What Is Pupillary Distance (PD) When Ordering Prescription Glasses? How to Measure It Accurately?

What Is Pupillary Distance (PD) When Ordering Prescription Glasses? How to Measure It Accurately?

When you're buying new prescription glasses—whether online or in-store—you’ll need more than just your eye prescription. One crucial detail that’s often overlooked is your Pupillary Distance, commonly known as PD.You may have seen this term on your prescription form, but do you really know what it means and why it matters?

In this guide, we’ll explain:

What PD is?

Why it’s essential for clear, comfortable vision

And how to measure it accurately—on your own or with professional help

1. What Is Pupillary Distance (PD)?

Pupillary Distance (PD) is the distance in millimeters (mm) between the centers of your two pupils—the black dots in the middle of your eyes.Think of it as the measurement that ensures your glasses’ lenses are perfectly aligned with your line of sight.Average adult PD: Typically between 54mm and 74mm

Children’s PD: Smaller, and changes as they growThere are two types of PD:

· Binocular PD: The total distance from the center of one pupil to the other (e.g., 62mm)

· Monocular PD: Measured separately from each pupil to the center of your nose (e.g., 31mm / 31mm)

Tips: If you have a high prescription, wear progressive lenses, or choose large-frame glasses, even a 1–2mm error in PD can cause discomfort. Precision matters!

2. Why Is PD So Important for Prescription Glasses?

Many people think that as long as the lens power is correct, the glasses will work fine. But if your PD is off, your vision won’t be optimal—even with perfect prescription strength.What Happens If Your PD Is Incorrect?

· Blurry or double vision

· Eye strain, headaches, dizziness

· Difficulty focusing, especially during long reading or screen use

· Reduced depth perception and visual comfort

Why Correct PD Makes a Difference:

· The optical center of each lens aligns exactly with your pupils

· Clearer, more natural vision

· Reduced eye fatigue

· Better visual performance for driving, working, or studying

Imagine wearing glasses that shift your focus slightly off-center—like a camera with misaligned lenses. No matter how powerful the lens, the image won’t be sharp.

3. How Is PD Measured? Can You Do It Yourself?

Yes—you can measure your PD at home, but accuracy is key. Here are the most reliable methods:Method 1: Professional Measurement (Most Accurate)Where: Eye doctor’s office, optometrist, or optical store

Tool: Pupillometer (a small handheld device)

Accuracy: Typically within 0.5mm

Best for: First-time wearers, high prescriptions, progressive lenses, or custom framesThis is the gold standard. If you’re unsure, always get your PD measured by a professional.Method 2: Use a PD Measurement App (Convenient & Reliable)Many trusted apps can help you measure PD using your smartphone:

· PD Meter App (iOS / Android)

· EyeMeasure

· GlassesUSA PD Calculator

How to use:

1. Stand 40cm (about 16 inches) from your phone

2. Hold your phone at eye level, facing a well-lit mirror or use the front camera

3. Align the crosshair with your right pupil, then left

4. The app calculates your PD automatically

5. Repeat 2–3 times and take the average

Tips: Keep your head straight, eyes level, and avoid tilting the phone.Method 3: Manual Measurement (For Emergency Use)What you need: A ruler (mm scale), a mirror, and a pen.

Steps:

1). Sit in front of a mirror, lighting well

2). Place the ruler on the bridge of your nose

3). Close your left eye, align the ruler’s zero with the center of your right pupil

4). Now close your right eye, and read the measurement at the center of your left pupil

5). That number is your binocular PD

Example: Right pupil at 31mm, left at 63mm → PD = 63 – 31 = 62mmNote: This method has higher error risk. Take multiple readings and average them.

4. How to Enter PD When Buying Glasses Online

Most online eyewear retailers (like aurooa.com) will ask for:

· Right and left eye prescriptions (SPH, CYL, AXIS)

· Your PD value

How to enter it:

· If you have monocular PD: Enter Left: 31mm / Right: 31mm

· If you only have binocular PD: Enter 62mm

· Not sure? Some sites offer a default (e.g., 63mm), but avoid this if you have high myopia or astigmatism

Always double-check before placing your order!

5. Frequently Asked Questions (FAQ)

Q: Does PD change over time?

A: In adults, PD is usually stable. In children and teens, it may increase slightly as the face grows.Q: Do I need PD for non-prescription sunglasses?

A: For plano (non-prescription) sunglasses, PD isn’t critical. But if your sunglasses have prescription lenses or polarized optics, accurate PD ensures better visual clarity.Q: Should I measure PD while wearing glasses?

A: No. PD is a physical measurement of your eyes, not affected by whether you’re wearing glasses or not.Final Thoughts: Don’t Skip the PD! Key Point: What is PD?

Recommendation: Distance between pupils (in mm)Key Point: Why does it matter?

Recommendation: Ensures sharp, comfortable visionKey Point: How to measure?

Recommendation: Professional > App > ManualKey Point: Buying online?

Recommendation: Always provide accurate PDRemember:

A great pair of glasses = Accurate prescription + Correct PD + Well-fitted frame + Quality lenses.

Don’t let a small number ruin your clear vision.Next time you get your eyes checked, ask: “What’s my pupillary distance?”

It could make all the difference.Provided by the vision care team at aurooa.com — helping you see clearly, comfortably, and in style.