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How to read an eyeglasses prescription

We understand that many look at their eyeglasses prescriptions and see only a confusing jumble of numbers, symbols, and abbreviations. The following guide will help you understand this important information.


Here are some examples of how your eyeglasses prescription might look:
Example 1:
  SPH CYL AXIS ADD
O.D. -3.75 -1.25 178 +2.5
O.S. -3.00 -1.50 180 +2.5
Example 3:
      (SPH) (CYL) (AXIS)
(O.D.) R: -3.75 / -1.25 x 178
(O.S.) L: -3.00 / -1.50 x 180
(ADD + 2.50)
Example 2:
    SPH CYL AXIS PRISM
DISTANCE O.D. -3.75 -1.25 178  
O.S. -3.00 -1.50 180  
NEAR O.D. -1.25 -1.25 178  
O.S. -0.50 -1.50 180  
Reading your prescription

The "spherical error" (that is, nearsighted or farsighted). A"+"means the prescription is farsighted,A"-"means the prescription is nearsighted. The higher the number after the+or-,the stronger the prescription.

This number is used for bifocals, it gets added to the regular sphere prescription to get the near vision prescription.

Tells you which eye the prescription is for,"O.D."is the right eye.Some prescription simply List "L" and "R"

If you don't know your P.D
Learn how to measure your PDz

These mumbers describe any astigmatism.The "Cyl" number indicates the severity of the astigmatism.Axis tells you which way the astigmatism is oriented.

Enter your prescription
  Sphere (SPH) help Cylinder (CYL) help Axis help Addition (near) ADD help
Right Eye (OD)
  Sphere (SPH) help Cylinder (CYL) help Axis help Addition (near) ADD help
Left Eye (OS)
Pupillary Distance (PD): help  
Save this prescription as:

First, let's translate the abbreviations.

O.D. O. D. simply means 'right eye'. It is the short form of the latin term 'oculus dextrous'.

O. S. O. S. simply means -- you guessed it -- 'left eye'. It is the short form of the latin term 'oculus sinister'.

Sphere The number under the heading 'sphere' is the main part of your eyeglasses prescription. The number itself denotes the strength of the lens as measured in diopters. A diopter is a unit of measurement that is simply the inverse of the focal distance of the lens as measured in meters. For example, if a lens has a strength of 2 diopters, then parallel light rays that pass through this lens will focus together at a distance of 1/2 meter (50 cm) away from the lens. If you are near-sighted (i.e. - you have trouble seeing far away but can see fine up close), then you can make a rough calculation of the strength of your glasses.

Cylinder If there is no value under the cylinder heading, then you have a very simple eyeglasses prescription. If there is a value under this heading, then you have astigmatism. The majority of optometrists write the cylinder value with a minus sign in front while the majority of ophthalmologists (physicians who specialize in the eye) write the cylinder value with a plus sign in front. Regardless of which way this is written, your glasses will be made the exact same way -- these are just two different ways to write the same spectacle eyeglasses prescription. Like sphere power, the cylinder power is also measured in diopters.

Axis As mentioned above, a special cylindrical lens is needed in order to correct astigmatism. Not only does the strength of the cylindrical lens need to be specified, but the lens itself must be rotated into a specific position in order to provide the proper vision correction. The axis represents the amount of rotation of the cylindrical lens in degrees ranging from 1 to 180.

Add
(or add power)
If there is a value under the 'add' heading, then you have a bifocal (or Progressive) eyeglasses prescription.

Further information

D.S. = diopters sphere which indicates that you have only a sphere value and no cylinder value; therefore you need no corrention for astigmatism.

P.D. = pupillary distance. Learn how to measure P.D.

D.V. = distance vision

O.U. = both eyes

X = axis

N.V. = near vision, sometimes written as N.V.O.

Learn more about 'single vision' & 'multi-focal' prescriptions Learn more about abbreviations
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