European Journal of Applied Physiology

, Volume 119, Issue 2, pp 531–538 | Cite as

Utility of lacrimal caruncle infrared thermography when monitoring alterations in autonomic activity in healthy humans

  • J. Huggins
  • Mark RakobowchukEmail author
Original Article



Physiological markers that estimate sympathetic activation may be used to infer pain and stress in humans. To date, effective reproducible methods are invasive and pose an undesired risk to participants. Previous work in animal models has used infrared thermography to measure the temperature of the lacrimal caruncle region and may be a promising method for measuring stress and pain non-invasively. The current study aimed to determine whether this method is useful in humans.


Sixteen young healthy participants (age: 18–35) were recruited and underwent sympathetic activation using a cold pressor test (CPT) and a muscle chemoreflex (MCR), and completed a control trial. Throughout all trials, infrared thermographic imaging of the lacrimal caruncle, heart rate, heart rate variability, mean arterial blood pressure and pulse transit time were measured.


Heart rate (MCR: 4 ± 3 bpm, CPT: 17 ± 4 bpm p < 0.01) and mean arterial pressure increased (MCR: 6 ± 2, CPT: 5 ± 2 mmHg, p < 0.01) and pulse transit time decreased (p = 0.03) with both sympathetic activation interventions. However, lacrimal caruncle temperature did not vary under any condition remaining at 35.2 ± 0.2 °C which was similar to baseline.


Our findings suggest infrared thermographic monitoring of eye temperature in humans does not reliably relate to sympathetic activation. This could be due to hemodynamic responses at the lacrimal caruncle that may be more complex than previously proposed with sympathetic activation. Alternatively, pulse transit time seems like a promising non-invasive measure of changes in sympathetic activation in humans.


Sympathetic nervous system activation Thermography Infrared imaging Muscle metaboreflex Muscle chemoreflex 



Cold pressor test


Heart rate


Heart rate variability


Infrared thermography


Muscle chemoreflex


Mean arterial pressure


Pulse transit time


Pulse wave velocity

\(\dot {Q}\)

Cardiac output


Sympathetic nervous activity



We would like to thank Dr Neil Eves at the Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan for loaning the applanation tonometry equipment.

Author contributions

MR conceived of the project, JH and MR completed the data collection, JH analysed the data and wrote the draft manuscript, MR edited the manscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Extracellular Vesicles and the Endothelial Dynamics Laboratory, Department of Biological SciencesThompson Rivers UniversityKamloopsCanada

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