HOW TO READ YOUR EYEGLASSES PRESCRIPTION?
You’ve just had an eye exam and your optometrist or ophthalmologist has given you an eyeglass prescription, but what do all those numbers on your eyeglass prescription mean?
And what about all those abbreviated terms, such as OD, OS, SPH and CYL?
What OD and OS mean?
They are abbreviations for oculus dexter and oculus sinister, which are Latin terms for right eye and left eye. Your eyeglass prescription also may have a column labeled “OU.” This is the abbreviation for the Latin term oculus uterque, which means “both eyes.” Some doctors and clinics have opted to modernize their prescriptions and use RE (right eye) and LE (left eye) instead of OD and OS.
Other terms on your eyeglass prescription
Your eyeglass prescription contains other terms and abbreviations as well. These include:
Sphere (SPH)
Sphere indicates the amount of lens power, measured in diopters (D), prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted.
Cylinder (CYL)
Cylinder indicates the amount of lens power for astigmatism. If nothing appears in this column, either you have no astigmatism, or your astigmatism is so slight that it is not really necessary to correct it with your eyeglass lenses. The number in the cylinder column may be preceded with a minus sign (for the correction of nearsighted astigmatism) or a plus sign (for farsighted astigmatism). Cylinder power is always written after sphere power in an eyeglass prescription.
Add
Add is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia. The number appearing in this section of the prescription is always a “plus” power, even if it is not preceded by a plus sign. Generally, it will range from +0.75 to +3.00 D and will be the same power for both eyes.
Prism
This is the amount of prismatic power, measured in prism diopters (“p.d.” or a superscript triangle when written freehand), prescribed to compensate for eye alignment problems. Only a small percentage of eyeglass prescriptions include prism.
An example of an eyeglass prescription
