Reading Your Prescription

Trying to make sense of your glasses prescription? Let’s it break it down.


OD is Oculus Dexter – Right Eye

OS is Oculus Sinister – Left Eye


The first column is the sphere measurement. Plano means zero, a negative in front denotes myopia, a positive sphere denotes hyperopia.


The second and third columns relate to the amount and direction of astigmatism. The second column is the cylinder value, or the difference in the secondary curvature of the eye from the spherical curvature. 


The third column is the axis, or the direction, of the astigmatism, on a 180° scale.


A fourth column can be the ADD power – this is a strength that is added to the spherical value to create the near strength required to read. This is usually applicable to those with presbyopia.


Sometimes recommendations may be included on the prescription – for instance Dr. Grewal very strongly recommends UV protection to all of her patients and this recommendation is often right on the prescription to remind you. 


Additionally, in some circumstances, special prisms are added to the prescription to move images up, down, to the left or right. If applicable, these would be column 5 and beyond.


Now that you know how to read your prescription – you should also check that it isn’t expired! 🙂

For more information and more blog posts, visit us at Look & See Eyecare, and check out our Education Centre!

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