Interpupillaire

Interpupillaire, or interpupillary distance (IPD, sometimes abbreviated PD), is the distance between the centers of the pupils of the eyes. It is usually measured in millimeters and is primarily a horizontal measurement, as that is the orientation most lenses and optical systems align to. Some contexts also consider a vertical component, but the horizontal distance is the standard reference for eyewear and devices.

IPD is a key parameter in optics and vision care. In eyeglasses, correct PD ensures that the optical centers of lenses align with the wearer’s pupils, minimizing blur, prismatic effects, and eye strain. In devices that rely on binocular vision, such as virtual reality headsets, binoculars, and some cameras, matching the device’s IPD to the user’s IPD is important for comfortable viewing and accurate stereo perception. Differences between individuals’ IPD can influence fit, comfort, and visual performance.

Measurement methods include using a pupillometer or a PD ruler, often performed by an optometrist or trained dispenser. A typical procedure involves having the person look at a distant target and measuring the distance between the centers of the pupils. There are two common values: distance PD (for distance vision) and near PD (for reading or close work); near PD is usually slightly smaller than distance PD. Average adult values commonly fall in the mid-60s millimeters range, with children having smaller PD and significant individual variation.

Variations in IPD can occur with gaze direction, age, and anatomical differences. Accurate PD measurements support proper lens design, ergonomic device setup, and comfortable, clear vision.