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Big Change in New Prescription

This is a discussion on Big Change in New Prescription within the General Contact Lens Care and Questions forums; Okay, these past couple of years I've been getting my prescription from Costco.The last two ...


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  #1 (permalink)  
Old 02-27-2011, 02:25 PM
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Default Big Change in New Prescription

Okay, these past couple of years I've been getting my prescription from Costco.The last two years I've gotten the same doctor, who gave me the exact same prescription (-4.75) for both eyes.

Today I had a new doctor, who gave me quite a different prescription: My right is now -5.25, and my left is -5.50.

Admittedly I see clearer now, but how did my eyesight change so much within the course of one year, especially when it apparently held steady for over two years in the past?

I also found the eye exam a lot more difficult this time, in terms of telling the optometrist which power was clearer (the whole "which looks clearer? one or two?" process). Everything looked about the same to me.

Frankly, I'm worried that my prescription isn't optimal. I'm not going as far to say this new guy was incompetent, but I'm curious how my lens powers changed so much. Is it possible that my last doctor held back (I'm starting to vaguely remember something about him keeping my prescription under a certain power, as that would increase the likelihood of headaches/dizziness, though that could be my imagination)?
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Old 02-28-2011, 10:32 AM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Dec 2007
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Default

Quote:
Originally Posted by Megalith View Post
Okay, these past couple of years I've been getting my prescription from Costco.The last two years I've gotten the same doctor, who gave me the exact same prescription (-4.75) for both eyes.

Today I had a new doctor, who gave me quite a different prescription: My right is now -5.25, and my left is -5.50.

Admittedly I see clearer now, but how did my eyesight change so much within the course of one year, especially when it apparently held steady for over two years in the past?

I also found the eye exam a lot more difficult this time, in terms of telling the optometrist which power was clearer (the whole "which looks clearer? one or two?" process). Everything looked about the same to me.

Frankly, I'm worried that my prescription isn't optimal. I'm not going as far to say this new guy was incompetent, but I'm curious how my lens powers changed so much. Is it possible that my last doctor held back (I'm starting to vaguely remember something about him keeping my prescription under a certain power, as that would increase the likelihood of headaches/dizziness, though that could be my imagination)?
Hi there, Megalith. Welcome to Lens 101.

I have to admit that it's strange for a prescription to stay the same for years, and then suddenly change. Usually when people are in their teenage years, their prescriptions change a lot. You sound like you've got a long history though, and unless you started wearing contacts when you were about ten years old, you're probably not a teenager now. Still to go from -4.75 to a 5 point something is not that big of a jump. I think that going from -4.75 to a -5.0 is the smallest change you can make.

My guess is that your new doctor has a different technique for calculating your prescription, and since you said you see more clearly now, I'd say this new doctor is an improvement. I don't think your former doctor "held anything back." Did you notice anything different about the eye exam you were given by your new doctor?
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Old 03-27-2011, 03:01 PM
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I didn't note anything drastically different, although I think there was one additional test administered using a separate device I don't remember having to sit at before.

I'm bumping this because I just had my visit to another doctor yesterday. Well, now it's even more frustrating because the prescription he gave me is even more different and higher than the other guy.

Previous: OD -5.50 -0.75 180 / OS -.5.75 -0.75 175
New: OD -6.25 +0.50 x 90 / OS: -6.00 (The rest was left blank---I assume it's the same measurements as OD)

I did a quick search to figure out why I'm given pluses instead of minuses now, and apparently it's because one was provided by an optometrist and the other by a ophthalmologist? Does that completely explain why the measurements are inconsistent?

Also, it's funny how the guy from yesterday acknowledged that I wore contacts and went on about making sure to rewet by eyes with drops, but after I left, I realized that he only gave me a prescription for glasses. Or are prescriptions provided by ophthalmologists identical for both glasses and contacts? Can't be, right?
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Old 03-28-2011, 10:21 AM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Dec 2007
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Quote:
Originally Posted by Megalith View Post
I didn't note anything drastically different, although I think there was one additional test administered using a separate device I don't remember having to sit at before.

I'm bumping this because I just had my visit to another doctor yesterday. Well, now it's even more frustrating because the prescription he gave me is even more different and higher than the other guy.

Previous: OD -5.50 -0.75 180 / OS -.5.75 -0.75 175
New: OD -6.25 +0.50 x 90 / OS: -6.00 (The rest was left blank---I assume it's the same measurements as OD)

I did a quick search to figure out why I'm given pluses instead of minuses now, and apparently it's because one was provided by an optometrist and the other by a ophthalmologist? Does that completely explain why the measurements are inconsistent?

Also, it's funny how the guy from yesterday acknowledged that I wore contacts and went on about making sure to rewet by eyes with drops, but after I left, I realized that he only gave me a prescription for glasses. Or are prescriptions provided by ophthalmologists identical for both glasses and contacts? Can't be, right?
It looks like you're having a tough time of it, Megalith. I'll see what I can do to help.

When your prescription has plus numbers, it means the lenses help you see things close up, like when you read or use the computer. The minus prescriptions help you see to drive and look out the window; stuff like that.
The way I like to remember it is to imagine reading a newspaper without your contacts. If you have to bring the paper closer--decrease the distance between it and your eyes, you need a minus prescription. If you have to move it farther way, increasing the distance, then you need a plus prescription.

You never mentioned your age, but if you're in your early forties you may be starting to develop farsightedness. It happens to everyone, or so I hear.

Okay, now the difference between an optometrist and an ophthalmologist. For that we turn to our ABC News correspondent Richard Rosen, M.D. on abcnews.go.com.

"An ophthalmologist is a medical physician who has specialty training in the diseases of the eye and is also trained to recognize systemic diseases, which may affect the eye, or to recognize diseases within the eye which may affect the rest of the body.

An optometrist has specialty training in creating glasses and contact lenses in order to give a person the best corrected vision. He also has training to recognize possible abnormalities of the eye which need to be referred for medical care. An optician is a technician who is trained to make and dispense glasses based on the prescription from an ophthalmologist or an optometrist."

Does that explain the inconsistent measurements? It might. It doesn't mean that an optometrist will only prescribe plus lenses while an ophthalmologist will only prescribe minus, or the other way around though.

Finally, a prescription for glasses is not the same as one for contact lenses mostly because contact lenses are actually touching your eye while the lenses in a pair of glasses are about an inch in front of your eyes. They may turn out to be pretty close, but it's rare. Did you know that -40 degrees Celsius is also -40 degrees Fahrenheit? It's just coincidence but it does illustrate the principle.
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Old 03-29-2011, 12:15 PM
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Quote:
Originally Posted by Railfan View Post
It looks like you're having a tough time of it, Megalith. I'll see what I can do to help.

When your prescription has plus numbers, it means the lenses help you see things close up, like when you read or use the computer. The minus prescriptions help you see to drive and look out the window; stuff like that.
The way I like to remember it is to imagine reading a newspaper without your contacts. If you have to bring the paper closer--decrease the distance between it and your eyes, you need a minus prescription. If you have to move it farther way, increasing the distance, then you need a plus prescription.

You never mentioned your age, but if you're in your early forties you may be starting to develop farsightedness. It happens to everyone, or so I hear.

Okay, now the difference between an optometrist and an ophthalmologist. For that we turn to our ABC News correspondent Richard Rosen, M.D. on abcnews.go.com.

"An ophthalmologist is a medical physician who has specialty training in the diseases of the eye and is also trained to recognize systemic diseases, which may affect the eye, or to recognize diseases within the eye which may affect the rest of the body.

An optometrist has specialty training in creating glasses and contact lenses in order to give a person the best corrected vision. He also has training to recognize possible abnormalities of the eye which need to be referred for medical care. An optician is a technician who is trained to make and dispense glasses based on the prescription from an ophthalmologist or an optometrist."

Does that explain the inconsistent measurements? It might. It doesn't mean that an optometrist will only prescribe plus lenses while an ophthalmologist will only prescribe minus, or the other way around though.

Finally, a prescription for glasses is not the same as one for contact lenses mostly because contact lenses are actually touching your eye while the lenses in a pair of glasses are about an inch in front of your eyes. They may turn out to be pretty close, but it's rare. Did you know that -40 degrees Celsius is also -40 degrees Fahrenheit? It's just coincidence but it does illustrate the principle.
Thank you for taking the time to research and explain all that, Railfan. I appreciate your effort.
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Old 05-10-2011, 03:50 PM
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Originally Posted by Shade Maiden View Post
Thank you for taking the time to research and explain all that, Railfan. I appreciate your effort.
Your welcome. I have to admit, though, that Google makes it pretty easy.
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Old 05-12-2011, 01:27 PM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Dec 2007
Posts: 476
Default You Have Failed Me For the Last Time

Quote:
Originally Posted by Railfan View Post
Your welcome. I have to admit, though, that Google makes it pretty easy.
That's mostly true, Railfan, but I just experienced Google failure a few minutes ago.
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Old 11-21-2011, 02:53 PM
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Join Date: Nov 2011
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Hi,
I just stumbled across this on Google. I know it was a few months ago and I hope all the issues have been sorted.
Just a quick thing I wanted to clarify for you though:

"Previous: OD -5.50 -0.75 180 / OS -.5.75 -0.75 175
New: OD -6.25 +0.50 x 90 / OS: -6.00 (The rest was left blank---I assume it's the same measurements as OD)"

Using the + lens in this situation is purely a different way of expressing your prescription.
The new OD one is exactly equivalent to

-5.75/-0.50x180

(just expressed in a different form - probably, as you said, due to the difference between an optometrist's training and an opthalmologist's training., but it makes absolutely no difference)

As you can see this is much closer to the previous OD, and the difference you will find between them is minimal. (remember lenses come in 0.25 steps)


As for the 2nd OS one, it would be terribly lax of an opthalmologist to leave a bit blank. He almost certainly didn't mean that it's just the same as the OD measurements. What he probably meant was that he found no astigmatism in that eye. (are you aware about the 2 different parts of the prescription? The first bit is the spherical correction and the second bit corrects for astigmatism)
It's a bit worrying that an optometrist has found an 0.75 astigmatism and the opthalmologist found nothing - this doesnt sound right at all as you would very much notice if that part of your prescription was so wrong.

All I would say is, I hope they sorted it out for you and you have excellent vision now! If not, you ought to go in and demand a retest. And also, your contact lens prescription will almost certainly be different from your glasses prescription. I'm not sure how it works in america but in the UK we have a whole seperate test to find the contact lens prescription, so get them to book you in for that.

Hope this is at least vaguely interesting....
(I am a student optometrist btw)
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Old 11-21-2011, 04:53 PM
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Join Date: Nov 2007
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Quote:
Originally Posted by midnighthiccup View Post
Hi,
I just stumbled across this on Google. I know it was a few months ago and I hope all the issues have been sorted.
Just a quick thing I wanted to clarify for you though:

"Previous: OD -5.50 -0.75 180 / OS -.5.75 -0.75 175
New: OD -6.25 +0.50 x 90 / OS: -6.00 (The rest was left blank---I assume it's the same measurements as OD)"

Using the + lens in this situation is purely a different way of expressing your prescription.
The new OD one is exactly equivalent to

-5.75/-0.50x180

(just expressed in a different form - probably, as you said, due to the difference between an optometrist's training and an opthalmologist's training., but it makes absolutely no difference)
Hold on a second. Are you saying that a -6.25 sphere measurement is the same as -5.75? You lost me, which isn't difficult to do as I don't always follow very well.
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Old 11-21-2011, 05:16 PM
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Quote:
Originally Posted by unclebuck View Post
Hold on a second. Are you saying that a -6.25 sphere measurement is the same as -5.75? You lost me, which isn't difficult to do as I don't always follow very well.
It's all to do with the 2 parts of the prescription: it's not very helpful just to look at one part by itself as it's also affected by the other part.

The first part of the prescription is the spherical part, so you can think of this as being the same power all over the lens.
The second part, which corrects for astigmatism, is a cylindrical part. This means that it has a power only in one direction on the lens. (at the axis specified in the prescription)

So you have to add these parts together to get the resulting lens that works for your prescription.

so in our example here
-6.25/+0.50 x 90

The first part specifies a lens with the power -6.25DS all the way round the lens.
The second part specifies that at its 90 degree axis there is +0.50 of power (the vertical axis - imagine the lens is a clock face - the line that joins the 12o clock and 6o clock is the 90 degree axis)

This then allows the lens to have different powers in different meridians. we can see here that in our 90 degree meridian we have added the extra +0.50, so the resulting power is -5.75, compared to the power in the opposite meridian (the 180 degree axis, or from 3 o clock to 9 o clock) which is still -6.25.

However here we have expressed it by putting a bit of extra POSITIVE [ + ] power to change the power in one meridian. It makes sense that we can describe it the opposite way by changing the initial spherical power of the lens and putting a bit of extra NEGATIVE [ - ] power in the OPPOSITE meridian.

So if I said that the first part of the prescription was actually -5.75, then to make the other meridian the correct power I would need to add more negative power: -0.50

hence

-5.75/-0.50x180 = -6.25/ +0.50 x 90






Hope this is useful!! I am no teacher so not amazing at explaining things, but if you're interested in this stuff, google lens transpositions and sphero-cylindrical lenses and it might help you out more
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Old 11-22-2011, 12:42 PM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Dec 2007
Location: United States
Posts: 442
Default Transposition

Quote:
Originally Posted by midnighthiccup View Post
It's all to do with the 2 parts of the prescription: it's not very helpful just to look at one part by itself as it's also affected by the other part.

The first part of the prescription is the spherical part, so you can think of this as being the same power all over the lens.
The second part, which corrects for astigmatism, is a cylindrical part. This means that it has a power only in one direction on the lens. (at the axis specified in the prescription)

So you have to add these parts together to get the resulting lens that works for your prescription.

so in our example here
-6.25/+0.50 x 90

The first part specifies a lens with the power -6.25DS all the way round the lens.
The second part specifies that at its 90 degree axis there is +0.50 of power (the vertical axis - imagine the lens is a clock face - the line that joins the 12o clock and 6o clock is the 90 degree axis)

This then allows the lens to have different powers in different meridians. we can see here that in our 90 degree meridian we have added the extra +0.50, so the resulting power is -5.75, compared to the power in the opposite meridian (the 180 degree axis, or from 3 o clock to 9 o clock) which is still -6.25.

However here we have expressed it by putting a bit of extra POSITIVE [ + ] power to change the power in one meridian. It makes sense that we can describe it the opposite way by changing the initial spherical power of the lens and putting a bit of extra NEGATIVE [ - ] power in the OPPOSITE meridian.

So if I said that the first part of the prescription was actually -5.75, then to make the other meridian the correct power I would need to add more negative power: -0.50

hence

-5.75/-0.50x180 = -6.25/ +0.50 x 90

Hope this is useful!! I am no teacher so not amazing at explaining things, but if you're interested in this stuff, google lens transpositions and sphero-cylindrical lenses and it might help you out more
I did like you said and Googled "lens transposition." Because of my short attention span my eyes began to glaze over at around "the second part, which corrects for astigmatism, is a cylindrical part" area.

Here's what I found:

Transposition

To transpose a lens is to rewrite the expression of its powers without actually changing them.

To transpose from one sphere-cylinder form to another:

Add the sphere and cylinder powers together. (If the signs are the same add; if they are not the same subtract.) The result is the sphere power.
Retain the power of the cylinder, reverse its sign and change the axis by 90 degrees.


Thankfully there's a calculator on that site where I can just plug in the numbers if necessary, and I think it will be.
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Old 02-02-2012, 05:07 PM
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Posts: 380
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Quote:
Originally Posted by Wendy94 View Post
I did like you said and Googled "lens transposition." Because of my short attention span my eyes began to glaze over at around "the second part, which corrects for astigmatism, is a cylindrical part" area.

Here's what I found:

Transposition

To transpose a lens is to rewrite the expression of its powers without actually changing them.

To transpose from one sphere-cylinder form to another:

Add the sphere and cylinder powers together. (If the signs are the same add; if they are not the same subtract.) The result is the sphere power.
Retain the power of the cylinder, reverse its sign and change the axis by 90 degrees.


Thankfully there's a calculator on that site where I can just plug in the numbers if necessary, and I think it will be.
Thanks for giving us the information, Wendy94, and for being brave enough to admit that you don't get it.
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