Pupillary Distance

What's pupillary distance(PD)?

Pupillary distance (PD) is the distance between the center of your pupils, which is measured in millimeters. 

When you are going to have a pair of prescription eyeglasses, this is an important number because it tells the lens maker where to put the optical center on each lens. If PD doesn’t match up with the optical centre of lenses, you may feel discomfort and difficult in seeing.

Why is the PD different for each eye?

The word called Monocular PD means the distance from the center of one pupil to the center of your nose. You will have two numbers if your lenses are progressive, bifocal or trifocal because your each eye has different needs.

Can pupillary distance change?

As the child growing up, the pupillary distance will likely change over the time. But it will not change in adult. The average pupillary distance for adults is between 50 and 70mm.

Is pupillary distance written on glasses?

In general, you couldn’t find your PD value on glasses frame or lenses. The numbers in a specific format, a-b-c(Lens Width-Bridge Width-Arm Length) on the inside of the temple are some sizes of your frame.

Difference Between Distance PD And Near PD

Distance PD refers to the distance between the pupils when you are looking at a distant object, which is suitable for people with farsightedness. 

Near PD is the distance between the pupils of the eyes when looking at a near target, which is suitable for people with nearsightedness. Compared with distance PD, near PD usually be smaller.

How to measure pupillary distance (distance PD)?

1. PD Ruler

You need a friend or a mirror to help you measure.

 Steps：

Click here to print a PD ruler

• Prepare a ruler by printing our PD ruler page.
• Look straight and place the ruler horizontally above your brows.
• Close your right eye then align the ruler’s 0 mm with the center of your left pupil.
• Look straight then keep your left eye closed.
• The mm line corresponding to the center of your right pupil is your distance PD number.

2. APP

Download a relevant PD test app.

Prepare a credit card for assistance and specific operations depend on different app's instructions.

3. Digital PD Meter

The first two ways above may not be accurate due to the movement of pupils or improper operation. 

A digital PD meter is the most precise way to measure your pupillary distance. Unlike manual methods, it minimizes errors caused by pupil movement or misalignment. Opticians and eye care professionals often use this tool for highly accurate measurements.

By ensuring you have the correct PD measurement, you can improve visual comfort and clarity when wearing prescription eyeglasses. If you're unsure about your PD, consider visiting an optometrist for a professional measurement.