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cm Measurement

The cm measurement uses a basic optics formula to calculate the diopters of correction you need to see clearly long distance.

  1. Hold a ruler up to your eye, and measure how far away you can still read text without blur in centimeters. This is your "cm measurement".
    • The ideal precise measurement is from the surface of your eyeball, but this is obviously not safe, so measure from some facial structure near your eye.
    • Consistency is more important than accuracy, you want to be able to track your small changes over the course of a day, and larger changes over time.
  2. Calculate diopters from the measurement: Diopters = -100cm/cm measurement.
  3. If your result is stronger than -4D, and you wear glasses, you'll need to correct for vertex distance to convert this from contacts diopters to glasses diopters.
  4. If your result is stronger than -10, you'll likely have problems getting consistent readings.

Trial Refraction

If your vision is worse than -10D, you may need a trial lens kit to measure your own myopia, or you may just stick to professional optometrist exams.