Just as we can’t live without food or water, we also can’t live without sleep. But while eating and drinking are voluntary actions, sleep is not: whether that is trying to sleep when you can’t or trying not to sleep when you need to be awake.
The global market for sleeping pills is estimated to be worth $10 billion per annum, and it is believed 10-20% of the global population currently uses sleeping pills to relieve insomnia. Historically, when the pharmaceutical industry has tested new drugs to promote sleep, studies have been using the Multiple Sleep Latency Test (MSLT) as the gold standard. On the other end of the scale, there are a number of medical conditions (i.e. sleep apnea, narcolepsy) or occupational demands (i.e. shiftwork) that cause excessive daytime sleepiness. Similarly, in pharmaceutical trials, patients with these conditions are tested using the MSLT or Maintenance for Wakefulness Test (MWT).
Changes in eye and eyelid movements, referred to as ‘ocular dynamics’, provide a direct link to fluctuations in human attention and alertness. Ocular movements, particularly eye blink parameters, are considered reliable physiological indicators of drowsiness levels. Blink characteristics during the eyelid closure and reopening show unique properties that can objectively quantify changes in drowsiness.
In 2003, Founding Director of Optalert and world-renowned sleep researcher, Dr Murray Johns introduced amplitude-velocity ratios (AVRs) for blinks as a measure of the relative velocity of their movements.
His research found that in alert people, the amplitude (size) of upper eyelid movement during each blink is known to be very closely related to its peak velocity (speed). He also found the AVRs for the eyelid’s closing phase of a blink are different from those for the eyelid’s reopening phase of a blink, even though their amplitudes are usually the same.
The AVRs have been shown to increase with drowsiness, particularly for the eyelids reopening, i.e., the upper eyelid moves more slowly when re-opening after a blink in people when drowsy than when alert. These ratios avoid the need for calibration of either the amplitude or velocity in absolute terms. The ratios are also very stable between people, which mean they do not have to be adjusted for individuals.
Through his research, Dr Johns developed the patented Johns Drowsiness Scale (JDS) He also developed the Epworth Sleepiness Scale (ESS), which is now a world-standard method for measuring a subject’s general level of sleepiness in daily life. The JDS was developed specifically for use with Optalert’s technology, which uses a system of infrared (IR) reflectance oculography positioned in a sensor to monitor eye and eyelid movements, with particular emphasis on the velocity and duration of the upper eyelid during blinks. The system of IR oculography has enabled several ocular variables to be identified that can be used in combination to objectively quantify drowsiness with the ten-point scientifically-validated JDS.
Optalert’s patented JDS has now been packaged into a product specifically for the pharmaceutical industry – the eagle RESEARCH – which due to its ability to continuously and objectively monitor patients in real-time, is destined to positively change the nature and costs of pharmaceutical and clinical trials.