How to Read the Eyeglass Prescription?

If you ever visit an optometrist or ophthalmologist to get your eyesight checked then after examining your eyes, he will give you a prescription.

He may also tell you that either you are farsighted or nearsighted or sometimes you may also have astigmatism. You may also find in your prescription certain terms like OS, OD, SPH or CYL etc. Do you know what they mean?

Let us try to explain the meaning of all these terms after you have undergone eye exam near me.

What will OS and OD mean?

OS actually stands for “oculus sinister” while OD stands for “oculus dexter”. Both these are Latin terms of left and right eye.

Your prescription may also have the term OU which stands for “oculus uterque” that means both eyes. Many prescriptions may also write this in English rather than writing in Latin and mention it as LE (left eye) or RE (Right eye).

Few other terms used

Following are few other terms also used in the prescription:

  • Sphere (SPH)

SPH indicates the lens power which is measured in diopters which is prescribed for correcting your sight. Minus sign (-) indicates that you maybe nearsighted while plus sign (+) indicates farsighted.

The sphere term is used for indicating that your farsightedness and nearsightedness is spherical that is equal in all the meridians of your eye.

  • Cylinder (CYL)

CYL will indicate the lens power for your astigmatism. Sometimes it is left blank in this column, which means either you have got no astigmatism or very negligible amount of astigmatism that does not need any correction.

  • Axis

This will describe the lens meridian which contains no amount of cylinder power for correcting astigmatism. The axis will be defined with number from 1 – 180.

Number 90 will correspond to vertical meridian of your eye, and number 180 will correspond to horizontal meridian.

  • Add

This is an additional magnifying power applied at the bottom part of the multifocal lenses for correcting presbyopia. The number in this section is always in “plus” power, if nothing is mentioned.

Generally, it may range between 0.75 – 3.00 D and for both eyes it will be same power.

  • Prism

Prism indicates prismatic power amount which is measured in the prism diopters or it is superscript triangle when it is written freehand.

This is prescribed for compensating for problems of eye alignment. Only very few eyeglass prescriptions will include prism.