Nash II Cosmos

SPH = Sphere or Spherical, refers to the main correction in the prescription. Minus (-) values are for nearsightedness, and Plus (+) values are for farsightedness. If "PL" or "Plano" is written for this value then you should select 0.00 for this field.
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CYL = Cylinder, refers to a correction for astigmatism. It can be either positive or negative. A CYL value will always have an Axis value. If "DS" or "SPH" is noted in the CYL space on your prescription, you have no astigmatism in that eye. In that case, enter 0.00 for the CYL and Axis.
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Axis refers to the angle of the correction for the astigmatism (CYL) in the eye from 1 to 180 degrees. If there is no CYL value then there is no Axis value. The Axis value may be written as 3 digits, which means if your Axis value is 5, it is often written as 005.
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Prism is power, measured in diopters, used to correct vision displacement, like double vision or an eye turn. Most eyeglass prescriptions do not have prism correction. A prescription with prism will have two values per eye: a Prism (power) and Base (direction). Covry is able to accommodate prism powers with a range of 0.25 to 5.00 diopters in any direction or combination of directions.
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