What is PD?

Your PD or 'pupillary distance' is the distance between the centre of your pupils (the black central area of each eye). As a general guide, most adult PD measurements fall between 50 and 70mm. An accurate PD measurement is a crucial part of fitting and making your glasses and should not be overlooked.

A good optician will always take a measurement of your PD before making your glasses for you. An accurate measurement is needed to supply glasses and minimise any discomfort or distortion of vision to the wearer. We use an accurate machine to measure your PD and would not recommend using a PD measurement taken without the proper training and tools.

When we make glasses we specify 'monocular PDs' for your right and left eye individually. Most people's faces are not perfectly symmetrical so this method is more accurate as the PD measurement for one eye might be slightly higher than for the other.  We also consider what you'll be using the glasses for as, since your eyes converge when looking at near objects, your reading PD will be slightly lower than for your distance glasses.

At the Eye Centre we also take other measurements using a special camera and computer software that not only measures your eyes but also records the shape and size of the glasses frame you've chosen. This helps us to ensure the glasses lenses sit in the exact position needed to offer you the clarity of vision you require. This is because even a slight error, particularly with higher prescriptions, can cause problems with your glasses.

We call all of the above the "fitting" of the frame and it is an essential part of making a good pair of glasses.