How to Measure Pupillary Distance

Ensuring the perfect fit for your glasses starts with an accurate pupillary distance (PD), the space between the pupils of your eyes. This measurement is crucial for the proper alignment of your prescription lenses. While your optician can measure this for you, Zenni Optical offers a convenient digital PD ruler and an easy-to-follow online tutorial for measuring your PD at home. It’s quick, precise, and user-friendly, allowing you to order glasses that are tailor-made for your vision needs with confidence. Learn how to measure your PD with Zenni’s informative guide and video tutorial.

Why is PD Important?

Your PD is essential because it ensures that the optical center of your lenses is aligned with your pupils. When you wear glasses, the lens has a specific area—called the optical center—that helps focus light precisely onto the retina. If the center of the lens doesn’t line up with your pupils, it can cause distortion or eyestrain. Having an accurate PD measurement helps in:

• Preventing eyestrain and discomfort
• Ensuring the correct focal point in the lenses
• Providing a more comfortable, clearer visual experience

Types of PD Measurements

There are two types of PD measurements:

• Monocular PD: This is the distance from the center of one pupil to the center of the nose. It is measured for each eye individually.
• Binocular PD: This is the total distance between the centers of both pupils, measured from one eye to the other. This is the most common type of PD measurement required for glasses prescriptions.

Tips for Accurate Measurements

• Use Good Lighting: Make sure the lighting in the room is bright enough to clearly see the pupils.
• Keep Your Head Straight: Maintain a neutral head position—tilting your head can lead to incorrect measurements.
• Avoid Squinting: Relax your eyes and avoid squinting, as this could affect the alignment of your pupils.
• Take Multiple Measurements: It’s always wise to measure your PD a few times to ensure accuracy.

Dr. Steven Liem

Dr. Steven Liem, O.D., F.A.A.O. is an optometrist based in Pasadena, California. After obtaining his doctorate from UC Berkeley’s School of Optometry, he completed his residency in Pediatrics, Vision Therapy & Rehabilitation and became a Fellow of the American Academy of Optometry. When he isn’t busy streaming or making Youtube videos about video games, Dr. Liem aims to broaden accessibility to vision health through his involvement in optometric industry and tech.