Indeed it can.  In fact, people with convergence insufficiency use
their accommodation all the time to help them converge.  This
inevitably leads to against-the-rule astigmatism, with/or without a
small amount of accommodative myopia.

We can teach, but it's up to you to learn.

DrG

Excessive accomodation does not cause myopia, but it can lead to astigmatism.

Live and learn!

(These Dr.s do have their weapons!)

--
Dicky

They're not all the same now are they?  Of course not.
The astigmatism probably comes from habitually over-accommodating to
the 10 year-old prescription.  SHAME ON YOU.  You're not a very
compliant patient, are you?

Plano comes from plane surface which means no power = 0.

You put yourself in the position of having to decide among several
different prescriptions.  Maybe you should try all of them.

I guess the term "error" was an unfortunate term.  Let's use the term
"variability."  Try weighing a ball bearing on an analytical balance 5
times.  You will get a different weight each time.

You are literally fretting over 0.25 diopter differences, when the fact
of the matter is that you have been wearing a ten year-old prescription
that is off by a factor of 7!

DrG

This is a prescription i got mabye 10 years ago, I'm now 41.

I doubt you

well, all the Optometrists have given me a much lower 'power figure'
(?), and Im told this is something to do with ageing. Also there was no
astigmatism before.

Because of this, your eyes have a tendency to

I dont know that 'plano' means.

would seem rather

Yes, and what im after is someones opinion as to whether i should go
0.25, or 0.50. Also whether prescription B is the best / average. I've
been put in a position where I have to make a decision about what
Prescription to go for, whilst know close to nothing about Optometry.

I'm not sure what you mean by this.. A power of -0.25 has 'more plus'
than -0.50; um, therefore is 0.25 the 'built in error in favour of more
plus? Therefore I should go for 0.50?

Thanks, I'm trying to 'take this' somewhere, but I'm still confused. I
was hoping some guru would just tell me whether to go for prescription
A B C, or D. :)

B and D are the average Prescriptions, the only difference is the -0.25
or -0.50 power.
They are also the prescriptions where the Optometrist didnt know that i
used to wear -1.75..

Andy
ps, I thought Optometry would be less subjective.. During many of the
eye tests, I couldnt tell the difference, especially the astigmatism
tests (a bunch of dots on a hexagram (?)), I usually had to decide
whether I 'preferred' the bolder fuzzier dots, to the lighter/fainter
sharper ones. In hindsight, it was only in the last test that i was
also concentrating on the shape of the hexagram, and using that as a
factor as to which one I 'preferred'. when things are equally but
*different;y* distorted, its hard to select which one is 'better',
unless the patient is told what criteria to use for 'better'. At least
with the eye charts, you can either read the correct letter, or not.
The Optometrist D, when i later showed her the previous results and
asked her if 0.25 would be ok for power simply said that I read more
letters with 0.50. Does this settle the matter, or does it say more
about my subjective performance on the day.. im so confused..

Given all the information, -1.75 seems way too much power.  I doubt you
would be comfortable driving w/o correction if indeed that was your
true prescription.  Because of this, your eyes have a tendency to
"prefer" more minus.  Going from -1.75 to plano would seem rather
extreme, and you would probably "reject" that prescription.  The other
prescriptions do not seem "significantly different" from each other.
There is built-in error in every measurement, and the process of
refraction is designed to truncate the error in favor of more plus
rather than too much minus.

Take it from there.

DrG

Hi Dr G,

well, re: power , the average of
0.00
0.25
0.50
and
0.75,

= 0.25, OR 0.50

Should I go for the lower one?

Also, I gave Optometrist A my prescription sunglasses, so he knew what
my previous prescription was, as did the Eye Specialist (Prescription
C).  Prescriptions B and D were done with no mention of my previous
prescription. Could this have been a factor? How relevant is my past
prescription in determining my prescription today?

Andy

Calculate the average?

DrG

To all people who know more about Optometry than 1:

Hi,

Short version:
I'm trying to find the best prescription for my eyes, but my initial
attempt to get a second opinion has resulted in me going to 3
Optometrists, and 1 eye specialist, and now I have 4 different
prescriptions! They are pretty close, and of course no Optometrist is
going to say that the *other* optometrists prescription is the one to
go for, so im stuck! Which one should I choose?

Long version:
I'm 41,  musician / IT person, and last time I got an eye test (late
90's) was prescribed -1.75. I lost my glasses years ago, and have been
simply getting around without them. Main problem is driving, especially
at night, and I occasionally use disposable contacts (My old contect
lens box says -1.75, BC9.0, dia 14.2, if that helps) and marvel at how
sharper everything is. However I needed new glasses, and hence a new
prescription

The first Optometrist (A) prescribed this:

Prescription A:

-0.75    -1.0    x110
-0.75    -1.0     x60

When I put the mock-up frames on they seemed too strong (as he said
they would). He said it would take a couple of weeks to adjust! I've
been getting around for ages without glasses, and this seemed just
counter-intuitive. I said no offense but Id like a second opinion, he
said no problem.

So I rang my eye specialist/doctor, but he was away. His secretary
recommened Optometrist B. I made sure I got enough sleep, and spent
less time in front of the computer (in case these factors had affected
Prescription A)

Optometrist B gave me

Prescription B:

-0.25    -1.0     x95
-0.25    -0.75    x55

Ok, so its different, weaker power, and from what I understand
'significantly' different axis's (?) for the astigmatism. This
Optometrist B said I needed to see an Eye Specialist, so I thought,
cool, whilst I'm there I can get a third definitive opinion.

A few months go by, but the Eye Specialist was very fast and very
dismissive. I explained my dilemna, and showed him the two
prescriptions. He smiled, and said my eyes are fine, and that I didnt
need glasses. I said "well, when im driving at night things can look
pretty blurry", in the end he rushed through a few really quick tests
(took him less than 5 minutes). I did show him the two previous
prescriptions so his contribution IS biased, but anyway here's what
the Eye Specialist recommended:

Prescription C:

-0.50    +0.5    x15
-0.50    +0.5    x165

I realised this was a different code to the other two, and he admitted
that he did this on purpose so I wouldnt worry about it anymore. I
didnt really appreciate this condescending attitude. When I asked him
whether this result was close to presciption A or B, (or in between),
he refused to answer the question, and flippantly kept saying 'This
is the right  prescription for your eyes'. I was not impressed.

I walked into another optometrists shop, and got the guy there to
translate Prescription C to match the notation (?) of the other two,
and got

Prescription C:

0.00    -0.50    x105
0.00    -0.50    x75

So, he didnt think I needed *any* power correction (VERY different to
Prescription A), and the astigmatism seemed different yet again!

I thought to myself , 'well, I'll just go with Prescription B, it seems
the middle of the road between the two'.

But I couldnt help thinking about how flippant the Eye Doctor was, and
since his 1st response was that I didnt need glasses, mabye I sould
discard his prescription from consideration. I knew there had to be a
4th Prescription. And so it came pass, that I walked into another
optometrists, and explained the situation, and without showing them my
previous results, obtained:

Prescription D:

-0.50    -1.00    x90
-0.50    -0.75    x55

Ok, this was very close to Prescription B, and seems to be in between A
which was stronger, and C which had 0.0 power..

I realise these are very similar, and I'm currently trying to decide
between B and D, with the main issue being whether to go for 0.50, or
0.25. On one hand I'm told to get the one which made me read more
letters ( 0.50 rather than 0.25), but otoh, will 0.25 encourage my eyes
to work more, and be 'better for me'? I'll be wearing them mostly
for driving, movies, and other outdoor situations (looking at views
trees, clouds )

Do these results reflect the competency of the optometrists, or my
subjective performance during the test? Factors such as:
1.    How much sleep I'd had
2.    Whether I was regularly blinking during the examination or staring,
which was drying up my eyes
3.    How stressed I felt (in general) on the day.
4.    How much time Id spent in front of the computer that week.

If Optometrist B thought I needed 0.25 power, doesn't that mean that
that's how well my eyes can perform? Ie therefore I wasn't at my
'peak' when I needed 0.50?

your comments welcome,

Andy