Clinical Research Assistant Kevin Jackson uses AlgometRx Platform Technology on Sarah Taylor's eyes to measure her degree of pain at the Children's National Medical Center in Washington, Monday, Dec. 10, 2018. Children's National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. (AP Photo/Manuel Balce Ceneta)
camera (The Associated Press) Clinical Research Assistant Kevin Jackson uses AlgometRx Platform Technology on Sarah Taylor's eyes to measure her degree of pain at the Children's National Medical Center in Washington, Monday, Dec. 10, 2018. Children's National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. (AP Photo/Manuel Balce Ceneta)

There's no stethoscope for pain. Now, U.S. health officials are pushing for development of a pain meter, the first objective way to measure it.

The National Institutes of Health stresses the goal isn't a lie detector for pain, but to spur better treatment.

A device that peeks into patients' eyes is among the approaches in early-stage studies. The theory is that patterns of pupil reactions could signal pain, and what drug might help. Other researchers are testing if brain scans or measuring brain waves could work.

Today, many patients must convey how bad it is using a 1-to-10 scale.

That's problematic for lots of reasons. For example, the aching that one person rates a 7 might be a 4 to someone else. That can make it hard to test potential new painkillers.