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How to Read Your Eyeglass Prescription

Close up of glasses focusing on vision prescription

If you suffer from specific eye problems, your eye care professional may prescribe glasses to help your eyesight. However, your prescription for glasses contains numbers and abbreviated words that you may be unable to understand. Therefore, the first step towards reading your prescription is to understand the meaning of these abbreviations.

What your prescription means

Below is a list of the most common abbreviations found on eyeglass prescriptions to help explain what they mean.


You are likely to see the abbreviated terms OD, OS and OU. OD refers to Oculus Dexter, while OS represents Oculus Sinister. They are Latin words that mean right eye and left eye, respectively. OU refers to Oculus Uterque. It stands for both eyes. These are the traditional abbreviations that are used when making prescriptions for eyeglasses. However, some eye care professionals prefer to use modernized prescriptions. Re stands for the right eye, while E stands for the left eye.


The abbreviation SPH stands for Sphere. It describes the amount of lens measured in diopters needed for good vision. The term means that the correction for your sight is spherical. If you are shortsighted, the number under the abbreviation will include a (-) sign. The number will have a (+) sign if you are long-sighted. If your prescription has the word Plano, PI, or an infinity sign, it means that you do not have distance problems. You may, however, have astigmatism. Most values will be 0.00 to +/-20.00.


Axis is the lens meridian that has no cylinder power to correct astigmatism. The axis number helps your eye care professional know the direction in which they should position a cylindrical power in the lenses of your glass. For example, the number may be between 1 and 180, where 90 represents the vertical position while 180 represents the horizontal one. The numbers only describe the position of astigmatism; they do not explain the strength of your prescription. The Axis can be present if there is a CYL value.


The abbreviation stands for Cylinder. It represents the amount of lens power you need for astigmatism. If you do not have astigmatism, you may not have anything indicated in this column. The value may be a plus or a minus, and in most cases, the value will be between +/-0.25 to +/-4.00.


Add stands for Addition. It stands for the additional correction that you need for reading. It is used in bifocal glasses, reading glasses, or varifocal glasses. It represents the additional power over the distance prescription. It only appears once in your prescription because the additional power is the same for both eyes. The value is typically between +0.50 to +3.50. 


A prism corrects lazy eyes. In addition, it may correct mild conditions, including particular eye disorders and conditions that need the image in focus to change its position. A prism is measured in Prism Dioptre. They come with directions such as UP, DOWN, IN, and OUT. The value may go up to ten.


PD stands for Pupillary Distance. It is the distance between the centers of your pupils. It is measured in millimeters. The measurement ensures that when you get your glasses, you are looking through the right spot in your lenses. It is possible to take this measurement on your own if your eye care professional does not provide it. The average number is 62mm for women and 64mm for men. However, it can range from 58 to 68mm.


Dist. stands for Distance, and inter stands for Intermediate. Distance is the prescription needed to correct short or long-sightedness. The glasses suit all activities, including walking, running errands, and driving. Inter stands for intermediate. This prescription is for people who need to correct their intermediate vision. Near-prescription glasses correct near-sightedness and are suitable for work that requires you to pay attention to detail.


BVD stands for Back Vertex Distance. It represents the distance from the back of your glasses’ lens to the cornea’s apex. It can be adjusted to change the power of the lens in relation to the eye. You’ll need the measurements when changing prescriptions for your eyeglasses. It is essential when the prescription goes beyond +/- 4.00D.

Remember: Your eyeglass prescription does not apply to contact lenses because the lens power differs. Eyeglasses are positioned at a distance from the eyes, whereas contact lenses sit directly on the eyes. Therefore, an eyeglass prescription should be used to buy eyeglasses only. 

If you do not understand your prescription, ask your eye care professional for help!


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