What is a Sphere reading
There is no need to go into detailed explanation except to say that this reading specifies the optical power of a lens and tells us amount of long or short sighted ness required. This value is in diopters.
OD and OS
OD simply means Right eye and OS means Left eye. Rarely used is OU which means Both eyes.
No Sphere reading
If your script does not have a Sphere reading then do not be concerned. It is Not Required.
Only one Sphere reading
There could be a sphere reading for you Left Eye and not your Right (or visa versa) and this is also fine.
Positive and negative readings
Spheres can be either positive or negative and you will see on your script a minus (-) or a plus(+) sign in front of your reading if it is a positive or negative reading. There should always be one or the other although some optometrists do not put a plus (+) in front of positive numbers as any number without a sign in from is in fact a positive number.
Plano means plane or zero or "no reading".
Bal (or balance)
If your vision in one eye is very poor the word 'balance' or 'bal' may be written in the Sphere Section. Just leave the Sphere reading as Plano, make a note in the comments section and send us a copy of your script with your order.