Toric contact power increments

I'm trying to get into some toric contacts, but I also want to keep my
current prescription without overcorrecting. I'm looking for -0.5x180
and -1x180. My eye doc said the minimum possible is -0.75, and just
surveying online stores it looks like they all go in 0.5 increments, so
I couldn't hit the -1 either.

Is there any brand that could hit my Rx exactly? I can only assume
that most people just over or undercorrect by 0.25 and don't care, but
I'm pretty sensitive to it. Thanks.

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how myopic are you? If all you have is a bit of astigmastim, I dont see
why you even need correction. Many people are still 20/20 or 20/25 with
-1 astigmastim or less.

 

Up to -0.75 to -1.00 cyl at axis 180 is ususally ver easily masked by a
conventional lens. The stronger the myopia or hyperopia, the less
likely the need for a cyl correction at 180. If your prescription is
only astigmatism, then it may be necessary to wear those powers.
Generally, -0.75 cyl s is the lowest power available.

Dr. Tom

 

if you can't answer peoples questions then why even bother to respond.
go away twit.

 

Thanks for the replies. I'm basically all astig; my spherical is +0.25
and PL. I guess there's few enough people like me that there's no
market.

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Depending upon your interest, it might be worth trying whatever your OD
recommends as best. A pair of .75s sounds attractive to me, because
then you don't have to worry about getting them mixed up!

As others have posted, toric contact lens powers aren't always the same
as glasses astigmatism powers. You'll need to get some, stick them in
and then get overrefracted to find out what they do to *your* eyes.

On the other hand, if you are as picky as it sounds like you are, it
might just not be worth the hassle.

 

"On the other hand, if you are as picky as it sounds like you are, it
might just not be worth the hassle."


thats what I thought. He probably sees 20/20 or 20/25 without
correction. Toric contacts would cost him money, cause some discomfort,
blur vision when they rotate, have a small risk of infection, etc. He
can try but its not gonna make a difference since they wont be the
right power and with his pescription so low, theres no market for it.

 

People "like you" that love a really accurate correction do best with
RGP contacts. If you wore a sherical RGP with aspheric peripheral
curves you could see at least as well as you have ever seen with
glasses, perhaps even better. I have quite a few patients that have
..50 to 1.0 D cylinders who read the 20/10 line with their aspheric RGPs
on!

 

Can you give me a ballpark price that I'd expect for something like
that?

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Reading about RGP, it sounds like since they are rigid, they can
reshape the cornea to some extent and "mask" astigmatism without
actively correcting for it. The one site I read said that up to 3
diopters can be addressed this way sometimes. Does it ever make sense
(with a low astigmatism-only Rx) to prescribe something like a zero
power RGP and let it just reshape the eye rather than correcting it
"optically"?

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To answer both of your posts at once, your cost should be between $150
and $250 for a pair of lenses that can last 2 to 3 years. Disposable
soft torics can easily cost 80 to 100 dollars every three months, so
the RGPs are very cost effective.

As far as fitting philosophy is concerned, I'm trying not to be
trite when I say "That's why your optometrist went to college for 8
years." In essence, the fitting of RGPs is both a science and an art,
and when your doctor selects a back surface curve on the contact that
beautifully covers the odd front surface of your eye, you just might
see better than 20/20 with a zero power contact. Once the lens is on
your eye, the doctor performs an "over refraction" in which he sees if
any minimal amount of power adds to your quality of vision. As I said
in an earlier post, soft lenses are "monkey lenses"...as in any monkey
can take them out of a foil wrapper and hand them to you. They fit
like fitting bedroom slippers, when two sizes work for 90% of all who
try them. Well-fit RGPs are like a custom shoe or a well fit
suit...nothing works better.

 

Here's what I'm thinking. Since I have astigmatism, my cornea is not
shaped the way I'd like it to be shaped. I haven't given up hope that
my astigmatism could go away some day (it appeared out of the blue 10
years ago). Reading about RGP and it's effects leads me to think that
the contacts could subtly "train" my cornea by reshaping it the way I'd
like it to be shaped. Reading other descriptions, such as the one
below, makes it sound more like a retainer; I show up with mis-shapen
corneas, and you make a contact that conforms exactly to that shape.
Seems like that would tend to make my eye stay the same rather than
change -which could be good or bad of course.

I guess the different descriptions seem to be slightly in conflict.
Does RGP reshape the cornea, or fit it like a glove? I thought that
hard contacts tended to improve uncorrected vision in the short term,
but that doesn't fit with the "fit like a glove" description.

Thanks.

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I wasn't really talking about myopia. I only have astigmatism.

I've heard that pilots used to try to pass their eye tests by wearing
hard cotacts and then taking them out just prior to the test. The
examiners had to develop a method to tell whether this was the case.
Unless this isn't true, it indicates some kind fo retainer effect.

But maybe you're simply saying that nothing like this can prevent
eyeball elongation or whatever causes myopia in most people. If I
understand astigmatism correctly though, it's all in the cornea?

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Here's what got me started:

http://www.wingeyecare.com/cl_torics.htm

"RGP lenses may also be used because their "stiffness" acts to shape
the cornea to a small degree and may correct mild to moderate cases of
astigmatism (RGP lenses may help mask up to 3 diopters of astigmatism)."

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Charles, the answer is that RGP lenses, over time, have a
"sphericalizing" effect on the cornea. The shape of the cornea is
indeed influenced by the shape of the lens back surface. This is why
long-time RGP lens wearers make poorer candidates for orthokeratology.
A patient with large amounts of corneal astigmatism is not going to do
well in a spherical back surface lens, no more than a square peg would
fit in a round hole. However, those with small to moderate amounts of
corneal astigmatism will see it diminish with RGP use in most cases.
Ortho-k can get rid of astigmatism within the treatment area, but not
peripherally.

I take advantage of the corneal shape changing effects of RGP contacts
all the time when working with failed LASIK cases. Patients invariably
see better once the lenses are removed. You can go to my website and
look at the Powerpoint presentation to see how and why.

DrG
http://www.coppellfamilyeyecare.com

 

Sorry to ask the same thing over and over, but how is it that the RGP
could sphericalize the cornea if the back of the RGP lens itself is not
speherical? Or is it? My understanding was that the back of the RGP
is a custom fit, so if I have astigmatism, the back of the RGP would
reflect that. Or is it that you sort of split the difference and err
on the side of slightly spherical to the extent that you think the
cornea can mold? So for mild astigmatism you use a mostly spherical
RGP, but for more you start to deviate?