What Do the Numbers Mean in My Eyeglasses Prescription?
When you get an eyeglass prescription in North Syracuse, NY, you may wonder what all the cryptic numbers actually mean. Typically, your optometrist hands you a prescription, which you hand over to an optometric technician when you order your frames. No one usually goes out of their way to translate the prescription since it’s not something you need in order to wear your new eyeglasses. but at McPherson Optometry, we like to empower our patients so you have all the information you need or want about your eye health. Following is an explanation of what the numbers mean in your eyeglasses prescription.
SPH stands for “sphere.” This is the main part of your eyeglasses prescription, and it tells the lens maker important information about the necessary refraction of each lens. A higher number in either direction indicates a bigger visual impairment. Positive numbers preceded by a plus sign (+) mean you’re farsighted. Negative numbers preceded by a minus sign (-) mean you are nearsighted. A person with a refraction of +4.0 has a larger visual impairment than a person with a refraction of +3.75. A person with a refraction of -2.75 has a larger vision impairment than a person with a refraction of -2.50. Finally, note that it’s common for each eye to have a different sphere measurement.
CYL stands for “cylinder.” This number may not be filled in on your prescription because it’s only relevant for people with astigmatism. Astigmatism is a unique refractive problem due to the cornea or lens being an irregular shape. The CYL number refers to the amount of correction needed and is the power needed to correct the astigmatism. A positive number here means that a certain point on your eye is aligned vertically, while a negative number means that a certain point on your eye is aligned horizontally. Higher numbers in either direction indicate more severe astigmatism.
Astigmatism is corrected in eyeglass prescriptions with a combination of the CYL measurement and the Axis measurement. The axis number is the angle of orientation of the CYL number. It’s used solely by the eyeglass maker so they can shape the lens properly for your vision needs.
This number references the direction in which the prism should be placed in your lenses to address your specific eye alignment problem.
When you need new eyeglasses prescription, contact your optometrist in North Syracuse, NY. We look forward to seeing you—clearly—soon!