Understanding Prescriptions
Decode the numbers and abbreviations on your eyeglass prescription to better understand your vision needs.
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.