How Do I Read My Prescription?

The abbreviations and numbers on your prescription may look unfathomable, but it's really a kind of medical shorthand - a professional way to tell a Laboratory what's needed to correct your vision.

An example of a glasses Rx

1. Right Eye = Oculus Dexter (OD) In Latin, Left Eye = Oculus Sinister (OS) In Latin. Binocular = Both Eyes.

2. SPH or RX SPH = Sphere or spherical correction describes the horizontal curve of your eye's Lens. Sphere is assigned a positive (+) or negative (-) number. And sphere is the lens power that it takes to focus an image on your retina correctly. A single-vision eyeglass prescription without astigmatism lists only SPH.

3. CYL = Cylinder or cylindrical correction fine tunes for astigmatism - The vertical curve of an eye shaped more like a football than a sphere. Astigmatism is very common. Cylinder is a positive (+) or negative (-) number between -6 and +6. Your prescription may or may not have a CYL Number.

4. AXIS = The Degree and Direction Of Astigmatism. If you have a CYL number on your prescription, you'll also have an AXIS measurement. It's a positive (+) number between 0 and 180, sometimes preceded by an "X". A single-vision eyeglass prescription with astigmatism lists values for SPH, CYL, And AXIS.

5. ADD: ADD is added magnifying power in the lower part of a multi-focal lens. It’s used to correct presbyopia which is the inability to focus on close objects.

6. PD: On your prescription, your pupillary distance may be a binocular PD (one number for both eyes) or a monocular PD (one number for each eye).

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