How to Read Your Eyeglass Prescription


The numbers on your eyeglass prescription relate to the shape of your eyes and

strength of your vision. The numbers determine whether you have

nearsightedness, farsightedness or astigmatism, and to what degree.


OD vs. OS – get to know your left from your right eye


Eye doctors use the abbreviations “OD” and “OS” to denote your right and left eyes. 

  • OD is your right eye. OD is short for oculus dexter, the Latin for right eye.

  • OS is your left eye. OS is short for oculus sinister, Latin for left eye.


Your vision prescription may also have a column labeled "OU". This is the abbreviation for oculus uterque, which means both eyes. It is possible to have the same or different strength of vision in each eye.


Some have opted to modernize their eye prescriptions by using RE (right eye) and LE (left eye) instead of the

Latin abbreviations. The information for your right eye (OD) always comes before the information for your left eye (OS). Eye doctors write prescriptions this way because, when they face you, they see your right eye on their left (first) and your left eye on their right (second).


Sphere (SPH)


Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness. Lens power is measured in diopters (D).

  • If the number under this heading comes with a minus sign (–), you are nearsighted.

  • If the number under this heading has a plus sign (+), you are farsighted.


Cylinder (CYL)


Cylinder indicates the amount of lens power needed for astigmatism. It always follows the sphere power on an eyeglass prescription. Astigmatism means that your eye has an oblong shape (more football shaped than basketball shaped).


If nothing appears in this column, you either don’t have astigmatism, or your degree of astigmatism is so small that it doesn’t need to be corrected.


The number in the cylinder column may have a minus sign (for correction of

nearsighted astigmatism) or a plus sign (for farsighted astigmatism).

The term "cylinder" means that this lens power added to correct astigmatism is not

spherical, but instead is shaped so one meridian has no added curvature, and the

meridian perpendicular to this "no added power" meridian contains the maximum

power and lens curvature to correct astigmatism.

Meridians of the eye are determined by superimposing a protractor scale on the

eye's front surface. The 90-degree meridian is the vertical meridian of the eye, and

the 180-degree meridian is the horizontal meridian.




If an eyeglass prescription includes cylinder power, it also needs to include an axis value, which follows the cylinder power. This number tells us the orientation of the “football”.

The axis is defined with a number from 1 to 180.

  • The number 90 corresponds to the vertical meridian of the eye.

  • The number 180 corresponds to the horizontal meridian of the eye.


The axis is the lens meridian that is 90 degrees away from the meridian that contains the cylinder power for astigmatism correction.



“Add” is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia, the natural farsightedness that happens with age. The number appearing in this section of the prescription is always a "plus" power, even when you don’t see a plus sign. Generally, it will range from +0.75 to +3.00 D and will be the same power for both eyes.

Additional notations are generally made on your prescription indicating the type of lens, material, coatings to give you the most comfortable vision correction possible.

Keep in mind some prescriptions may include more than what is explained here so if you have any further questions regarding your prescription a NOW Associate will be happy to explain!

Contact us for more assistance at 09 44 07 44 07.

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