Research

Stellar i-ris

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What is pupillometry?

Pupillometry is the measurement of the change in pupil size (diameter or area). Of particular interest is the finding that the contraction of the human pupil when exposed to light reflects significant changes in cognitive and emotional processing.

(Beyer, R. (2006). Pupillometrie. In J. Funke & P. Frensch (Hrsg.), Handbuch der Allgemeinen Psychologie: Kognition (S. 712–716). Göttingen: Hogrefe.)

The idea

Inspired by his work at the Institute for Technical Electronics, Color Image Processing, in Aachen, Germany, Johannes Junggeburth had the idea back in 1995 that the pupil light reflex can be an indicator of various influences that affect the human organism. The assessment of the visible change in pupil size (bright adaptation) is already used as a standard emergency diagnosis.

What is the pupil light reflex?

The human eye adapts to the light conditions in its surroundings by narrowing and widening the pupil. If it is bright, the pupil contracts, in darkness it widens. This reaction to light cannot be influenced arbitrarily and is therefore called pupil light reflex (PLR). The PLR reflects the current functionality of the autonomic nervous system. Through the simple application of the measuring technique, it is possible to detect individual changes in the functionality of the autonomic nervous system at an early stage, either by self-testing or by qualified personnel.

Stellar i-ris has developed a device with which the pupil light reflex can be triggered and measured. This device is called Stellar i-ris HEAD.

How does the Stellar i-ris HEAD work?

During a measurement, the eye is illuminated briefly - for a few milliseconds - with different wavelengths, i.e. with light in different colour tones.

This is done by measuring how fast the pupil reacts (latency time), how strongly it contracts (pupil diameter) and how long it takes for it to open again (relaxation time).

With a latency time of 150-200 milliseconds, an evaluation of the exact impulse response of the eye is only possible if the measurement error is less than two percent. At this magnitude, a video recording of the impulse response of the eye with at least 1,000 frames per second is required. An algorithm then evaluates the image data and converts it into a function within a few seconds. This function can then be graphically displayed and interpreted.

The measurement process from Stellar i-ris HEAD

Abb. 1: Schematischer Aufbau, Beschreibung Messablauf (1) Brille (2) LED-Setting (3) Kamera, hochauflösend (4) Controller, Hauptplatine (5) Rechner, Steuerung

Abb. 2: Schematischer Aufbau, Fokus optische Einheit: (1) Rechner, Steuerung (2) Controller, Hauptplatine (3) LED-Setting (4) Infrarot-Beleuchtung (5) Kamera, hochauflösend

Where can the Stellar i-ris procedure be used?

We know that a number of factors can influence the reduction and enlargement of the pupil. These include fatigue, alcohol or drugs. But also a disturbed signal transmission on the nerve tracts - as is the case with neurodegenerative diseases - can result in an altered reflex response of the pupil. All these factors influence the human body’s ability to concentrate and react. As a consequence, there may be impairments when participating in air, rail and car traffic or at work.

So far, there are only insufficient measuring methods for the rapid detection of acute incapacity to work. For this reason, the Stellar company, with the support of the RWTH Aachen University, supported by the EU and the Ministry of Economics, has set itself the task of developing a suitable measuring method for this purpose. In the future, this method can potentially be used in fields of application such as traffic safety (especially in the police force), occupational safety or even in medicine for (early) detection of neurodegenerative diseases.

What is the innovation of the Stellar i-ris measuring method?

The basis of the new non-invasive method is the exact, reproducible measurement of the pupil light reflex. With 1,000 images per second and high resolution, the reflex response of the eye can be graphically displayed and interpreted by the innovative i-ris measuring method.

Using 43 parameters, it is possible for the first time to record the “neuronal fitness” of the autonomic nervous system and to define biomarkers for “fatigue”, “alcohol influence” and “drug consumption” with prognostic and/or diagnostic significance. Further clinical studies are planned to determine a biomarker for neurodegenerative diseases and for diseases of the optic nerve and eye.

Abb. 3: Funktion eines Probanden aus der klinischen Studie (1) erster Lichtreiz, rot, (2) zweiter Lichtreiz, rot, (3) erster Lichtreiz, blau, (4) zweiter Lichtreiz, blau