eye math question

Recently I have noticed that my vision was not quite as sharp at a distance.
Based on this group, I have tried using the plus lens for close work in
hopes to improve the crispness of my distance vision.

After using the plus lenes for about a month, here is what I have found:

With +1.25 lens if I start out close and move away from an object, it starts
to blur at the following distance:

Left Eye: 21"
Right Eye: 26"

Prior to using the plus lenes for close work here were my measurements.
Left Eye: 19"
Right Eye: 22"

I don't know the math, but believe it should be possible to calculate an
approxamite D value. I want to compare the before and after. I'm not
intested in a discussion about plus lenses, just in the math.

How much worse is my left eye than my right eye?

 

42

 

Dear Dennis,

The baisc equation for distance to diopters is:

Diopters = 1/ focal-distance

Thus a plus with a focal length of 1 meter
will have a power of 1 diopter. A focal length
of 1/2 meter, a power of 2 diopters.

Using your distance method, and assuming a refractive
state of zero for you:

39.4 / 19 = 2.07 diopters

22 / 39.4 = 1.8 diopters

Change in power after wearing a +1.25 diopter lens.

39.4 / 21 = 1.87 diopters

39.4 / 26 = 1.51 diopters.

If you were consistent, then your refractive STATE changed
SLIGHTLY in a positive direction.

I am certain you will get some more commentary
on this one.

Best,

Otis

 

That's good one!! I assume you're not being serious.

Rather it has to do with lighting and illumination
levels.

frank

 

Sure, it's simple optics that even "He Who Must Not Be Named"
[elevator engineer] could understand: the aperature effect
from the iris being open wider during low-light. There
are also contrast effects if you like MTF.

-- Robert

 

Don't forget the drops that run across your lenses. ;=)
-- Fermez le Bush

 

Keep using those plus glasses to clear your refractive state to plano
else you may develop stair-case myopia

 

It was the "escaltor" study, it had pictures.

 

Dear Dennis,

I also have worse vision when it is rainy than sunny.

Otis> This is because of a characteristic of a camera
called variously, "depth-of-field" or "depth-of-focus".

In a camera, if you "stop-down" the aperture, to 2 mm, (say),
the depth-of-field can increase by a diopter or so.

In sun light, the eye automatically does this. Thus your
Snellen would be clear on a bright day.

At dusk, your aperture "opens up" to 7 or 8 mm, and
your depth-of-focus can reduce to perhaps 1/2 to 2/4 diopters.


My theory is the
variation in barometric pressure causes the eye to expand or contract.

Anyone with other theories to explain this?

Otis> Depth-of-focus effects. If you used a "pin-hole" your
visual acuity could be 20/20 because of that effect.

Best,

Otis

 

So does everyone else on this planet.

No wonder people on this board consider you a moron.

Yeah, LIGHT.

 

Dear Dennis,

Subject: Some more math, and estimating your refraction
on the values you provided.

If you had a refractive STATE of zero, and 20/20 -- you would
be considered NORMAL.

This is an analogy to the "camera" concept developed by Donders,
Helmholtz
and others. Using this concept we can estimate the following.

+++++++++++++++++++

If you read at 20 inches (assuming you are young),
it takes a change of +2 diopters to read at 20 inches.

If you put a +1 diopter, you could read clearly at 20 inches.

With a +2 diopter lens on, letters would still see clearly
at 20 inches -- but not beyond.

Since your "blur" starts with +1.25 diopter lens, it is
possible to conclude that your refractive STATE must
be on the order of -1 diopters.

This would correspond to a Snellen of from 20/40 to
20/60.

Best,

Otis

 

Dear Ace,


Mike> So, you found a study that shows staircase myopia exists? I
haven't.

Otis> That is because he chooses to ignore studies that show
the effect.

The Oakley-Young study showed that the kids with full-strength
minus went DOWN at a rate of -2 diopters in four years.

The "plus" group went down by approximagely zero diopters
in those for years.

I would call "down" at a steady -1/2 diopter per year "stair-case"
myopia.

Majority-opinion Mike, denies it.

Make your own judgment accordingly.

Best,

Otis

 

Dear Ace,

Subject: Induced Stair-case myopia (from a minus lens)

I would suggest reading:

http://www.geocities.com/soonicansee/

For a graphic picture of the results produced by the
Oakley-Young study.

Best,

Otis

 

Dear Ace,

The natural eye's refractive STATE follows that minus lens.

A great "graphic" of this can be found at:

http://vision.berkeley.edu/wildsoet/myopiaprimer.html

Thus stair-case myopia develops in these steps.

1. The kid has his nose almost on the book -- reading
at -6 to -10 diopters. (6 inches to 4 inches). If
he did this for short times -- no problems. But
long hourse, and the eye adjusts its refractive STATE
in a negative direction. (As a natural process.)

2. After a year or two of this, the refractive state
changes from +1/4 to -1.0 diopters -- and a
Snellen of 20/60.

3. Now, the kid gets a strong minus. The
kid goes back to reading at -10 diopters, with
the strong minus, and that "animation" shows
how the natural eye "adapts" to BOTH the
"near" AND the minus.

4. Thus the term, stair-case myopia.

The majority-opinion says this "does not happen".

The second-opinion says it does.

You be the judge.

Best,

Otis

 

Ive seen children read with their wretched minus on. Its no wonder why
so many people are myopes, some in the double digits even! Im hoping
for a brave new world where second opinion optometrists come in control
and prevent the myopia epidemic what is today. Lasik is useless.
Prevent myopia, dont go around ruining eyes with glasses than lasik!

 

Still lying about Oakley-Young, huh, Otis??

You off the meds again?

 

schreef:

Normal?

Maybe the eye is emmetropic (no refraction error in the optical system
while the eye is not accommodating and looking far away)

Meanwhile it is possible the eye is one way or another just abnormal
instead of normal.

You are a real abnormal person Otis and your shortsightedness has
nothing to do with this condition.

Ah, Otis starting to beat a retreat seeing the words "and others" and by
his use of the word "camera" instead of his regular falsely stated term
" fixed box camera"
I should say, it is a start.
He knows he is a liar and a charlatan.
He never have read what Donders and von Helmholtz really did say about
the eye.



Free to Marcus Porcius Cato's "Ceterum censeo Carthaginem esse delendam"

In conclusion, I think that the "old plus lens junk recovered by Otis"
should be destroyed.

Jan (normally Dutch spoken)

 

schreef:

Normal?

Maybe the eye is emmetropic (no refraction error in the optical system
while the eye is not accommodating and looking far away)

Meanwhile it is possible the eye is one way or another just abnormal
instead of normal.

You are a real abnormal person Otis and your shortsightedness has
nothing to do with this condition.

Ah, Otis starting to beat a retreat seeing the words "and others" and by
his use of the word "camera" instead of his regular falsely stated term
" fixed box camera"
I should say, it is a start.
He knows he is a liar and a charlatan.
He never has read what Donders and von Helmholtz really did say about
the eye.



Free to Marcus Porcius Cato's "Ceterum censeo Carthaginem esse delendam"

In conclusion, I think that the "old plus lens junk recovered by Otis"
should be destroyed.

Jan (normally Dutch spoken)