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Glasses Prescriptions

After an eye exam with an eyewear prescriber, such as an optometrist or ophthalmologist, you may receive a glasses prescription. Glasses prescriptions are orders that specify the necessary corrections that need to be made in your new lenses in order to improve your vision. If you are nearsighted, farsighted, or have astigmatism, you will need a glasses prescription in order to get corrective lenses and fix the problem. Glasses prescriptions can also be used for sunglasses prescriptions and for reading glasses prescriptions. They cannot, however, be used for contact lens prescriptions. An additional fitting will be needed if you wish to get contact lenses. If you receive a glasses prescription from your optometrist or ophthalmologist, you will need to take your prescription to an optician who will fit you for your glasses. Many eye doctors have opticians in their office who are ready to see you right after your appointment. You will be able to select from a variety of frames, or you can provide your own. It generally takes about a week or two to receive your new corrective lenses.

Before you take your prescription to the optician, you may be curious as to what the numbers and letters on your glasses prescription mean.

What does Distance or DV mean?

Distance is the power of the lens prescribed in order for you to see distant objects clearly. If you have a bifocal lens, the distance is what will be placed in the top segment. Distance is determined based on how well you read different eye charts during the eye exam.

What does Add or NV (Near Vision) mean?

Add or NV, an abbreviation for near vision, is the magnifying power added to the bottom half of multifocal lenses. This is done to correct presbyopia and is always a positive, or plus, number whether or not it is preceded by the plus symbol. This number normally ranges between +0.75 and +3.00 and will be the same number for both of your eyes.

What do OD and OS, or OU, Mean?

OD and OS are for your two different eyes. OD is an abbreviation for oculus dexter. Oculus dexter means right eye, from your point of view, in Latin. OS is an abbreviation for oculus sinister. Oculus sinister means left eye, from your point of view, in Latin. If your prescription says OU instead, that is an abbreviation for oculi uterque. Oculi uterque means both eyes in Latin, meaning both of your eyes have the same prescription.

What does SPH, or Sphere, Mean?

The word "sphere," on a glasses prescription, means that the correction for farsightedness or nearsightedness is equal in all meridians of the eye, or spherical. Your prescription may say Sphere or it may use the abbreviation, SPH. This section gives the amount of lens power prescribed to correct far or nearsightedness. This is measured in diopters (D). If the number is preceded by a minus sign then you are nearsighted. If the number is preceded by a plus sign, or by no sign, then you are farsighted.

What does CYL, or Cylinder Mean?

Your prescription may have the word cylinder or just use the abbreviation, CYL. Cylinder means that the lens power needed to correct astigmatism is not spherical. If there is no number in this column, then you do not have astigmatism or your astigmatism is slight enough that no correction is needed. The number here may be preceded by a plus sign if you have farsighted astigmatism or by a minus sign if your astigmatism is nearsighted.

What does Axis Mean?

If your prescription has a value for the cylinder, then it must also contain a value for the axis. Axis describes the lens meridian that does not contain cylinder power in order to correct astigmatism. The axis column can contain a number from 1 to 180. The value of 90 relates to the vertical meridian of the eye, while the value 180 relates to the horizontal meridian.

What does Prism Mean?

Usually empty on a prescription, the prism column is the amount of prismatic power to correct eye muscle imbalance or other conditions, such as vergence dysfunction. These conditions cause problems in eye fixation or orientation. This measurement is taken in prism diopters (p.d.).

What does Base Mean?

The base is related to the prism and will be empty if Prism is. The base is the direction of the prism and relates to where the thickest edge of the lens will be. The base can contain four different abbreviations. BO means base out or toward your ear, BI means base in or toward your nose, BD means base down or toward your cheeks, and BU means base up or towards your forehead.

These are the most common terms you will come across on your glasses prescription. If you have any other terms that you are unfamiliar with, it is best to consult the optometrist or ophthalmologist who gave you the prescription.