How to measuring your PD(Pupil Distance)?

This should be done with glasses off, if the numbers on a ruler are difficult to see, then a magnifying mirror may help.

1. Whilst looking into a mirror hold a ruler against the bridge of the nose with one hand.

2. Close your left eye, and line the '0' up with the centre of the pupil of your right eye as shown in the diagram.

3. Without moving your head or the ruler open the left eye and close the right eye. Read the number that lines up with the centre of the pupil of the left eye. This number represents your Distance PD in millimetres. You have just used this technique to measure your distance PD.

4. Repeat this whole process at least 3 times to try and get a consistent measurement in millimetres. Make sure your head and the ruler do not move after lining up the zero on the ruler until you take the reading.