Does Pupillary Distance Have to Be Exact?
Pupillary distance – also known as interpupillary distance – is a measure of the distance between a subject’s pupils.
Finding Pupillary Distance
Pupillary distance can be measured by machine – a “corneal reflex pupillometer” – or with a millimeter ruler by any optometrist or optical assistant. It can also be measured by you at home with a small ruler, if you’re careful. The pupillary distance measurement does not have to be 100% precise to be useful, as it can tolerate a fairly small error range. If you do measure your own pupillary distance, it is recommended that you try several attempts to be sure you get a fairly accurate measurement.
To give you an idea of the kind of measurement readings you should get, here are the typical ranges for various groups:
- Average pupillary distance for an adult is between 54-68mm, with acceptable measurement deviations generally falling in between 48mm and 73mm.
- The range for children is approximately 41-55mm.
- The large majority (95 percentile) of adult males in the USA have a pupillary distance of 70mm while a small minority (5 percentile) measure 55mm.
- The range for adult females in the USA is between 65mm and 53mm.
- For Europeans the figures equate to roughly 1mm smaller than the above measurements.
If you recently had an eye exam and were given a written prescription, or have an older prescription on file, the prescription may already indicate your pupillary distance. If it does not, you’ll need to obtain that measurement. To do it yourself, follow these steps:
- Obtain a millimeter ruler and place it against your eyes, resting on the bridge of your nose.
- Line up the 0mm starting point with the outer side of either your left or right pupil.
- Look straight ahead and have someone else note the reading, or look directly into a mirror and note the reading yourself. (If using an assistant be sure they are at the same height as you when they record the measurement.)
- Once lined up correctly as stated in step 2, the millimeter mark that falls in the center of your opposite pupil is your pupillary distance.
- Repeat the process a few times to be sure you get the same result.