Understanding your prescription
On a typical prescription, you will see two sets of rows. OD is for your Right Eye and OS is for your Left Eye. These will be clearly marked.
Standard layouts of prescriptions are as given below:
SPH or SPHERE
The sphere value (SPH) determines the strength of the lens, and therefore its thickness. The SPH is in 0.25 increments
. For Distance Correction (Short-Sightedness), the value under sphere (SPH) will be marked as negative (-).
f you require Near-Sight correction, then the SPH value will be marked with a positive sign e.g. +3.00
Opticians often indicate these – or + values above the number as well.
Also, some opticians DO NOT INCLUDE THE DECIMAL POINT eg, -175 means a SPH value of -1.75
Note : If the sphere reading is negative in one eye then it is normally negative in the other eye and vice versa. Similarly, if the SPH reading is positive in one eye it is usually positive in the other eye as well.
In this box you may also see the following signs:
This sign is quite common and looks like an 8 on its side but it stands for ‘Infinity’. Sometimes ‘PL’ is used instead. PL stands for Plano. You should select the value 0.00 in the drop down if you either this Infinity sign or have Plano on your prescription.
CYL or CYLINDER
The cylinder value determines the strength of the astigmatism correction. It is usually a number between -4 to +4, in 0.25 increments.
Cylinders could be either positive (+) Cylinder or negative (-) Cylinder; there is a BIG difference between the two so please pay close attention to the signs.
Not all prescriptions have Cylinder (CYL)/AXIS values. If you do not have astigmatism correction, doctors may leave the CYL blank but they might also put SPH, 00, Plano, or DS – all of which mean that there is no CYL value for your prescription. In any of these cases, please leave the CYL value blank while filling in your prescription online.
The axis value is the angle of the astigmatism correction.
Please note that that Cylinder (CYL) and Axis are always provided together. For any value of Cylinder there should always be a value for Axis. Axis should be from 1-180 degrees. If you see a number like ‘6’ under axis, it is also the same as ‘006’ or ‘6 degrees.’ It should always be a whole number and never with a decimal point.