Studies of owls showed that their pupils dilate in accordance with the volume of the sound they hear. This is a normal response to an environmental change. When the sound perceived was repetitive the physical response disappeared.
In a study carried out among humans by researchers from the University of Oregon in Eugene, Oregon, USA, the same seemed to occur.
22 participants with normal hearing were asked to listen to several sounds. At the same time, their eye movements were recorded with a camera while their heads remained still. Researchers observed that every time a new sound was introduced, the pupils changed size in proportion to the loudness of the sound. Results were compared to an audiometric test and a significantly similar response was found.
Potential alternative to a hearing test
Further analysis is yet to determine if testing the eye movements could become a clinical tool for the detection of hearing loss. But researchers believe that this discovery is a step forward in the search for an alternative method to detecting hearing loss when a standard hearing test cannot be performed. This would be useful, in particular, when dealing with infants and adults with brain damage, who are unable to participate actively in a hearing test.
The findings of the study were presented at an Association for Research in Otolaryngology meeting in Phoenix, Arizona, USA.