An important aspect of glazing a pair of lenses into a frame is to ensure that the optical centre of each lens is precisely centered in front of the customerâ€™s pupil, to provide the sharpest image possible. This measurement is known as the Pupillary Distance (or PD) and can be measured in various ways. Â As an internet company, in most cases we will measure it from a customerâ€™s existing pair of spectacles. If the customer has no spare pair to send in, then it would need to be measured by an optician face-to-face.
When this issue was first raised with Glasses Direct, we did a survey of 4,000 customers and we found the average to be 63mm for distance vision and 60mm for reading. PD tends to have a more significant affect on customers with particularly high prescriptions, multifocals or bifocals. However most prescriptions we receive are weaker (as a guide this is between +2.50 to â€“2.50) and so we can use this average measurement, at the discretion of our dispensing opticians.
When an order is now placed, a dispensing optician reviews each order carefully and will decide whether the average will suffice or if we need it measured using another alternative. Customers’ sensitivity can vary however, as some customers can have a very strong prescription combined with a mismatched PD and have no adverse problems at all.
If the specs are made up and the customer experiences any problems seeing through them, that we find are due to an inaccurate PD, then we will remake the specs to the correct PD with no quibbles at all.