Science: Depth of Field for the Primate Eye

Dear Sci.med.vision members,

One poster raised the issue of optical dead-band,
and then told some one to F. O. when he
asked questions about it -- if you are a professional.

That is NOT the way you deal with scientific
questions. And it is NOT the way you talk
to the public about this scientific issue.

So here is the correct response:

===============

Subject: Depth-of-focus, and range of values.

Re: Range of "travel" of accommodation.

I think you know this concept as "depth of field",
or optical dead-band.

In engineering it is called dead-band, or DSO, or
Dead Space Operator.

What is means is that a signal is blocked,
and must exceed the dead-band -- for effective
refractive control to exist. Or for that matter
for an image to be blurred on the retina.

Here is the accurate reference:

"Accommodative Oscillation Can Enhance
Average Accommodative Response:
A Simulation Study"

George K. Hung, John L. Semmlow ang
Kenneth J. Ciuffreda

IEEE Transactions on Systems, Man and Cybernetics,
Vol. SMC-12, No. 4, July/August 1982

Statement:

The deadspace operator reflects the optical depth of field, and is
normally a function of pupil diameter, ranging from +/- 0.15 D
for a 8-mm diameter pupil to +/- 0.85 D for a 1-mm pupil [15].

15. F. W. Campbel, "Depth of Field of the Human Eye", Optica Acta,
Vol. 4 pp 157-164, 1957

For a sun-light pupil of 2.5 mm, the depth-of-field would be about 1.2
diopters, as I suggested. (+/- 0.6 diopters).

That is the source I am using.

Thus the eye could have a theoretical positive STATE,
of +1/2 diopter and still have a clear image on the retina,
because of the eye's depth-of-focus.

This explains why you can have no "accommodation",
and good far an near vision.

Otis

Sorry. Rishi Giovanni Gatti (Zetsu), Lena102938, and Otis Brown are
trolls who haunt s.m.v.

Rishi has published, and is trying to sell worthless books.

Otis is pathologically dishonest and actually hurts people.
Following his advice can induce double vision in those
not working closely with an eye doctor.

Lena102938 uses anti-eye doctor rhetoric as a substitute for ANY
actual information. It seems she now has to wear glasses and has
developed a pathological (and ILLOGICAL) resentment toward the
industry that "foisted these glasses upon her."

You'd do well to ignore them and wait for responses from the
caring, compassionate eye doctors who DO also participate in this
site.

Incidentally, Otis: HAVE you spoken to Dave Granet about the Delayed
Adjustable Suture technique yet?

I mean ... you wouldn't want to keep lying, now would you?

Now if Otis were as smart as an ape, he might have some credibility.

On Sep 27, 12:49 pm, "otisbr...@pa.net" <otisbr...@pa.net> wrote:
> Dear Sci.med.vision members,
>
> One poster raised the issue of optical dead-band,
> and then told some one to F. O. when he
> asked questions about it -- if you are a professional.
>
> That is NOT the way you deal with scientific
> questions. And it is NOT the way you talk
> to the public about this scientific issue.
>
> So here is the correct response:
>
> ===============
>
> Subject: Depth-of-focus, and range of values.
>
> Re: Range of "travel" of accommodation.
>
> I think you know this concept as "depth of field",
> or optical dead-band.
>
> In engineering it is called dead-band, or DSO, or
> Dead Space Operator.
>
> What is means is that a signal is blocked,
> and must exceed the dead-band -- for effective
> refractive control to exist. Or for that matter
> for an image to be blurred on the retina.
>
> Here is the accurate reference:
>
> "Accommodative Oscillation Can Enhance
> Average Accommodative Response:
> A Simulation Study"
>
> George K. Hung, John L. Semmlow ang
> Kenneth J. Ciuffreda
>
> IEEE Transactions on Systems, Man and Cybernetics,
> Vol. SMC-12, No. 4, July/August 1982
>
> Statement:
>
> The deadspace operator reflects the optical depth of field, and is
> normally a function of pupil diameter, ranging from +/- 0.15 D
> for a 8-mm diameter pupil to +/- 0.85 D for a 1-mm pupil [15].
>
> 15. F. W. Campbel, "Depth of Field of the Human Eye", Optica Acta,
> Vol. 4 pp 157-164, 1957
>
> For a sun-light pupil of 2.5 mm, the depth-of-field would be about 1.2
> diopters, as I suggested. (+/- 0.6 diopters).
>
> That is the source I am using.
>
> Thus the eye could have a theoretical positive STATE,
> of +1/2 diopter and still have a clear image on the retina,
> because of the eye's depth-of-focus.
>
> This explains why you can have no "accommodation",
> and good far an near vision.
>
> Otis

Otis, it is true.

>From that point of view we can estimate
real precision of autorefractor measurements in dynamic eye.
We should consider:

1. Step of autorefractor (as a rule) 0.25 D
2.Pupil size
3.Chromatic aberration
4.Distance to eye from light source.
5.Eye movement
6.Accomodation
7.Cornea is not spherical

Does not sounds like it will give too precise refraction.

Then second step:
Glasses prescription (i mean when refraction error low)
1. Light is dim - pupil is wide
2.Person is a little nervous,
3.OD asks fast. No time for accomodation or relaxation.
4.Main thing: OD asks "which better "
Person will chose the higher power:

Miopic:
-1 lens gives extremely crisp vision even for person with 20/20
Hiperopic :
Even if person needs only +1 for reading , reading in +2 even more
comfortable.

That is widely advertised scientific approach.

Lena