Read Your Prescription.

O.S.-

This is oculus sinister, meaning left eye.

O.U.-

This is oculus uterque, meaning both eyes.

O.D. -

This is oculus dexter, meaning right eye.

Now that you just finished having your eye exam, you have your prescription in your hand and you’re wondering what style eyeglass frames will look best on you. You also happen to look at your prescription and start to wonder what all those letters and numbers exactly mean. Whether you’ve worn glasses for years, or this is your first time, understanding your prescription will give you an insight into the health of your eyes as well as your overall health.

Standard Grid Format

This is the most common format with clearly printed fields for OD, OS, SPH, CYL, etc.; values are usually entered with computer, but may be handwritten by doctor.

Rx Notes: Sphere (SPH) and Cylinder (CYL) always have a (+) or (-) sign.

 

On any prescription, PD can be written in different ways: e.g., 62 (Single PD), 33/31 (Dual PD), or 62/60 (Distance PD/Near PD).

Reading glasses / Progressive / Bifocal Format

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.

Rx Note: The type of Rx glasses may be noted on a prescription, such as DV [Distance Vision/nearsightedness] and NV [Near Vision/reading].

Spherical (SPH)

Spherical indicates the lens power. It’s pretty much the basic number by which we judge how much vision correction is required, and is measured in diopters (D). The numbers that you see in this part are either in positive or negative (+ or -). The plus sign denotes farsightedness, and the minus sign denotes shortsightedness. The term itself means that the whole eye has to be corrected, and that the correction is spherical, or equal in all meridians of the eye.

Cylindrical (CYL)

Cylindrical lenses are required for astigmatic people, and are also measured in diopters. Astigmatism is a condition in which the optics of the eye cannot focus a point object sharply enough into a focused image on the retina. This usually happens due to an irregular curvature of the lens or cornea. It’s corrected by using cylindrical lens. If your prescription has nothing in this section, it means that you don’t have astigmatism, if you see a number, it means that a particular median has to be corrected. Similar to the spherical section, + denotes farsighted astigmatism, and – denotes shortsighted astigmatism.

Axis

Now, if you require a cylindrical lens, the lensmaker will need to understand at what meridian angle the correction is required, as we mentioned earlier. You will find a number from 1 to 180 here, which is angle at which correction is required. 90 denotes the vertical meridian, and 180 denotes the horizontal meridian of the eye. Without this value, the cylindrical value mentioned above would make no sense at all.

Prism

Very few prescriptions have something written under the prism section. This is the amount of prismatic power, measured in prism diopters, required to compensate for eye alignment problems. Any sort of imbalances or muscle issues can be corrected by the value prescribed in this section.

Base

Finally, we have base, which is connected to the value prescribed in the prism section. Base refers to the direction of displacement of the prismatic correction. Here, if there’s a prism value, you will find one of four abbreviations. They are:

Rx Note: The type of Rx glasses may be noted on a prescription, such as DV [Distance Vision/nearsightedness] and NV [Near Vision/reading].

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