Pupillographic Sleepiness Tests (PST) use a camera to measure the pupil diameter of people for a standard 11 mins. The subject wears a pair of goggles which shields the eyes from any residual visible light and only a dim red spot is visible for them to focus on. Changes in pupil diameter are measured by the goggles, and more changes in the pupil diameter (pupil instability) in the dark setting gives a value thought to be a measure of sleepiness.
A study recently published in the journal of sleep has investigated if the results of the PST have any real link to performance measures.
In this pilot study, 18 young healthy adults were kept awake for 40 hours continuously. Every 2 hours they completed a PST, a Karolinska sleepiness scale and a 10 min Psychomotor Vigilance Task (PVT) to measure performance. Electroencephalography was recorded and analysed for signs of sleepiness, including microsleeps, and slow eye movements.
The results showed that the pupils were much more unstable after 18 hours of wakefulness. Microsleeps, slow eye movements and PVT lapses were also noted after 18 hours suggesting that attention was impaired during the performance task.
The investigators proposed that from the data, cut-off scores ranging from 10-11.5 mm/min of pupillary movement could be used for young adults.
Further research in more real world applications with larger study numbers should be performed and if results are similar, the PST may be a strong candidate for a fitness to drive / work tool to detect fatigue related impairment.
Citation
Maccora J, Manousakis JE, Anderson C. Pupillary instability as an accurate, objective marker of alertness failure and performance impairment. J Sleep Res. 2018;e12739. https://doi.org/10.1111/jsr.12739
