How To Read Your Prescription


Your Child’s prescription usually has two columns, one marked right or OD, and one column marked left or OS. This refers to the prescription for the right eye and the left eye, respectively. See example below.

  Right (OD) Left (OS)
Sph +2.00 pl
Cyl -1.00  
Axis 90  
Add +0.75 +0.75
Prism 2BI  
PD 54/52
S/V Near


SPH or Sphere stands for spherical power. It is a + if your child is long sighted and – if your child is short sighted. The further from zero this number is, the thicker the lens will be and the stronger their prescription is. Occasionally you might see a “ PL” or PLANO. This means the sph power is zero. In the example above, the sph is +2.00 in the right and zero or plano in the left eye. Sometimes you migh see a “BAL” or “BALANCE”. This means the prescription in that “BAL” eye is the same as that of the other eye.


Cylinder is the measure of astigmatism . It usually means the difference between the spherical power of the two meridians of an oval shaped eye. For some very oval eyes, the astigmatism is a higher number while for other eyes maybe a very small number or even none at all. No two eyes are the same an it is quite normal to have cyl in one eye and not the other. When there is no astigmatism, your optometrist or ophthalmologist may not write anything in the cyl or may write “DS” meaning no astigmatism. Opthalmologists usually write cyl in a "+" format while optometrist write cyl in a "-" format. Whatever format it is, all you need to do is enter as it is written on your prescription and leave it to us to do the rest of the work.


Axis stands for the orientation of the astigmatism or cyl. In simple terms, where is the longest part and shortest part of the oval eye oriented. It is measured in degrees from 1 to 180.


Add stands for addition and is used with multifocal, extended focus and reading glasses. It simply means the extra power needed to be added to the distance prescription for the reading prescription. If your child does not need a multifocal, extended focus or a reading glasses that is different from the distance glasses, you will not see an "ADD".


Prism is used the align eyes that may not be focussing or co-ordinating very well together. It is often used to correct a squint or eyeturn, or double vision. Prism lenses are custom made, hence additional fee applies when placing an order with prism. Prims lenses will usually add to the thickness of the lens. It is therefore recommended that you choose a thinner lens to ensure optimum outcome. Prism shifts images in different directions. can be oriented in many different ways. Please see below for examples of how your ophthalmologist or optometrist may write the prism. Whatever format it is, all you need to do is enter as it is written on your prescription and leave it to us to do the rest of the work.

  • "BI" = "Base In" = "In"

  • "BO" = "Base Out" = "Out"

  • "BU" = "Base Up" = "Up"

  • "BD" = "Base Down" = "Down"

There is extra cost with grinding prism into your glasses. Please email us on for further details. 


PD is 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 your ophthalmologist or optometrist has left it blank, please ask them for this number otherwise you can simply look at the link on our website on "how to measure your child's PD"


At the bottom of your prescription, your ophthalmologist or optometrist may write a the lens type they recommend. For example reading glasses, distance glasses, multifocal, extended focus, bifocal, and sunglasses lenses Here are some recommendations they may write and what they mean or other names it may be called.

  • SVN : SV Near, Single Vision Near or Reading glasses

  • SVD : SV Distance, Single Vision Distance glasses

  • MF : Multifocal

  • BF : Bifocal

  • EF : Extended Focus, Interview Lens, Access Lens, Desk Lens

  • Mild Add : Mild add, Young Progressive, Antifatigue lenses

If you need to clarify any details of your prescription you can email us at



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