Eyeglass Prescriptions: What Do They Mean?

You've had your latest visit to the eye doctor and finally received your official prescription for eyeglasses. The piece of paper is filled with acronyms and numbers that are very precise to your specific eye care needs. But what do all of those letters and numbers really mean? Here's a look into what your eyeglass prescription is telling you about your eyesight.

OD and OS

One of the first things you'll probably notice are the letters OD and OS. Simply put, this interprets the readings for your right and left eye. The letters OD are short for the Latin term "oculus dexter," meaning your right eye, and the OS is also a Latin term for "oculus sinister," meaning your left eye. If you notice that your prescription also shows the letters OU, this simply means it is referencing both eyes. The Latin term for this is "oculus uterque."

Other Prescription Terms

There are many other terms you will find on your eyeglass prescription. Here are the different things you might see and what each one means:

  • Sphere: The term sphere refers to how much power the lenses need to have in order to correct either near or farsightedness. If there is a minus sign in front of the sphere number, it means you are nearsighted; if it is preceded by a plus sign, you are farsighted.
  • Cylinder & Axis: If the terms cylinder and axis are found on your prescription, it indicates that you have an astigmatism. Not everyone will see this term on their eyeglass prescription since it only affects certain people. The cylinder is indicative of the lens power needed in order to correct the problem. If there are no numbers showing here, then you do not have an astigmatism. The axis is a number ranging from 1 to 180 and determines the vertical and horizontal meridians of the eye. These two numbers work together to determine how best to correct the astigmatism.
  • PD: If you're getting eyeglasses, you will also see the term PD along with a number. This stands for pupillary distance and determines how far apart the center of each of your pupils are from one another. This term is essential for eyeglasses, since it helps the lens maker determine how to center the lenses to give you the optimum fit and eyesight capability. The PD is measured in millimeters, and patients can actually determine their own pupillary distance by holding a ruler up to their eyes that has millimeter measurements.

For more information, contact Premier Eye Care & Surgery or a similar location.