Experimental evaluation of eye-blink parameters as a drowsiness measure

Abstract

Drowsiness and increased tendency to fall asleep during daytime is still a generally underestimated problem. An increased tendency to fall asleep limits the efficiency at work and substantially increases the risk of accidents. Reduced alertness is difficult to assess, particularly under real life settings. Most of the available measuring procedures are laboratory-oriented and their applicability under field conditions is limited; their validity and sensitivity are often a matter of controversy. The spontaneous eye blink is considered to be a suitable ocular indicator for fatigue diagnostics. To evaluate eye blink parameters as a drowsiness indicator, a contact-free method for the measurement of spontaneous eye blinks was developed. An infrared sensor clipped to an eyeglass frame records eyelid movements continuously. In a series of sessions with 60 healthy adult participants, the validity of spontaneous blink parameters was investigated. The subjective state was determined by means of questionnaires immediately before the recording of eye blinks. The results show that several parameters of the spontaneous eye blink can be used as indicators in fatigue diagnostics. The parameters blink duration and reopening time in particular change reliably with increasing drowsiness. Furthermore, the proportion of long closure duration blinks proves to be an informative parameter. The results demonstrate that the measurement of eye blink parameters provides reliable information about drowsiness/sleepiness, which may also be applied to the continuous monitoring of the tendency to fall asleep.

Influence of neurological lesion level on heart rate variability and fatigue in adults with spinal cord injury

“…20 Fatigue was assessed using a psychometric scale called the Iowa Fatigue Scale (IFS), 21 as well as an electrophysiological measure of eye blink rate duration. 22 The IFS was used to measure self-reported fatigue and is composed of 11 Likert items covering 4 subscales: cognitive, fatigue, energy and productivity. 21 The purpose of using the IFS was to determine the impact of a SCI on subjective fatigue levels, as well as determine whether associations exist between fatigue and HRV.…”

“…21 Fatigue was also assessed by eye blink duration, provided by EOG, which has been shown to provide a sensitive physiological measure of fatigue. 6,22,23 Eye blink duration was counted and measured from the unfiltered EOG raw signal at 500 mV in 2-s intervals on a low-pass filter. For the purposes of this study, eye blink duration included both the closing and reopening times.…”

“…For all participants, three cutoff times were noted and recorded: those under 300 ms, shown to be within normal blink closure duration; those between 300-500 ms, shown to be long lasting spontaneous blink rate, and those above 500 ms, which included eyes closed, believed to be associated with fatigue. 10,22 Baseline EOG was taken from the second minute of the 5-min baseline measure.…”

Workload assessment of surgeons: correlation between NASA TLX and blinks

“…Changes in blink frequency and duration are correlated with the moment of mental fatigue, lapsed attention, and stress overload. This has been documented in various studies outside the context of surgery, including checking the drowsiness of individuals [15] and evaluating the mental workload of drivers [16,17] and pilots [18].…”

Capturing and evaluating blinks from video-based eyetrackers

“…1b, the pupil is the darkest part in the image and has a relatively brighter ring around it (the iris), so we can easily separate the pupil from the remaining parts of the eye. Third, the eyelid moves speedily during the start of a blink (Caffier et al, 2003). To identify the best parameter settings and test the sensitivity and specificity of the algorithm, a series of threshold values were used, and receiver operating characteristic (ROC) curves were plotted.…”