Have you ever gotten an eye exam and wondered, what do all these numbers mean on my prescription? We are here to help clear up any confusion and explain how you can figure out your prescription range. Once you understand what each number and abbreviation means, you’ll have a better understanding of what type of frames can hold your prescription and what vision type best suits your needs.
What does OD and OS mean on my prescription?
The OD and OS simply refers to your right and left eye. OD is the abbreviation for your right eye while OS is for your left eye. OD comes from the Latin phrase “oculus dexter”, which means right eye. OS comes from the Latin phrase “oculus sinister”, which means left eye.
In some instances, your doctor may abbreviate the eye column with OU. OU comes from the Latin phrase “oculus uterque”, which means both eyes.
What does Sphere (SPH) mean on my prescription?
If you need lenses to correct nearsightedness or farsightedness then a power will be listed under this section. The Sphere number indicates the lens power prescribed to correct one of those two vision needs. If the number under Sphere has a (+) sign then you are farsighted. Vice versa if the number under Sphere has a (-) sign then you are nearsighted.
What does Cylinder (CYL) mean on my prescription?
Cylinder tells you the amount of power needed in the lens to correct the astigmatism in either your right or left eye. Like the Sphere, if your Cylinder has a (+) sign then you need correction for nearsighted astigmatism. If you have a (-) sign then you need a correction for farsighted astigmatism.
Sometimes you will see the doctor leave this section blank indicating your astigmatism is not too strong and doesn’t need to be corrected.
What does the Axis mean on my prescription?
If your prescription has a Cylinder power listed then it will always have an axis value. Essentially, the axis describes the lens meridian needed to correct your astigmatism. The axis will contain a number between 1 to 180. This number indicates in which direction the Cylinder power must be placed on your lenses. 90 indicates the vertical position while 180 is the horizontal position.
What does Add mean on my prescription?
The Add you will see on your prescription stands for the “added magnifying power”. This is only applied to the bottom of the lens for progressive or multifocal lenses to correct presbyopia. Presbyopia is the natural farsightedness that comes when your eyes get older. The add power will always be a (+) power and it will range from +0.75 to +3.00.
What does Prism mean on my prescription?
The Prism correction you might see on your prescription is to help correct diplopia, also known as double vision. This is when someone looks at an image and sees two of it. The Prism helps align those two images and ensure you only one.
Only a small amount of people needs a Prism correction on their prescription lenses. Prism will be listed in two different ways. Either as a metric (0.5) or a fraction (1/2). Then the direction of the Prism on the lens will be on the thickest edge. The four abbreviations you may see are BD (Base down), BU (Base up), BO (Base out), or BI (Base in).
What is the Rx range for my prescription?
When reading your prescription it’s important to understand what the total power is. Many prescription dealers, including GUNNAR, will list the prescription range for each individual frame. For example, the popular GUNNAR Intercept has a prescription range of -6 to +5. Let’s see if the example prescription above would work for the Intercept.
When reading a prescription, you combine the Sphere and CYL to get your total power for each eye. So, in the example above the Right Eye: (-1.25) plus (-1.50) equaling a -2.75 Total Power. The Left Eye: (-2.75) plus (-1.25) equaling a -4.00 Total Power. This prescription would work with the Intercept since it does not exceed the -6 range.