American heath executives are pushing for the development of a device that measures a patients pain to evaluate relief measures.

Currently the National Institute of Health uses questions like whether their pain is 'stabbing or burning', estimating on a scale from 1 to 10 and even emojis.

But the system, which is often imprecise and subjective, is said to contribute - at least in part- to the opioid addiction crisis that killed 49,000 people in 2017.

The 'pain-o-meter' or POM is a potential answer to improving assessment and management of pain in acute and chronic pain patients.

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American doctors are pushing for the development of a device that measure a patients pain called a 'pain-o-meter' to evaluate relief measures. Here, arthritis sufferer Sarah Taylor is pictured having her pupils tracked with the device to see how they react when she's in pain

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NIH-funded scientists have begun studies of brain scans, pupil reactions and other possible markers of pain in hopes of finally 'seeing pain' so they can better treat it.

Patient Sarah Taylor struggled to make doctors understand her sometimes debilitating levels of pain, first from joint-damaging childhood arthritis and then from fibromyalgia, a long-term condition that causes pain all over the body.

'It's really hard when people can't see how much pain you're in, because they have to take your word on it and sometimes, they don't quite believe you,' Ms Taylor said.

Now scientists are using the experimental device to look into Sarah's eyes and track how her pupils react when she's in pain and when she's not.

There also isn't a way to determine what kind of pain someone has - to decide whether opioids are necessary - or whether the pain, like Sarah's, is better suited to nerve-targeting medicines.

The growing drugs crisis sweeping across the US is deadlier than gun violence, car crashes or Aids, according to figures.

Dangerous synthetic opioid fentanyl was the biggest driver - which killed more than 29,000 people that year.

'We're not creating a lie detector for pain,' stressed David Thomas of NIH's National Institute on Drug Abuse, who oversees the research.

'It's early-stage research, and it's not clear how soon any of the attempts might pan out.

'My vision is that someday we'll pull these different metrics together for something of a fingerprint of pain.'

The growing drugs crisis sweeping across the US is deadlier than gun violence, car crashes or Aids. Dangerous synthetic opioid fentanyl was the biggest driver - which killed more than 29,000 people that year (stock image)

Recently arthritis sufferer Sarah Taylor climbed onto an acupuncture table at Children's National, rated that day's pain a not-too-bad 3, and opened her eyes wide for the experimental pain test.

'There'll be a flash of light for 10 seconds. All you have to do is try not to blink,' researcher Kevin Jackson told Ms Taylor as he lined up the pupil-tracking device, mounted on a smartphone.

The eyes offer a window to pain centres in the brain, said Dr Julia Finkel, who directs pain research at Children's Sheikh Zayed Institute for Pediatric Surgical Innovation.

This is because some pain-sensing nerves transmit 'ouch' signals to the brain along pathways that also alter muscles of the pupils as they react to different stimuli.

Dr Finkel's device tracks pupillary reactions to light or to non-painful stimulation of certain nerve fibers, aiming to link different patterns to different intensities and types of pain.

Children's National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. 'If we can't measure pain, we can't fix it,' said Julia Finkel, who invented the eye-tracking device, pictured here with Sarah Taylor (left)

Acupuncture needles are applied on Sarah Taylor's back. She uses a combination of medications, acupuncture and lots of exercise but the 17-year-old struggled to make doctors understand her sometimes debilitating levels of pain, first from joint-damaging childhood arthritis and then from fibromyalgia

Consider the shooting hip and leg pain of sciatica: 'Everyone knows someone who's been started on oxycodone for their sciatic nerve pain. And they'll tell you that they feel it - it still hurts - and they just don't care,' Dr Finkel said.

'The problem is that an opioid like oxycodone brings some relief by dulling the perception of pain but not its transmission - while a different kind of drug might block the pain by targeting the culprit nerve fiber.

Certain medications also can be detected by other changes in a resting pupil, Dr Finkel said.

So far, scientists at Harvard and Massachusetts General Hospital found MRI scans revealed patterns of inflammation in the brain that identified either fibromyalgia or chronic back pain.

Other researchers have found changes in brain activity - where different areas 'light up' on scans - that signal certain types of pain.

Still others are using electrodes on the scalp to measure pain through brain waves.