Typically, there will only be one number in your PD measurement - this is called Single PD, and it can be used to order most types of prescription eyeglasses.
But if you have two different numbers, you have been measured for Dual PD (also known as monocular PD). In this scenario, the numbers are measurements of the distances from each pupil to the bridge of your nose - the first number refers to the left eye distance and the second to the right. Added together, these numbers should equal the full distance measured between your two pupils. Dual PD is required for reading glasses, but not usually necessary otherwise.
- Two of the same number (e.g. 30/30): This is the same as a Single PD measurement between the pupils. When entering this information to order your glasses, you can just add them together and we’ll automatically divide it equally.
- Two low numbers (e.g. 30/31): The first number is the monocular PD for the right eye (O.D.) and the second number is for the left eye (O.S.).
- Two high numbers (e.g. 62/59): This is used only for reading glasses. The first number is your Distance PD and the second number is your Near PD.
What is PD?
- PD stands for Pupillary distance or interpupillary distance, which is the distance between the centers of the pupils of the eyes.
How do you find the pupillary distance on a prescription?
- Pupillary distance measurements are not always listed on your prescription, but it’s easy enough to obtain using a ruler and a mirror. How To Measure Your Pupillary Distance (PD)
How is the pupillary distance measured?
- Stand in front of a mirror.
- Hold a ruler against your brow.
- Close your right eye and then align the ruler’s 0 mm with the center of your left pupil.
- Look straight, close your left eye, then open your right eye.
- The line that lines up to the center of your right pupil is the PD.
How important is the PD for glasses?
- Pupillary distance is needed to make a pair of prescription glasses because it tells the manufacturer of the glasses where to put the optical center on each lens.
What happens if the pupillary distance is wrong?
- If your pupil distance does not match the centers of your pupils, your vision will be affected. The wrong pupillary distance induces eye strain, fatigue, headaches, and blurry vision.