The pupil responds to light, which is essential for our vision and how we see our surroundings. Three known mechanisms change the pupil’s size: the amount of light, focus distance, and cognitive factors like emotion or mental effort.
A new study by researchers at the Karolinska Institutet in Sweden reports a fourth mechanism that affects pupil size: breathing.
The study suggests that the pupil is smallest during inhalation and largest during exhalation, which could impact our vision.
This mechanism is unique because it is cyclical, always present, and doesn’t need external stimuli. Since breathing affects brain activity and cognitive functions, this discovery could help us understand how our vision and attention are regulated.
Life motion perception develops in eye pupils
The researchers conducted five experiments with over 200 participants to see how breathing affects pupil size in different conditions. The results showed that the effect remained whether participants breathed quickly or slowly, through their nose or mouth, and under various lighting and focus conditions, whether they were resting or doing visual tasks. The difference in pupil size between inhalation and exhalation was significant enough to affect vision potentially.
Researchers are now curious to see if changes in pupil size during breathing also impact vision.
According to a previous study, smaller pupils make it easier to see details, while larger pupils help us find hard-to-see objects. Martin Schaefer, the study’s first author, said, “Our results suggest that our vision may switch between optimizing for distinguishing small details when we inhale and detecting faint objects when we exhale, all within a single breathing cycle.”
How blue and red light affects concentration in adolescents?
There may also be clinical applications. Artin Arshamian mentioned, “One potential application is new methods to diagnose or treat neurological conditions such as Parkinson’s disease, where damage to pupil function is an early sign of the disease. This is something we want to explore in the future.”
Journal Reference
- Martin Schaefer, Sebastiaan Mathôt, Mikael Lundqvist, Johan N. Lundström, Artin Arshamian. The Pupillary Respiratory-Phase Response: Pupil size is smallest around inhalation onset and largest during exhalation. The Journal of Physiology, online 21 February 2025, DOI: 10.1113/JP287205.
