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    How Do I Read My Prescription?

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    Eyeglass prescriptions are printed a few different ways, but they all provide the same information. Here is an example of what your prescription could look like:

    Sample Prescription
    This is a Printed Rx, which is easiest to read. They also included the PD, which is helpful.
    This Rx was handwritten, but in a boxes, so that it is clear which number is for which measurement.
    This Rx is the most difficult to read, but we can assist if you need help.

    This is what it will look like on our site:

    The Rx entry on payneglasses.com

    Most state’s laws say that an eyeglass prescription is valid for 2 years, however most states allow for the doctor to adjust this based on their professional judgment. Unless otherwise noted, your Rx is out of date after 2 years. 

    1. OD, OS, OU

    OD is oculus dexter (latin) which refers to the RIGHT EYE

    OS is oculus sinister meaning LEFT EYE

    OU is oculus uterque meaning BOTH EYES

    2. Sphere (SPH)

    This indicates the strength of the lens power, measured in increments of 1/4 Diopters (D). This value is the prescribed amount of correction for Nearsightedness (Myopia) or Farsightedness (Hyperopia). If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or no sign, you are farsighted. When there is no spherical correction, some doctors write 0.00 or Plano (PL).

    3. Cylinder (CYL)

    This indicates the strength of the lens power to correct Astigmatism. If nothing appears in this column, the value is 0 or “SPH”, it indicates that there is no astigmatism. If an eyeglass prescription includes cylinder power, it also must include an axis value. Conversely, if there is no cylinder power, there will be no axis.

    4. Axis

    Axis on your prescription refers to where on this scale the CYL power should be.

    The Axis will be a value between 1 and 180 where 90 corresponds to the vertical meridian of the eye, and 180 corresponds to the horizontal meridian. To avoid mistakes, doctors usually write this as 3 digits. For example, an axis value of 45 is the same as 045. When written freehanded, the axis value comes after an “X”, such as: +1.00 -1.50 x145. 

    5. Add or NV-ADD

    This is the added magnifying power applied to the bottom part of Bifocal, Trifocal or Progressive lenses that allows you to see up close. The number in this section of the prescription is always a plus power, even if there is no symbol (+). The add power is usually the same for both eyes, however in certain rare occasions it could be different between the 2 eyes. If you have 2 different ADD values, click the “Two Values” link.

    Sometimes the prescription will contain the term Near Vision Only (NVO). This means that the prescription glasses will be reading glasses. With these on, the near vision should be clear, however distant objects will appear blurred.

    6. Prism

    Prism is prescribed to correct for problems with eye alignment. This is measured in prism diopters 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. 

    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 ; BO = base out. 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). 

    Most prescriptions do not contain prism and the spaces for prism value are then left blank or simply not included. If your prescription includes prism, you will need to check the box labeled “Need Prism Correction”. If you have more than one Prism value for each eye, click the box that says “Has More Values”.

    Only use this box if you have prism correction on your Rx.

    7. PD (Pupillary distance)

    Pupillary distance, sometimes referred to as pupil distance or just PD, is the distance between the center of each pupil and the bridge of your nose measured in millimeters. PD is essential for crafting prescription glasses because it helps us know where to place the power on your lenses. Without a correct measurement, the prescription power of your lenses will be off-center from your eyes and you won’t be able to see out of your prescription glasses, even if your prescription is otherwise 100% correct.

    Binocular PD, sometimes referred to as single PD, is total distance between the center of both pupils.

    Monocular PD, sometimes referred to as dual PD, is the measurement of the center of each pupil to the bridge of the nose. To enter monocular PD, click on the Monocular PD tab. 

    What do I do if my PD is not on my Prescription? Call the doctor’s office. They don’t always write it on your Rx, but they will usually have the number on file. If obtaining your measurement from your optometrist isn’t possible, no worries—you can measure it from home using our special ruler! For more information on measuring your PD, go to https://www.payneglasses.com/pupillary-distance

    8. Additional Comments

    There is often an area for the doctor to write additional comments or recommendations. This is usually where they would specify NVO (Near Vision Only) or if the Prescription Eyeglasses are to be used for a specific task like music or computer work. Other recommendations written in this section would be to specify the lens material, or lens coatings such as coatings for Anti-Reflective lenses, Photochromic (Light-Responsive) lenses. It may also indicate which type of multi-focal (bifocal or progressive) you should choose.


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