What Is PD on a Prescription (Pupillary Distance)?
PD, or pupillary distance, is the distance in millimetres from the middle of one pupil to the middle of the other. Lens labs use that number to put the optical centre of each lens right in front of the correct eye.
PD Definition for Glasses: What Does PD Stand For?
PD stands for pupillary distance. Another term you may hear from some eye doctors is IPD, which stands for interpupillary distance and carries the same meaning (Cleveland Clinic). For adults the measurement, in millimetres, usually lands somewhere between 50 and 70.
How Can You Find PD on a Prescription, and Where Do You Look?
The label you need is PD, P.D. or IPD, shown in a box or a row. It often sits either to the right of the table or under it. Inside that space you might see one number, two numbers with a slash between them, or nothing at all.
A prescription for eyeglasses
| SPH | CYL | AXIS | ADD | PD | |
|---|---|---|---|---|---|
| OD (right eye) | -2.25 | -0.50 | 180 | +1.50 | 31.5 |
| OS (left eye) | -2.00 | -0.75 | 175 | +1.50 | 32 |
The PD box can also hold a single figure such as 63.5, or a distance-and-near pair like 64/61.
How to Read PD, OD and OS on Your Prescription
- One number, like 63, is your single PD: it is the same as binocular PD.
- When you see two numbers that are close, like 31.5/32, that is a dual PD. It supplies one value per eye, beginning with the right eye, or OD (Cleveland Clinic).
- Two numbers about 3 mm apart, such as 64/61, give a distance PD and a near PD for reading.
Not certain which type you are looking at? Need to change one type to the other? Open the dual PD vs single PD calculator.
No PD on Your Prescription?
That is a common situation. In the US, the federal Eyeglass Rule requires your eye doctor to give you your prescription, and it notes that some states also require the PD to appear on it. If the number is missing, request it from the office, or take about a minute to measure your PD yourself.
Is PD Important for Glasses?
A lens is built with a single spot you are supposed to look through. When the lenses are made to match your PD, those spots align with your pupils. When the alignment is off, the image moves a little, and you may sense it as eye strain. How strong the lenses are determines how big an error starts causing trouble: wrong PD covers the details.
Questions About What PD Means
What does PD mean on an eye prescription?
The distance in millimetres from one pupil to the other: it sets the placement of each lens centre.
Are PD and IPD the same?
Yes. IPD, or interpupillary distance, is another name for PD. VR headsets use the term IPD: read more at find your IPD.
Is a PD of 60 considered normal?
Yes. The typical adult range is 50 to 70 mm, so 60 falls well within it. Check the PD chart to see how often each measurement occurs.
Does PD matter for contact lenses?
That is not the case. Because a contact lens rests right on the eye and travels with it, a contact lens prescription never lists a PD number.