iPD

IPD is an acronym that can refer to several concepts across different fields. The three meanings most often encountered are interpupillary distance, individual participant data, and integrated project delivery.

Interpupillary distance refers to the distance between the centers of the pupils of the eyes. It is a key parameter in fitting eyeglasses, binoculars, and virtual reality headsets, ensuring proper optical alignment and comfortable viewing. Typical adult values range roughly from 54 to 74 millimeters, though measurements can vary by individual. Methods for measuring IPD include manual rulers, optical pupillometers, or digital imaging, and accuracy is important for image fusion, depth perception, and comfort in devices that present separate images to each eye.

Individual participant data denotes raw data collected from each participant in a set of studies. In evidence synthesis, IPD meta-analyses reanalyze these data rather than using summary statistics alone. Advantages include the ability to harmonize outcome definitions, perform uniform statistical models, and conduct detailed subgroup analyses. IPD meta-analyses can yield more reliable estimates and enable time-to-event or covariate-adjusted analyses, but they require data sharing arrangements, privacy protections, and substantial data harmonization efforts.

Integrated project delivery is a construction industry approach that emphasizes early involvement of key parties, collaborative contracting, and aligned goals to improve project outcomes. IPD seeks to reduce waste, shorten schedules, and control costs by fostering joint planning, shared risk and reward, and open information exchange, often supported by integrated technologies such as building information modeling.

Other uses of IPD exist in different disciplines, but these three are among the most widely recognized.