How To Interpret Contact Lens Case Abbreviations

Lens AbbreviationsAD (add): the additional power in bifocal contact lenses. Usually between +1.00 and +3.00.

AX (axis): location of astigmatism in degrees (°). Value between 0° and 180°. This is only used on prescriptions for toric lenses and is accompanied by the term CYL.

BC: base curve, or radius (in millimetres). Refers to the curvature of the eye lens. Usually between 8.0 and 9.5, with 8.6 being one of the most common values.

CYL: cylinder. In toric lenses, the area of extra power to correct astigmatism. Usually between -0.50 and -3.00.

DD: daily disposable or disc diameter

DW: daily wear

DIA: diameter of the lens (in millimetres). Typical values are 13.8, 14.0, 14.2 and 14.5.

EW: extended wear

FTW: full-time wear

OD: oculus dextrus, or right eye (also RE)

OS: oculus sinister, or left eye (also LE)

OU: both eyes

PWR: power or SPH, SF: sphere. The strength of the contact lens in diopters (D). A negative value means nearsightedness (myopia) and a positive value means farsightedness (hyperopia).

RGP: rigid gas permeable

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