Please note that your prescription may not include all the values listed above and some boxes may be blank.
O.D. / O.S. – OD and OS values tell which eye the prescription is for. “O.D” refers to the right eye and “O.S” refers to the left eye. In some prescriptions, the right and left eyes may simply be called “R” and “L”.
SPH – Spherical power is the most common value contained in almost all prescriptions and refers to the amount of distance vision correction required. A minus sign (-) means that the prescription is for myopia (myopia) and a plus sign (+) means that the prescription is for hyperopia (hyperopia). In some prescriptions, SPH may also be referred to as “Sphere”, “Power” or “PWR”.
CYL – The value of the Cylinder measures the degree of astigmatism you have and the strength required to correct it. The higher the number, the more astigmatism you have.
AXIS – The value of the Axis also refers to astigmatism and informs the orientation of astigmatism. The Axis is displayed in degrees and is required for lenses that correct astigmatism.
B.C. – The base curve of a lens (measured in millimeters) indicates the curvature inside the contact lens. This value is used for contact lenses and is not required for glasses.
DIAMETER – The diameter (measured in millimeters) is the distance from one lens edge to the other. This value is used for contact lenses and is not required for glasses.
ADD power – This value indicates the additional amount of energy required to ensure clear vision in the near range and is used for individuals with presbyopia.
Pupillary Distance (PD) – Your eyeglass prescription may also include your pupillary distance. This value is usually a single number and refers to the distance (in millimeters) from the middle of one eye to the other. Some prescriptions may show two PD values - one on the right and one on the left. In this case, each value refers to the distance from the middle of the nose to the middle of the eye.
To measure your pupillary distance (PD):
1. Place a ruler on the bridge of your nose.
2. Measure the distance between the center of your pupils. You can measure distance by looking in the mirror or you can have a friend do it.
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