PD stands for pupil distance, that is, the distance from the center of one pupil to the center of another pupil. Your PD is an important factor, telling you where to see through the lens of the glasses, it should be as accurate as possible. This is especially important for people with strong prescriptions. You can usually find your doctor on your prescription.

1. The pupil distance of both eyes is represented by a single number, such as "63", which indicates the total distance between the pupils.
2. Monocular PD is the distance from the bridge of the nose to the pupils on both sides. It is represented by two numbers around 30mm, such as 31 and 32.
3. Sometimes PD is labeled "61/58". 61 is your distance PD, which can be used when you need single vision telephoto glasses, bifocal glasses, and progressive glasses. And 58 is your reading PD can only be used when you need single vision reading glasses. (Reading PD is usually 3mm smaller than the distance to PD because the eyes will be closer when reading.)

Remember, PD is not always part of the prescription when you have an eye exam. If it's gone, don't worry, we can help.

It is easy to measure your PD at home, especially with friends or family. If you wear glasses, take them off and look at things 10-20 feet away.

Ask your friend to hold the PD ruler on your eyes while placing the zero in the center of your right pupil. Read the measured value. The number directly above the center of the left pupil is your pupil diameter. Ask your friend to repeat the measurement several times to make sure the measurement is correct.

It is also easy to measure your PD all by yourself. All you need is your ruler and a mirror.
1. Fold your PD ruler so that the side marked "use mirror" faces outward.
2. Stand 8 inches or 20 cm away from the mirror.
3. Raise the ruler over your eyes. Put zero on your left pupil.
4. Close your left eye, open your right eye, and look straight at the same time. The number directly above the student on the right is your PD.

Note: For reading glasses, you can subtract 3mm from the PD measurement.