from
http://www.curedisease.com/Perspectives/vol_5_1995/Neurobiology.html

Myopia (nearsightedness)

Margarete Tigges and colleagues have studied myopia due to eye
elongation in normal rhesus monkeys and in monkeys who experienced
different kinds of visual deprivation.41 These projects originated
with David Hubel and Torsten Wiesel's observation in the 1960s that
kittens' eyes that were sutured shortly after birth grew longer than
unmanipulated eyes.42 In fact, even prior to Hubel and Wiesel's
finding, there had been numerous prior studies with human subjects
aimed at determining whether visual deprivation causes an eye to
elongate.43 These studies had conflicting results, but more recent
clinical studies have shown that certain kinds of visual deprivation
do cause human eyes to elongate.44-47 Several hereditary and
environmental factors contribute to human pathological myopia, and,
despite a plethora of monkey and cat studies, only human studies will
untangle this complex issue. Nonhuman primate studies have been
conflicting, making their applicability doubtful. For example,
atropine administration prevents eye elongation from eyelid suturing
in Macaca arctoides but not Macaca mulatta. This suggests that even
closely related primate species can have different mechanisms of eye
elongation. Furthermore, in both Macaca species eye elongation was
highly variable among individuals in the same species, suggesting that
hereditary factors or other factors contribute to the eye's final
size, similar to the differences in cortical representation of body
surfaces found in squirrel and owl monkeys.22 Given that
species-specific as well as individual factors influence eye size in
nonhuman primates, it is difficult, if not impossible, to extrapolate
such variable experimental findings to humans.

The inadequacy of the animal "model" in studies of myopia have been
illustrated by later research by Elio Raviola and Wiesel; their
photographs42 have revealed the poor correlation of this model with
human myopia. One photograph shows a myopic M. mulatta eye with very
visible choroidal blood vessels, a common finding in human myopic
eyes. However, choroidal blood vessels are also easily visible in the
"normal" monkey eye Raviola and Wiesel have provided for comparison.
Another supposed parallel between monkey and human myopia is a
temporal crescent adjacent to the optic nerve, which represents
retinal and choroidal tissues not reaching the nerve during
development. But, the photographed myopic monkey has only a small
temporal crescent, which is a common finding in non-myopic human eyes,
and differs from the large temporal crescent often seen in
pathological human myopia. Raviola and Wiesel have not reported in
monkeys other common findings of human myopia, such as lacquer cracks,
Fuch's spots, or posterior staphylomas. Noting the inconsistent
presentation of visible choroidal vessels and temporal crescents in
these monkeys, Raviola and Wiesel have remarked, "Similar
inconsistency in the appearance of the fundus is a common clinical
finding in advanced human myopia." This is not a sound basis for an
animal model of human myopia.

My knee-jerk response to that would be that in the absence of strong
supporting evidence, parallels between primates and humans are
EXTREMELY dangerous to draw in a medical context.

Otis has been reminded of this time and again, that the theories he
espouses affect real people, and only in the past couple of months has
resigned to explicitly appending his posts with 'I AM NOT A DOCTOR', or
some such - but he still does not get it.

I have no CV in anything remotely medical (I'm also an observer), but
look at the behavior differences: I think it's fair to say that
primates have a lot more 'variation' in how they focus their eyes on
objects through the course of the day. Humans will spend hours and
hours looking at exactly the same thing (be it a book, a computer
screen, a TV)... Animals in the 'wild' are very likely NOT letting
their accomodation sit at a specific distance for hours on end. I
strongly suspect that animals who do not have persistent stimuli at a
static focal length will not maintain focus at any specific focal
length for much more than a few seconds.

We're all told that in our workplaces we should 'relax our eyes' once
and awhile, and take them off the screen for a few moments several
times a day. Do we need to ensure that the baboon down in the zoo takes
a break from studying his banana so that he doesn't get a headache?
Obviously not. Because he varies his focal length all the time -
looking from trees, to the bee buzzing around his lunch, to the bug he
just picked off of his wife's head, and at then to those dorky humans
who walk by staring all flippin' day.

Could this mean that the muscles around the primate lens cause the lens
to change shape more often than do humans? Sounds reasonable. Could
more frequent accomodation changes be a variable that will affect the
results of vision studies? I certainly expect so.

Regardless, before results of primate studies are deemed relevant, the
behavioural differences between the species (and there ARE differences)
should be quantified, measured, and eliminated from the list of
variables. For example - if we could teach monkeys to read, to watch TV
or enjoy movies, and thereby expose them to the same stimuli and
accomodation patterns as humans to, THEN we might be able to look at
primate studies and begin to draw analogies.

But given that we are dealing with different species, and that there
are easily quantifiable behavioral distinctions between these species,
I believe that the onus is on those who posit a relevance of the
information to establish that relevance before it is accepted.

If not, why can't we do studies on sloths, or penguins, or goats, and
extend the results to humans? Do not all mammals have similar
structures in their eyes? What about pigs? Pigs are often compared to
humans as being very 'biologically similar' - does this apply to eyes?
Can we start to run studies on pigs and infer relevance of the results
to humans?

I've asked Otis a number of times to educate the group on why we should
consider his oft-quoted 'primate studies' as having any bearing here,
and he's either not seen the requests, or ignored them.

I think that those who advocate the use of primate studies in this
fashion are just anthropomorphizing. Or plain 'reaching'.

If so, does it not behoove us to establish one way or the other before
accepting his words? Especially since we're dealing with real people
with real problems who may be taking his advice? If this forum were
theoretical in nature, it might be interesting. But in a 'medical'
forum such as this, I see it as dangerous and irresponsible to proceed
on theories that have not been verified / explained to the satisfaction
of all concerned.

If so, does it not behoove us to establish one way or the other before
accepting his words? Especially since we're dealing with real people
with real problems who may be taking his advice? If this forum were
theoretical in nature, it might be interesting. But in a 'medical'
forum such as this, I see it as dangerous and irresponsible to proceed
on theories that have not been verified / explained to the satisfaction
of all concerned.

Dear Eye Question,

Subject:  The natural eye's behavior for a "engineering" perspective.

If you wish to understand my approach, I have posted my
autobiography on my site:

www.myopiafree.com

I remember having some "bad visual habits" as a kid.
I did wonder if these "habits" produced a situation
where my natural eyes changed their refractive
state from a positive value to a negative value.

Obviously as a 6 year old -- I did not know.
But, as an engineer --  I wished to find out.
Rather that relying on "opinions" I felt is wise
to run the experiment myself.  (In principle.)

Since I can not run this type of confirming experiment
on human-primates, I MUST run the experiment
on adolescent primates.

That is how I reach the conclusion that a population
of natural-eye primates change their refractrive state
when:

1.  Placed in a more negative (in diopters) enviroment, and

2. A -3 diopter lens is placed in front of their eyes.

This is my scientific conclusion.  You can form your
own judgment.

If you wish to through this scientific data out the window,
then that is the end of our discussion.

But to further respond:

To prove or disprove the "Otis"  theory would require a large
controlled
group.

Otis> Yes, but is is very hard to "control" young children.  You
can not even check to see if they look through the "plus"
part of the glass.  The primate  studies as NOT BLIND STUDIES,
and are reliable for that reason.  In the blind studies,
you simply can not even verify "compliance".  Indeed
a very difficult situation.

Eye>   I have yet to see a large study such as 1000 kids all slightly
myopic, where 500 have constant wearing of minus lenses and the other
500
use plus lenses.

Otis>  The Oakley-Young study had about 250+ kids.

Eye>  They would then need to be tracked for a period of several
years to have accurate results.

Otis> The Oakley-Young study ran four years.  The + group
showed a down rate of approximately zero diopters (0.025 D)
while the minus group went down at an average of
-1/2 diopter per year, or 2 diopters in four years.

Eye>   Has anyone performed such a study that
would totally invalidate the Otis theory?

Otis>  Depends on who you talk to -- and what
you personally wish to believe.

Otis> The Oakley-Young study convinces me that if
you wish "prevention" you better start before
you begin wearing the minus.  The primate
data is even more powerful on a scientific
level -- because of the complete control
you have over the experimental situation.

Otis> But the Oakley-Young study also
intimates that the decision to prevent
is necessarily an either-or decision,
i.e., there is no getting out of it
once you start wearing that minus.

Eye>  Look at it from the other point of view:

I have seen several responses claiming that research on monkeys is not
considered applicable to humans.

Otis> This is of course crucial. Given the critical nature
of this type of decision, and the fact that PREVENTION
is the second opinion -- I would suggest that
an individual interested in protecting his
vision should review these issues PERSONALLY -- as
the best course of action for him.  Because
once you "commit" to that minu lens,
then that is "it".

Eye>   In many other medical fields, research
done monkeys can be a very useful tool for prediction of human
response.

Otis> Or to test if a device (even in long term use) is even safe!

Otis> Even after all these years -- it is still a good idea to check.
In fact red-dye #2 was checked in this manner.  Why
not the minus?

Why should results of research conducted on monkeys and apes NOT be
considered applicable to humans??

Otis>  Eye -- that is the question you must ask youself.
For me, the primate data is crucial.  If not for you,
then you are restricted to the "bifocal" studies.

Is there evidence to prove or disprove that human eyes respond
differently
than monkey eyes when subjected to long term use of negative lenses?

Otis> This is an "open" question.  I certainly have made
my judgment on that question.  You should also.

Does
anyone know how similar or dissimilar monkeys and apes eyes are to
human
eyes?

Otis>  Genetically, I think there is about a 4 percent difference
in our DNA.  But the crucial issue is your word "dissimilar".

Best,

Otis

I'm just a casual observer, but I see little evidence by either side to

substantiate their claims.

There's evidence that those monkeys don't respond after a certain age, and
that some species don't respond at any age.

-MT