Interpupillary distance (IPD)
Short definition
Interpupillary distance (IPD) is the distance between the centres of the pupils of the two eyes, which a virtual reality headset must match for the image to be sharp and comfortable.
In plain language
It varies from person to person and is, on average, smaller in children than in adults. If the headset lenses are misaligned with the eyes, the image may look blurred or doubled and cause eye strain. For this reason, many devices allow the distance between the lenses to be adjusted before the session begins.