How To Read Your Prescription

How To Read a Basic Contact Lens Prescription


 SPH / D / Power / Spherical  refers to the strength of vision correction for contact lenses.  Measured in diopters, it is scaled in 0.25 increments and is always preceded by a + (plus) or a – (minus).  Minus means the prescription is a correction for nearsightedness (shown here) and a plus would mean a corrective prescription for farsightedness.  The further away from zero, in either direction, the more correction you need.  It is very common to need different corrective powers for each eye.  If you do not require corrective vision, please select the Plano (0.00) option when purchasing contact lenses.  


 BC  is the mesurement of the "back curvature" of a contact lens and is mesured in millimeters.  The lower the number, the steeper the curve.

 DIA  is the diameter of the contact lens, mesured in millimeters.


 OD  is the abbreviation for "oculous dexter" which means "right eye."

 OS  is the abbreviation for "oculous sinister" which means "left eye."

Prescription Paper

Prescription Box

This is an example of the most basic, but necessary, information on a contact lens prescription.  In adition to the above information, your prescription could also include aditional mesurements, if you have an astigmatism or if you require specialized lenses, and information about the brand or length of wear time for your lenses.  Your eye care professional knows what is best for your eyes and your health, be sure to discuss any questions or concerns you have with them.