Your Prescription Explained
An optical prescription, provided by an optometrist or ophthalmologist, outlines the lens power needed to correct vision, typically for nearsightedness or farsightedness, and sometimes to address astigmatism. The prescription lists the “SPHERE” value (SPH) for spherical correction, the “CYLINDER” value (CYL) for astigmatism, the “AXIS” to specify the direction of the astigmatism, and potentially an “ADD” for reading or intermediate vision.
Here’s a breakdown of the key components:
SPH (Sphere)
This indicates the power of the lens needed to correct short sightedness (negative values) or long sightedness (positive values).
CYL (Cylinder)
This value is present if you have an astigmatism, an irregular curvature of the cornea.
AXIS
The axis indicates the orientation of the cylindrical correction needed for astigmatism, typically a number between 1 and 180 degrees.
ADD:
This is the additional power needed for reading or intermediate vision (like computer work), often used in progressive or bifocal lenses.
The higher the numerical value in the SPH and CYL, the stronger the prescription.
Important Notes:
Plano:
If you see “Plano” on your prescription, it means there is no spherical correction needed.
Diopters:
The units used to measure lens power are called diopters (D).
