Eyeglasses Rx FAQ
How to read your eyeglasses prescription and enter it for your online order
Your prescription is one of the most important parts of buying your glasses online – it’s what enables us to custom make each pair, but it can be difficult to understand. So, to help you understand your prescription, this section will take you through the various parts and explain what to look out for.
In case you’re not comfortable with entering your eyewear prescription online, feel free to contact us using the contact us form or toll free number during business hours.
On a typical prescription, you will see two sets of rows. Most of the time the top portion is for your Right Eye or OD while the bottom portion is for your Left Eye or OS.
Prescriptions are generally laid out as follows:
- Please pay close attention to plus and minus signs as it will affect your lens.
- Eye doctors will often leave out the decimal point on the sphere, cylinder, and addition. For instance, -5 or +150 is understood as -0.50 and +1.50.
Let’s explain what all of these measurements mean.
SPH or SPHERE
Sphere indicates the strength of your prescription in 0.25 increments. For distance correction, there is usually a value under sphere (SPH) and it generally marked as negative (-). The abbreviation is “D.V.” or Distance Vision.
In this box you may also see the following signs:
This sign is quite common and looks like an 8 on its side but it stands for ‘infinity’. Sometimes ‘PL’ is used instead. You should enter 00 or ‘plano’ for that part.
CYL or CYLINDER
This figure is required if you have something called an ‘astigmatism’. It should be a number between +/-4, in 0.25 increments. Doctors will often use positive (+) cylinder but some use negative (-), there is a BIG difference between the two so please pay close attention to the signs. Not all prescriptions have Cylinder (CYL)/AXIS values. If you don’t have astigmatism correction, doctors may leave it blank but they might also put SPH or DS which means sphere or Diopter Sphere. If fill your prescription online you can enter either nothing (leave the column blank), or select the phrase none or 00 in the drop down.
AXIS
Please note that that Cylinder (CYL) and Axis are always provided together. For any value of Cylinder there should always be a value for Axis. Axis should be from 1-180 degrees. If you see a number like ‘6’ under axis, it is also the same as ‘006’ or ‘6 degrees.’ It should always be a whole number and never with a decimal point on the axis.
ADD or Near Addition
The Add is mostly for people over 40 and concerns Bifocal/Progressive reading and near correction. Sometimes opticians write the addition as a complete additional line on your prescription, sometimes once (same for both eyes) and sometimes once for each eye. Only one ADD means that the addition for both the left and right eyes are the same.
If you have a prescription for multi-focal glasses but only want to purchase single-vision lenses, just leave off the ADD part which is for the bottom near or reading correction of the Bifocal.
PD
In order for our glasses to perform at their best, we need to create lenses that can match the distance between your eyes, so the center of each lens aligns with the center of your pupils. For this reason, we need your Pupillary Distance measurement – also known as the PD measurement.
Unfortunately, many opticians don’t include your PD in the prescription. However, you can ask your optician for it directly during your eye exam. If you already have your prescription, we can make your glasses using the average PD measurement. While it works well for most customers, it can cause discomfort or strain for others. If you have a strong prescription or your PD is significantly differently from the average, you may experience some problems with eyeglasses that have the average PD measurement.
Pupillary Distance can be measured on your own with a tape measure. If you chose to measure your own PD, please do so in millimeters. Simply have someone measure from the middle of the left pupil through to the middle of the right pupil. Make sure you are looking straight forward at a distant object.
Average PD is about 62/63mm and most people fall within the 54 to 74 range. If your number is outside this range, you may have made a mistake. Please do not guess or assume your PD.
Occasionally, PD is written like 32/34.5 (for example), which means the measurement from the center of the nose to either eye plus your PD is the sum of the two – 32+34.5=66.5 (Mono R + Mono L = PD) and you can enter this as 66 or 67.
In your measurement, if you are off by a millimeter or two it’s OK. Try to be as accurate as possible, especially for Progressive lenses.
You may also be able to get your PD from a previous optician. Unlike a prescription, your PD does not expire with age. Opticians are required, under federal law, to give you your PD as well as your full prescription. It is considered to be your property.
In case you’re still not comfortable with entering your eyeglasses prescription online please email or call our toll free number at the contact us page at the top of page, during business hours, EST.
Below is another eyeglass prescription example written in a standardized format with standardized notation so it can be interpreted worldwide. Let’s look at it and break it down:
-2.00 -1.00 x 180. The first number (-2.00) tells us the spherical refractive error (farsightedness or nearsightedness). In this case, because there is a minus sign in front of the 2.00, this patient is nearsighted. A plus sign would indicate farsightedness.
The second number (-1.00) is the astigmatism. If there is no astigmatism, we generally write the letters DS or SPH after the first number to let the optician know that we didn’t just forget to write in the astigmatism.
The final number (180) is the direction of the astigmatism. Astigmatism, a football-shaped eye, can be measured in any direction around the clock. We use the numbers from 1 to 180 to indicate the orientation of the football shape.
There may be additional numbers in a glasses prescription. For instance, if the basic prescription is followed by a small number with a superscript (1^) it indicates prism correction. There may be more than one set of prism numbers for each eye.
Lastly, there can also be numbers denoting the amount of near reading strength needed (Bifocal or Progressive). They usually go from +0.75 to +3.00, depending on age and visual need.
The letters OD and OS in front of a prescription let us know which eye each string of numbers is for. OD stands for right eye and OS for left eye, while OU means both eyes.
Need more information on buying your eyeglasses online? Then click the below eyeglasses prescription tips:
How to measure PD
PD ruler
Eyewear Frame Size
