Keeping an Eye on Stress: Using Continuous Eye Tracking to Evaluate Stress Levels

The Intensive Care Unit (ICU) never stops, and some days it never even slows down. The patients who end up there require the most critical level of care, and it isn’t uncommon for their lives to be hanging in the balance. For doctors and nurses who work in this high-pressure setting, a deep understanding of life-threatening conditions is a necessity, and they need to be able to react quickly and make split-second decisions in order to provide urgent care within a very short period of time. 

While it’s understood that ICU doctors are under a high level of stress, nurses often experience an even higher level, one which is much more frequently overlooked. One study has shown that the reported prevalence of stress among ICU nurses was 68.29%, while for doctors it was around half that, at 36.58%. Nurses often work very long shifts and provide regular care that patients need, as well as responding to critical acute trauma. Intubations, ventilations, and administration of multiple IV-units are day-to-day tasks for an ICU nurse, and these life-or-death situations inevitably leads to stress for the caregivers involved. 

As stress can be dangerous, and lead to diminished job performance as well as a plethora of personal and health-related issues for these nurses, efforts have been made in recent years to evaluate and hopefully reduce their level of stress. One of the most exciting among these is a recent study, published in Human Factors, the journal of the Human Factors and Ergonomics Society (HFES). In that study, researchers observed the level of stress of nurses working in the ICU using a cutting-edge technique: continuous eye tracking. 

Eye Movements Speak Volumes

Eye tracking technology itself is nothing new. It has been used for decades in diverse fields such as vision research, language and usability. Eye tracking involves charting and measuring the eye’s movements and field of focus. This allows scientists to learn a tremendous amount about a subject’s vision, and other areas secondary to this, such as fatigue, stress and aesthetic interest.

The first contact lens-mounted eye tracking devices were invented in the early 1900s, and by the middle of that century, researchers were analyzing the eye’s movements un-intrusively using beams of light. Nowadays, utilizing advances in optical motion sensing and portable electronics, eye tracking usually involves lightweight, portable glasses which a wearer barely even notices. This enables researchers to utilize eye tracking in myriad real-world applications. Known as continuous eye tracking, this freedom of movement provides data for study of a subject’s eye movements in a variety of situations. 

It should come as no surprise that eye tracking has numerous eye care applications. Neuro-optometrists frequently use eye tracking to diagnose and treat conditions such as ocular motility dysfunction and problems with oculomotor function. Eye tracking is frequently used in diagnosing and following up on treatable eye muscle problems such as strabismus and amblyopia. 

Eye tracking is built into numerous diagnostic and imaging platforms such as optical coherence tomography (OCT) and microperimetry, crucially reducing motion artifacts and decreasing signal-to-noise ratios. It also forms a crucial part of automated laser surgery platforms to correct cataracts, astigmatism, and many other ophthalmic conditions, adjusting the laser along with the eye’s most minute movements in order to prevent injury. 

Physicians have also used eye tracking outside the eye care field. It has been used diagnostically to establish correlations between neurological conditions like dyslexia and Alzheimer’s disease and eye’s movement patterns. Psychiatrists have also used it to diagnose harmful effects, like stress. 

Using Eye Tracking Technology to Study Stress Levels

One of the most effective areas of recent study in continuous eye tracking has been in evaluating the stress levels of patients based upon their eye movements. Going back as far as the 1950s, researchers have identified connections between heightened stress levels and the movements of a subject’s eyes. As continuous eye tracking has been made possible by advances in eyeglass technologies, many recent studies have yielded a tremendous dearth of information on patient responses to stress. 

One such study has used eye movements to track fatigue and stress levels in soldiers. As these levels are a significant cause of accidents and preventable injury, monitoring physiological and psychological readiness of soldiers and other professionals is a high priority for researchers and military policy makers. 

Similarly, another study examined the eye movements of aviation, maritime and construction workers with the aim of reducing accidents in these highly dangerous fields. This study examined fixation, saccades, pupil size and blink rate in order to evaluate the concentration levels of workers in these fields, providing useful guidance in workplace performance in these dangerously precise fields.

Returning to the ICU

Of course, few workplaces are so stressful, and require so much precision, as the ICU. Because of the critical nature of the medical work done there, it follows that studies such as this recent one in Human Factors, studying stress levels through continuous eye tracking, are vitally important. 

In this study, the researchers collected continuous eye movement data from 15 ICU nurses working 12 hour shifts. Using Tobii Pro Glasses 2 to track the nurses eyes in conjunction with Empatica E4 wrist-worn data collection devices, the researchers used mixed-effect models and an ordinal regression model with a random effect to analyze the changes in eye movement when the nurses experienced stress throughout their shifts. 

The findings of the study revealed several interesting results about the nurse’s stress levels. Though workloads vary significantly between day and night shifts, no significant difference was observed in the nurses’ eye movements. The eye metrics did show a higher level of stress during the handoff period at the beginning and end of the nurses’ shifts, however. 

The researchers concluded that their findings on the nurses’ eye movements could be used to effectively evaluate their workplace stress levels, thereby potentially creating a higher level of care in the ICU and a more positive work environment for the nurses. They also suggested that a real-time eye tracking system could be implemented in order to continually monitor stress and workload. All of these findings can be very useful in creating a safer and more positive ICU.

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