Because instruments such as binoculars and microscopes can be used by different people, the distance between the eye pieces is usually made adjustable to account for IPD. 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. IPD is also used to describe the distance between the exit pupils or optical axes of a binocular optical system. IPD data are used in the design of such systems to specify the range of lateral adjustment of the exit optics or eyepieces. These viewing systems include binocular microscopes, night vision devices or goggles (NVGs), and head-mounted displays (HMDs). 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. įor 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. Monocular PD refers to the distance between either the right or left visual axis to the bridge of the nose, which may be slightly different for each eye due to anatomical variations but always sums up to the binocular PD. Intermediate PD is at a specified plane in between distance and near. Near PD is the separation between the visual axes of the eyes, at the plane of the spectacle lenses, as the subject fixates on a near object at the intended working distance. Interpupillary Distance Classifications ĭistance PD is the separation between the visual axes of the eyes in their primary position, as the subject fixates on an infinitely distant object. Pupillary distance ( PD), more correctly known as interpupillary distance ( IPD) is the distance in millimeters between the centers of each pupil. If the measurement is 6.4cm then your PD will be 64.Distance in millimeters between the centers of each pupil Monocular PD can be measured during an eye test. If you have a reading of 6cm then type in our prescription page a PD distance of 60.
Take off your glasses and measure the distance between the two markings. You will now have two lines directly in front of you whilst wearing your spectacles.Ask your friend to stand opposite you and mark on your lenses the position of your pupils with a non-permanent marker. Put your glasses on so that they are comfortable and steady.Please see the diagram above to help you further.Īsking a friend to help you using your current glasses Your friend will then read off the measurement to the centre of your left pupil. Ask your friend to close their left eye and for you to look directly into their right eye.Ask your friend to slide the ruler so that the zero value is in the centre of your right pupil and to keep the ruler very steady across your forehead. Ask your friend to close their right eye and you then look directly into their left eye.With your friend sitting opposite you at the same height, ask them to place a ruler across your forehead just above your eyes with the millimetre side facing upwards.This is the easiest method for measuring you PD. Please include a note with your name, telephone number and your reference number that will be provided on the completion of your purchase.Īsking a friend to help you using a ruler We will return the glasses with your new pair. Send us an old pair of your glasses and we will match the centres to these.Though the spectacles will not harm the eyes, they could cause discomfort and eye strain. For people with stronger prescriptions it would be better to measure your PD. This will not be a problem for most people who either are the average or have weak prescriptions (-2 to +2 spheres). Use an average PD measurement which is about 62mm for women and 64mm for men. Measure the distance yourself using a mirror and a ruler as explained below.When written like this it is the individual distance from you right and left pupils to the centre of your nose.
It is usually written as one measurement such as 60 (60mm) but can also be shown as R 29 L 31.
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