Glasses VS Contact Prescriptions

Prescriptions for glasses versus contacts

In many cases, both eyeglasses and contact lenses can be used for vision correction. Nearsightedness, farsightedness, presbyopia, and even astigmatism can be treated with either method. However, if you want to use both contacts and glasses, Calgary Optometrists unanimously agree that you'll need two different prescriptions. While it can be a bit of a letdown to have to pay the extra fee involved, the two types of vision correction each require their own type of diagnosis and measurements. To ensure your safety, as well as the best possible fit and comfort level, you'll require two distinct prescriptions.

Adjusting your prescription for contact use

Unlike glasses, which typically sit approximately 12 millimetres away from your eyes, contacts rest directly on the surface of your cornea. If the exact same prescription that you use for your glasses is applied to your contacts, the degree of magnification will be far too intense. Your optometrist needs to apply a mathematical formula to adjust for this discrepancy. While those with very mild vision loss may not see any difference in the numbers on their prescription, those with more severe vision loss certainly will.

Measurements unique to contacts

If contacts aren't fitted to your unique eye shape and size, they'll be uncomfortable to wear. It's important that your optometrist determine the following measurements:

  • Base curve. The curvature of one person's eye can be very different from that of another. The base curve (BC) measurement determines what depth of arch in your contacts will provide the best fit. The most comfortable contacts to wear are neither too loose, nor too snug.
  • Diameter. The lens diameter (DIA) measurement conveys the size of lens most suited to your eyes. For soft contact lenses, this falls somewhere between 13.5 and 15.5 millimetres.

Other factors that need to be considered with contact lenses

In addition to making sure they fit correctly, it's also important that the right type of contact be selected for your lifestyle and type of vision impairment. Your optometrist will help you assess which types and brands will be best given your unique circumstances.

Contact lens prescriptions are valid only for a demarcated term

Vision and optical health can change over time, so it's important that you adhere to recommendations made by your optometrist as to when you should get a new contact lens prescription. Contact lens prescriptions expire in one year, it is important to see your optometrist yearly for your eye exam.

Calgary optometrists in your neighbourhood

Dr. Bishop & Associates comprises a team of caring and qualified optometrists who are available to help you find eyeglasses and contact lenses that meet your needs. With three convenient locations, you're sure to find an optical centre that's close by. Contact us today to set up an appointment or visit us at one of our Calgary clinics.

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