Mathematical procedures in data recording and processing of pupillary fatigue waves

Area of Science:

• Ophthalmology
• Neuroscience
• Sleep Medicine

Background:

• Spontaneous pupillary behavior in darkness offers insights into vigilance levels.
• Infrared video pupillography (IVP) requires robust numerical parameters for objective vigilance assessment.
• Accurate pupil size measurement is crucial, even with occlusions from eyelids or eyelashes.

Purpose of the Study:

• To establish IVP as a reliable and objective method for detecting and quantifying daytime sleepiness.
• To define numerical parameters that adequately characterize spontaneous pupil behavior for statistical analysis.
• To develop methods for accurate pupil size measurement despite occlusions.

Main Methods:

• Mathematical artifact management, including blink detection, elimination, and interpolation.
• Fast Fourier Transformation (FFT) applied to pupil diameter data for frequency analysis (0.0–0.8 Hz).
• Calculation of pupillary unrest index (PUI) based on cumulative changes in mean pupillary diameter.

Main Results:

• Pupil size data were analyzed using FFT, yielding absolute and relative power in frequency bands.
• Graphical representation of mean pupillary diameter changes over time.
• Pilot study demonstrated significant differences in power and PUI between self-reported alert and sleepy groups (Mann-Whitney U-test).

Conclusions:

• The developed mathematical procedures enhance data quality for IVP as an objective vigilance test.
• The pupillary unrest index (PUI) and power parameters show potential for differentiating vigilance states.
• IVP, with these new parameters, shows promise for objective quantification of daytime sleepiness.