Monocular PD can be measured during an eye test.<unk>  (PD) or interpupillary<unk>  (IPD) is the<unk>  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<unk>  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 an optician helps to ensure that the lenses will be located in the optimum position. 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. These viewing systems include binocular microscopes, night vision devices or goggles (NVGs), and head-mounted displays (HMDs). IPD data are used in the design of such systems to specify the range of lateral adjustment of the exit optics or eyepieces. IPD is also used to describe the<unk>  between the exit pupils or optical axes of a binocular optical system. The distinction with IPD is the importance of anthropometric databases and the design of binocular viewing devices with an IPD adjustment that will fit a targeted population of users. Because instruments such as binoculars and microscopes can be used by different people, the<unk>  between the eye pieces is usually made adjustable to account for IPD. In some applications, when IPD is not correctly set, it can lead to an uncomfortable viewing experience and eye strain.
Pupillary distance
Supplementary eye field
Underwater vision
Cup-to-disc ratio
Pinch 
Pupillary light reflex
Corneal reflex
Eye drop