My eyeglasses prescription
What is it:
An eyeglasses prescription is an order written by an optometrist or ophthalmologist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient
How to read Example, printed version:

R and L
‘R’ refers to your right eye, ‘L’ to your left.
SPH (sphere)
The amount of power required to correct your vision.
Plus (+) lenses are used to correct long sight.
Minus (-) lenses to correct short sight. The higher the number, the stronger the lens required.
CYL (cylinder)
Amount of correction (if required) to remove any visual distortion, caused by an irregularly shaped cornea known as an astigmatism.
AXIS
The direction that the cylinder (if required) will be built into your lenses to correct your astigmatism. It is measured in degrees between 0 and 180
PRISM
Any correction (if required) to help balance your eye muscles so they work as a pair more comfortably.
BASE
The direction that the prism (if required) will be built into your lenses.
ADD Near
This is the amount of correction that must be added to your distance prescription to enable you to see near objects clearly, such as reading a book or map.