Anonymous
Anonymous asked in HealthOther - Health · 1 decade ago

Contact vs spectacle presciptions - different?

Hi. I got my eyes tested for contact lenses in the netherlands: one eye was -2.00 and the other -2.50. When I got an eye test in the UK a couple of months later for glasses, the prescription was -1.75 and -2.00 respectively. In the UK, they said that in Holland they don't have to be trained ophthomologists to do testing, so its not that detailed.

But basically, I bought contact lenses to the strength of my original presciption (-2, -2.5). Do the numbers vary because the first test was not good, or might it vary because contact lenses are different from glasses? Cheers.

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    In the UK a qualified optometrist examines your eyes. When you are young, you have plenty of focusing ability (accommodation). Sometimes during an eye examination, if you over accommodate, a stronger prescription will be found. There are ways to check for this during the examination. I would imagine the weaker of your 2 prescriptions would be correct. You can see clearly through a prescription that is too strong, but not through one one that is too weak.

    The other relevant point is that when a lens for myopia (shortsightedness) is taken away from the eye, it becomes effectively weaker. (increased vertex distance). therefore, when it is placed closer to the eye, or on the eye in the case of a contact lens, it is effectively stronger. It therefore does not need to have the same prescription as the spectacle lens, but a weaker one.

    Although slight variations between practitioners results might be found when examining eyes for refractive errors, with your moderate prescription, -0.50 difference in the two left eye prescriptions is quite considerable and "circle of least confusion" irrelevant in this case.

    The number in your prescription, if divided into 1, is the furthest away you can see clearly, in metres. ie -2.00 is 1/2m or 50cm.

    -2.50 is 1/2.5 or .4m or 40cm.

  • 1 decade ago

    You do not have to worry about this.

    Reasons:

    1) If you are above 16 years of age, comfort is what is more significant. These varied powers do not influence the health of your eyes

    2) No two doctors give you same prescription. We really are not "measuring" something here. We are only finding a power that can form "circle of least confusion" on retina. This means, several different powers can achieve this, therefore different doctors prescribe different powers

    3) Contact lenses are fitted on a different philosophy. Do not attempt to pick contact lenses "over the counter"

    4) Spectacles have power in lens only. Contact lenses are (lens power+power of tear film trapped under the lens). So the contact lenses & spectacles may need different powers

    Trust one doctor and follow him.

    Source(s): I am an optometrist (27+ years of practice)
  • Anonymous
    1 decade ago

    I think it's just that one of the tests was no good.

    I have contacts and I do not believe there's any difference in the prescriptions, but I often don't pay attention to the important details. So, I could be wrong :)

  • Jethro
    Lv 5
    1 decade ago

    I don't know. Lol.

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