How To Read Your Eyeglass Prescription?

If you just had an eye examination and if your ophthalmologist has suggested that you should wear eyeglasses, just because you have farsightedness, nearsightedness or astigmatism and if a prescription is given for the same, you will be confused with it for sure, if this is your first eyeglass prescription. You might be wondering what are those numbers in the prescription denote and you might also be confused with the abbreviations given in the prescription like CYL, SPH, OS and OD. When you are aware of these terms, you can talk with confidence and knowledge when you visit a store to place order for your eyeglasses.

OD and OS – what are they?

These two are short forms for Oculus Dexter and Oculus sinister and these are nothing, but Latin terms used for denoting the right and the left eye respectively. You will also find something called as ‘OU’ in your prescription, which means oculus uterque and this is a term used for denoting both eyes.

Even though, these short forms are used traditionally by ophthalmologists in their prescription, many clinics and doctors’ these days specify just as right and left eye for the benefit of their patients as against OD and OS. In general, in prescriptions, the details about the power in right eye will come next to left eye. Prescriptions are written by eye doctors in this way because they see the right eye of the patients first and then come to the second eye.

Other terms:

Even the prescription will have other terms like SPH and CYL as well. Here are some details about these terms:


This is a term expanded as sphere and it is something that identifies, the level of the power of lens and it is measured in the Diopters or D scale. This remedy is suggested for nearsightedness and farsightedness. If SPH has a negative sign, it denotes nearsightedness. On the other hand, if it is not preceded by a plus sign or a minus sign, it is an indication of farsightedness. The term ‘SPH’ means the correction of near or far sightedness and it is equal to all meridians of the eyes.


This is nothing, but a short form of cylinder and it identifies the level of strength power for astigmatism. If nothing is specified in the column, it means that either you do not have astigmatism or it means that the astigmatism is very slight, such that it is not necessary to correct it with the help of lenses.

The ophthalmologist will also by superimposing a protractor scale for identifying meridians on the eyes. The 900 meridian is the vertical meridian of the eye and 1800 meridian in the horizontal one.

The cylinder column will have numbers that might be preceded with a minus sign, which is prescribed for correction of nearsighted astigmatism or play sign for farsighted astigmatism. In a prescription for eyeglass, the cylinder power will follow the sphere power.

Axis, add and prism are other terms that can be found in a prescription given by your ophthalmologist.

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