Vision Rx Decoder
Enter the values from your eyeglass or contact lens prescription to get a plain-language explanation of what each field means and what your vision correction entails.
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Sphere (SPH)
Cylinder (CYL)
Axis
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Prism
OD (Right)
OS (Left)
Prescription Field Reference
OD (Oculus Dexter)
Latin for "right eye." Always listed first on prescriptions.
OS (Oculus Sinister)
Latin for "left eye." Listed second.
Sphere (SPH)
Overall lens power. Negative = nearsighted (myopia). Positive = farsighted (hyperopia). Unit: diopters.
Cylinder (CYL)
Amount of astigmatism correction needed. Blank or 0 = no astigmatism.
Axis
Orientation of astigmatism in degrees (1–180). Only present if CYL is non-zero.
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Extra magnification for reading (presbyopia). Found in bifocal/progressive prescriptions. Always positive.
Prism
Correction for eye alignment problems (strabismus). Measured in prism diopters.