Your PD - (Pupillary Distance Measurement)
Your PD or Pupillary Distance Measurement is the distance in millimeters between your pupils, typically when your eyes are focused at a distance of 20 feet or so. We need these measurements because we want to line up the optical centers of the lenses to your pupils so you can see properly, whether for distance, intermediate, or for reading.
Typically, there are two types of measurements, either Total PD or Monocular PD.
As you can see from the image above, the total PD is the total distance between pupils. The monocular PD is the distance from each pupil to the center of the bridge. Some people have the same mono PD from pupil to pupil but most folks have different measurements.
Examples- When the PD is recorded by your eye care professional, it will look like:
62 (Total Distance PD) or
30/32 Right and Left Monocular PD(The first # is always for the right eye) or
62/59 Total Distance and Near PD.
PD Measurements- Traditional and New Methods
When Opticians measure your PD, they usually measure your distance PD. This means that the measurement is made while your eyes are looking at about 20 feet away. When measuring for reading glasses they will subtract 3mm. They do this because when you read, your eyes converge approximately 3mm.
Currently, the most accurate PD measurements are taken with a Pupilometer which the Optician uses to see reflections off of each of your retina. Measurements can be adjusted for distance, near, or intermediate.
There are new apps online which we have tested with varying results. The most common method requires that you have a picture taken of yourself holding a credit card under your nose. This works because credit cards have a standard width of 85mm which is used as a template for mm measuring. Depending on the software, these methods can be very accurate. For us, the real issue with these methods is security. The credit card account number on cards today are embossed. Unless you tape over the number, expiration date, and security code, this info can be read putting your security at risk. Both sides need to be covered.*
Obtaining Your PD Measurement
If you do not know your Pupillary Distance measurement, there are several ways to get it.
- Ask your Eye Doctor- They can, and should, in my opinion, measure your PD, but usually they leave it to the Optician to do.
- Ask your Doctor or Optician to read a current pair of your eyeglasses and measure the optical centers. This is only accurate to your eyeglasses, not your eyes.
- See if your PD is recorded on a receipt or invoice from a previous eyeglass purchase.
- *Have us measure it remotely. If you order a pair of prescription glasses from us we can send you simple instructions on to get the PD measurement. And it is very accurate and very secure!