Does pupillary distance change with age?

A child's face grows around the eyes, and the orbits move apart as the skull widens. That is why children's glasses need the pupillary distance, PD, measured again at each new pair rather than copied from the last prescription. Growth slows through the teens and the figure settles once the face stops growing, which is in the late teens or early twenties for most people.

In adults the interpupillary distance is set by bone and does not move with age, weight or any routine. Soft tissue around the eye changes over the decades, lids loosen and brows drop, and that can change how the eyes look, but not where the pupils sit. If your prescriptions disagree, the usual causes are:

• Near versus distance PD. When you look at something close, the eyes converge, so the near figure for reading glasses is smaller than the distance figure.
• Single versus split figures. Some prescriptions give one total, others a figure for each eye. Faces are asymmetric, so the halves are rarely identical.
• Measuring method. A ruler, a pupillometer and a photo estimate each carry their own small error, and gaze direction during the measurement matters.

Ask the optician who last examined you; most will give your PD from the record. The pupillary distance tool estimates it from one photo by scaling the gap between the pupils against the width of the iris, which varies little between adults. That is enough for a single-vision online order when the photo is sharp and straight-on, and not enough for progressives, strong prescriptions or children, which should be measured in person.

PD is a number for lenses, not a looks score. How far apart your eyes look is a proportion, covered in how far apart should your eyes be?, and it is equally fixed, as can eye spacing be changed? explains.