Your Pupils Change Size as You Breathe

Our eyes play a crucial role in how we perceive the world. They also reveal insights into our inner states, from imagination to early signs of hearing loss. Interestingly, recent research shows that pupil size can vary with our breathing.

Researchers from Sweden and the Netherlands have discovered that pupil sizes fluctuate with each breath we take. This finding sheds further light on how pupils respond to more than just light exposure, a fact known for over a century.

Previous studies have yielded mixed results regarding whether pupils expand and contract with breathing. Some suggest that pupils dilate during inhalation. However, a 2022 review indicated there was "inconclusive evidence" about this correlation.

To address the inconsistencies of earlier studies, neuroscientist Martin Schaefer from the Karolinska Institute and his team conducted a focused investigation. They employed a specialized camera to measure the pupil sizes of over 100 volunteers during rest and visual tasks.

In their findings, the researchers noted, "Pupil size consistently reaches its minimum around inhalation onset and its maximum during exhalation."

The same pattern emerged in both visual tasks and simpler situations, whether participants breathed through their nose or mouth. This opposes earlier claims that pupils are smallest during exhalation. The variability in pupil size is influenced by various factors, making these measurements challenging.

Despite the uncertainties, the researchers propose theories about these pupil size fluctuations. Historical research indicates that smaller pupils may enhance detail discrimination, while larger pupils improve low-light detection capabilities.

Schaefer and his team explain their findings suggest visual perception might alternate between optimization for detail during inhalation and better detection during exhalation within a single breath.

Pupil sizes also vary based on emotional states, such as widening during fear or as a result of drugs like antidepressants.

Doctors utilize pupil size as a metric for gauging consciousness and diagnosing mental health issues. Therefore, understanding pupillary behavior could enhance its relevance as a diagnostic tool.

While scientists have recently recognized mechanisms behind some pupil size changes, the reasons for many fluctuations remain elusive, including the relationship to our breathing cycles.

Earlier, SSP reported that travel may combat premature aging.