Pupilometer

Pupilometer, also spelled pupillometer, is a name for two different devices—one used to measure the pupillary light reflex, and the other used in ophthalmology, which measures the distance between pupils through visual stimuli.

Automated Pupillometry

An automated pupillometer is a portable, handheld device that provides a reliable and objective measurement of pupillary size, symmetry, and reactivity through measurement of the pupillary light reflex. Independent of examiner, an automated pupillometer eliminates variability and subjectivity, expressing pupil reactivity numerically so that both pupil size and reactivity can be trended for changes, just like other vital signs. An automated pupillometer also provides a reliable and effective way to quantitatively classify and trend the pupil light response.

Using automated pupillometers and algorithms, NeurOptics' Neurological Pupil index (NPi) can offer a consolidated parametric approach to mitigate subjectivity. The NPi and automated pupillometry have also recently been included in the updated 2020 American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) as an objective measurement supporting brain injury prognosis in patients following cardiac arrest. Studies published in peer-reviewed journals continue to demonstrate the effectiveness of NeurOptics' NPi in helping clinicians improve patient outcomes.
The most effective way to use an automated pupillometer is to establish the earliest possible baseline measurement when the patient is admitted into the critical care unit or emergency department, and then trend for changes over time.

Pupillary Distance Measurement

In the most common sense, a pupilometer is a tool for measuring pupillary distance (PD). It is used for fitting eyeglasses so that the lenses are centered in the visual axis. This is the most common nomenclature. It may also be used to verify a PD measurement taken from a millimeter ruler placed across the bridge of a patient's nose for distance and near focus.

Pupils are consisted of many parts, so it’s hard to determine where. There are a variety of ways of measuring one's pupil distance. Historically a ruler is used by optometrists. State of the art are video centration devices which provide higher accuracy and repeatability compared to manual measurements. The accuracy is especially a concern for progressive lenses where small deviations severely reduce the performance of the lens.
In addition to having it measured when one visits an optometrist, there are a variety of mobile phone apps and web apps that a person can use. The apps are available for the Android and IOS phones and tablets. The web app is used by a variety of online sellers of eyeglasses. In order to use the phone app or web app, a camera and a credit card with a magnetic strip are needed to assist in the measuring processes.

Pupil response

Alternatively, a pupilometer is a type of pupil response monitor — a monocular device measuring the amount of dilation of the pupil in response to a visual stimulus.

In ophthalmology, a pupillary response to light is differentiated from a pupillary response to focus (i.e. pupils may constrict on near focus, as with the Argyll Robertson pupil) in the diagnosis of tertiary syphilis. Although a pupillometer can be used, the diagnosis is often made with a penlight & near-point card

The extent of dilation of the pupil in the eye could be an indicator of interest and attention. Methods of reliable measurement of cognitive load, such as the dilation or constriction of the pupils, are used in marketing research to assess the attractiveness of TV commercials. Dilation of the pupils reflects an increase in mental processes, whether it be attentiveness, or psychomotor responsiveness. The pupil response has also been found to reflect long-term memory processes both at encoding, predicting the success of memory formation, and at retrieval reflecting the operation of different recognition outcomes.

See also

*Pupil
*Pupillometry
*Neurological Pupil index (NPi)
* Psychophysiology

References

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Ophthalmic equipment
Human pupil