Measuring your pupillary distance is important if you want your glasses to have a personal fit. But what is the pupillary distance (PD)? In simplest terms, this is the space between the center of each of your pupils. The pupillary distance is measured in millimeters, and the size allows the lens maker to adjust your optical center for each of your lenses. The next time you go to your doctor’s appointment, you can ask your eye doctor to include getting your pupillary distance measurement.
There are two methods in measuring this – the single pupillary distance and the dual pupillary distance. Single PD (binocular PD) is the distance from pupil to pupil between the eyes. On the other hand, dual PD (monocular PD) is the distance from your pupil to the bridge of your nose. Between the two, the dual PD is trusted to be the more accurate. Your pupillary distance is most important if you are planning on fitting personalized glasses with progressive lenses. This type of lens needs precise lens-to-pupil alignment for your vision to be comfortable at all distances.
However, there are simple ways to check the pupillary distance on your own. All you need is this guide and a mirror.
For the first step, you have to stand eight inches away from a well-lit mirror. Take a small ruler in one hand and make sure you have your pencil and paper ready. Look straight into the mirror and put the ruler by the bridge of your nose.
The second step is to start lining. Begin with your right eye and line up the zero end of the ruler at your pupil. Check the millimeter that aligns with your left pupil—that measures your pupillary distance. Another option is to grab a friend. Simply face your friend and look straight ahead with your eyes open. Let your friend hold the ruler to your right, lining up the zero to the right pupil. Allow your friend to measure the distance from your right to your left pupil, and the number that aligns your left pupil is your pupillary distance measurement. Ask your friend to do it a few more times to ensure accuracy. Repeat the process with your left eye.
Measuring your PD has to be accurate because this is where your lenses are based. If the measurement is inaccurate, the lens will cause headaches, dizziness, discomfort, and eye strain. Even a tiny error in the measure can cause pain. Aside from that, an off-pupillary distance measurement would make your lenses ineffective in improving your vision. This is why repeated measurements are necessary.
There are, however, some risks in doing the tests at home. Several websites today offer do-it-yourself measurements. There are also apps available to measure the PD. Just remember that these methods aren’t completely accurate, and getting the help of professionals to do the measurement for you still remains the best option.
If you want your pupillary distance taken, you can talk with our representative, and we’ll have an appointment scheduled for you.