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Pupillary Analysis Science background

SOBEREYE technology measures alterations of the Pupillary Light Reflex (PLR), the pupil's reaction to changing light intensity.

The Pupillary Light Reflex (PLR) is an involuntary reflex that controls the size of the eye’s pupil in response to changing light intensity.


Pupil constriction and dilation are controlled by the Autonomic Nervous System (ANS)


The ANS regulates bodily processes like heart rate, digestion, respiratory rate, and pupillary response without conscious control.


Pupillary Analysis

Over the last 70 years, medical and scientific studies have established that an individual PLR response is an excellent, non-invasive index of central nervous system functionality.

As a result, PLR alteration analysis is a proven and accepted method to reveal neurological anomalies. 


Pupillary analysis is used by doctors, in hospitals and intensive care units and involves the use of a pupillometer, an instrument that provides measures of pupillary size, symmetry, and reactivity.

Expensive medical grade designated pupillometers are used in a wide range of areas including anesthesiology, drug addiction, endocrinology, psychiatry, refractive surgery and sleep disorders. 

Pupillary analysis is used by police, it is performed in a subjective manner by using a penlight or flashlight to manually evaluate pupil reactivity and using a pupil gauge to estimate pupil size. However, this kind of manual pupillary assessment is subject to significant inaccuracies and inconsistencies.

Police pupillary analysis, impairment testing


Pupillary analysis in Fitness-for-Duty screening

​Fitness-for-Duty means that an individual is in a physical and mental state to be able to perform the essential tasks of his or her work assignment in a manner that does not threaten the safety or health of oneself, co-workers, property, or the public at large. The Pupillary Light Reflex is sensitive to a variety of impairing drugs, sleep deprivation, and other impairing neurological conditions, as such, pupillary analysis can be used as warning in Fitness-for-Duty applications.

SOBEREYE has pioneered the use of smartphones for pupillary analysis. The company has developed the unique know-how of using available smartphone cameras, designed for consumer use, to make reliable and accurate biometric measurements.


The patented technology uses a testing device, comprising of an opaque enclosure containing a latest generation smartphone, to analyze pupillary responses.


Each measurement is compared against the individual’s baseline to detect alterations of pupillary response. The results are specific to each person and therefore extremely accurate. 

The supplied testing devices include smartphones pre-configured and locked to work exclusively with SOBEREYE patented software.

SOBEREYE Smartphone pupillometer

Interpreting the Test results

Test results are specific for each individual enrolled in the service. The system automatically learns about their normal PLR response and a reference PLR baseline is established for each user.


During a test, the measured PLR response is compared against the individual’s baseline.  Alterations of PLR response are reported as "PLR alteration detected".


A "No PLR alteration found" result indicate the absence of PLR alterations compared to baseline.


PLR Research summary

(Bibliographic references)

The correlation between PLR alterations and impairing neurological conditions has been extensively studied, here is summary of some of the findings and bibliographic references.

  • Pickworth [1] [2] [3], Jasinski [4] and Cone [5] have demonstrated a strong effect on pupil diameter and amplitude (both reduced) by all the major opiates including heroin, morphine, and codeine. 

  • Rowbotham [6] [7] has reported significant increases in pupil diameter for subjects given intravenous and oral cocaine. 

  • Tennant [8] has reported similar increases for amphetamines. Tennant also describes pupillary changes resulting from marijuana, benzodiazipines (Valium), alcohol and phencyclidine (PCP). 

  • Lowenstein [9] and Yoss [10] studied changes in the shape and stability of the pupil light reflex as a person moves from alertness through fatigue to sleep. The findings show that extreme fatigue causes reduced pupil diameter and unstable pupil responses. 

  • Pupillary changes also occur in some neurological conditions. Profound pupillary changes are often observed as a result of brain lesions or tumors as well as impending stroke [11].


[1]     H. L. a. P. J. F. Wallace B. Pickworth, Buprenorphine- Induced Pupillary Effects In Human Volunteers, vol. 47, Life Sciences, 1990, pp. 1269-1277.

[2]     P. W. J. H. a. E. C. Wallace B. Pickworth, Opiate-Induced Pupillary Effects In Humans, vol. Methods And Findings In Experimental Pharmacology, 1989, pp. 759-763.

[3]     R. V. F. a. E. B. B. Wallace B. Pickworth, "Effects of abused drugs on pupillary size and light reflex," in Drug Abuse Handbook, CRC Press LLC, 1998.

[4]     P. J. F. A. R. E. J. Donald R. Jasinski, "Sublingual Versus Subcutaneous Buprenorphine in Opiate Abusers," Clinical Pharmachology & Therapeutics, 1989.

5]     E. J. Cone, "Testing Human Hair For Drugs Of Abuse. Individual Dose And Time Profiles Of Morphine and Codeine In Plasma, Saliva Urine and Beard Compared to Induced Effects On Pupils And Behavior," Journal Of Analytical Toxicology, no. Jan-Feb, 1990.

[6]     R. J. A. N. B. M.C. Robotham, "Trazadone-Oral Cocaine Interactions," Archives Of General Psychiatry, vol. 41, pp. 895-899, 1984.


[7]   W. H. J. M. a. R. J. M.C. Rowbotham, "Cocaine- Calcium Channel Antagonist Interactions," Psychopharmacology, no. 93, pp. 152-154, 1987.

[8]   F. Tennant, "The Rapid Eye Test To Detect Drug Abuse," Post Graduate Medicine, vol. 84, pp. 108-114, 1988.

[9]   O. L. a. I. Lowenfeld, "Types Of Central Autonomic Innervation And Fatigue," Archives Of Neurology And Psychiatry, vol. 66, pp. 581-599, 1951.

[10]   N. M. a. R. H. R. Yoss, "Pupil Size And Spontaneous Pupillary Waves Associated With Alertness, Drowsiness and Sleep," Neurology,, vol. 20, pp. 545-554, 1970.

[11]   P. S. a. J. T. R. Burde, Clinical Decisions In Neuro- Ophthalmology, The C.V. Mosby Company, 1985, pp. 221-245.

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