Diopters to 20/something conversion. The math and science behind this!

Hello everyone, post your dioptric pescription(how bad are your eyes),
your UCVA(uncorrected) and BSCVA(corrected by glasses) Also if you know
anyone's vision, post that too. I have done much research on the
correlation of diopters and 20/xxx and have compiled several charts,
formulae, tables and comments on the results obtained thus far. To test
for this, do it in room light or dim light. Make sure the eyechart is
well illuminated and your not squinting at all or recalling from memory
or guessing. Blur preception is of course allowed.

I and most optometrists have found that -.25 diopters doesnt cost you a
single line but makes the existing line blurry but still readable. Some
say it costs half a line. Such as if you can see half of 20/15 with a
-.25 lens, youll be a full 20/20 but wont be able to see better than
that uncorrected. Another example is if your seeing all of 20/20, you
may miss half of the 20/20 with -.25 diopters. Others have said it
didnt affect their ability to read a line, just made it harder to do
so.

Minus half diopter(-.5) is generally accepted as resulting in one full
line loss. This means 20/15 becomes 20/20 and 20/20 becomes 20/25. If
you can see half of 20/15 youll be seeing half of 20/20.

Minus one diopter(-1) generally gives you half visual accuracy. My
friends who see 20/20 with glasses see 20/40 without their -1 glasses.
Ditto for 20/15 with -1, 20/30 uncorrected. I was 20/50 corrected to
20/25 with a -1 lens years ago.

Higher dioptric values become harder to calculate and predict,
especially when you get to -6 and up. Someone could be -4.5 another
-5.25 and both see 20/400 UCVA. The -5.25 probably will see a much
blurrier 20/400 than the -4.5 but generally, 20/400 represents a
moderate of myopia around -5 diopters. One website said the range was
-4 to -6 for 20/400 and your best corrected vision played a big factor.
Someone whos 20/15 corrected needs more diopters to see the same blur
as another with 20/30 corrected. For me, my left eye at -5 or so
couldnt see 20/400 while my right eye at -4.5 or so just barely, barely
saw 20/400. I know two people who passed V3 requirement which states
you have to be 20/400 or better uncorrected and both were barely 20/400
with -5.5 pescriptions with 20/15 corrected. Those two guys said they
dont know anyone else -5.5 or more who passed V3 which requires 20/400.
They probably didnt have the great 20/15 corrected vision with glasses
so for them, -5 was the limit(20/20 corrected) I am not correctable to
20/20 so my limit is even less.

Few eyecharts go beyond 20/400 so info is scarce past this. I have a
solid grasp on dioptric values below -6(mild to moderate myopia), but
for -6 and up which is high myopia I am less certain how this converts
to diopters. I do know high myopes are worse than 20/400 but how bad
exactly? Also theres much fewer high myopes than low and moderate
myopes so much of my info is on low(er) myopes and their diopters to
snellen accuracy.

One could stand closer but then accomodation needs to be taken into
account. I can see the 20/200 E from 10 feet less blurry than the
20/400 E from 20 feet. At 5 feet I see the 20/70 line but im certainly
worse than 20/280. I experienced .67 diopter accomodation from the 5
feet mark.

If any of you have charts and formulae, on what expotentional scale
does this equal to? I know that going from -1 to -2 is only twice as
bad(20/40 and 20/80), but going from -3 to -6 is definately more than
twice as bad(20/150 and 20/500?), blurs much more than twice. Does this
gap become even larger still at -6 to -12(20/500? and 20/????) where
the number of times more blurry increases expotentionally?

Me and many others are curious about this and this topic has been
posted before many years ago. Its also useful for some occupations such
as pilot, soldier, law enforcement, etc where they have a requirement
for both corrected(BCVA) and uncorrected(UCVA) vision and people ask
all the time if their UCVA is good enough to make the cut.

 

ive edited and deleted trying to make the paragraphs show correctly.
Let me retry


Hello everyone, post your dioptric pescription(how bad are your eyes),
your UCVA(uncorrected) and BSCVA(corrected by glasses) Also if you know
anyone's vision, post that too. I have done much research on the
correlation of diopters and 20/xxx and have compiled several charts,
formulae, tables and comments on the results obtained thus far. To test
for this, do it in room light or dim light. Make sure the eyechart is
well illuminated and your not squinting at all or recalling from memory
or guessing. Blur preception is of course allowed.

I and most optometrists have found that -.25 diopters doesnt cost you a
single line but makes the existing line blurry but still readable. Some
say it costs half a line. Such as if you can see half of 20/15 with a
-.25 lens, youll be a full 20/20 but wont be able to see better than
that uncorrected. Another example is if your seeing all of 20/20, you
may miss half of the 20/20 with -.25 diopters. Others have said it
didnt affect their ability to read a line, just made it harder to do
so.

Minus half diopter(-.5) is generally accepted as resulting in one full
line loss. This means 20/15 becomes 20/20 and 20/20 becomes 20/25. If
you can see half of 20/15 youll be seeing half of 20/20.

Minus one diopter(-1) generally gives you half visual accuracy. My
friends who see 20/20 with glasses see 20/40 without their -1 glasses.
Ditto for 20/15 with -1, 20/30 uncorrected. I was 20/50 corrected to
20/25 with a -1 lens years ago.

Higher dioptric values become harder to calculate and predict,
especially when you get to -6 and up. Someone could be -4.5 another
-5.25 and both see 20/400 UCVA. The -5.25 probably will see a much
blurrier 20/400 than the -4.5 but generally, 20/400 represents a
moderate of myopia around -5 diopters. One website said the range was
-4 to -6 for 20/400 and your best corrected vision played a big factor.
Someone whos 20/15 corrected needs more diopters to see the same blur
as another with 20/30 corrected. For me, my left eye at -5 or so
couldnt see 20/400 while my right eye at -4.5 or so just barely, barely
saw 20/400. I know two people who passed V3 requirement which states
you have to be 20/400 or better uncorrected and both were barely 20/400
with -5.5 pescriptions with 20/15 corrected. Those two guys said they
dont know anyone else -5.5 or more who passed V3 which requires 20/400.
They probably didnt have the great 20/15 corrected vision with glasses
so for them, -5 was the limit(20/20 corrected) I am not correctable to
20/20 so my limit is even less.

Few eyecharts go beyond 20/400 so info is scarce past this. I have a
solid grasp on dioptric values below -6(mild to moderate myopia), but
for -6 and up which is high myopia I am less certain how this converts
to diopters. I do know high myopes are worse than 20/400 but how bad
exactly? Also theres much fewer high myopes than low and moderate
myopes so much of my info is on low(er) myopes and their diopters to
snellen accuracy.

One could stand closer but then accomodation needs to be taken into
account. I can see the 20/200 E from 10 feet less blurry than the
20/400 E from 20 feet. At 5 feet I see the 20/70 line but im certainly
worse than 20/280. I experienced .67 diopter accomodation from the 5
feet mark.

If any of you have charts and formulae, on what expotentional scale
does this equal to? I know that going from -1 to -2 is only twice as
bad(20/40 and 20/80), but going from -3 to -6 is definately more than
twice as bad(20/150 and 20/500?), blurs much more than twice. Does this
gap become even larger still at -6 to -12(20/500? and 20/????) where
the number of times more blurry increases expotentionally?

Me and many others are curious about this and this topic has been
posted before many years ago. Its also useful for some occupations such
as pilot, soldier, law enforcement, etc where they have a requirement
for both corrected(BCVA) and uncorrected(UCVA) vision and people ask
all the time if their UCVA is good enough to make the cut.

 

Dear Aceman,

Subject: Establishing a relationship between eye-chart and trial-lens

To do what you request, you just need the tools to do it.

(Assume that a MEDICAL exam has been made -- and there
are no MEDICAL problmems -- like glaucoma, etc. All
ODs are required to check for these conditions, and
report them to you. There is GREAT VALUE in this
part of the exam. I always INSIST that the person
go through this process BEFORE the begin
working on true-prevention with the plus.)

In a well lighted room, have the person look at the eye chart.

Let us say he reads 20/60. You then start placing
stronger minus lenses in front of his face until
one lens "clears" the 20/20 line. That is
how you measure the refractive state
of the natural eye.

Do this systeematically, under "room" illumiantion
and you can establish this relationship or "curve" very
quickly.

Was that you question?

Best,

Otis

 

THAT IS *NOT* HOW IT IS DONE, AND WILL NOT WORK EXCEPT FOR SOME MYOPES
WITH NO ASTIGMATISM.

Re the conversion idea, I suggest ace go into deja news and research
"The Dead Horse" equation I and others developed several years ago on
this news group. Been there, done that.

w.stacy, o.d.

 

Dear Ace,

Please disregard Otis's postings. He is not in the medical profession and
not in the position to give medical advice.

Sure looks like medical advice above.....

Allen

 

Dear Allen,

Subject: The difference between measureing the refractive
state of the natural eye -- and calling a measurement
a "medical problem".

The objective measurements could be made by ANYONE with
some traning an experience.

Assuming the retina is inherently capable of 20/20 (not
amblyopic), then let us talk about measureing a
POSITIVE refractive state for the natural eye.

In this case, you have the person read the Snellen (in room
illumination) and he reads 20/20.

His refractive state might be zero -- or some positive value.

What you do then, is to take your tria-frame, and using
your trial-lens kit, you place increasintly stronger PLUS lenses
in front of his eyes, until you find a lens-strength that "just blurrs"
the 20/20 line.

This is a measure of a positive refractive state for the young eye.

In NONE of these measurements have I suggested "medicine"
or anything like that. These are simple objective measurements --
i.e.,
science -- not medicine.

If I said that I was going to write a "prescription" then everything
would "change".

BUT I NEVER SAID THAT!

Get it? Yet?

Otis

 

And then he goes on to describe a SUBJECTIVE method of measuring
hyperopia (a very primitive, and certainly NOT an *objective* method).
Any body who doesn't know the difference between objective refraction
and subjective refraction should NOT be telling ANYONE how to "do it".

Speaking of subjective and objective evaluations, I recommend the
recliner for otis, handcuffs for dick, and a straight jacket for ace.

Why do old reruns of the 3 stooges keep popping up in my mind???

w.stacy, o.d.

 

Dear Mike,

There you go again, converting refarctive-state measurements
into "medicine" which they are manifestly NOT.

Otis

 

Lets not argue about other topics in this thread. I will go back on
topic and talk about diopters to 20/xxx correlation. So guys, post your
pescription, UCVA and BCVA and the results of anyone you know for us to
learn

 

Dear Wiliam,

If I paid $ 100 k for college, and
120 K for OD school, I guess
I would be stuck on my
God-hood.

Ace is asking straight questions.

Why not attempt to give him
straight answers -- rahter
than insulting him.

Ace is learning a great deal -- about
you arrogance in this discussion.

It that profesional?

What does Ace-Man think
of your response -- I wonder.

Otis

 

Who gives a shit -- I wonder.

 

-0.00, 20/15
-0.25, 20/15
-0.50, 20/20
-0.75, 20/25
-1.00, 20/30
-1.25, 20/30
-1.50, 20/40
-1.75, 20/40
-2.00, 20/50

These are for mild myopia. Moderate myopia will come soon.

 

And what is your accuracy of your estimate?