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A stray eyelash, the sting of a fresh-cut onion, the chill of midwinter air — all are causes of pain to the eye.

But why do these seemingly minor inconveniences cause such intense pain? The answer, according to Ian Meng, Ph.D., director of the Center of Biomedical Research Excellence (COBRE) for the Study of Pain and Sensory Function at the �Թϱ���, lies in the cornea, the outermost layer of the eye.

“The cornea is the most densely innervated structure in your entire body, and, as such, it is exquisitely sensitive to anything that can be potentially damaging to your eyes,” Meng explained. “Because vision is so important to everything that we do, the nerves in the cornea are there to protect your eye and keep them from getting damaged.”

To better understand the physiological and emotional impacts of damage to the eye, Meng, along with collaborators at Tufts University School of Medicine and Brigham and Women’s Hospital, will use $6.6 million from the National Eye Institute (NEI), a division of the National Institutes of Health (NIH), to map out the corneal nerves with the goal developing new, more effective treatments for corneal pain.

The five-year grant will allow the team to examine changes to the corneal nerves in response to injury and chronic dry eye, both serious clinical problems, Meng said.

The first part of the study will involve comprehensively mapping the nerves innervating the cornea, while later studies will explore how injury to those nerves impact the brain’s emotional responses to trauma via a complex of neurological structures that feed into the limbic system, the area of the brain that regulates emotion and behavioral responses.

“We believe that the neurons innervating the cornea have a uniquely strong connection to the limbic system to elicit an emotional response to corneal pain,” Meng explained. “It’s like an express train to the brain’s emotional center.”

The study could also help explain why some forms of chronic pain — headaches and migraines, in particular — are so closely related to corneal pain, Meng added, and why they cause such severe emotional reactions.

This grant from the NEI is unique, Meng said, because the organization is funding several research groups as part of a multi-principal-investigator consortium, in which all researchers will regularly convene to discuss their progress, findings, and methodologies. Meng’s research is just one of eight such groups participating in what he said is a novel, transparent method of scientific inquiry.

“This is a bold initiative from the National Eye Institute,” Meng remarked. “Oftentimes, scientists will develop their own techniques and keep the details to themselves; however, with this project, we’re all trying to advance the field in collaboration with each other. I’m very much looking forward to learning from those other groups and possibly applying what I learn to the science that I do.”