
    greater correlation of myopia, than none identical twins.

    If myopia was related to some other environmentally related factor we
    would expect twins who are treated similarly to have similar myopia.

    Alternatively we could argue that myopia has a genetic component that
    may be influenced by environmental factors - this is more or less what
    you are suggesting.

    Therefore a study that statistically examines twins must also take
    into account environmental factors.

    The Classical Twin Study methodology makes an assumption that excludes
    environmentally **different** treatment of identical twins compared to
    none identical twins and **therefore** assumes that, in this Classical
    Twin Study methodology, environment is not an issue that causes
    distortion of results.

    Other scientists have argued that this is a flawed assumption and have
    they have got statistically meaningful results to support that
    argument. Identical twins are commonly observed to be dressed the
    same, confused for one another by care givers etc.

    Further I have found that St Thomases hospital (Hammond et al)
    Classical Twin Study designers ask all of their twin sets if they were
    differently treated. If the answer is yes then they are not included
    in the study. This clearly skews results in favour of genetics if
    environment (being treated differently) is then later not considered a
    factor in the results.

    I can appreciate that the nature versus nurture argument creates
    strong views.

    But for example no study on intelligence in races for example would
    ever be taken seriously with this kind of Classical twin study
    methodology.

    Andrew
     
    andrew Judd, Mar 17, 2005
    #14
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