Your PD is the distance between your eyes, measured between the centre of your pupils. For a pair of glasses to perform as well as possible for you, the lenses need to be made to match this distance between your eyes, so that the centre of each lens aligns with the centre of your pupils. This is important if you have a high-strength prescription or require varifocals for example.
Usually the optician will not include this with your prescription, so you should ask your optician for your PD following your eye test. Alternatively we can take this measurement from your existing glasses - your PD doesn’t change from one prescription to the next. One of our opticians will call you if we feel this is necessary. If you would rather not send them, we can make your glasses using an average PD measurement (based on a survey of 4,000 people).
Very occasionally, people with strong prescriptions and whose pupillary distance diverges significantly from the average, may experience problems with glasses made using an average PD measurement. An incorrect PD won't harm the eyes but may cause discomfort or strain which would be noticeable upon wearing the glasses. If you decide to order a pair of average PD measurement glasses and find yourself getting along with them less than perfectly, do tell us, and we'll either replace your glasses once we've collected a correct PD from you or an old pair of your glasses, or give you a full refund.