Pupillary distance (PD) is the distance between your pupils that determines comfort and how well your glasses fit. Having a PD is just as considerable as your prescription when it comes to ordering a new pair of prescription glasses or sunglasses. The average value of the pupillary distance for an adult is about 63 mm.
After all, measurements can vary widely – between 51 mm and 74.5 mm for women and 53 mm and 77 mm for men. There are two main methods of PD measurement: single PD and dual PD.
Single PD is the pupil-to-pupil measurement between each eye. Double PD is the measurement from the nasal bridge to each eye.
Double PD is considered the most accurate. PD is especially important when fitting glasses with progressive lenses, which require precise alignment of the lens with the pupil to ensure comfortable vision at all distances.
Can you measure it yourself?
You can measure the pupillary distance yourself. For this, you need a millimeter ruler and a mirror. If there is no ruler, you can print a particular scale for measurement, but you first ensure that the printer doesn’t distort the scale.
The room should be well lit. Stand in front of the mirror at a distance of 20 cm. Locate the ruler above the eyeballs, parallel to the eyebrow line. Held the head straight to obtain more accurate measurements.
First, you should close one eye and place zero on the ruler opposite the left center of the pupil. The more precisely the center is determined, the better the result is.
Next, you should open the second eye and find the division on the ruler, which will be accurate in the middle of the pupil. At this time, you can’t move your head or the ruler. Direct eyes to the mirror for the measurement to be correct. The obtained data in millimeters is the pupillary distance. You should make measurements 3 or 4 times.
Another person’s help
You can measure with the help of another person. Following simple rules, you can understand how to measure the pupillary distance with an assistant. For this, it’s necessary to face each other. The distance between people should be 20 cm. A larger or smaller interval will distort the result.
The measured person should look over the assistant’s head. The head should be lower than the eyes of the subject. Look at an object that is at a distance of 3-6 meters from a person. For the accuracy of the measurement, you can’t move, move your head and turn your eyes. You should fix the view. You should position the ruler above the eyes parallel to the eyebrow line. Zero should be set in the center of the pupil of one eye and determine at what distance the other pupil will be.
Examination by an ophthalmologist
Measuring the pupillary distance at an ophthalmologist will show a more accurate result. Choosing glasses, the doctor holds a special ruler at different intervals. It depends on the degree of nearsightedness or farsightedness.
Ophthalmologists use a pupillometer to determine the diameter of the pupils and the distance between them. The modern device is rich in settings and guarantees the high accuracy of the result. Compared to other methods, the pupillometer has the following advantages:
• quick and accurate result;
• accuracy is not affected by uncontrolled movements of the pupils and the degree of illumination of the office;
• the result is displayed on the device display.
The device can measure from the nasal bridge to each pupil. It shows data for asymmetry, farsightedness, and myopia. The ability to measure the pupillary distance helps to adjust it when using optical devices. Some of them require settings to see the images.