pupillary distance

Someone with training in the field of optics can accurately measure a person's pupillary distance.

There are also mobile phone and web apps that can also measure one's pupillary distance.

The one crucial piece of data most consumers are probably missing is the pupillary distance, which is how close the eyes are to each other.

The typical pupillary distance for adults is around 54-68 mm, while measurements generally fall between 48 and 73 mm.

In other words, as the pupillary distance from the foveal achromatic axis is increased, perceived depth also increases.

Diagram at solobambini.com (measure of Pupillary distance)

It's a tool for measuring pupillary distance (PD).

In the most common sense, a Pupilometer is a tool for measuring pupillary distance (PD).

Additionally, an eyeglasses prescription may include a monocular pupillary distance ("monocular PD").

Pupillary distance (PD) also describes the distance between the two pupils, but is an optometric term used to specify prescription eyewear.

Store-bought reading, or magnifying glasses, have an arbitrary pupillary distance; nor do they compensate for spherical or chromatic aberration as a quality lens would.

From the measurements taken, the specialist will write an eyeglass prescription that contains at least 6 numerical specifications (3 for each eye): sphere, cylinder, and axis and possibly pupillary distance.

It is written as two values if the prescription is for bifocals or progressive lenses - these are the pupillary distances for the distance and near fixation (essentially, the upper and lower part of the lenses).

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.