On Mar 4, 10:56*pm, "Mike Tyner" <mty...[at]mindspring.com> wrote:
- quote -

In my last session with her. This is what I told her to do.. adjust
the
frame closer to my eyes so it would be clearer and it is already
adjusted closest with nothing more to go except by removing the
nose pads.

- quote -

Well. Even if I stick the lens to my eyes (by pushing it to my eyes
by hand). I can still see the barrel distortion so the problem
is not vertex distance as it is already the nearest. What glasses
defects can cause barrel distortion? Could it be because the
frame is 3/4 smaller than my original? In my country, the trend
nowadays is smaller wide rectangular glasses with shorter
vertical and wider horizontal (wonder if this is also the trend
in the United States). Do you think smaller frame and lens
can contribute to barrel distortion?

Also she used 1.7 thick gauge glasses. She told me that 1.8 gauge
glasses ordered from the US would cost twice (at $100) and plastic
glasses would be thicker. Can glass quality contribute to barrel
distortion? She won't fix the barrel distortion since she doesn't
want to waste $50 replacing it so I have to get another pair
of glasses with other optometrists and I don't want to take
chances without a good theoretical understanding first of
the situation.

- quote -

Although I experienced that the new glasses with barrel distortion has
clearer close images probably because of the lower power
which optimizes the near view. But unfortunately, even if I literally
stick the glasses a few mm from from cornea. I can still see the
barrel distortion so it is not just a vertex distance problem.

- quote -

No. It is commonly believed that the eyes and teeth have
close nerve connections. So one feelng can be referred to
another such as sensitive bites after eye strain. I always
experience sensitive bite after looking thru the new glasses with
barrel distortion even at a few mm vertex closest distance.

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Supposed the distance to the book is 1/3 meter or 13 inches,
how do I take the inverse of 13 inches and reduce the glasses
by the result. The inverse of 13" is 1/13", so the power of
the glasses be lowered by 1/13 or in the case of the
-8.0 D.. -8.0 - 8.0/13 = -7.3D?

I'd like to have a bit of theoretical understanding first before
actually having test glasses fitted and more money paid as
I'd have to spend another $100.

I'd still have 4 years to go before my eyes crystalline lens
get stiff so I need to take advantage of less muscle strain
since I read many books in a week on evolutionary
biochemistry.

Pia

- quote -

"Pia" <pia_myo[at]yahoo.com> wrote

- quote -

The distance between the lens and your eye will figure into the calculation
of true power. You cannot specify "-8.75" without assuming a certain
distance between the lens and the eye (vertex distance.)

If your new frame fits further from your eye, a "-9.00" lens can easily
amount to -8.50.

Have it adjusted so it fits closer and you could conceivably make it -9.50.

Almost all distortions decrease when you decrease the vertex distance.

- quote -

A quarter-diopter of cyl is almost negligible. Vertex distance is more
important.

- quote -

That wouldn't create blur. It would make you see double. Do you see double?

- quote -

"Distorted field of view" sounds like increased barrel distortion from a
larger vertex distance. Barrel distortion decreases with decreasing vertex
distance. Adjust the frame to fit closer.

- quote -

This is a "size" effect, like barrel distortion. The 025 lesser lens should
give the _same_ or _better_ acuity at the monitor distance. Size effects
increase with vertex distance. Have the frame adjusted. This is exactly the
sort of problem that "neurological adaption" will cure.

- quote -

It means you worry too much, quite likely.

- quote -

Are your other sphincters wearing out too?

Measure the distance to the book in meters. Take the inverse. Reduce the
glasses by the result. At your age, it's a waste of time and money but
that's how it's done.

And you will find it's TERRIBLY blurry at a distance. Maybe a quarter
diopter is enough?

- quote -

I believe some of your problems can be improved by reducing the vertex
distance. Then the other problems will improve on their own.

-MT

Hi,

I promised this would be my last inquiry so please have patience
and answer

I recently got a pair of new eyeglasses and end up quarelling with the
optometrist as she didn't want to change the glasses nor refund
because it's already made (eyeglasses cost a lot in my country
so it is not something that can be replaced easily if there slight
problem, the optometrist would rather fight it out with customers).

My original eyeglasses prescription was
OD -8.0D with 0.25D Astigmatism
OS -9.0

I spent half time wearing glasses and contacts the past 20 years.

The frame was quite old so I got my vision tested to get a new
frame. It was found out that my old glasses still show 20/20
and since Im comfortable with it. She just told me she'd
make the glasses similar to my old ones by reading the
power in her machine. After I got the new glasses, I found
out it is less clear. When I confronted her. She angrily defended
that her machine showed -8.0 OD -8.75 OS (no astigmatism both)
for my old glasses when other machines from other optometry
shops showed -8.0D OD with 0.25D Astigmatism and -9.0 OS.
And she based it on her machine which resulted in less
power glasses compared to my original.

Now the following questions bug me for 2 days already with no
solutions in sight even researching at internet so to ask you
guys is the last resort (I have tried other ways!)

1. When looking far. My new glasses look less clear. In the
case of the right lens with both new and old pair similar -8.0D but
the new one not having the 0.25D astigmatism of the old. Is
the clarify significant for the one with the astigmatism
correction?

2. Should eyeglasses need to be aligned in the optical
axis so that both images would merge perfectly?

3. My new glasses are smaller than the old ones. Could
smaller glasses show a more distorted field of view at the
centers with more field curvature at the mid centers?

4. This is the biggest dilemma. Everytime I was looking at the
computer LCD monitor. The new pair with 0.25D lesser minus
power shows the images in the monitor as not flat but
floating with the centers of the LCD closer to me. While
the original glasses that is clear at far shows flat LCD image.
What can produce this effect where glasses with less
power and showing more blurred faraway images can
have closer images that float or not flat??

5. After using the new glasses for an hour or two looking
at the LCD monitor. My front teeth become sensitive from
probable referred ocular feeling. What does this mean?
Could the new glasses be causing strain to my eyes with
the floating LCD view (yet lesser power and more blurness
when looking at afar compared to old glasses)?

6. Is it possible to lower the power of my original
prescription -8.0D OD with 0.25D Astigmatism and
-9.0 OS in such a way that my ciliary muscles would
be TOTALLY relaxed when reading a book? How
low should the powers be decreased approximately
assuming I have zero presbyopia. Some formula would be
appreciated.

I'd spent more money to get new glasses and see more
optometrists. But I need to know the theoretical answers
to the above questions so I'd at least have some ideas
before spending more hard earn moneys for 3rd
glasses or more (and optometrists not multidisciplinary
enough which is usual in a third world country where I
live).

Please, this is the last questions for those who are
losing patience answering my inquiries. Thank you.

PIa