Ordering eyeglasses online offers convenience and a wide selection, but it requires you to have accurate pupillary distance (PD) measurement. Your PD is crucial for ensuring your lenses are positioned correctly in your frames for optimal vision. While your eye doctor may include your PD on your prescription, it’s not always the case. Fortunately, measuring your PD at home is a straightforward process. This guide will walk you through everything you need to know about pupillary distance and how to measure it accurately yourself or with the help of a friend.
Understanding Pupillary Distance (PD)
Pupillary Distance, commonly known as PD, is the measurement of the distance between the centers of your pupils, expressed in millimeters. This measurement is vital when making eyeglasses because it dictates the optical center of each lens, the point through which you should be looking. An accurate PD ensures that you are looking through the sweet spot of your lenses, providing the clearest and most comfortable vision.
There are two main types of PD measurements:
- Monocular PD (or Dual PD): This measurement consists of two numbers and indicates the distance from the center of the bridge of your nose to the center of each pupil individually. It is usually written as two numbers, for example, 32 and 31, representing the PD for the right and left eye, respectively.
- Binocular PD (or Single PD): This is a single measurement representing the total distance between the centers of both pupils. A typical single PD value might be 60mm or 64mm.
Both single and dual PD measurements are acceptable when ordering glasses online. Understanding which type you have or are measuring is important for accurate order placement.
Methods to Measure Your PD
You can measure your pupillary distance using a few simple methods. The easiest way is with the help of another person, but you can also measure it yourself using a mirror. For both methods, you’ll need a PD ruler, which is often printable and readily available online.
Measuring PD with a Friend: Step-by-Step Guide
Having a friend measure your PD is generally considered the most accurate method for home measurement. Here’s how to do it:
- Prepare: Download and print a PD ruler. Ensure it is printed to scale for accurate measurements.
- Positioning: Have your friend sit comfortably and instruct them to focus on a distant object at least 10 to 20 feet away. This helps to keep their eyes steady and prevents them from focusing on the ruler itself.
- Ruler Placement: Fold the PD ruler to the side marked “Using a friend.” Place the ruler against your friend’s forehead, resting it just above their eyebrows. Align the zero millimeter mark on the ruler directly with the center of their right pupil.
- Measure: While keeping the zero aligned with the right pupil, look straight ahead. Close one eye (either your left or right) to help you read the ruler more precisely. The number on the ruler that aligns with the center of your friend’s left pupil is their pupillary distance.
- Record: Note down the measurement in millimeters. It’s a good idea to repeat the measurement a couple of times to ensure consistency and accuracy.
Measuring PD by Yourself Using a Mirror: Step-by-Step Guide
If you are by yourself, you can still measure your PD using a mirror. Here are the steps:
- Prepare: Use the same printed PD ruler as in the previous method.
- Mirror Setup: Stand approximately 8 inches away from a mirror. This distance allows you to see your pupils clearly and manipulate the ruler.
- Ruler Position: Fold the ruler to the side marked “Using a mirror.” Hold the ruler horizontally across the bridge of your nose, just above your eyebrows. Center the zero millimeter mark directly in line with your left pupil’s reflection in the mirror. You can use your fingers to stabilize the ruler against your forehead.
- Measure: Cover or close your left eye. Looking straight ahead at your reflection in the mirror, identify the number on the ruler that lines up with the center of your right pupil’s reflection. This number is your pupillary distance.
- Record: Record the measurement. Similar to measuring with a friend, repeat the process a few times to ensure you get a consistent reading. Calculate the average of multiple measurements for the most accurate PD.
Measuring Near PD
For those needing progressive or bifocal lenses, a near PD measurement is also necessary. This is because your eyes converge when focusing on close-up objects. Measuring near PD requires assistance from another person for accurate results.
To measure near PD, follow the same steps as measuring regular PD with a friend, but with one key difference: Instead of focusing on a distant object, you should focus on a small object, like the tip of a pen, held about 14-16 inches in front of your face, between you and the person measuring. While you are focused on this near object, your friend can measure your near PD using the ruler.
Finding Your PD on Your Glasses Prescription
Your PD might already be on your glasses prescription provided by your eye doctor. It is usually listed as “PD” and is often located somewhere near the section detailing your lens powers.
- Single PD Value: If you see just one number listed as PD (e.g., PD: 64), this is your binocular or single PD.
- Dual PD Values: Sometimes, your PD will be listed as two numbers (e.g., PD: 32/31 or R: 32, L: 31). This indicates your monocular or dual PD, specifying the pupillary distance for each eye separately. The first number usually corresponds to the right eye (OD) and the second to the left eye (OS).
If your prescription includes PD, you can use that value when ordering your glasses. If it’s missing, home measurement is a reliable alternative.
Average Pupillary Distance Ranges
While it’s important to measure your own PD for accuracy, understanding average ranges can provide context. The average pupillary distance for adults typically falls between 48mm and 73mm. Women tend to have a slightly lower average PD, around 60mm, while men average around 64mm. However, PD varies significantly from person to person, and these are just averages. Children generally have a smaller PD, which increases as they grow.
Single vs. Dual PD: Which to Use?
When ordering glasses online, you will often be asked for your PD. Most online retailers accept both single (binocular) and dual (monocular) PD measurements. If your prescription provides a dual PD, entering those two numbers is perfectly acceptable. If you only have a single PD or have measured a single PD, that will also work. The key is to provide accurate measurements, regardless of whether they are single or dual.
Measuring your pupillary distance at home is a simple and valuable skill, especially for purchasing eyeglasses online. By following these steps, you can ensure your new glasses are made to your exact specifications, providing you with clear and comfortable vision.
