How to Read, Decode, and Enter Your Eyeglass Prescription
As if deciphering your doctor’s handwriting isn’t hard enough, when reading your new eyeglass prescription you’ve got a multitude of other letters, numbers, and abbreviations to further complicate the process. If you’re staring at a jumble of letters and numbers with uncertainty, you are not alone. To help you better understand your Rx, we’ve created the following guide.
Abbreviations, Symbols, Numbers, and Letters Defined
Your prescription shouldn’t be an optical illusion, so before we start dissecting your prescription it is important to understand what all of the numbers, letters, and abbreviations mean:
OD Oculus Dexter- Right Eye, in Latin. Some prescriptions use RT instead.
OS Oculus Sinister- Left Eye, in Latin. Some prescriptions use LT instead.
OU Oculus Uterque- Both Eyes, in Latin.
SPH Spherical Correction- The amount of lens power needed to correct near or farsightedness.
CYL Cylindrical Correction- The amount of power needed to correct astygmatism.
Astygmatism- Essentially, this means that your cornea is slightly more football shaped than basketball shaped. Because of this slightly oblong shape, distortion occurs as light passes through your cornea.
Axis Axis- The position of astigmatism, measured in degrees 1-180˚. This tells the angle at which your cornea is more football shaped.
- Myopia Nearsighted. This corrects your vision so you can see far away.
+ Hyperopia- Farsighted. This corrects your vision so you can see near objects.
PL Plano- This means no correction, or non-prescription. Also known as 0.00 or none on your prescription.
PD Pupil Distance- This is the distance between the centers of your pupils.
SV Single Vision- This means you need correction only for near or farsightedness, but do not need reading magnification.
ADD Reading Magnification- The amount of power needed in the reading portion of your progressive or bifocal lens.
Progressive Lineless Bifocal- This is a lens that corrects both distance vision, and near vision at the same time. Unlike a traditional lined bifocal, a progressive lens gradually progresses from your distance vision at the top of your lens, to your reading magnification at the bottom of your lens. This gradual progression means less strain on your eyes.
Bifocal Traditional Lined Bifocal- This lens corrects both distance vision and up close vision. Bifocals are notorious for the visible line that separates the two, so looking above the line, your distance vision will be corrected. Looking below the line, you will be able to read up close.
Seg Height Segment Height- The measurement in a progressive or bifocal lens that indicates the height at which your reading power will begin. This is measured in millimeters, and will vary from frame to frame, depending on the lens height.
Δ Prism- Correction for double vision caused by a muscle imbalance in your eyes. Prism helps your eyes to work together to fuse 2 images created by each eye into one coherent image. Prism correction will range from 0.50 to 5.00 and will indicate direction using the following abbreviations: BU-Base Up, BD-Base Down, BI-Base In, or BO-Base Out. Most prescriptions will not have any prism correction.
Prescriptions come in all shapes and sizes, and the same prescription can be written a number of different ways by different doctors. Whether your doctor scribbles your Rx on a sheet of paper, or provides you with a typed copy with a thousand different boxes, all prescriptions contain the same fundamentals, in the same universal order.
Because most doctors are filling out a prescription form, it is likely that your prescription looks very similar to the chart above. If not though, here is what the most basic version of your prescription may look like:
A few notes about this very shorthand Rx:
If you see a number in the Sphere or Cylinder column without a + or - sign, it is a + . Some doctors do not indicate the + , but will always indicate if the number is to be - .
Not all doctors use the decimal point. The first number in the OD row translates to +0.75, not +7.50. The latter would be 750. The second number in the OD row similarly translates to -1.00.
Because Axis is measured in degrees, the "x" means the degree at which your astigmatism needs correction, as in -1.00 at 120 degrees.
Now that we’ve covered the fundamentals of reading your prescription, you may realize that there is still bountiful information on your prescription that we haven’t covered:
Lens Type- This will indicate if your new lenses will be single vision, progressive, bifocal, or trifocal. If you see a lens type notated on your prescription that you do not see available on SaltCityOptics.com, feel free to reach out to us via phone at 888-507-1230 or email at email@example.com and one of our helpful team members will happily assist.
Lens Materials/Treatments- Some prescriptions have check boxes that correspond to different lens materials or coatings, and some doctors will just write what you need on the prescription without checkboxes. For more information on lens types and treatments, check out our handy guide HERE. If you see a lens material or treatment recommended by your doctor on your prescription that you do not see in our lens offerings, feel free to reach out to one of our knowledgeable professionals and we are eager to help. 888-507-1230 or firstname.lastname@example.org is the best way to get in touch with us via phone or email.
Use- Some prescriptions will notate if you need your new eyewear for full-time or part-time, or distance use or reading use. While you won’t have to enter this on our website, this is more of a reference for you, as the individual wearing the glasses.
Visual Acuity- If you’ve ever heard the phrase 20/20, that is referring to perfect visual acuity, or perfect vision. Some prescriptions will notate how well your new prescription will correct your vision and will include 20/20 or a similar number. Similar to the “use” section, you won’t have to enter this into your prescription information. This number is for your reference.
Putting Your Prescription To Good Use- How to Enter Your Rx on SaltCityOptics.com
Now that we’ve decoded your prescription, let’s review how to enter all of this good info when ordering prescription eyewear on SaltCityOptics.com. You will enter your prescription in the 3rd step in checkout, after entering your billing and shipping information. This is what the page will look like:
This screen is designed to mimic your prescription, and filling out our form is as easy as clicking and picking! Simply click on the drop-down boxes and find the sign and number that match your prescription. You’ll want to scroll down about half way to find the + options in the Sphere and Cylinder columns.
If your doctor wrote your PD as one combined number, go ahead and click and pick the appropriate selection in the Pupilary Distance (PD)* drop-down menu. If your doctor wrote your PD as two separate numbers, one for your right and one for your left, go ahead and enter those numbers in the Mono PD drop-down menus.
If your doctor did not include a PD on your prescription, don’t worry. We have a helpful guide to explain how to find your PD if it is not on your Rx. Just click HERE. If you are purchasing single vision glasses, a PD measurement isn’t critical and can be omitted. If you are ordering progressive lenses on the other hand, we will definitely need this measurement to ensure that the progressive portion properly lines up with your pupils.
Any extra information you would like to share with us about your prescription can go in the big box under the drop-down menus. Our lab technician will see any notes written here as he reviews your order.
If you have Prism on your prescription, you can enter that in the additional information box as well. Here is how you would want to input your prism adjustment (of course the number and direction-BU, BD, BI, BO-will vary from prescription to prescription):
Prism OD 1.00 BU, OS 1.00 BD