How to Measure PD
What is PD?
PD, or pupillary distance, refers to the distance in millimeters between the center of one pupil to the center of the other.
Having a correct PD on your glasses prescription ensures that you are looking through the ideal spot in your lenses.
If this number was not provided on your prescription by your eye care professional, you can measure it yourself.
①Stand 8 inches away from a mirror and hold a millimeter ruler against your brow.
②Close your right eye and align the 0-millimeter mark to the center of your left pupil.
③Looking straight ahead and then close your left eye and open the right eye.
④The millimeter line that lines up to the center of your right pupil is your PD.
Printable PD Ruler
What are distance PD and near PD?
The distance PD is the separation between the visual axes of the eyes. The corneal reflection is considered sufficiently close or at the point where the visual axis exits the eye that it can be used to locate the distance between the lines of sights.
The near PD is the separation between the visual axes of the two eyes when turned to look at a near object.
The pupillometer can be set for any near or intermediate distance and a PD taken for that working distance.
1. Can I just guess my PD?
Pupillary distance must be accurate for prescription glasses to properly work. If your lenses aren’t centered correctly, they can cause discomfort and eye strain. Guessing will result in you not being able to see out of your prescription glasses properly and you will have to order a new pair with the correct pupillary distance. A small margin of error might not cause problems, but it’s better to be as accurate as possible.
2. What are single and dual PD?
A ‘single’ PD number is the distance in millimeters between one eye’s pupil to the other eye’s pupil. A ‘dual’ PD number is the distance in millimeters from each eye’s pupil to the center of your nose. A single PD will be just one number, while a dual one will have a number for each eye, marked ‘right’ and ‘left’. (Some prescriptions may have ‘OD’ for the ‘right’ eye, and ‘OS’ for the ‘left’ eye.)
3. What is the average PD?
The average range is between 54-74 mm.
Questions you may concern about:
How to order prescription glasses online.
What are SPH, CYL, and AXIS prescriptions?