When patients present with pain symptoms, the subjectivity of the experience and reliance on patient-reported descriptions create a frustrating situation for everyone involved. However, a newly published study from a Japanese research team may have found a way to objectively measure discomfort in an effort to give eye doctors more data and, hopefully, more of a fighting chance.

With a sensitive organ such as the eye, “even subtle unpleasant stimuli can cause discomfort,” the report reads. And that can cause serious reductions in quality of life. The investigators decided to apply functional near-infrared spectroscopy (fNIRS)—a relatively noninvasive neuroimaging technique—to dry eye patients to test its documentation capability in this cohort. Although typically used to monitor brain activity, its ability to highlight primary motor and sensory areas suggests fNIRS may be able to provide a way to map subtle unpleasant stimuli in dry eye patients by monitoring their prefrontal cortex activity.

The team reviewed six known dry eye patients—none of whom wore contact lenses, had glaucoma or were chronic pain sufferers—and six healthy subjects, monitoring their corneal sensitivity as they ran a number of artificially induced uncomfortable situations, such as facial wind. Cerebral activities were monitored using the fNIRS system, which detects increases in cerebral blood flow due to elevated cerebral nerve activity in terms of cerebral hemoglobin.

They found the healthy group experienced low-level prefrontal cortex activation without stimulation that could be increased when faced with discomfort-causing stimuli. However, the patients known to have dry eye started out with high activation, even before the stimulus, which, when applied, increased activation even more. Prefrontal cortex activity was confirmed with ocular discomfort when the eyes were open, decreased with lubricant and almost disappeared with anesthetic for all participants.

“The results of this study on ocular discomfort show a clear correlation with prefrontal cortex activities,” the report reads.

Ono M, Takano Y, Haida M. Objective ocular discomfort: noninvasive evaluation by functional near-infrared ray spectroscopy. IOVS. 2018;59(9):4683-90.