Glossary of Eye Definitions and Glasses Terms

Want to discover all things eyewear? Find out more about your eyeglasses and sunglasses, word by word.


Glasses Cylinder

The glasses cylinder prescription (the cyl eye prescription value) indicates the power required to correct for astigmatism. The cylinder eye prescription is always accompanied by the sphere power value on your eyeglass prescription because the cyl glasses meaning does not address the strength of the power required to correct the refractive error. The value associated with the cylinder eye prescription may be positive or negative (indicating near or farsighted astigmatism, or zero if the astigmatism is so slight that it does not need specific correction.

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