page_title: Pupillary distance
section_title: Measuring pupillary distance
hierarchical_section_title: Pupillary distance / Measuring pupillary distance
caption_attribution_description: Deutsch: Bildinhalt: Messbrille Aufnahmeort: Baden-Baden, Deutschland
context_page_description: Pupillary distance or interpupillary distance is the distance measured in millimeters between the centers of the pupils of the eyes. This measurement is different from person to person and also depends on whether they are looking at near objects or far away. Monocular PD refers to the distance between each eye and the bridge of the nose which may be slightly different for each eye due to anatomical variations. For people who need to wear prescription glasses consideration of monocular PD measurement by the optician helps to ensure that the lenses will be located in the optimum position. Purchasing glasses online can be a potential problem if the PD measurement isn't available.
  In both the UK and most of Canada, the PD measurement is classed as a dispensing tool rather than a part of the actual prescription of the person whose eyes were tested, thus there is no obligation for a PD to be provided on patient request. Whilst PD is an optometric term used to specify prescription eyewear, IPD is more critical for the design of binocular viewing systems, where both eye pupils need to be positioned within the exit pupils of the viewing system.
context_section_description: Different methods for measuring exist but accurate measurement can usually be determined by an ECP during an eye examination. This is normally done with a small millimeter ruler referred to as a "PD stick" or with a corneal reflex pupillometer, which is a machine calibrated to help the optical professional more accurately measure the pupillary distance. There are also mobile phone and web apps that can measure one's pupillary distance.
caption: Monocular PD can be measured during an eye test.
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