How To Read Your Child's Eye Prescription

How To Read Your Child's Eye Prescription

If this is your first time with a child in glasses, you may not know where to start, let alone how to read a prescription for glasses. It may feel intimidating, but don't worry! It's actually easier than you might think to read a prescription. Follow our how-to guide below and you'll be a prescription-reading guru in no time.

how to read eye prescription

What's on a glasses prescription?

Rows on prescription:

  • OD: Oculus Dexter, Latin for "right eye."
  • OS: Oculus Sinister, Latin for "left eye."

Columns on prescription:

  • SPH: Sphere. This indicates the lens power prescribed to correct nearsightedness (-) or farsightedness (+). In general, the further away from zero, the more vision correction your child will need. The higher the number (ignoring + or -), the stronger the prescription
  • CYL: Cylinder. This reveals the lens power required to correct astigmatism. Astigmatism means that the front of the eye has an irregular shape, leading to distorted vision at various angles. This results in blurry vision and oftentimes headaches. Do not fret. This is very common. According to Eyecare Business, it is estimated that about "70 percent of all Rx’s written in the U.S. include astigmatism correction." 
    • Note: often times MDs use plus (+) and ODs use minus (-) for the CYL value. If you see a plus (+) in the CYL value this means that a conversion needs to take place and the SPH and AXIS values will be affected. Nothing you need to do on your end. We will do this for you, but wanted to let you know so you're informed.
  • AXIS: This number (measured in degrees) represents the orientation of the cylindrical (CYL) power for astigmatism correction. If you have a CYL number, you will also have an axis number.
  • Additional details you may find to the right of the AXIS:
    • ADD: Addition. This value is added to the sphere for bifocal or progressive lenses. 
    • PRISM: This is used to help people with muscular imbalance in their eyes. Prism helps to reduce eyestrain and correct double vision.
    • PD: Pupillary Distance. The distance between the centers of the pupils, which is used to position the lenses in frames. A PD measurement is required for us to fill your prescription order. If you do not see a PD listed on your child's prescription, simply ask your optician; they should have your PD on file. Or you can also learn how to measure pupillary distance yourself using our resources and easy measuring tool.
      • Pupil distance can be measured in two ways:
        • Binocular which is a pupil-to-pupil measurement, this type of measurement will be between 42-60 mm for most children.
        • Monocular which is a per-eye measurement from the pupil to the middle of the face - example : 25/24.5 - the first number (25) is for the right eye (O.D.) and the second number (24.5) is for the left eye (O.S.) - total these together to get 49.5 binocular.

Being able to read and understand your child's eye prescription empowers you to make informed decisions about their eyewear. Remember that eye prescriptions can change over time, so it's essential to have regular eye exams to ensure you have the most accurate and up-to-date prescription for your child. 


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