How to Read Eyeglasses Prescription
It’s essential to know how to read an eyeglasses prescription! Therefore, we whipped up this guide to help you learn about it and be able to order your new set of eyeglasses as quickly as possible.
1. How To Read Eyeglasses Prescriptions?
While there might be some minor variations between different eyeglasses prescriptions, whether it's on paper or digital, your eye prescription probably looks like a small grid or chart with rows, columns, and cells. The chart incorporates a mix of letter abbreviations.
The key to reading your eyeglasses prescription, regardless you have nearsightedness, farsightedness, astigmatism, or anything else, is knowing what OD and OS stand for. They sometimes appear as O.D. and O.S. (oculus dexter and oculus sinister), which are abbreviations in Latin for right eye (OD) and left eye (OS). Some doctors may use O.U. which means both eyes. Or RE and LE for the right eye and left eye respectively.
There are other abbreviations in your eye prescription. Here is what each of them means:
● SPH(Sphere/Spherical): This indicates the amount of lens power, prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted. The larger the number following the +/-, the stronger the prescription.
● CYL(Cylinder/Cylindrical): This indicates the amount of lens power for astigmatism. This number also has a "+" or "-" sign. If "DS", "SPH", "spherical", or "PL" is stated under CYL, it means you have no astigmatism.
● AXIS: This number indicates the orientation of your astigmatism and is measured in degrees. It will be between 1 and 180. If an eyeglass prescription includes cylinder power, it must also include an axis value, which follows the cylinder power.
● ADD (also NV-ADD): The Near Vision (NV) Reading ADDition correction on a multifocal Rx. Can be used for bifocal or progressive glasses, or for single-vision reading or computer (intermediate) vision glasses.
● Prism: Prism involves a special way of making lenses that bend light differently than regular lenses. Prism is prescribed to correct problems with eye alignment. It is measured in prism diopters ("p.d." or a superscript triangle when written freehand) and written in ¼ diopter increments (I.E. 0.25, 0.50, 0.75, 1.00). Unlike SPH and CYL, there are no (+) or (-) signs. Most prescriptions do not contain prism and the spaces for prism value are then left blank or simply not included. When prism is present, the direction for the position of the prism "base" (the thickest edge) must also be written. Abbreviations are used for prism direction: BU = base up; BD = base down; BI = base in (toward the wearer's nose); BO = base out (toward the wearer's ear). It is possible to have both horizontal (BI or BO) and vertical (BU or BD) prism. It is also common to have different directions between the eyes (I.E. BU in the right eye and BD in the left eye).
● PD: Pupillary Distance is the distance between your pupils, measured in millimeters. Dual PD would be provided with two numbers, which means the measurement of each pupil's center to the center of the bridge of the nose. Dual PD usually appears in the following format: "31.5/31.5". Your PD is very important for accurately fitting your lenses to achieve visual acuity. If by some chance, your eye doctor didn’t write it down for you in your RX note, you can easily measure it by yourself.
2. Eyeglasses Prescription Chart Example
A prescription written for someone with nearsightedness.
A prescription written for someone with farsightedness and astigmatism.
Progressive prescriptions (multifocal)
Prescriptions with prism correction
3. Reminders
● Your eyeglasses prescription is also eligible to use for sunglasses, but not for contact lenses.
● Expiration Date: Your eye prescription probably won’t be the same forever—it’s important to have your eyes examined regularly to make sure they’re seeing as best as they possibly can. Eye prescriptions are normally valid for a year or two before they expire (the exact time period can vary depending on state laws). After that, you’ll need to renew it by scheduling an eye exam.
● If you have any problems reading your prescription, please contact our customer service and we will help you purchase your favorite new glasses!