vision in 1250 A.D.
Paul Hathaway
the centuries before the development of glasses. How can they focus to
see the
world?? Just wondering because if I remove my glasses with 900 grade,
I can't
see what's 2 meters in front of me.. so how can the people with myopia
centuries ago see? How can they work with blur visions? Are they
confined to
rooms like bedridden patients?
Paul
maf
news:c39a940b.03012...@posting.google.com...
Most people did live to be very old back then due to disease, illness, and
wars. Remember that without antibiotics, a regular infection could easily
kill someone. Also, no one was driving cars, so seeing off into the distance
was not as critical. If you can see 2 meters, you can scrub floors on your
hands and knees, or work in the fields tending crops.
maf
> wars. Remember that without antibiotics, a regular infection could easily
> kill someone. Also, no one was driving cars, so seeing off into the
distance
> was not as critical. If you can see 2 meters, you can scrub floors on your
> hands and knees, or work in the fields tending crops.
>
"Most people did NOT live to be very old back then"
MS
"maf" <m...@switchboard.net> wrote in message
news:axRX9.963$H14....@news.uswest.net...
That would only be of importance if we were discussing presbyopia. Since
most people didn't read back then, presbyopia wouldn't be a problem anyhow.
Paul was discussing myopia, which usually begins in childhood, so if the
same percentage of people had myopia then as now, starting at the same age,
and if there were no kinds of corrective lenses available (when were glasses
first invented?), I also can't imagine how myopes got by. I couldn't
function at all without corrective lenses.
If the theories of those who say that a lot of close work at an early age
induce myopia, then there were far less myopes, because not many people went
to school and did a lot of reading at an early age. (Have there been studies
with illiterate tribes nowadays, concerning frequency of myopia?) If the
theory that myopia is completely genetic, not at all environmental, is true,
then there should have been the same frequency of myopia then as there is
now, which does make one wonder how high myopes could have survived without
corrective lenses or corrective surgery. If they all died out early due to
the "survival of the fittest", myopia would have become extinct, and we
would not have such a high percentage of myopes today.
I suspect a combination of genetics and environment, although that's just a
guess.
>
>
>
William Stacy
The visual demands were much different in those days, so much so that
myopia development was probably fairly limited anyway (no computers, no
books, very little sustained close work). Having said that, those that
did develop myopia probably gravitated toward close work, like artisans,
jewlers, seamstresses, etc. BTW I think myopia was an evolutionary
positive, since myopes probably stayed more at home and had more
opportunity to procreate. They could also get a closer, detailed look at
the potential mates.
As to being disabled, I once examined an 18 year old girl who had never
had an eye exam and was -11.00 O.U. She was bussing tables at a
restaurant, and seemed somewhat mentally challenged, messy and clumsy,
although she *was* making a living at it. I fit her with contacts and her
personality changed 1000%. She turned into a vibrant, beautiful and
obviously intelligent person.
One of the finer rewards of being an optometrist.
w.stacy, o.d.
Edward
> > "Most people did NOT live to be very old back then"
>
> That would only be of importance if we were discussing presbyopia. Since
> most people didn't read back then, presbyopia wouldn't be a problem
anyhow.
Actually, it would also be of importance if he were suggesting that
uncorrected myopes died prior to reaching reproductive age (i.e. natural
selection). That may have been true to some extent, however, I’m not sure
if that is what he was suggesting.
> Paul was discussing myopia, which usually begins in childhood, so if the
> same percentage of people had myopia then as now, starting at the same
age,
> and if there were no kinds of corrective lenses available (when were
glasses
> first invented?),
Not sure where you got that the same percentage of people had myopia then as
now.
> I also can't imagine how myopes got by. I couldn't
> function at all without corrective lenses.
I think maf was suggesting that uncorrected quite a few myopes could “get
by” because they didn’t have the same visual requirements that most of us
have today.
> If the
> theory that myopia is completely genetic, not at all environmental, is
true,
> then there should have been the same frequency of myopia then as there is
> now,
The “then” is not supported by the “if”. If myopia is completely or
primarily genetic, it makes sense that there would be MORE myopes now
because it was much more of a life-threatening condition to the caveman or
someone in the Middle Ages than it is to a 21st century San Franciscan.
> which does make one wonder how high myopes could have survived without
> corrective lenses or corrective surgery.
I think maf was suggesting that quite a few uncorrected myopes could “get
by” because they didn’t have the same visual requirements that most of us
have today.
> If they all died out early due to
> the "survival of the fittest", myopia would have become extinct, and we
> would not have such a high percentage of myopes today.
Not all “genetic” myopes “died out”; however, I would venture to say that
they “died out” or failed to pass on their DNA more than their emmetropic
counterparts, though.
Edward
Edward
> The visual demands were much different in those days, so much so that
> myopia development was probably fairly limited anyway (no computers, no
> books, very little sustained close work). Having said that, those that
> did develop myopia probably gravitated toward close work, like artisans,
> jewlers, seamstresses, etc. BTW I think myopia was an evolutionary
> positive, since myopes probably stayed more at home and had more
> opportunity to procreate. They could also get a closer, detailed look at
> the potential mates.
That's assuming they didn't walk off a cliff or into a lion's den prior to
reproducing. Those -3.00 or -4.00 myopes that survived to reproductive age
might have had trouble scouting-out potential mates to get that close to
them, too.
> As to being disabled, I once examined an 18 year old girl who had never
> had an eye exam and was -11.00 O.U. She was bussing tables at a
> restaurant, and seemed somewhat mentally challenged, messy and clumsy,
> although she *was* making a living at it. I fit her with contacts and her
> personality changed 1000%. She turned into a vibrant, beautiful and
> obviously intelligent person.
I think an -11.00 (uncorrected) 18 year old was more likely to reach that
age in the 20th century than in the 13th century. Being "mentally
challenged, messy and clumsy" doesn't help a person to propagate his or her
genes, either.
> One of the finer rewards of being an optometrist.
Good work!
Edward
Otis Brown
Re > Paul was discussing myopia, which usually begins in childhood, so
if the
same percentage of people had myopia then as now, starting at the same
age,
and if there were no kinds of corrective lenses available (when were
glasses
were first invented?), I also can't imagine how myopes got by. I
couldn't function at all without corrective lenses.
You were right about 1250 AD, and also "right" about
1813 AD, as confirmed by Dr. James Ware. Very
few eyes would have a negative focal state if they
are always looking in the distance. Their focal
state would normally be between 0.0 to +1.5 diopters.
Best,
Otis
******
From a paper on nearsighedness prevention:
The evidence began to surface a long time ago about the problem of the
reading environment. In a paper presented to the Royal Society of
London, in 1813, the Honorable James Ware related his observations on
nearsightedness, [5]. He found that the educated officers of the
Queen's Guard were frequently nearsighted while among the 10,000 foot
guards a scant half-dozen were nearsighted!
None of the foot guards had been educated enough to be able to read.
Nearsightedness, myopia, was correctly attributed to the habit of
looking at near objects.
In modern times, Dr. Frances Young studied the Eskimos of Point Barrow
before and after the introduction of schools. You can guess the
results of his study. There was found a sudden and dramatic increase
in myopia where nearly none was present in the past. A very large
percentage of the children in schools became myopic, [6]. A reading
environment can be hazardous for the health of your eyes!
Tom S
distant vision a good portion of the time, so their eyes had no reason to
adapt to nearpoint stress like they do today. Also, they probably ate a
much better diet than most people today, so when they did focus it didn't
put much stress on their eyes. The fact that myopia has increased so
sharply as societies have become modernized points to environment playing a
big role.
Edward
> Myopia was probably close to non-existant back then. Most people used
their
> distant vision a good portion of the time, so their eyes had no reason to
> adapt to nearpoint stress like they do today.
That assumes myopia is an adaptive condition and not a genetic trait. It's
similar to saying the long neck of a giraffe is an adaptive condition and
not a genetic trait.
> Also, they probably ate a
> much better diet than most people today, so when they did focus it didn't
> put much stress on their eyes.
First of all, I'm skeptical that people in the Middle Ages ate diets better
than most people today. Secondly, I don't recall any research that has
compared the affects of diet on accommodation in 21st Century people to that
of people in the Middle Ages.
> The fact that myopia has increased so
> sharply as societies have become modernized points to environment playing
a
> big role.
That could mean two different things, and I'm not sure which one you had in
mind. You could be implying that the visual tasks of modern societies
involve more nearwork, and that that nearwork environment is causing myopia.
Or you could be implying that myopia is less likely to be a life-threatening
condition in the environment of modern societies, therefore, myopes in
modern societies are more likely to reach reproductive age and pass along
their myopic genes. There is an environmental factor to both ideas.
Edward
Han Sibot
by fluorescein angiography. My main practical problem was a blurred ring
around center of the visual field, having the same diameter as the fovea (5
degrees). These days it is active again, with the same blurred ring, so next
week I have an appointment at ophtalmologist.
Now I am curious about two observations:
1) When shining with a narrow pen torch through the eyelid and the sclera,
and looking away at the same time, the area of the ring together with the
central circle within it appears dimly illumated, uniform except for retinal
blood vessel shadows. In addition a brighter light spot appears at the
perimeter of the ring, at a position which is diametral opposite compared to
the pen torch. I was wondering if this could be a manifestation of the
foveal reflex that is otherwise seen by the ophtalmologist during
funduscopy. It only occurs in my right eye, not in my normal left eye.
2) why might the blurred area be ring shaped? Outside that ring, as well as
inside it, vision is sharp.
Paul Hathaway
> > sharply as societies have become modernized points to environment playing
> a
> > big role.
>
Hi, are there really documented case histories of myopia in centuries past?
If not, the invention of electric lamp may have sparked myopia. I mean,
in centuries past, there is only candle light and fire at night and people
don't use their eyes but sleep early. In the modern age, we see bright light
everywhere at night in the flourescent lamp, light bulb, TV, computer monitor,
etc. Could any of these increase myopia or even create myopia in case
there was no such documented case in centuries past?
Paul
MS
"Edward" <n...@spam.com> wrote in message
news:iDVX9.11531$eM6....@rwcrnsc51.ops.asp.att.net...
> " MS" wrote:
> > > "Most people did NOT live to be very old back then"
> >
> > That would only be of importance if we were discussing presbyopia. Since
> > most people didn't read back then, presbyopia wouldn't be a problem
> anyhow.
>
> Actually, it would also be of importance if he were suggesting that
> uncorrected myopes died prior to reaching reproductive age (i.e. natural
> selection). That may have been true to some extent, however, I’m not sure
> if that is what he was suggesting.
But if that was the case, the trait would have died out in evolution (from
myopes not reproducing), and what would account for the high percentage of
myopes today? (If one assumes that myopia is solely genetic. I'm not making
that assumption, but just looking at the theory.)
> > Paul was discussing myopia, which usually begins in childhood, so if the
> > same percentage of people had myopia then as now, starting at the same
> age,
> > and if there were no kinds of corrective lenses available (when were
> glasses
> > first invented?),
>
> Not sure where you got that the same percentage of people had myopia then
as
> now.
I didn't say they did. Don't you see the word "if" in that sentence? Again,
I was speculating about the theories of whether myopia is purely genetic or
purely environmental, or some of both.
> > I also can't imagine how myopes got by. I couldn't
> > function at all without corrective lenses.
>
> I think maf was suggesting that uncorrected quite a few myopes could “get
> by” because they didn’t have the same visual requirements that most of us
> have today.
They didn't have the same CLOSE visual requirements--they didn't do all the
paperwork, computers, etc., that we do today. I would assume that they had
great need for distance visual acuity--if you didn't see that saber-toothed
tiger coming at you until it bit off your foot, you would be in trouble, no?
>
> > If the
> > theory that myopia is completely genetic, not at all environmental, is
> true,
> > then there should have been the same frequency of myopia then as there
is
> > now,
>
> The “then” is not supported by the “if”. If myopia is completely or
> primarily genetic, it makes sense that there would be MORE myopes now
> because it was much more of a life-threatening condition to the caveman or
> someone in the Middle Ages than it is to a 21st century San Franciscan.
I think you have evolution backwards, Edward. You do seem now to agree with
me that myopia would have been a life-threatening condition to the caveman.
(Before you wrote that they had "lesser visual requirements".) If all the
myopic cavemen had been killed of early before they could reproduce, the
gene for myopia would have become rarer over generations, as less myopes
would have reproduced, and there would be less myopes today than there were
then. (Again, just speculating about the theory that myopia is purely
genetic, I'm not agreeing with it.)
MS
"William Stacy" <wst...@obase.net> wrote in message
news:3E30217D...@obase.net...
> As to being disabled, I once examined an 18 year old girl who had never
> had an eye exam and was -11.00 O.U. She was bussing tables at a
> restaurant, and seemed somewhat mentally challenged, messy and clumsy,
> although she *was* making a living at it. I fit her with contacts and her
> personality changed 1000%. She turned into a vibrant, beautiful and
> obviously intelligent person.
This is hard for me to imagine, that someone could have -11.00 diopters of
myopia, and have reached the age of 18 without ever having an eye exam
previously. And that she could have functioned at all in life, including
bussing tabels at a restaurant (even if clumsy).
(I'm not doubting the veracity of your story, only that it's very
surprising!)
(Perhaps she was using some other cues besides vision, as a blind person
would--hearing, touch, etc. I don't know if there are any totally blind
restaurant buspersons. Did she have a seeing-eye-dog?)
That is over twice as much as my myopia (my latest glasses prescription had
distance of -5.00 in right eye, -5.50 in left), and I couldn't function one
day without corrective lenses, even staying home all day. With -11, how
could she even see the tables, the people, the dishes, etc.?
I guess she had never gone to get a driver's license!
What myopia prescription is considered 'legally blind"?
Z.Z.
>
> This is hard for me to imagine, that someone could have -11.00
> diopters of myopia, and have reached the age of 18 without ever having
> an eye exam previously. And that she could have functioned at all in
> life, including bussing tabels at a restaurant (even if clumsy).
> That is over twice as much as my myopia (my latest glasses
> prescription had distance of -5.00 in right eye, -5.50 in left), and I
> couldn't function one day without corrective lenses, even staying home
> all day. With -11, how could she even see the tables, the people, the
> dishes, etc.?
While I agree that someone getting to that age without having an eye exam
is hard to imagine, I think you greatly exaggerate how 'blind' the person
would be. I'm -12 and -13 and I could function without glasses. I
couldn't see movies or TV but from what I have seen of them I wouldn't be
missing much. I could probably read, too, except that my nose gets in the
way. I probably couldn't drive (not safely, anyway) but I can get around
without running into things and I could certainly see well enough to bus
tables.
I find it amusing that so many people with mild myopia (better than -5)
think they have it so bad. I hear of people with -1 or -2 having lasik
because they're so miserable. Sorry, I don't have much sympathy. I've
worn glasses for almost 50 yrs and don't consider them a handicap. There
is almost nothing they've kept me from doing except joining the Army and
probably getting myself killed in Vietnam.
I think you greatly overestimate how debilitating it would be and
underestimate how adaptive people are. To a large extent, myopia (and any
other condition) is only a handicap if you let it be one.
Polar
<m...@nospam.com> wrote:
>
>"Edward" <n...@spam.com> wrote in message
>news:iDVX9.11531$eM6....@rwcrnsc51.ops.asp.att.net...
>> " MS" wrote:
>> > > "Most people did NOT live to be very old back then"
>> >
>> > That would only be of importance if we were discussing presbyopia. Since
>> > most people didn't read back then, presbyopia wouldn't be a problem
>> anyhow.
>>
>> Actually, it would also be of importance if he were suggesting that
>> uncorrected myopes died prior to reaching reproductive age (i.e. natural
>> selection). That may have been true to some extent, however, I’m not sure
>> if that is what he was suggesting.
>
>But if that was the case, the trait would have died out in evolution (from
>myopes not reproducing), and what would account for the high percentage of
>myopes today? (If one assumes that myopia is solely genetic. I'm not making
>that assumption, but just looking at the theory.)
This reminds me of an theory articulated to me by an O.D. years ago.
He noted that near-sightedness might have been a *plus* during, say,
the Dark Ages, and even Middle Ages, when the rulers were illiterate.
People who could read, which were mostly Jews (and some monks) had
their lives spared because they were useful to the savage rulers.
They therefore lived to pass on their genes, and so on down the line.
Any opinions? I note that below in this thread someone also mentions
the Middle Ages.
--
Polar
MS
environmental or hereditary, or a combination of the two. (As I wrote, I
suspect the third option.)
Those who suspect environmental causes point to the increasing amount of
close work in the modern age--reading, writing, computers, etc., at a young
age, having a connection to the increase in myopia in modern times. That
certainly makes some sense to me, although it is probably not the entire
equation, as some children who do just as much close work do not become
myopic.
What just occurred to me is the following--what about television? Has anyone
studied whether a lot of television watching at a young age might increase
incidence of myopia?
For this we wouldn't have to go back to 1250 AD. Have there been any studies
of the incidence of myopia in people born before 1950, and those born after
that date?
It occurred to me that of my two parents, one born 1n 1918, the other born
1920, neither was ever myopic. Yet I and my two brothers, all born in the
1950's, are all three very myopic.
Yet my parents were both always avid readers. Although there weren't
computers in their early years, they certainly did a lot of close work. My
father's profession was as a civil engineer, so he did a lot of drawing
diagrams, etc. My mother was a writer--so besides reading, did a lot of
writing and typing.
Are there statistics of the incidence of myopia in people born between
1900-1950, compared with those born after 1950? We (baby boomers) were the
first generation to grow up watching television. Could that possibly have
affected our vision?
Just wondering, thinking about two parents, both of whom did a lot of close
work, neither was myopic, having three very myopic sons.
Edward
> > > > "Most people did NOT live to be very old back then"
> > >
> > > That would only be of importance if we were discussing presbyopia.
Since
> > > most people didn't read back then, presbyopia wouldn't be a problem
> > anyhow.
> >
> > Actually, it would also be of importance if he were suggesting that
> > uncorrected myopes died prior to reaching reproductive age (i.e. natural
> > selection). That may have been true to some extent, however, I’m not
sure
> > if that is what he was suggesting.
>
> But if that was the case, the trait would have died out in evolution (from
> myopes not reproducing), and what would account for the high percentage of
> myopes today? (If one assumes that myopia is solely genetic. I'm not
making
> that assumption, but just looking at the theory.)
Why do you think that ALL myopes would have failed to reach reproductive
age? There is probably a higher percentage of myopes today because it isn't
a life-threatening condition as it might have been for the some cavemen or
people in the Middle Ages.
> > > Paul was discussing myopia, which usually begins in childhood, so if
the
> > > same percentage of people had myopia then as now, starting at the same
> > age,
> > > and if there were no kinds of corrective lenses available (when were
> > glasses
> > > first invented?),
> >
> > Not sure where you got that the same percentage of people had myopia
then
> as
> > now.
>
> I didn't say they did. Don't you see the word "if" in that sentence?
Again,
> I was speculating about the theories of whether myopia is purely genetic
or
> purely environmental, or some of both.
To speculate means to infer, theorize, or predict from incomplete evidence.
Given that the evidence is incomplete, you inherently make assumptions about
what is not known when you speculate. I was simply wondering how you were
able to assume that the same percentage of people had myopia then as they do
now from the fact that myopia usually begins in childhood. Your speculation
involves a bunch of assumptions about the genetic compostion of caveman
parents or parents in the Middle Ages.
> > I think maf was suggesting that uncorrected quite a few myopes could
“get
> > by” because they didn’t have the same visual requirements that most of
us
> > have today.
>
> They didn't have the same CLOSE visual requirements--they didn't do all
the
> paperwork, computers, etc., that we do today. I would assume that they had
> great need for distance visual acuity--if you didn't see that
saber-toothed
> tiger coming at you until it bit off your foot, you would be in trouble,
no?
They didn’t have the same CLOSE visual requirements nor (as maf suggested)
did they have the same DISTANCE visual requirements. Cavemen, or knights in
the Middle Ages (i.e. 1250 AD), didn’t have to worry about guiding a car
down the freeway or crowded side streets. However, I tend to agree with you
that having poor distance vision was more of a detriment than having good
near vision was a benefit. I was just telling you what maf had suggested.
> > If myopia is completely or
> > primarily genetic, it makes sense that there would be MORE myopes now
> > because it was much more of a life-threatening condition to the caveman
or
> > someone in the Middle Ages than it is to a 21st century San Franciscan.
>
> I think you have evolution backwards, Edward. You do seem now to agree
with
> me that myopia would have been a life-threatening condition to the
caveman.
> (Before you wrote that they had "lesser visual requirements".)
Are you quoting ME? If so, you had better fact check. I might have said
that they did not have the same visual requirements, but I don’t recall ever
writing that they had “lesser visual requirements”.
I agree with you that myopia probably would have been a life-threatening
condition to the caveman, but you’re implying that somewhere in this thread
I changed my view or presented contradictory information to that view.
> If all the
> myopic cavemen had been killed of early before they could reproduce, the
> gene for myopia would have become rarer over generations, as less myopes
> would have reproduced, and there would be less myopes today than there
were
> then. (Again, just speculating about the theory that myopia is purely
> genetic, I'm not agreeing with it.)
You are assuming a major false premise in your speculation. Check it and
you’ll find who has evolution backwards.
What you have assumed is that there were a lot of myopic cavemen to begin
with THEN natural selection took its toll on them. Natural selection had
its affect and because of that there were not a lot of myopic cavemen. Even
so, not ALL myopic cavemen were killed off before they could reproduce.
Mild myopes almost certainly survived to reproduce which eventually gave
rise to moderate myopes then high myopes.
Some inherited traits may be purely genetic, but the process of natural
selection is not; it involves a complex combination of genetics and
environmental factors. Whether you believe it is fully or only partially
genetic, think of myopia as being “suppressed” (not eliminated) in the
population until conditions were right for it to become prevalent. In
modern times, conditions are right and myopia is prevalent.
Edward
Edward
> This reminds me of an theory articulated to me by an O.D. years ago.
> He noted that near-sightedness might have been a *plus* during, say,
> the Dark Ages, and even Middle Ages, when the rulers were illiterate.
> People who could read, which were mostly Jews (and some monks) had
> their lives spared because they were useful to the savage rulers.
> They therefore lived to pass on their genes, and so on down the line.
>
> Any opinions? I note that below in this thread someone also mentions
> the Middle Ages.
I mentioned the Middle Ages because I thought that was the time period to
which the subject line referred (i.e. 1250 AD). Assuming we are talking
about enough myopia to read and not so much that you're walking off cliffs
or into lion's dens, I think your optometrist was probably right. Given
mortality rates in the Dark and Middle Ages, I doubt myopes had much
advantage over emmetropes and low hyperopes; however, their myope probably
made them useful and productive citizens.
Edward
Edward
> While I agree that someone getting to that age without having an eye exam
> is hard to imagine, I think you greatly exaggerate how 'blind' the person
> would be. I'm -12 and -13 and I could function without glasses. I
> couldn't see movies or TV but from what I have seen of them I wouldn't be
> missing much. I could probably read, too, except that my nose gets in the
> way. I probably couldn't drive (not safely, anyway) but I can get around
> without running into things and I could certainly see well enough to bus
> tables.
>
> I find it amusing that so many people with mild myopia (better than -5)
> think they have it so bad. I hear of people with -1 or -2 having lasik
> because they're so miserable. Sorry, I don't have much sympathy. I've
> worn glasses for almost 50 yrs and don't consider them a handicap. There
> is almost nothing they've kept me from doing except joining the Army and
> probably getting myself killed in Vietnam.
>
> I think you greatly overestimate how debilitating it would be and
> underestimate how adaptive people are. To a large extent, myopia (and any
> other condition) is only a handicap if you let it be one.
I think you greatly overestimate how successful in life you would have been
with -12.00 as a caveman or even in the relatively recent Middle Ages.
Edward
Dan Abel
<m...@nospam.com> wrote:
> What myopia prescription is considered 'legally blind"?
I'm not in the business, but I would say "none". Legally blind, for IRS
purposes, is defined as 20/200 *corrected* vision. It doesn't matter how
myopic you are, if it is fully correctable then you really aren't vision
impaired. My worst myopia was -12D.
--
Dan Abel
Sonoma State University
AIS
da...@sonic.net
Paul Hathaway
forward and stretching it. In watching television, is it possible that those
who become myopic are so atune to the television and they want part of the
action that they literally and subconsciously exert their eyeball to stretch
forward closer to the TV and action. And in time, the elongation become
permanent and they become myopic?
Paul
" MS" <m...@nospam.com> wrote in message news:<10435190...@news-1.nethere.net>...
MS
> To speculate means to infer, theorize, or predict from incomplete
evidence.
> Given that the evidence is incomplete, you inherently make assumptions
about
> what is not known when you speculate. I was simply wondering how you were
> able to assume that the same percentage of people had myopia then as they
do
> now from the fact that myopia usually begins in childhood. Your
speculation
> involves a bunch of assumptions about the genetic compostion of caveman
> parents or parents in the Middle Ages.
I'm sorry, but I didn't assume that at all. I did not predict. I did not
assume the genetic composition of cavemen.
> They didn’t have the same CLOSE visual requirements nor (as maf suggested)
> did they have the same DISTANCE visual requirements. Cavemen, or knights
in
> the Middle Ages (i.e. 1250 AD), didn’t have to worry about guiding a car
> down the freeway or crowded side streets.
Well, as I said, they did have to see that wild animal coming from far away,
or the knight on horseback coming from far away to attack their castle! I
would say they definitely had strong visual requirements for distance, more
so than today, in which we spend most of our time indoors, not looking so
far away.
> > If all the
> > myopic cavemen had been killed of early before they could reproduce, the
> > gene for myopia would have become rarer over generations, as less myopes
> > would have reproduced, and there would be less myopes today than there
> were
> > then. (Again, just speculating about the theory that myopia is purely
> > genetic, I'm not agreeing with it.)
>
> You are assuming a major false premise in your speculation. Check it and
> you’ll find who has evolution backwards.
Well, evolution is usually considered to be "survival of the fittest".
Uncorrected myopia would have been a big drawback to survival in those days.
If many people became myopic in childhood in those days as they do now (note
the word "if", I don't "assume" that was the case at all), many of those
children would not survive to become adults and reproduce, a much higher
percentage of non-survival than among emmetropes. With less myopes
reproducing, the gene for myopia would become less widespread in future
generations.
Is that "backwards evolution"? Seems pretty straightforward to me.
Once again, i was just examining the theory that myopia is purely genetic. I
was not agreeing with it (I don't, as stated) or assuming anything.
> What you have assumed is that there were a lot of myopic cavemen to begin
> with
I didn't assume that at all. Once again, i was just examining the theory
about myopia being purely genetic, a theory that I think is probably not
true (although there quite probably is some kind or genetic predilection for
becoming myopic). If it were purely genetic, then one would have to assume
that it always existed in human beings, even if they were not engaged in
close work, and did not have lenses to correct it. If that were the case
(please not the use of "if", subjunctive case), uncorrected myopia would
certainly have been a detriment to survival in those days, and as less
myopes lived long enough to reproduce, the trait would have decreased in the
population.
> Some inherited traits may be purely genetic, but the process of natural
> selection is not; it involves a complex combination of genetics and
> environmental factors. Whether you believe it is fully or only partially
> genetic, think of myopia as being “suppressed” (not eliminated) in the
> population until conditions were right for it to become prevalent. In
> modern times, conditions are right and myopia is prevalent.
I don't disagree with that. I think you really misread what I wrote,
assuming "assumptions" that weren't there. I wrote that in my uninformed
opinion (in other words, my guess) myopia is probably caused by a
combination of of genetic and environmental factors. That statement is not
really very different from what you write in the above paragraph.
MS
"Polar" <sme...@mindspring.com> wrote in message
news:59h53vogagh7fr72c...@4ax.com...
> This reminds me of an theory articulated to me by an O.D. years ago.
> He noted that near-sightedness might have been a *plus* during, say,
> the Dark Ages, and even Middle Ages, when the rulers were illiterate.
> People who could read, which were mostly Jews (and some monks) had
> their lives spared because they were useful to the savage rulers.
> They therefore lived to pass on their genes, and so on down the line.
That doesn't make any sense to me. Why would it be easier for myopes to read
than emmetropes? Perhaps later in life, at the time of presbyopia, but
people probably didn't live long enough to become presbyopic in those days.
MS
"Z.Z." <nob...@nowhere.com> wrote in message
news:Xns930E66CAA1B...@68.6.19.6...
> While I agree that someone getting to that age without having an eye exam
> is hard to imagine, I think you greatly exaggerate how 'blind' the person
> would be. I'm -12 and -13 and I could function without glasses. I
> couldn't see movies or TV but from what I have seen of them I wouldn't be
> missing much. I could probably read, too, except that my nose gets in the
> way. I probably couldn't drive (not safely, anyway) but I can get around
> without running into things and I could certainly see well enough to bus
> tables.
Well, that's hard for me to imagine. I know that with my -5 vision, without
glasses or contacts I could hardly function at all. It's hard even to see
what is on the floor, much less so the clients at the tables with their food
and plates. Yes, I can see that something is there, but it's all quite
blurry and unclear.
Why don't you spend a day without your glasses (and don't spend all day in
bed! ;-) ), and tell us what it is like.
I can't imagine how that girl functioned in school. It sounds like she
hadn't been a good student, but I can't see how she functioned at all there,
and how her myopia could not have been noticed, and no one recommended she
get an eye exam, before reaching the age of 18.
Polar
OK, I omitted something. (whole thing is rather cloudy in my mind
anyway, as you could probably tell): I think he was talking about
people who wore glasses; therefore were able to see the documents they
worked on. Did they have eyeglasses in the Dark/Middle Ages?
Straight question.
Also, to your point about longevisty: ISTR that Jews lived longer
(when they weren't murdered by Christians) because of Biblical rules
about cleanliness, etc. Maybe monks did also, because of isolation in
the monasteries.
--
Polar
suzee
>
> On Sat, 25 Jan 2003 20:13:07 -0800, " MS"
> <m...@nospam.com> wrote:
>
> >
> >"Polar" <sme...@mindspring.com> wrote in message
> >news:59h53vogagh7fr72c...@4ax.com...
> >
> >> This reminds me of an theory articulated to me by an O.D. years ago.
> >> He noted that near-sightedness might have been a *plus* during, say,
> >> the Dark Ages, and even Middle Ages, when the rulers were illiterate.
> >> People who could read, which were mostly Jews (and some monks) had
> >> their lives spared because they were useful to the savage rulers.
> >> They therefore lived to pass on their genes, and so on down the line.
> >
> >That doesn't make any sense to me. Why would it be easier for myopes to read
> >than emmetropes? Perhaps later in life, at the time of presbyopia, but
> >people probably didn't live long enough to become presbyopic in those days.
>
> OK, I omitted something. (whole thing is rather cloudy in my mind
> anyway, as you could probably tell): I think he was talking about
> people who wore glasses; therefore were able to see the documents they
> worked on. Did they have eyeglasses in the Dark/Middle Ages?
> Straight question.
I'm not sure there were glasses until maybe... 15/16th Century? Not
certain about that. I thought he meant that those who were nearsighted
anyway had an advantage in reading.
> Also, to your point about longevisty: ISTR that Jews lived longer
> (when they weren't murdered by Christians) because of Biblical rules
> about cleanliness, etc. Maybe monks did also, because of isolation in
> the monasteries.
The Jewish dietary laws were also more healthful, so could have
contributed to longer lives, as well. I'm not so sure about the
cleanliness habits in monasteries (weren't baths forbidden by the
Church?), but they probably had good wholesome food and weren't exposed
to the outside world much.
sue
Jan
"Paul Hathaway" <paulha...@myeweb.com> schreef in bericht
news:c39a940b.03012...@posting.google.com...
> In Myopia. The eye is elongated, it's like someone is pulling your eyeball
> forward and stretching it. In watching television, is it possible that
those
> who become myopic are so atune to the television and they want part of the
> action that they literally and subconsciously exert their eyeball to
stretch
> forward closer to the TV and action. And in time, the elongation become
> permanent and they become myopic?
>
> Paul
Thanks to you Paul,
Now I discovered why my arms get longer.
Watching TV, I always have to reach out for the chips on the table in front
of me.
Jan (normally Dutch spoken)
Polar
>Polar wrote:
>>
>> On Sat, 25 Jan 2003 20:13:07 -0800, " MS"
>> <m...@nospam.com> wrote:
>>
>> >
>> >"Polar" <sme...@mindspring.com> wrote in message
>> >news:59h53vogagh7fr72c...@4ax.com...
>> >
>> >> This reminds me of an theory articulated to me by an O.D. years ago.
>> >> He noted that near-sightedness might have been a *plus* during, say,
>> >> the Dark Ages, and even Middle Ages, when the rulers were illiterate.
>> >> People who could read, which were mostly Jews (and some monks) had
>> >> their lives spared because they were useful to the savage rulers.
>> >> They therefore lived to pass on their genes, and so on down the line.
>> >
>> >That doesn't make any sense to me. Why would it be easier for myopes to read
>> >than emmetropes? Perhaps later in life, at the time of presbyopia, but
>> >people probably didn't live long enough to become presbyopic in those days.
>>
>> OK, I omitted something. (whole thing is rather cloudy in my mind
>> anyway, as you could probably tell): I think he was talking about
>> people who wore glasses; therefore were able to see the documents they
>> worked on. Did they have eyeglasses in the Dark/Middle Ages?
>> Straight question.
>
>I'm not sure there were glasses until maybe... 15/16th Century? Not
>certain about that. I thought he meant that those who were nearsighted
>anyway had an advantage in reading.
Yes, that's probably nearer to the explanation. People who were not
allowed to own land, so they could be farmers and cattle-raisers like
in the Old Country, had to turn to book work to earn a living. The
"nobility" of that period were actually *proud* of being illiterate.
Their ideal was the sword, combat, war. "Clerks" were treated with
contempt as unfortunate necessities.
>
>> Also, to your point about longevisty: ISTR that Jews lived longer
>> (when they weren't murdered by Christians) because of Biblical rules
>> about cleanliness, etc. Maybe monks did also, because of isolation in
>> the monasteries.
>
>The Jewish dietary laws were also more healthful, so could have
>contributed to longer lives, as well. I'm not so sure about the
>cleanliness habits in monasteries (weren't baths forbidden by the
>Church?),
Ouch! That bad?? I know people weren't too cleanly during the time
under discussion. In fact, I have read more than once that when the
Spaniards arrived in the New World, they stank so badly that the
near-naked natives, who bathed regularly, could hardly bear to be near
what wafted out of their heavy clothes and sweaty bodies.
but they probably had good wholesome food and weren't exposed
>to the outside world much.
Yes, that stress factor is very, very important, as we are finding out
in our consumerist, materialist-driven society!!
And your point about "good, wholesome food" is well taken!
Organic. No chemical additives, no GM, no irradiation. Sigh!
Back to basics!
(excuses self to go into garden to munch on the first pea pods, and
survey the ripening oranges).
--
Polar
Otis Brown
Re
Paul> Could any of these (TV, bright lights, etc.) increase myopia or even
> create myopia in case there was no such documented case in centuries past?
It is always pleasant to speculate on these matters. From the
report of James Ware, (where only the educated officers were nearsighed
versus the soldiers, where only 1 in 1,000 were nearsighed) I would
suggest that the general population who could not read had
a consistent positive focal state of from zero to +2.0 dipters
and associated clear distant vision.
Opinions vary on that point however.
When the original theory of nearsighedness was proposed in the
1860's (Donders-Helmholtz), the percentage of people who
were "nearsighted" was very small indeed.
For that reason, nearsightedness was considered an
abberation, and very rare indeed.
Times change, and now a huge number of people have made
themselves nearsighed (i.e., their eyes adapt their
focal state to the "reading" enviroment. Here are
the statistics of the eye adapting to both
a minus lens and a reading enviroment -- IMHO.
MYOPIA PREVALENCE FOR MEDICAL STUDENTS
Re: Changes in ocular refraction and its components
among medical students - a 5-year longitudinal study", Optom.
Vis. Sci., 73:495-498, 1996) found that in a study of 345
National Taiwan University medical students, the myopia
prevalence increased from 92.8% to 95.8%! over the five year
period.
At this point, it would be difficult to say that the same
percentage of normal "cavemen" were nearsighed as compared with
today's normal "modern man".
Do we "blame" our genetics, or do we "blame"
the minus lens?
Enjoy,
Otis
Edward
>
> > To speculate means to infer, theorize, or predict from incomplete
> evidence.
> > Given that the evidence is incomplete, you inherently make assumptions
> about
> > what is not known when you speculate. I was simply wondering how you
were
> > able to assume that the same percentage of people had myopia then as
they
> do
> > now from the fact that myopia usually begins in childhood. Your
> speculation
> > involves a bunch of assumptions about the genetic compostion of caveman
> > parents or parents in the Middle Ages.
>
> I'm sorry, but I didn't assume that at all. I did not predict. I did not
> assume the genetic composition of cavemen.
An IF/THEN statement is a supposition. To “suppose” is to “assume”.
> > They didn’t have the same CLOSE visual requirements nor (as maf
suggested)
> > did they have the same DISTANCE visual requirements. Cavemen, or
knights
> in
> > the Middle Ages (i.e. 1250 AD), didn’t have to worry about guiding a car
> > down the freeway or crowded side streets.
>
> Well, as I said, they did have to see that wild animal coming from far
away,
> or the knight on horseback coming from far away to attack their castle! I
> would say they definitely had strong visual requirements for distance,
more
> so than today, in which we spend most of our time indoors, not looking so
> far away.
And as I said in the rest of the preceding quote that you snipped:
“However, I tend to agree with you that having poor distance vision was more
of a detriment than having good near vision was a benefit. I was just
telling you what maf had suggested.”
> > > If all the
> > > myopic cavemen had been killed of early before they could reproduce,
the
> > > gene for myopia would have become rarer over generations, as less
myopes
> > > would have reproduced, and there would be less myopes today than there
> > were
> > > then. (Again, just speculating about the theory that myopia is purely
> > > genetic, I'm not agreeing with it.)
> >
> > You are assuming a major false premise in your speculation. Check it
and
> > you’ll find who has evolution backwards.
>
> Well, evolution is usually considered to be "survival of the fittest".
> Uncorrected myopia would have been a big drawback to survival in those
days.
> If many people became myopic in childhood in those days as they do now
(note
> the word "if", I don't "assume" that was the case at all), many of those
> children would not survive to become adults and reproduce, a much higher
> percentage of non-survival than among emmetropes. With less myopes
> reproducing, the gene for myopia would become less widespread in future
> generations.
>
> Is that "backwards evolution"? Seems pretty straightforward to me.
It is most definitely backwards to “speculate”, as you did previously and
are doing again, that there was a population of myopic cavemen or cavemen
children THEN natural selection took its toll. It ignores that natural
selection governs how many cavemen and cavemen children (therefore cavemen
parents) exist in the first place.
> Once again, i was just examining the theory that myopia is purely genetic.
I
> was not agreeing with it (I don't, as stated) or assuming anything.
Whether you call it “speculating” or “examining a theory”, an IF/THEN
statement is a supposition. And to “suppose” is to “assume”.
> > What you have assumed is that there were a lot of myopic cavemen to
begin
> > with
>
> I didn't assume that at all.
An IF/THEN statement is a supposition. To “suppose” is to “assume”.
> Once again, i was just examining the theory
> about myopia being purely genetic, a theory that I think is probably not
> true (although there quite probably is some kind or genetic predilection
for
> becoming myopic). If it were purely genetic, then one would have to assume
> that it always existed in human beings, even if they were not engaged in
> close work, and did not have lenses to correct it. If that were the case
> (please not the use of "if", subjunctive case), uncorrected myopia would
> certainly have been a detriment to survival in those days, and as less
> myopes lived long enough to reproduce, the trait would have decreased in
the
> population.
IF ONE made the conclusion that “the trait (of myopia) would have decreased
in the population”, then that conclusion would NOT be supported by the
assumption that ONE “had to” assume. If ONE assumed fewer and fewer myopes
lived long enough to reproduce, then inherent in ONE’S assumption is that
ONE also assumed there was a population of myopes to begin with for which
natural selection could take its toll on. If ONE assumed that there was a
population of myopes to begin with for which natural selection could take
its toll on, then ONE’s assumption would be supported by a theory of
creationism, NOT a theory of evolution or natural selection.
If ONE assumed that myopia in humans is purely (or partially) genetic, then
ONE would assume that it initially existed in a human being that had a DNA
mutation for myopia who was able to reproduce and pass along his or her DNA
containing that gene. If ONE assumed that myopia were a detriment to
survival in those days, then ONE could assume that not every myopic human
(or human carrying the DNA for myopia) would survive to reproduce and pass
along his or her DNA. If ONE assumed that myopia were a detriment to
survival in those days, then ONE could NOT assume that every myopic human
(or human carrying the DNA for myopia) would not survive to reproduce and
pass along that DNA. If ONE assumed that myopia were a detriment to
survival in those days, then ONE could assume that some myopic humans (or
humans carrying the DNA for myopia) would survive to reproduce and pass
along their DNA. If ONE assumed that some myopic humans (or human carrying
the DNA for myopia) would survive to reproduce and pass along their DNA,
then ONE could make similar assumptions about their offspring. Even if ONE
assumed that myopia were a detriment to survival at a particular time in
history, ONE could assume that the DNA for myopia would not necessarily be
eliminated from the gene pool. Even if ONE assumed that myopia were a
detriment to survival at a particular time in history, ONE could assume that
the DNA for myopia would remain in the gene pool until myopia reached a
point where it was neutralized as a detriment for survival. If ONE assumed
that the DNA for myopia remained in the gene pool until myopia reached a
point where is was neutralized as a detriment for survival, then ONE could
assume that there would be more and more myopes over time until reaching
today’s significant number of myopes.
The bottom line: If ONE assumed that myopia in humans is purely (or
partially) genetic, then ONE could assume that there would be a significant
number of myopes today.
(Incidentally, I’m glad that you pointed out in your second sentence above
that IF/THEN suppositions, which form our opinions, inherently include
assumptions.)
> > Some inherited traits may be purely genetic, but the process of natural
> > selection is not; it involves a complex combination of genetics and
> > environmental factors. Whether you believe it is fully or only
partially
> > genetic, think of myopia as being “suppressed” (not eliminated) in the
> > population until conditions were right for it to become prevalent. In
> > modern times, conditions are right and myopia is prevalent.
>
> I don't disagree with that. I think you really misread what I wrote,
> assuming "assumptions" that weren't there. I wrote that in my uninformed
> opinion (in other words, my guess) myopia is probably caused by a
> combination of of genetic and environmental factors. That statement is not
> really very different from what you write in the above paragraph.
I’m glad that we are in agreement, because, evidenced by my previous
paragraph, the semantics in this discussion are ridiculous.
Edward
Edward
> That doesn't make any sense to me. Why would it be easier for myopes to
read
> than emmetropes? Perhaps later in life, at the time of presbyopia, but
> people probably didn't live long enough to become presbyopic in those
days.
Myopes would NOT have necessarily have had a reading advantage over
pre-presbyopic emmetropes, but they might have had a reading advantage over
pre-presbyopic moderate to high-hyperopes.
Edward
Edward
> Yes, that stress factor is very, very important, as we are finding out
> in our consumerist, materialist-driven society!!
Yeah, compared to the Middle Ages, life in the 21st century is incredibly
stressful.
Edward
MS
> An IF/THEN statement is a supposition. To “suppose” is to “assume”.
Absolutely not. I was looking at the theory that myopia is purely genetic, I
was in no way agreeing with it. I didn't assume anything.
Han Sibot
> Half a year ago I had central serous retinopathy in my right eye.
> Now I am curious about [the following] observation:
> When shining with a narrow pen torch through the eyelid and the sclera,
> and looking away at the same time, the area of the ring together with the
> central circle within it appears dimly illumated, uniform except for retinal
> blood vessel shadows. In addition a brighter light spot appears at the
> perimeter of the ring, at a position which is diametral opposite compared to
> the pen torch. I was wondering if this could be a manifestation of the
> foveal reflex that is otherwise seen by the ophtalmologist during
> funduscopy. It only occurs in my right eye, not in my normal left eye.
The above observation seems to correspond to a description that I
found on the website of an Opthalmology School: "The classic
presentation of Central Serous Retinopathy shows a transparent blister
or dome-like elevation in the macula area. There will be a light
reflex around the perimeter of the dome which replaces the normal
vitreo-macular reflex. The central foveal reflex and normal foveal
depression will be absent."
(http://www.ne-optometry.edu/faculty/sleightcourse/macular/csr/csr_note_body.htm#)
Any comment?