Understanding Your Eyeglass Prescription
Understanding your eyeglass prescription is easier once you know what the abbreviations and numbers mean. This guide explains SPH, CYL, Axis, ADD and PD so you can better understand how your lenses are prescribed.
How to Read Your Eyeglass Prescription
SPH (Sphere) Sphere power measures the degree of nearsightedness or farsightedness.
A negative number indicates myopia (nearsightedness), while a positive number indicates hyperopia (farsightedness). The higher the number, the stronger the prescription needed.
CYL (Cylinder) Cylinder power measures the degree of astigmatism.
This value corrects the irregular curvature of your cornea or lens. If this field is blank, you have little to no astigmatism. The number can be positive or negative.
Axis Axis describes the orientation of astigmatism correction.
Measured in degrees from 1 to 180, this tells the lab where to place the astigmatism correction in your lenses. This field only appears if you have a cylinder value.
ADD (Addition) Addition power for multifocal lenses to correct presbyopia.
This is always a positive number and represents the additional magnifying power for reading. It’s typically needed for people over 40 who have difficulty focusing on close objects.
PD (Pupillary Distance) The distance between your pupils, measured in millimeters.
This measurement ensures your lenses are properly centered over your pupils for optimal vision and comfort. It’s crucial for accurate lens positioning.
Need Help Understanding Your Prescription?
Our eye-care team can explain your prescription and help you choose lenses suited to your vision, lifestyle and everyday needs.