Your eyeglass prescription is a document from your eye doctor detailing the corrective lenses you need. While it may appear confusing at first, knowing what each part means is crucial for getting the right lenses.
OD and OS
The prescription will include “OD” and “OS,” which stand for “oculus dexter” (right eye) and “oculus sinister” (left eye) in Latin. Sometimes, you may see “OU,” which means “oculus uterque,” referring to both eyes.
Sphere (SPH)
The sphere (SPH) value represents the main correction for nearsightedness (myopia) or farsightedness (hyperopia) and is measured in diopters (D). A negative value indicates nearsightedness, while a positive value indicates farsightedness. The further the value is from zero, the more severe the condition.
Cylinder (CYL)
The cylinder (CYL) value reflects the degree of astigmatism, a condition where the cornea is shaped more like a football than a sphere, leading to blurred or distorted vision. This value is also measured in diopters and can be positive or negative. If there’s no CYL value, it means you don’t have astigmatism.
Axis
The axis is a number ranging from 0 to 180 degrees that shows the orientation of the astigmatism. This measurement only appears if there’s a cylinder value.
Add
The “add” value indicates the additional power needed for reading or close work. This positive number is relevant only for bifocal, trifocal, or progressive lens prescriptions.
By understanding these components, you can better interpret your prescription and ensure you get the correct lenses for your vision needs.
