Difference between revisions of "Measure Your Interpupillary Distance"

Your inter-pupillary distance (PD) is the distance between your pupils, measured in millimeters. Eye doctors always measure this distance to ensure an accurate fit when they write prescriptions for eyeglasses. The average adult PD is 62 millimeters, though the normal range for most individuals is between 54 and 74 millimeters.<ref name="rf1">https://www.glassesusa.com/prescription-guide</ref> You can measure your PD at home by yourself or with the help of a friend, or you can have it done professionally by an eye doctor.

#Grab a ruler with millimeter units. In order to measure your PD at home, you will need a ruler that has millimeter units.<ref name="rf2">http://www.zennioptical.com/measuring-pd-infographic</ref> If you do not have a ruler at home, you can print out a PD measurement ruler online from many vision center and eyeglass retail websites. Just be sure that when you print the page you set your printer so that it does not scale the image.<ref name="rf3">http://static.zennioptical.com/media/Zenni-Optical-PD-Ruler.pdf</ref>

#* Some online eyeglass retailers use programs that allow you to photograph yourself holding a credit card up to your face for scale, but most require you to manually measure the distance.<ref name="rf4">https://www.warbyparker.com/pd/instructions</ref>

#Stand in front of a mirror. If you're measuring your own PD, you'll need to use a mirror. Make sure that you're in a well-lit area so that you can line up the ruler and see the ruler markings. In order to get a good reading, you'll need to stand approximately eight inches (20 centimeters) from the mirror.<ref name="rf3" />

#Close your right eye to center your left pupil. It's easiest to measure one eye at a time by closing the other eye. Start by closing your right eye and holding the zero millimeter mark right above the exact center of your left pupil. Try to get an exact alignment with the zero mark, as this could alter the reading for your whole measurement.<ref name="rf3" />

#Read and measure the distance to your right pupil. Without moving your head or the ruler at all, open your right eye and find the exact millimeter mark that falls on your right pupil. Make sure you're looking straight ahead at the mirror to ensure an accurate reading. The number (in millimeters) that lines up with the center of your pupil, or as close to center as you can measure, is your PD.<ref name="rf3" />

#* It's best to try remeasuring your PD three or four times to make sure that your reading is consistently accurate.<ref name="rf2" />

#Stand close to your friend and face one another. You should stand approximately 8 inches (20 centimeters) away from your friend, just as you would stand if you were measuring your own PD in the mirror.<ref name="rf3" /> Do not stand too close or too far away to ensure an accurate reading.

#Look above your friend's head. Unlike measuring your own PD in the mirror (where you can't avoid looking at your own reflection), having a friend measure your PD requires you to look past that individual. Try having your friend crouch or sit in front of you while you stand so that she is outside your field of vision, and stare at something in the distance about 10 to 20 feet away.<ref name="rf2" />

#Have your friend take your measurements. You'll need to keep your eyes perfectly still while your friend measures your PD. He should line the ruler up just as you would on yourself in the mirror. Your friend should align the zero millimeter mark with the center of one pupil and measure across where the center of your other pupil falls.<ref name="rf2" />

#Schedule an appointment with your eye doctor. Having your PD measured by an eye doctor will typically require an appointment. While you're there, your eye doctor will most likely want to test your vision to make sure that your optical prescription is up to date. This may include testing your eye muscles, visual acuity, visual field, as well as a refraction and retinal exam.<ref name="rf5">http://www.mayoclinic.org/tests-procedures/eye-exam/details/what-you-can-expect/rec-20189669</ref>

#Have your pupil size measured. Depending on the tests you have done, your doctor may decide to check the size of your pupils using a digital pupillometer.<ref name="rf6">http://www.slideshare.net/indrapsharma/measuring-interpupillary-distance</ref> Your eye doctor may also choose to use an ocular measurement device.<ref name="rf7">http://www.ophthalmologyweb.com/25212-Ocular-Measurement-Device/5509416-Volk-Eye-Check-Handheld-Ocular-Measurement-Device/?ncatid=5897&ppim=5509416_1_0</ref> Both of these handheld devices can measure the size of your pupil and the distance between your pupils.

#* A pupillometer looks like a large pair of binoculars, and all you need to do is look through the lenses while your doctor takes your measurements.<ref name="rf8">http://www.medicalexpo.com/prod/essilor-instruments/product-70776-435127.html</ref>