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What are "Cylinder" and "Axis"?

This is a discussion on What are "Cylinder" and "Axis"? within the Toric Contact Lenses forums; Cylinder and Axis. Sounds like a cartoon. I don't wear toric contacts lenses, but I ...


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  #1 (permalink)  
Old 01-09-2008, 11:05 AM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Nov 2007
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Default What are "Cylinder" and "Axis"?

Cylinder and Axis. Sounds like a cartoon.
I don't wear toric contacts lenses, but I like reading the questions on this site and I just like to learn new things. Sometimes when someone asks a question about their toric contacts they mention their "cylinder" and "axis."
I can tell that "axis" has something to do with the fact that a toric contact lens cannot be rotated from a certain position on the eye. They have to stay in place in order to properly correct the astigmatism. When people say "my axis is 180" that sounds like 180 degrees. So . . . 180 degrees from what?
I have no idea what "cylinder" means. Can someone help?
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Old 01-23-2008, 01:13 PM
Contact Lenses Forum - Senior
 
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Default What are "Cylinder" and "Axis"?

You're right, ICU2. It *does* sound like a cartoon. "Thanks for watching `Sponge Bob SquarePants' kids. Now stay tuned for 'Cylinder and Axis' right here on Cartoon Network!"
Sorry. Your question. While searching for some proper terminology to post a question on this site, I found the answer to your question.

*Ahem*

"Cylinder" is a measurement of astigmatism. As you may or may not know, astigmatism is caused by the eye's cornea (corneal astigmatism) or lens (lenticular astigmatism) being oval rather than round. The cylinder number shows just how oval the eye is. If the cylinder number is positive, it means the person is far sighted. A minus sign means they're near sighted.
"Axis" communicates where the cylinder needs to be in order to correct the astigmatism.

I hope that helps, and readers, if I made any mistakes, please don't hesitate to correct my error(s).
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Old 10-16-2009, 04:36 PM
Contact Lenses Forum - Bachelors Degree
 
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Default

Quote:
Originally Posted by Bonkers View Post
You're right, ICU2. It *does* sound like a cartoon. "Thanks for watching `Sponge Bob SquarePants' kids. Now stay tuned for 'Cylinder and Axis' right here on Cartoon Network!"
Sorry. Your question. While searching for some proper terminology to post a question on this site, I found the answer to your question.

*Ahem*

"Cylinder" is a measurement of astigmatism. As you may or may not know, astigmatism is caused by the eye's cornea (corneal astigmatism) or lens (lenticular astigmatism) being oval rather than round. The cylinder number shows just how oval the eye is. If the cylinder number is positive, it means the person is far sighted. A minus sign means they're near sighted.
"Axis" communicates where the cylinder needs to be in order to correct the astigmatism.

I hope that helps, and readers, if I made any mistakes, please don't hesitate to correct my error(s).
Thanks for your input, Bonkers. I like your "stay tuned" announcement.

As far as I can tell, you've got things right, but I'm the one who asked the question so I'll believe just about anything you say.

Anybody else want to take a shot at Bonkers' explanation?
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Old 06-15-2010, 10:07 AM
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Default

Quote:
Originally Posted by Bonkers View Post
You're right, ICU2. It *does* sound like a cartoon. "Thanks for watching `Sponge Bob SquarePants' kids. Now stay tuned for 'Cylinder and Axis' right here on Cartoon Network!"
Sorry. Your question. While searching for some proper terminology to post a question on this site, I found the answer to your question.

*Ahem*

"Cylinder" is a measurement of astigmatism. As you may or may not know, astigmatism is caused by the eye's cornea (corneal astigmatism) or lens (lenticular astigmatism) being oval rather than round. The cylinder number shows just how oval the eye is. If the cylinder number is positive, it means the person is far sighted. A minus sign means they're near sighted.
"Axis" communicates where the cylinder needs to be in order to correct the astigmatism.

I hope that helps, and readers, if I made any mistakes, please don't hesitate to correct my error(s).
Okay, you're gonna hafta help me with that axis thing. If the axis of a prescription is 90 degrees, what is 90 degrees from what?
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Old 06-15-2010, 10:16 AM
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Quote:
Originally Posted by LP39A View Post
Okay, you're gonna hafta help me with that axis thing. If the axis of a prescription is 90 degrees, what is 90 degrees from what?
If I recall correctly, a previous poster said it was 0 Deg at horizontal.

knotlob
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Old 06-15-2010, 11:06 AM
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Quote:
Originally Posted by Knotlob View Post
If I recall correctly, a previous poster said it was 0 Deg at horizontal.

knotlob
Okay, I'm a little fuzzy (No pun.) about this axis thing. So if someone's axis is 90 degrees, what is that 90 degrees measuring?

I'm going to take a swing at it. So if my axis is measured at 90 degrees, that means that my cornea (in the case of corneal astigmatism) is shaped like a football (European rugby ball) which is oriented vertically, which would be 90 degrees off from the 0 degrees horizontal you said used as a starting point, right?
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Old 06-15-2010, 02:38 PM
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Quote:
Originally Posted by Kyleden View Post
Okay, I'm a little fuzzy (No pun.) about this axis thing. So if someone's axis is 90 degrees, what is that 90 degrees measuring?

I'm going to take a swing at it. So if my axis is measured at 90 degrees, that means that my cornea (in the case of corneal astigmatism) is shaped like a football (European rugby ball) which is oriented vertically, which would be 90 degrees off from the 0 degrees horizontal you said used as a starting point, right?
Yes, I believe so.

knotlob
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Old 06-15-2010, 03:24 PM
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Default Mystery Solved

Quote:
Originally Posted by Knotlob View Post
Yes, I believe so.

knotlob
Well, that wasn't so hard. Thank you knotlob, and nice work Kyleden.
So a person with an axis of 90 would have a cornea shaped like that upright prolate spheroid up there, correct? (I found that term "prolate spheroid" in another thread here.)
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Old 06-17-2010, 11:49 AM
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Default

Okay, that's axis, but what cylinder. How is a contact lens like a cylinder?
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Old 06-17-2010, 12:08 PM
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Quote:
Originally Posted by LP39A View Post
Okay, that's axis, but what cylinder. How is a contact lens like a cylinder?
The astigmatism correction bit of the lens is like an elongated or stretched sphere so that it is longer in one direction than it's diameter. Some people think of it as like an American football/UK Rugby ball, but it is not so pointed as that at the ends.

knotlob
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Old 06-17-2010, 01:33 PM
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Default I Think I've Got It . . . Then Again

Quote:
Originally Posted by Knotlob View Post
The astigmatism correction bit of the lens is like an elongated or stretched sphere so that it is longer in one direction than it's diameter. Some people think of it as like an American football/UK Rugby ball, but it is not so pointed as that at the ends.

knotlob
Ah, so it's more like an oval than a circle, is it? So the cylinder is the stretched bit of the lens, and the axis is what direction it's oriented? Is that it?

Oh wait. One more thing just occurred to me. If the axis is measured in degrees, where is 0?
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Old 06-17-2010, 03:41 PM
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Quote:
Originally Posted by RawBob View Post
Ah, so it's more like an oval than a circle, is it? So the cylinder is the stretched bit of the lens, and the axis is what direction it's oriented? Is that it?

Oh wait. One more thing just occurred to me. If the axis is measured in degrees, where is 0?
Please see post #5. Zero is horizontal.

knotlob
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  #13 (permalink)  
Old 06-25-2010, 04:44 PM
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Quote:
Originally Posted by Knotlob View Post
Please see post #5. Zero is horizontal.

knotlob
Just because I'm That Kind of Chap, I'm going to copy and paste post #5 right here so you don't have to scroll back up.

"If I recall correctly, a previous poster said it was 0 Deg at horizontal."

You're welcome, my lovelies.
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  #14 (permalink)  
Old 07-27-2010, 04:49 PM
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Default

Quote:
Originally Posted by Bonkers View Post
Just because I'm That Kind of Chap, I'm going to copy and paste post #5 right here so you don't have to scroll back up.

"If I recall correctly, a previous poster said it was 0 Deg at horizontal."

You're welcome, my lovelies.
You're too kind, Bonkers.

So have we got this straight everybody?
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Old 07-29-2010, 12:18 PM
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Default Does This Help

What this thread needs is a diagram clearly illustrating what cylinder and axis look like. As they say, "A picture is worth a thousand words."

Here's the closest thing I found, but it still doesn't quite do it. Imagine you were to come to Lens 101 because you just heard of something called cylinder and axis for the first time, would this picture be of any help to you?
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Old 07-30-2010, 12:26 PM
Contact Lenses Forum - Bachelors Degree
 
Join Date: Nov 2007
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Default

Quote:
Originally Posted by Kyleden View Post
What this thread needs is a diagram clearly illustrating what cylinder and axis look like. As they say, "A picture is worth a thousand words."

Here's the closest thing I found, but it still doesn't quite do it. Imagine you were to come to Lens 101 because you just heard of something called cylinder and axis for the first time, would this picture be of any help to you?
Not especially, Kyleden. It has those "slab-off zones" that I don't understand and doesn't have the word "axis" by itself.

I tried, but I couldn't find anything better.
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Old 08-16-2010, 02:54 PM
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Default Here's a Picture

I found this image of an astigmatic cornea. I hope it helps.
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Old 08-16-2010, 03:29 PM
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Default Astigmatism Illustrated

Quote:
Originally Posted by Guinness View Post
I found this image of an astigmatic cornea. I hope it helps.
I like that picture, Guinness. It give me a good idea what astigmatism looks like. I'm guessing that the back of a toric lens would match this bulging shape?
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Old 08-20-2010, 04:36 PM
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Default

Quote:
Originally Posted by Kyleden View Post
I like that picture, Guinness. It give me a good idea what astigmatism looks like. I'm guessing that the back of a toric lens would match this bulging shape?
I think it does . . .

Guinness?
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