What is a Pupillometer?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 09 October 2019
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A pupillometer is a device that measures the reactivity of the eyes' pupils. The pupillometer can be a large machine, connected to a wall, with a chair that allows one to sit and go through about 10 minutes of testing to evaluate the pupil’s reactivity to light. Handheld pupillometers are often used in preliminary examinations of patients who are suspected of being under narcotic influence, or for those who have sustained a significant head injury.

The pupillometer is used in many different applications. Those who are being examined for Parkinson’s disease, rheumatoid arthritis or lupus, may all show significant difference in pupil size or reactivity. In these cases the pupillometer can be an important diagnostic device that can show signs of such illnesses. In other cases, the pupillometer might be used to assess degeneration of eye tissue in people with severe diabetes.

Pupillometer examinations are frequently conducted on those undergoing physical exams to become firemen, emergency workers, or policemen. The reactions of the pupil can, of course, suggest the use of narcotics, especially when the pupil remains less reactive and small. The pupillometer may also suggest early symptoms of progressive joint or tissue disorders, which would disqualify one to serve as an emergency or law enforcement worker.


Law enforcement officials and doctors often use hand pupillometers to assess those behaving as if they are under the influence. Since viewing the eye is non-invasive, it can be a helpful and safe tool for assessing someone who may have taken narcotics. When an overdose of narcotics is suspected, doctors can then evaluate the pupils for signs of constriction, and treat patients according. This use of the pupillometer is safer than methods that involve potential contact with bodily fluids, such as in urine and blood tests.

Perhaps one of the most interesting applications of the pupillometer is its use in the study of people with sleep difficulties. Those who are exhausted, or who suffer from narcolepsy frequently have either small, nonreactive pupils in the dark, or overly reactive pupils. These studies are still in preliminary stages but may prove helpful in determining whether treatments for sleep disorders are effective. Theoretically, those who are being treated for sleep disorders would gradually show more normal pupil reactions during pupillometer examinations. Failure to improve would be a sign that treatments were not effective.

One criticism of this current application is that pupil fluctuations are graphed and interpreted, and a graph may be subject to several interpretations. That makes this new study somewhat less scientifically correct, though the experiment may still be helpful in addressing sleep disorders at a future date.


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