snip
> "Dr" Judy has jumped to a whole series of false conclusions
> about the correct use of the plus lens at the threshold.
[quoted text clipped - 4 lines]
> "farsighted", i.e., myopic or hyperopic. There is no such thing
> as a "normal eye".
I , other eye doctors, vision scientists and vision researchers do not use
the value laden term "normal" (implying that myopia and hyperopia are
abnormal) to describe emmetropia, . Only you use that term and only you
consider non emmetropic eyes to be abnormal.
Vision scientists need to precisely measure and describe refractive error.
The precise definition of emmetropia is "image of object at optical infinity
is focused on the retinal plane when accommodation is at rest", myopia is
defined with the image in front of the retinal plane and hyperopia is
defined with the image behind the retinal plane. These are the accepted
definitions, live with it.
> The entire process of "clearing" your distant vision from
> -1.5 diopters to +0.5 diopters means that the natural eye MUST
> change its refractive status by +2.0 diopters, i.e., you go from
> "myopia" to "hyperopia". Thus your eyes are NEVER normal,
> by using the "false words".
If you feel a need for eyes to be called "normal", try using either
uncorrected or corrected visual acuity instead of refractive error in your
definition. Feel free to specify any minimal level as "normal". Some
examples for best corrected in current use are:
20/20 as "normal" for flying Navy planes
20/30 as "normal" in amblyopia treatment
20/40 to 20/60 as "normal" for driving
better than 20/200 as "normal" for legal/ tax benefit purposes
Generally, we don't consider an eye abnormal if vision can be corrected
with refraction. So there are fewer samples for uncorrected definition in
current use. Here is some:
20/20 as "normal" to apply to some local police forces
20/40 as "normal" to apply to the RCMP
20/40 to 20/60 as "normal" for driving without glasses
If you were to use best corrected VA of better than 20/40 as your
definition, you would likely find close to 90% of people to be normal.
Using 20/200 would define about 95% as normal. Even if you use uncorrected
VA of better than 20/40, you would get about 70% of pre presbyopes and close
to 50% of presbyopes as normal.
> She then talks about "causing" hyperopia, as though it is a
> TERRIBLE situation in an adolescent!
DrJudy
> So, even if near work causes myopia -- and the
> plus-lens use prevents it -- how do we avoid the risk causing
> moderate to high hyperopia in 75% and illiteracy in 100% to save
> 25% of children from myopia? .
Well it is. Hyperopes will often experience discomfort, headaches and even
double vision at near and may have symptoms at far as well. The biggest
risk however, is that hyperopia is associated with poor reading, learning
disability and poor school performance.
J Am Optom Assoc. 1986 Jan;57(1):44-55.
Refractive error and the reading process: a literature analysis.
Grisham JD, Simons HD.
The literature analysis of refractive error and reading performance includes
only those studies which adhere to the rudaments of scientific
investigation. The relative strengths and weaknesses of each study are
described and conclusions are drawn where possible. Hyperopia and
anisometropia appear to be related to poor reading progress and their
correction seems to result in improved performance. Reduced distance visual
acuity and myopia are not generally associated with reading difficulties.
There is little evidence relating astigmatism and reading, but studies have
not been adequately designed to draw conclusions. Implications for school
vision screening are discussed.
The relationship between moderate hyperopia and academic achievement: how
much plus is enough?
Rosner J, Rosner J.
University of Houston, College of Optometry, Texas, USA.
BACKGROUND: There is evidence linking uncorrected hyperopia in children with
academic learning problems. METHODS: This study was designed to test that
hypothesis and--given supportive data--to then address a second topic: the
minimal amount of uncorrected hyperopia that appears to impede elementary
school performance. RESULTS: The refractive status and achievement test
scores of 782 first-through-fifth grade children were compared. CONCLUSIONS:
Statistical analysis indicated significantly lower achievement test scores
among hyperopic children whose refractive errors exceeded 1.25 D (ANOVA F =
12.51; df = 4; p = 0.014).
> To call natural and normal refractive states "defects" or
> "errors" boggles the mind.
As stated earlier, refractive error is the accepted term; "defect" is
neither used nor implied. Only Otis calls refractive error a "defect" and I
agree that calling it a "defect" boggles the mind.
snip
> I have no idea where she gets the "... and illiteracy in
> 100% to save 25% of children from myopia".
I was replying to suggestions by Cathy Hopson that if school children
genetically likely to become myopic used high plus (+10 to +15) full time
for several hours a day or greatly restricted near work that myopia might be
prevented. Since we can't predict who will become myopic, I was pointing
out that, if the animal models are relevant to humans (another topic
altogether), then the not predestined to become myopic plus lens users would
become +8 to +13 hyperopes and all kids would be illiterate due to lack of
reading.
snip
> I do not like becoming nearsighed -- if I
> have a choice to avoid it -- even if it DOES REQUIRE that I always
[quoted text clipped - 4 lines]
> to supply that type of information. Any hope she ever will do
> that?
What do you mean by obligation? I am obliged, as a health professional, to
obtain informed consent from patients before starting therapy. That means
providing to them the pros and cons of the therapy including success rate
and risks.
For your proposed plus lens therapy I would be obliged to say:
"There is a therapy for preventing myopia that, in human clinical studies,
has been shown to not work and to possibly increase the rate of myopia
progression rather than decrease it. If you are not yet myopic and do not
have the genes that will make you myopic then the therapy will likely make
you more hyperopic. There is no test to tell if you have the myopia gene,
so we cannot know in advance if the therapy will prevent myopia and leave
you emmetropic or if it will make you more hyperopic. If this therapy is
for your child, then I must also tell you that hyperopic children have more
problems with reading and poorer school performance than lesser hyperopic
children and myopic children."
How many parents will want to try this unproven therapy that may make their
children poorer readers?
snip
> Judy > We can determine who is actually myopic on an individual
> level. Human clinical trials have not shown any
[quoted text clipped - 4 lines]
> Young is not mentioned nor respected -- even as "the second
> opinion". OSB]
Of the body of research on the use of plus to prevent myopia, one study
(Young) showed a clinically significant effect and one study (O'Leary)
showed that it made things worse. The rest showed little to no effect. So
Otis, here is an offer. I will stop quoting O'Leary if you stop quoting
Young.
> Judy > The other predictors that are present before myopia exists
> only work on a population level, i.e., a population with a
[quoted text clipped - 7 lines]
> will clear his vision by getting his refractive status to
> move from a negative value to a positive value?
I have mentioned the risk of causing hyperopia.
> What
about the risk of the minus lens -- that you will develop
> "stair case" myopia?
Please provide evidence that stair case myopia exists. The animal studies
did not find it.
snip rest of message
Dr Judy
Cathy Hopson - 27 Aug 2004 22:27 GMT
> > I have no idea where she gets the "... and illiteracy in
> > 100% to save 25% of children from myopia".
[quoted text clipped - 7 lines]
> become +8 to +13 hyperopes and all kids would be illiterate due to lack of
> reading.
No suggestions were made to use high plus for several hours a day on
anybody. The studies referenced showed that a few minutes of high plus
counters the effects on axial length of a whole day of hyperopic defocus. I
suggested applying the idea to those who have already exhibited myopic
symptoms. Your erroneous line of thought that this would cause illiteracy
does not follow.
If the method was to be misapplied, you should be able to catch the
hyperopia before +8D, or, most likely, your patients will. Again, your
argument presents, but you don't recognize, environment trumping genetics.
Cathy
Dr Judy - 28 Aug 2004 19:39 GMT
> > > I have no idea where she gets the "... and illiteracy in
> > > 100% to save 25% of children from myopia".
[quoted text clipped - 16 lines]
> symptoms. Your erroneous line of thought that this would cause illiteracy
> does not follow.
If a few minutes a day of myopic defocus is enough to prevent myopia, then
how does myopia ever develop in the first place, as nobody spends all day
with near work? When I put that question to you earlier, you stated in
message news:Yb4Vc.8592aB1.6253@twister.socal.rr.com...
"Certainly the 30% that are myopes need closer to 50% of their time spent
viewing real distance, not just barely over one meter, to keep from
progressing due to near work. It's
likely you would find emmetropes and hyperopes can handle near work at other
points of the 50% to 90% range, but that's another discussion topic."
> If the method was to be misapplied, you should be able to catch the
> hyperopia before +8D, or, most likely, your patients will. Again, your
> argument presents, but you don't recognize, environment trumping genetics.
I think we have a disagreement on the meaning of genetic vs environment
cause. Further discussion is futile until we agree on terms.
By genetic, I mean that either the person has an unusual genetic response to
a normal environment (a response that people with different genetic makeup
do not have) or the environment does not affect the response at all . For
examples: eating wheat causes gastric damage in people with the celiac gene
but does not harm anyone else. The colour of my eyes is independent of
environment.
By environment, I mean that the person has a normal genetic response to an
unusual environment, and that unusual environment causes the same response
in all. For example, air pollution and smoking causes damage to lung tissue
in all people. Severe malnutrition can cause my hair to thin, fall out and
fade in colour. Exposure to sun causes my skin to tan.
With myopia, I have not yet seen an argument that something in the
environment causes myopia. The animal studies were looking at how the
visual system recovers from refractive error present at birth, they do not
provide insight into how myopia develops after birth, nor do they provide
evidence that near work is the primary cause of myopia. Human studies have
consistently found that family history of myopia is a strong predictor of
myopia and near work is not.
Dr Judy
Cathy Hopson - 29 Aug 2004 07:00 GMT
> I think we have a disagreement on the meaning of genetic vs environment
> cause. Further discussion is futile until we agree on terms.
[quoted text clipped - 21 lines]
>
> Dr Judy
Do you really see the same response, i.e., no range of response, in all who
are exposed to the sun? Do you really not see the sun as a viable component
of a normal environment?
Do you really still see family history as only a genetics source? When
adults smoke, saying they grew up with it, do they smoke because of family
history genetics? The damage response of smoking is, again, a range of
response. It is not the same for all. By your definition, doesn't the var
iance of a little lung damage in some and cancer in others mean it has a
genetic cause? But you named lung tissue damage from smoking as an example
of environmentally caused, the same response for all.
We can agree on terms when they make sense beyond your own convenience. I
know what you're trying to say just as well as you know what I'm trying to
say. We don't even agree on the meanings of near work, plus lens, research,
and purpose. You also seem to be substituting near work when you mean
accommodation. I argue only from what ODs on this newsgroup have presented
as support for their positions, without accepting unsupported conclusions,
of course. Want to try another set of made-up definitions, or shall we call
it a day?
Cathy