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Does anyone know how to convert a glasses rx to a contacts rx (astigmatism)

Discussion in 'Parents Off Topic' started by C6H12O6, Aug 17, 2013.

  1. C6H12O6

    C6H12O6 Approved members

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    My cylinder for both eyes is -1.00. none of the astigmatism brands have a cylinder of -1.00.
    My rx is
    right eye sphere -0.75 cylinder -1.00 axis 95
    left eye sphere -1.25 cylinder -1.00 axis 80
     
  2. swellman

    swellman Approved members

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    Not an expert but I do know that contact lenses come in discreet units for correction and you can't just "convert". You may very well have to try a few different combinations. Also, your eye chemistry and lifestyle affect what brand and type is recommended. You might have to go up on your dominant eye and down on the other or even the opposite. You might have to go through several pairs of lenses just to get it right.

    My recommendation is to have a professional do it for you.

    TL;DR: It's complicated ... let a doctor do it.
     
  3. Danielle2008

    Danielle2008 Approved members

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    I would also have a doctor write the script. I would think you would have to have an rx anyway to order your contacts?

    As for the contacts...I wonder if you don't require toric lenses, as your astigmatism is fairly mild. Maybe that is why there is no 1.00 option?
     
  4. C6H12O6

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    Well it seems that in Canada they purposely don't give your pupillary distance and the info you need for contact prescriptions to discourage ppl from ordering online.

    Once I buy two boxes from walmart. One box for my left eye and one box for my right eye I can get the info right off the box.

    Or walmart charges 40$ for the information

    The rx is from an optometrist though it just omits info you need to order glasses or contacts online. I even got glasses at walmart and they would not give me my pupillary distance for future reference
     
  5. C6H12O6

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    what is the lowest # you can have for cylinder and thus the mildest astigmatism? I really no nothing about this stuff ?
     
  6. swellman

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    For what it's worth I have to pay for a glasses Rx and additional for a contact Rx.
     
  7. funnygrl

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    You need a contact lens fitting. That's likely what the $40 is for. Every place here charges a contact lens fitting fee annually. There's no way to get the information you need to order contacts from a glasses prescription. Wearing poorly fitting contact lenses can cause corneal damage. Just not worth it. Either pay the $40 or stick with glasses.
     
  8. C6H12O6

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    I got a free sample of contacts and training on how to fit them. it was free bc I already bought glasses from walmart.

    They just refuse to release the info I need to order the contacts online :(
     
  9. ChristineJ

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    Have you had a contact lens exam? It's different from a regular eye exam, because they take certain measurements of your eyes that are specific for fitting contacts. They would then give you a contact lens prescription which, again, is different from a regular prescription for glasses. :cwds:

    Christine
     
  10. C6H12O6

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    The optometrist wrote the original rx. Than an optician ordered the sample lenses. The optician examined my eyes after the sample pair.

    I have to order 2 boxes (1 box per eye) so I can get the specific numbers she used.

    I like the contacts a lot, but the problem is I can't read very small fine print with them on. ( I would usually have to take off my glasses to read very small fine print.)

    I?m going to make an optometrist appointment about this issue.
     
  11. bladebarrier

    bladebarrier New Member

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    I realize this is a pretty old post, but I stumbled across it high up on the google list, and thought I would interject.

    Your astigmatism is right on the border, which is why you probably don't see many toric lenses for that level. They're annoying, more expensive, but important if needed. I believe the consensus is over -.75 you need them. I did not use toric lenses until I was over -1.25, and had no issues.

    Your PD (the distance between your pupils), is not part of your contact prescription, because the lenses are on them. PD is used for glasses, and should have been on your script. If they didn't write it on there, they messed up and you should go back and have them add it. You could actually measure it yourself, if you have someone help you. It's just the number of millimeters between your pupils. Look straight ahead, put a quality ruler on the bridge of your nose, have someone stand back a little and measure it. There's not much to it, but you do want to be accurate. Again, it's for glasses, not contacts.

    Your prescription is so low that you probably would use the same prescription for contacts as you do for glasses, the problem is that you need to be fitted by someone trained, because they have to measure the shape and size of your eye. If you don't get fitted you can damage your eye, or end up with a floating around lens. If they decide to go to a toric, it's even more important as they have to align correctly in your eye (which is the annoying part).

    Anyways, I just thought I would put that out there, even though it's an old post. If you can afford contacts, you can afford the fitting. On the other hand if your optometrist doesn't write down your PD, they made a mistake or are a jerk, and you should complain or measure it yourself, as your glasses prescription is worthless without knowing it.

    EDIT: Just to add in, the parts for your contact script, aside from your actual OD, OS, and Axis, is Base Curve and Diameter of each eye. If the OP went in only for a contact exam (which is odd in the US, but could be the case in other countries), that could be why the OP didn't receive a PD length. The numbers would look something like BC 8.x, and Diameter 14.x. Mine are 8.7, and 14.5, to give a rough estimate of how the numbers might appear, but it's very important to get those correct. It's easier to go backwards from a contact prescription to a glasses prescription, than the other way around, but the PD is very important because it places where the center of each glasses lens is. The PD also is different for near sighted and far sighted. They are normally two different numbers. Mine are 64 for distance, and 60 for reading (though I do not need reading glasses, the optometrist should still be including that on the script, in case you need "cheater glasses", as some call them). So the measurement suggestion I listed above is for distance glasses, not reading glasses. I should have explained that better, but then again most of us with mild reading issues just use cheap cheaters to get by. If you need both, your prescription should have that shown for bifocal requirements, and the separate scripts.

    /hope that helps (and stay away from polycarbonate and high index glasses, when possible), as they add distortion and color fringing. Trivex or basic CR-39 is better for vision in glasses. Don't fall for the hype, unless your script is so high that you need them. That's the sort of stuff that makes people get blurry vision around the sides, and dizziness, and why PD is an important measurement, as it keeps your pupil centered with the lens. Contacts don't have that issue, if fitted correctly, which is why the fitting is important, and PD is irrelevant.
     
    Last edited: Apr 19, 2014
  12. C6H12O6

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    Thanks for posting :)
     

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