[ Article crossposted from sci.med ]
[ Author was ]
[ Posted on Fri, 21 Feb 1997 05:35:27 GMT ]
just curious
what percentage of the population has 20/20 vision ?? 20/40 ?? etc..
do we all start out with essentially 20/20 vision and then it
degenerates from there ? – especially once school starts and reading
becomes a big part of our daily activity, not to mention working at
terminals !! 
do other more agrarian (3rd world) societies tend to have better vision
or are their percentages much the same as more technologically (better
educated and hence exposed to more reading) advanced societies ??
howabout visual acuity in our ancestors from say the 1800s, 1700s, etc ?
basically is close in detailed work (reading, etc) a reason for
nearsightedness ? and is visual acuity and its distrbution in the general
population the same now as ever ??
ps – what’s the best substantiated visual acuity ever recorded for
a human being ???
thanks, hope someone can answer
How old are you and are your glasses bifocals?
On 21 Feb 1997, Adam Smash wrote:
- Hide quoted text — Show quoted text -
> Date: 21 Feb 1997 16:58:04 GMT
> From: Adam Smash <asm…@mail2.sas.upenn.edu>
> Newsgroups: sci.med.vision
> Subject: Problems with new lenses
> I’m having some problems with the lenses in my new glasses. As a matter of
> fact, I’ve had this problem the last two times I’ve purchased new lenses.
> I hope someone can give me an explanation.
> My prescription is:
> OD -3.50 -2.75 004
> OS -4.00 -2.75 176
> I usually purchase high-index/thin lenses. I think the lenses in my new
> glasses are 1.60, if that helps.
> Vision with my new glasses seems to be fine initially, but then I notce
> that my eyes are straining when viewing close objects such as my computer
> screen. After about an hour or two, I simply can no longer wear them, as
> my eyes are completely fatigued.
> The last time I had lenses replaced in my old frames, I had to go to three
> optometrists and had five sets of lenses made. I believe that the
> prescriptions given by the optometrists did not vary much if at all, which
> leads me to believe that either the lenses were defective or that they
> were improperly cut
> I remember reading somewhere on the Net that the optical center of a high
> index lens must be perfectly centered on the wearer’s eyes, especially if
> the person is astigmatic. Could this be the problem? And if so, what is so
> difficult about cutting lenses properly? Is it difficult to cut lenses to
> the accuracy I need?
> Last time I went through this, I finally had success at LensCrafters
> (surprisingly). This time I went to a local "boutique" expecting that
> they would be competent in their manufacture, apparently without success.
> I even had them put dots on the demo lenses to make sure the new lenses
> would be properly centered.
> I’ll stop now before I start raving. Any help to get me through this
> ordeal is greatly appreciated
> -adam
It would also help to know what your prescription was before you began
having problems and the time course over which this has occurred.
*******************************************************************
Russell W. Read, M.D. (206) 543-3883
Department of Ophthalmology re…@u.washington.edu
University of Washington
Box 356485
Seattle, WA 98195
- Hide quoted text — Show quoted text -
In article <5ekk6s$…@netnews.upenn.edu> asm…@mail2.sas.upenn.edu (Adam Smash) writes:
>I’m having some problems with the lenses in my new glasses. As a matter of
>fact, I’ve had this problem the last two times I’ve purchased new lenses.
>I hope someone can give me an explanation.
>My prescription is:
>OD -3.50 -2.75 004
>OS -4.00 -2.75 176
>I usually purchase high-index/thin lenses. I think the lenses in my new
>glasses are 1.60, if that helps.
>Vision with my new glasses seems to be fine initially, but then I notce
>that my eyes are straining when viewing close objects such as my computer
>screen. After about an hour or two, I simply can no longer wear them, as
>my eyes are completely fatigued.
>The last time I had lenses replaced in my old frames, I had to go to three
>optometrists and had five sets of lenses made. I believe that the
>prescriptions given by the optometrists did not vary much if at all, which
>leads me to believe that either the lenses were defective or that they
>were improperly cut
I would not jump to that conclusion.
If three different doctors get almost the
same wrong result from their test, it would
indicate to me that the test was wrong.
How many of these three optometrists did
a retinoscopy for you?
Dr. Stacy has told us that doctors should always
do a retinoscopy on a new patient, but, so far,
no patient has told of getting one in the last 30 years.
Dennis Yelle
–
den…@netcom.com (Dennis Yelle)
"You must do the thing you think you cannot do." — Eleanor Roosevelt
Adam,
Your problem (other than if you are experiencing a condition
known as presbyopia) may stem from the over-focusing that you
must do to keep the letters clear on the computer screen. Your
glasses were determined by evaluations that compensate for the
distance seeing requirements. When you are having to focus on
the computer screen, you must continually accommodate (focus) for
that close distance versus the far distance your glasses were
made to work for. The constant focusing at the computer distance
is probably, unless there is presbyopia or manufacturing defects
in the lenses, the root cause of your problems. You need to go
to a practitioner who does both distance and near area computer
evaluations as far as assessing what lens powers are appropriate
for the seeing distances you use while doing computer work.
Sometimes the same powers for distance are appropriate for near
area focusing, but very often there needs to be an adjustment for
the near distance. Only by specific evaluations can this be
determined with any amount of reliability and validity. I, and a
number of other practitioners, utilize the PRIO evaluations to
assist us in helping to determine what lens powers are
appropriate for the computer distances the patient’s are using.
Click on their web site (PRIO.com) to learn more about it. An
evaluation for far seeing and reading distances (done on printed
letters) is not the same as an evaluation done at the computer
distances on images that approximate the ones encountered on the
computer screen.
Paul Planer,O.D.
Adam….
.. a few things to consider just because you had the optician put a "dot"
on the demo…that don’t mean crap to us lab people….it’s what they
write on the form the gives us when getting the glasses made….we lab
people don’t have the authority to do it any way we want…have to stick
to the order form….
now besides taking that fitting hght. they should always take a
monocular PD when working in an aspheric lense…and you said 1.6 well in
that high index range all the lenses are aspheric…thin and lite or
hyperial or whatever brand you got…at lensecrafter i’m sure it was the
featherwght. (poly)……
now i’ll give you the symptom and what causes that and you check off
the list…
pulling in the eye……wrong PD,induced prism,ground prism
sea sick feeling/slanted vision……..your axis is off
now with you complaint…sounds more to me you’re ready for a reading
area…you can get this in as little as a +.75 add..if your eyes are
showing fatigue after hour or hours of use than it sounds like an RX
problem….if it was axis or pd or fitting you would know almost as soon
as you put the glasses on…in fact you should notice it immediatly…and
over a period your eye will adapt to the wrong rx ..seen alot of that come
thru the lab…
why do you think the doc flips that lense so fast in the
phoropeter…you know.."better worse"…"one or two??"…ha ha…its
becuase the eye can accomidate but as soon as you hit that right power t
you’ll know..
now the easy way to go is take your glasses and go to a place that has
a top qaulity equipment…ask them when it was last calibrated…and when
they get ready to check your lenses ask the optician to go get a trial
lense and zero out the lensometer…if they don’t know what you are
talking about..RUN…they don’t know optics….
for your RX though the thing that is most important is the axis..you
have a pretty good astigmatism thing going there…at your RX the lenses,
by the ansi standard can be off no more than 2 degree’s, but chances are
you’ll notice one degree..ha ha….power wise…it isn’t supposed to be
off no more than 1/12th of a diopter..atleast in your RX so that -3.50
could be a -3.37 ..get it??…but the cyl. should still be a -2.75….
but from the problem you are having…and with that time table,,,"after
an hour or two." .sounds like to me…..i should or your doctor should be
saying "welcome to the land of presbiopes"..ha ha ha
..
let me know how it turns out….maybe for once everyone will not blame
us lab guys for the problem!!ha ha ha
hope it was helpful…
jeff trail
full spectrum inc.
ormond beach FL.
In article <19970222080901.DAA02…@ladder02.news.aol.com> spec…@aol.com (Specs31) writes:
[...]
> for your RX though the thing that is most important is the axis..you
>have a pretty good astigmatism thing going there…at your RX the lenses,
>by the ansi standard can be off no more than 2 degree’s, but chances are
>you’ll notice one degree..ha ha….power wise…it isn’t supposed to be
>off no more than 1/12th of a diopter..atleast in your RX so that -3.50
>could be a -3.37 ..get it??…but the cyl. should still be a -2.75….
No, I don’t get it.
You seem to think that 1/12 of a diopter is 0.13.
Actually 1/12 is 0.0833, 1/8 is 0.125 which is often rounded to 0.12
by those who work with spectacle lenses.
So, what is the tolerance for spectacle lenses?
–
den…@netcom.com (Dennis Yelle)
"You must do the thing you think you cannot do." — Eleanor Roosevelt
"paul m. planer" <papla…@atl.mindspring.com> wrote:
>I, and a
>number of other practitioners, utilize the PRIO evaluations to
>assist us in helping to determine what lens powers are
>appropriate for the computer distances the patient’s are using.
>Click on their web site (PRIO.com) to learn more about it. An
>evaluation for far seeing and reading distances (done on printed
>letters) is not the same as an evaluation done at the computer
>distances on images that approximate the ones encountered on the
>computer screen.
Anyone interested in PRIO should also look at numerous past newsgroup
posts on the subject which are archived in Dejanews on the Web (just
enter ‘prio’).
Ray
Dennis,
i take it you must not be a lic. optician or a doctor or work in a
lab…or you would br familiar with a list of rules we have to abide by
called the ansi standard..
the amount of power tolerance that you can be within depends on the rx
you are prescribing or grinding…depending on the prerson you are dealing
with…doctor optician ..lab person….
in any rx the tolerance has to be within a 12th…as the rx goes up or
down in power you are allowed a greater amount of tolerance…..i’ll look
up the exact # if you prefer.
what the standard does is set a given set of numbers we have to
maintain..but there are allowances to offset some of the problems that we
run into when grinding certian rx’s as well as allowing for different
degree’s of tolerance from pieces of equipment…say my lensometer to a
doctor’s vertometer…or humphrey annilyzer …i check each job three
times before it leaves my lab…
once on a compensating lensometer..when it comes off the cylinder
machine…and it’s getting ready to be layed out for edging…checking for
power,correct axis..and vertical imbalance and induced prism…
than after it is edged and inserted i check it again for axis and
vertical imbalance…this on a vertometer..
last time is on a rieckhart laser lensometer which gives readings down
to the sixth in power and prints out the final reading which is attached
to every job that leaves my lab…..
so some of us do understand the lense side of this optical game and we
always try to stay one step above the ansi standard….
so you seem to want to play the number game….well in the industry
we refer to 12ths when talking power…because mainly all the powers are
given in 12ths. check out the print out on a autorefractor and tell me
what it says…..
sorry if i was not technical enough for you but i thought the idea of
this group was to try to help people out not nick pick each other to death
on technical language….if i wanted to stay on the technicle side when
discussing lenses 99% of the people that ask the questions would be lost
when trying to read the post…so what was gained if i tryed helping in
this manor??…and people that know the industry already know what i’m
talking about anyway….
so lighten up with being so technical….when you prove to me you know
what you are talking about than i’ll get technical enough with you to
sitisfy your attempts to be so precise.
you get a copy of the ansi standard or get your optician lic. or
your degree in medicine….than we can talk in length on the technical
side…till than i plan to keep my post simple and answer the questions
asked in terms that the questioner can understand. if it something on the
technical side and i see the post was made by someone in the industry than
i usually just e-m them directly…why waste space sending technical
information that only the experianced people in the field will
understand….save the boring stuff for direct communication…ha ha ha
hope this answered some of your questions
jeff trail
full spectrum inc.
ormond beach FL.
In article <19970224041701.XAA20…@ladder02.news.aol.com> spec…@aol.com (Specs31) writes:
>Dennis,
> i take it you must not be a lic. optician or a doctor or work in a
>lab…or you would br familiar with a list of rules we have to abide by
>called the ansi standard..
You are right.
But, if I already know the answer to the question that you responded to,
I would not have needed to read your answer.
> the amount of power tolerance that you can be within depends on the rx
>you are prescribing or grinding…depending on the prerson you are dealing
>with…doctor optician ..lab person….
> in any rx the tolerance has to be within a 12th…as the rx goes up or
>down in power you are allowed a greater amount of tolerance…..i’ll look
>up the exact # if you prefer.
Yes I would like to see the exact number.
Thank you.
- Hide quoted text — Show quoted text -
> what the standard does is set a given set of numbers we have to
>maintain..but there are allowances to offset some of the problems that we
>run into when grinding certian rx’s as well as allowing for different
>degree’s of tolerance from pieces of equipment…say my lensometer to a
>doctor’s vertometer…or humphrey annilyzer …i check each job three
>times before it leaves my lab…
> once on a compensating lensometer..when it comes off the cylinder
>machine…and it’s getting ready to be layed out for edging…checking for
>power,correct axis..and vertical imbalance and induced prism…
> than after it is edged and inserted i check it again for axis and
>vertical imbalance…this on a vertometer..
> last time is on a rieckhart laser lensometer which gives readings down
>to the sixth in power and prints out the final reading which is attached
>to every job that leaves my lab…..
> so some of us do understand the lense side of this optical game and we
>always try to stay one step above the ansi standard….
> so you seem to want to play the number game….well in the industry
>we refer to 12ths when talking power…because mainly all the powers are
>given in 12ths. check out the print out on a autorefractor and tell me
>what it says…..
Sorry, I don’t seem to have any autorefractor print outs right
here in my office. Maybe you do. If you do, please let us
know what they say.
> sorry if i was not technical enough for you but i thought the idea of
>this group was to try to help people out not nick pick each other to death
>on technical language….if i wanted to stay on the technicle side when
>discussing lenses 99% of the people that ask the questions would be lost
>when trying to read the post…so what was gained if i tryed helping in
>this manor??…
If you say 0.12 when you mean 0.12,
and you say 1/12 when you mean 0.0833,
everyone here will understand you.
If you say 12th when you mean 0.12, then most of your readers
will misunderstand you.
Which do you prefer?
>and people that know the industry already know what i’m
>talking about anyway….
Maybe so, and maybe they are too polite to correct you,
but I am neither.
> so lighten up with being so technical….
No, I am not going to do that.
If you say 1/12 or 12th when you mean 0.12, you are posting
incorrect information. I reserve the right to correct
you or anyone else that posts incorrect information here.
>when you prove to me you know
>what you are talking about than i’ll get technical enough with you to
>sitisfy your attempts to be so precise.
Ha ha, very funny.
>you get a copy of the ansi standard or get your optician lic. or
>your degree in medicine….than we can talk in length on the technical
>side…
If I did, I would not waste my time talking to you.
>till than i plan to keep my post simple and answer the questions
>asked in terms that the questioner can understand.
I don’t think anyone who has never dealt with a lens lab
would know that when you say 1/12 or 12th, you sometimes mean 0.12.
>if it something on the
>technical side and i see the post was made by someone in the industry than
>i usually just e-m them directly…why waste space sending technical
>information that only the experianced people in the field will
>understand….save the boring stuff for direct communication…ha ha ha
Yes, it is pretty funny that you think the
difference between 1/12 and 0.12 is too technical for the
people here to understand.
ha ha ha to you too.
> hope this answered some of your questions
Yes, it did, sort of. Too bad I cannot trust your answers.
> jeff trail
> full spectrum inc.
> ormond beach FL.
Dennis Yelle
–
den…@netcom.com (Dennis Yelle)
"You must do the thing you think you cannot do." — Eleanor Roosevelt
In <dennisE5zB5z….@netcom.com> den…@netcom.com (Dennis Yelle)
writes:
>Dr. Stacy has told us that doctors should always
>do a retinoscopy on a new patient, but, so far,
>no patient has told of getting one in the last 30 years.
There you go again. What kind of study did you do on this?
Any doctor member of VSP will do a retinoscopy (or some other objective
refractive procedure) if he/she wants reimbursement for a comprehensive
eye exam on that patient.
If omitted, we lose about $5 for a 20 second test.
Most of us do it, Dennis. Really, even when it isn’t necessary! (which
is the thing I hate about 3rd party reimbursement).
Bill
dennis,
lets make this real simple….i tried being nice..that didn’t seem to
work with you…like you said you wanted it and you answered me on every
thing i posted in your usual smartass typical " i know everything" way….
well pea brain…optical measurements are given in .25 D. ….so when
the standards were established..to make it easier on all involved the
power was rounded off to the 12ths….where you come up with .0833 is way
out there….
thats one of the reasons i don’t like contributing to this group
anymore….when someone that has anything to say that actually has
knowldge they are usually flamed out by people like you that picked up a
tid bit here and there and now seem to think they are ready to start
refracting and giving medical advice……
all this usually does is cloud the issue and the person who asked the
question originally doesn’t know who to listen to so they leave
frustrated….
so a few things for you dr. smartass….
one…i have never given medical advice in this group…leave that to
the doctors can you claim the same??
two….only jumped in where i could contribute to a posting by helping
out the person asking by giving them some information…and than it is
mostly things that could be wrong and when they go to thier primary care
giver..they can go with a better understanding of what maybe the cause of
thier problem.is this what you do??
three….when people like you are trying to sound like they are actually
in the medical field because they found out what a retinoscope is is
pretty pathetic…and all your little smart ass answer’s to the post i
made just proves the piont you are childish and pathetic…giving you the
rule# would do no good since you don’t have a copy of the ansi
standard…and wouldn’t know what you were reading if you did…
your little wise crack about the autorefractor probably got some laughs
from all the people in this group that understands optics and is in the
field……
so since you are soooo smart and i’m so stupid in the field of
optics…lets test you wise guy…since you like getting so precise and
technical and tell everyone the either need to drop thier cyl. or find a
retinoscope…ha ha ha
so here’s an easy one for you …..is there a relatively simple
equation for the
aspheric surface required to correct spherical aberration of a plano-
convex (or concave?) lens based on the conjugates and index of
refraction???.
and you’ll be happy to know after contributing to this group for 2
years…i’ve had enough…..you come in and delute the attempts we try to
make to give someone advice on what maybe an answer to thier question by
making post after post of nonsense and garbage because you learned a
couple of phrases that are in the optics field….
well you win……you correct everyones problems…..i’ve had enough
by the way did you get around to figuring out the answer to my
question above???….. let me give you two hints…one. it doesn’t involve
a retiniscope. two…it won’t effect the cly. any…….
ohhh…yikes there goes your total knowldge on optics…now what??
since you prefer i be so precise…i wouldn’t like to leave you
hanging…If third order is close enough, the spherical aberration
contribution of an
asphere is given by
a = k*(c^3)*(y^4)*(n’-n) = 8*A4*(y^4)*(n’-n)
where k is the conic constant, c is the curvature of the surface (1/r), y
is
the semidiameter of the surface and n’ & n are the refractive indices of
the
media. (A4 is the fourth order coefficient in the standard aspheric
equation.)
Calculate spherical aberration using the Seidel formula:
S1 = -(A^2)*y*((u’/n’)-(u/n))
where S1 is the spherical aberration contribution for each surface, u is
the
marginal ray angle and A = n*u + n*y*c.
Then solve for the necessary conic constant or fourth order term to
balance the
surface contributions for the two spherical surfaces. As a check, you
should
end up with a hyperboloid for a plano convex lens with the plane side
toward
the infinite conjugate and an ellipsoid for the lens turned the other way.
I
vaguely recall that the eccentricity (k = -e^2) is the ratio of the
refractive
indices.
hmmmm…for someone that doesn’t meet your approval as having any knowldge
in the field of optics…not bad…ohh…i’m sure you’ll tell me it was a
lucky guess…..ha ha ha
had enough…can’t stand no more…let these guys keep battling you.
here’s looking atcha…
jeff trail
On 26 Feb 1997, Specs31 wrote:
> dennis,
> lets make this real simple….i tried being nice..that didn’t seem to
> work with you…like you said you wanted it and you answered me on every
> thing i posted in your usual smartass typical " i know everything" way….
> well pea brain…optical measurements are given in .25 D. ….so when
> the standards were established..to make it easier on all involved the
> power was rounded off to the 12ths….where you come up with .0833 is way
> out there….
While I agree that there is occasionally an overabundance of tripe here,
degenerating to name calling is ridiculous. Not only that, but your math
is wrong.
The problem we seem to be having is with the difference between decimals
and fractions.
0.25 is the decimal equivalent of the fraction 1/4.
0.125 (half of 0.25) is the decimal equivalent of the fraction 1/8 (half
of 1/4).
0.125 is NOT BY ANY MEANS the equivalent of 1/12.
The decimal equivalent of 1/12 is, as stated by Yelle, 0.083.
There can be no debate about this…it is basic mathematics.
Russell Read, M.D.
In article <19970226110400.GAA24…@ladder02.news.aol.com> spec…@aol.com (Specs31) writes:
>dennis,
> lets make this real simple….i tried being nice..that didn’t seem to
>work with you…like you said you wanted it and you answered me on every
>thing i posted in your usual smartass typical " i know everything" way….
> well pea brain…optical measurements are given in .25 D. ….so when
>the standards were established..to make it easier on all involved the
>power was rounded off to the 12ths….where you come up with .0833 is way
>out there….
Where I come from, a 12th is 1/12 is 0.0833.
If you don’t understand this yet, I guess you never will.
Dennis Yelle
–
den…@netcom.com (Dennis Yelle)
"You must do the thing you think you cannot do." — Eleanor Roosevelt
In article <Pine.A41.3.95b.970226211957.52056C-100…@homer05.u.washington.edu>, "R. Read" <re…@u.washington.edu> writes:
>0.25 is the decimal equivalent of the fraction 1/4.
>0.125 (half of 0.25) is the decimal equivalent of the fraction 1/8 (half
>of 1/4).
>0.125 is NOT BY ANY MEANS the equivalent of 1/12.
>The decimal equivalent of 1/12 is, as stated by Yelle, 0.083.
>There can be no debate about this…it is basic mathematics.
>Russell Read, M.D.
You’re correct. But most all lab men and most (old) OD’s will say 12th when really
meaning 0.125. One thing I don’t believe 0.12 increments are used much used
any more. In another post that cussed AOL hasn’t delivered to smv yet I explained
that I often wrote a script with 0.12 accuracy in order to know if during inspection of
finished lenses to pass or not to pass a job. Since eyes don’t come in .25 steps and I think patient needs a script no more than 2.25 nor less than 2.00 I would write 2.12. Helped hold down at least one "additive" step toward too much or too little "power".
Glad to have you aboard Dr. Read. You can be a real asset to this NG.
Vernon , retired optometrist
McAllen, TX
PS On our way to Tampico, Tamaulipas, Mexico for the weekend. Three birthdays
to celebrate! Mole, ceviche, jaibas, tortas de camarones para desayuno, sol y
playa! Pobres gringos alla’ temblando de frio.
Did you hear they just cloned a sheep?
Well it turns out that sheep duplicate, unlike its original, was very
nasty. He would try to mate with anything that walks, and in public, no
less.
The geneticist that did the cloning got so embarrassed by this behavior
that he took the clone up to the Golden Gate bridge and pushed it off
and it fell to its death.
The San Francisco cops arrested him for making an obscene clone fall.
In <19970228114400.GAA14…@ladder02.news.aol.com> vern…@aol.com
writes:
> Mole, ceviche, jaibas, tortas de camarones para desayuno
Hasta luego. I like it all but the mole. Something funny about
chocolate flavored meat.
Guillermo
"R. Read" <re…@u.washington.edu> wrote:
…………
>The decimal equivalent of 1/12 is, as stated by Yelle, 0.083.
>There can be no debate about this…it is basic mathematics.
>Russell Read, M.D.
I have seldom, if ever, stood up for the math of MDs, but I cannot
avoid crediting this MD for flawless grade-school math here.
Ray
vern…@aol.com wrote:
……………
>You’re correct. But most all lab men and most (old) OD’s will say 12th when really
>meaning 0.125.
I believe I was told the Ohio Legislature once considered changing pi
to 3.000000000000000, for convenience, withinthe state’s borders. I
guess lab men have more control over the laws of mathematics than most
other persons. Interesting that ODs and OMDs, who advertize their
super-professionality, go along with letting their artisan suppliers
call the shots and reinvent mathematics, while dumping on clients to
"take it home and try it", as being at the bottom end of the food
chain. If we can’t even have a conventional mathematics, I guess
we’ve totally had it.
Ray (1 and 1 are 1, ‘cuz they’re the same 1)