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How to Read Your Eyeglasses Prescription

When we get the eyeglasses prescription from the eye doctor, we always are confused by the series of numbers and abbreviations. It stops us from order prescription eyeglasses online. Let’s take some time to decipher and understand what do those numbers and abbreviations mean.

OD OD stands for the right eye.
OS OS stands for the left eye.
OU OU stands for both eyes.
Sphere (SPH) SPH refers to the refractive correction in the prescription. Minus (-) values are for nearsightedness, and Plus (+) values are for farsightedness.
Cylinder (CYL) & Axis Cylinder (CYL) refers to astigmatism. It can be either positive (+) or negative (-). Axis is recorded as an angle in degrees, between 1°and 180°. Therefore, if there is a CYL value on your prescription, then there must be an Axis for it.
ADD (Addition) The ADD value is also referred to as a "Near Addition" or "Reading Addition". Add value indicates how much extra power is required 'on top' of the distance prescription for near or intermediate glasses. This is always "+" value in 0.25 steps and the same value for both eyes.
Prism& Base Direction Diopters measure the amount of prism correction and indicate how misaligned your eyes are. The “base” is the thickest edge of the prism. It may be on the outer edge of the lens (Base Out, BO), the inner edge (Base In, BI), or at the top (Base Up, BU) or bottom edge (Base Down, BD).
Pupillary Distance (PD) It is the measurement of distance between the pupils. On any prescription, PD can be written in different ways: e.g., 59 (Single PD), 29.5/29.5 (Dual PD), or 59/62 (Distance PD/Near PD).
Below are some common prescription types to help you navigate yours.
Standard Grid Format
final refraction
Written Prescription with Prism

With no grid format, the information on this blank format with a written prescription

Written Prescription with Prism
Progressive/Bifocal

For multi-focal glasses, as well as reading and computer glasses, your Rx will include an ADD or NV value. This number always has a (+) sign and the same for both eyes.

Progressive/Bifocal

Prescriptions FAQ

1. what’s the PD

PD is short for pupillary distance. It measures the distance between the center of your two pupils. This number helps the lab to know where to center the optical center of the lens over the pupil to where the individual can get the best vision for how the lens curves. If this does not line up properly it can cause discomfort, blurriness, and headaches.

I have dual PD, how to enter it?

A dual PD is provided with two numbers and is the measurement of each pupil center to the center of the bridge of the nose in millimeters. For example: 32/32 When placing the order, please check “Dual PD” to enter your PD number for the right eye and the left eye.

3. I have PLANO /PL under SPH on my prescription.

Plano/PL means no nearsighted or farsighted correct is needed for a given eye. Just leave it as a 0.00 when entering the prescription on the order form on our website.

4. I have SPHERE/SPH/DS under CYL on my prescription.

SPHERE/SPH/DS in the cylinder space, it indicates that no correction need for a given eye and should be chosen as 0.00 on the order form.

5. I have BALANCE/BAL on my prescription.

The word Balance for either the right or left eye means that the eye is either damaged or the vision is so poor it is not correctable. So, they want the lens to seem like the eye that is correctable. (Same SPH as the other eye), in order to have the same lens thickness in appearance and weight.

6. Can I use my contact lens prescription when ordering eyeglasses?

Unfortunately, eyeglass and contact lens prescriptions aren't the same. Eyeglass lenses are positioned at a distance from the eyes, while contacts rest directly on the eyes. That distance affects the lens power required for eyes to focus properly. We suggest to contact your eye doctor to get your prescription for eyeglasses.

7. I have a prescription for multi-focal glasses, how to read it for single vision glasses.

For multi-focal glasses, as well as reading and computer glasses, ADD or NV value will be included in your Rx. This number always has a (+) sign and the same value for your both eyes.

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Multi-focal glasses

To get a prescription for single vision distance from a multi-focal prescription with ADD, simply remove the ADD values. Keep the cylinder and axis the same, regardless of the change in focal distance. Use the original distance PD 29.5/29.5 listed in the prescription

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Single Vision Distance Use

To get a prescription for the single vision reading from a multi-focal prescription with ADD, simply algebraically add ⅔ of the prescribed add power to the spherical portion of the distance prescription. If the original distance prescription contains a cylinder value, document the unchanged cylinder and axis behind the new sphere power. For the PD, use the middle value between the distance PD and near PD, that is 28.5/28.5.

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Single Vision Computer Use

To get a prescription for the single vision reading from a multi-focal prescription with ADD, simply algebraically add the full prescribed add power to the spherical portion of the distance prescription. The result of this addition is the new sphere of power. if the original distance prescription contains a cylinder value, document the unchanged cylinder and axis behind the new sphere power. For the PD, use the original distance PD 27.5/27.5 listed in the prescription.

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Single Vision Reading Use