Pupillary distance: the key element not to be forgotten when buying a pair of eyeglasses.
The pupillary distance is the measurement between the two pupils when looking at an object placed at infinity, i.e. a distant object. It’s measured in millimetres and is a fundamental piece of information for the correct fitting of ophthalmic lenses, as it serves to place the optical centre of the lens directly in front of the pupils. It can vary depending on the size of the face and is generally measured by the ophthalmologist or an optician and can be found in the ophthalmology prescription, under the heading PD, Pupillary Distance. If your ophthalmic prescription does not state this value, you can have your pupillary distance measured by any optician. You can also measure the pupillary distance yourself or with the help of a friend or family member.
Measuring the pupillary distance on your own
The first thing to do is to stand in front of the mirror at a distance of about 20 cm, with a ruler. Now look at yourself in the mirror and place the ruler on your forehead horizontally, at eyebrow level.
Close your right eye and align the zero of the ruler with the centre of your left pupil. Now open your right eye and note the measurement (in millimetres) at the centre of your right pupil. We suggest you repeat the measurement several times to make sure it’s right. To give you an idea, the average value for adults is usually around 62 mm, but any distance between 54-74 mm is correct.
Measuring the pupillary distance with the help of another person
In this case, you have to stand in front of the other person with your right eye closed, imagining that you are staring at an object about 3-5 metres away. The person in front of you will place the ruler on your forehead, just above your eyes, with the millimetre scale pointing downwards, placing the 0 mark in the centre of your left pupil.
Now open your right eye and close the left. Your friend can then complete the measurement, noting the length (in mm) at the centre of your right pupil.
Measuring the pupillary distance using the lenses of your glasses
With the help of a second person, you can measure the pupillary distance directly on your glasses. Put on your glasses and pretend that you are looking at an object about 3-5 metres away, placed behind the person standing in front of you. Using an erasable marker, the person should mark the centre of your pupils on the lenses of your glasses. Then use a ruler to measure the distance between the two marks to get your PD.
Now you know how to easily measure your PD. Remember to always provide this measurement to your optician so that your new prescription glasses are perfect for you.