The "sphere" corresponds to the correction of myopia or hyperopia.
If the value is negative (e.g.: -2.00), it means you are myopic (you can't see well at a distance).
If the value is positive (e.g.: +1.50), it means you're hyperopic (you have trouble seeing up close, especially when reading).
Where to find it on the prescription : It's usually indicated in a column entitled "Sphere" or "SPH", next to each eye (OD = right eye, OG = left eye).
Example:
Eye
Sphere
Cylinder
Axis
Addition
OD
-2.00
(-0.75)
180
+2.00
OG
-1.50
(-0.50)
175
+2.00
Here, the sphere is -2.00 for the right eye and -1.50 for the left.
The "cylinder" (or CYL) corresponds to the correction of astigmatism, i.e. a curvature defect of the cornea that makes vision blurred or distorted.
Where to find it on the prescription : It can be found in the "Cylinder" or "CYL" column , right next to the "Sphere" column , and is usually accompanied by an axis expressed in degrees. The value is often noted in brackets.
Example:
Eye
Sphere
Cylinder
Axis
Addition
OD
-2.00
(-0.75)
180
+2.00
OG
-1.50
(-0.50)
175
+2.00
Here, the cylinder is -0.75 for the right eye and -0.50 for the left.
Addition (or ADD) corresponds to the correction required for near vision, in addition to distance correction:
It is mainly used for presbyopes (near vision decreases with age).
It is the value added to the sphere to obtain good near vision.
It is always positive (e.g.: +2.00).
Where to find it on the prescription: It can be found in a column or row entitled "Addition" or "ADD", often under the distance corrections or at the end of the table.
Example:
Eye
Sphere
Cylinder
Axis
Addition
OD
-2.00
(-0.75)
180
+2.00
OG
-1.50
(-0.50)
175
+2.00
Here, the sum is +2.00 for each eye, which means that additional correction is required for reading or close-up vision.
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