How to Measure Pupillary Distance (PD)
What is Pupillary Distance (PD)?
Pupillary Distance (PD) is the measurement, in millimeters (mm), from the center of one pupil to the center of the other. PD is crucial for creating custom prescription glasses as it ensures your lenses are correctly positioned in the frame for optimal comfort and clarity.
Why is Pupillary Distance Important?
An incorrect PD can cause eye strain, fatigue, and improper vision correction. This is especially critical for high prescription lenses, making accurate PD measurement essential.
Types of Pupillary Distance
- Single PD (Binocular PD): The distance from the center of one pupil to the center of the other. This is used for most types of prescription glasses, except reading glasses.
- Dual PD (Monocular PD): The distance from the center of each pupil to the bridge of the nose. Dual PD includes two measurements: one for the right eye (OD) and one for the left eye (OS). This is often used for reading glasses.
How to Measure Pupillary Distance?
There are several methods to measure your PD at home:
Method 1: Using a Ruler and a Mirror
- Preparation: Stand about 8 inches (20 cm) away from a mirror, holding a millimeter ruler.(Download PD Ruler)
- Measurement:
- Place the millimeter ruler on the person's forehead, aligning the 0 mm mark with the center of the right pupil.
- Read the millimeter line above the center of the left pupil.
Method 2: With a Friend's Help
- Preparation: Have the person being measured sit down and focus on an object 10 to 20 feet away.
- Measurement:
- Place the millimeter ruler on the person's forehead, aligning the 0 mm mark with the center of the right pupil.
- Read the millimeter line above the center of the left pupil.
Method 3: Using Existing Glasses
- Preparation: Wear your glasses and focus on an object 20 feet away.
- Measurement:
- Use a non-permanent marker to mark the point on your right lens where you see the object.
- Repeat for the left lens.
- Remove your glasses and measure the distance between the two marks to find your PD.
Average Pupillary Distance
The average PD for adults ranges from 55 to 65 mm, while children typically have a PD between 42 and 54 mm. For women, the average PD is about 60 mm, and for men, it is around 64 mm.
By following these methods, you can easily measure your PD at home to ensure your custom glasses fit perfectly and provide clear vision. If you have any doubts about your measurement, it is always best to consult with a professional optometrist.
