1. Ocular Parameters Related to Fatigue
Kelene Fercho

2. Circadian Rhythms in the Human Pupil and Eyelid (Loving et al., 1996)
Studied every 30 minutes over a period of 24 hours
Pupil diameter measured using a Fitness Impairment Tester connected to a PC
Palpebral fissure distances computed using digitized frame images from video recordings

3. Circadian Rhythms in the Human Pupil and Eyelid (Loving et al., 1996)
19 hours after beginning the experiment, dapiprazole hydrochloride was administered to one eye
Comparing pupils would give an indication of sympathetic input to the unmedicated pupil
When comparing the two pupils, no circadian rhythm was detected

4. Circadian Rhythms in the Human Pupil and Eyelid (Loving et al., 1996)
All subjects experienced fatigue as evidenced by frequent blinking and the inability to hold a point of gaze
Pupil size was not affected by sleep deprivation
Palpebral fissure showed weak circadian rhythms.
Phase of rhythms was found at a mean time of 5:37 PM rather than the expected night-time rhythm.

5. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)
Believed eye blinks provide info on the general level of activity in the rostral CNS
Close physical relationship between the nucleus of the facial nerve and medullary structures involved in the sleep/wake process
Midbrain reticular formation structures integrate ocular activities to some degree
Lack of identifiable external triggers for endogenous blinks

6. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)
N = 10 (AF pilots)
Eye movement data collected using Beckman silver-silver chloride electrodes
Subjects completed the Crew Status Check Card and the Stanford Sleepiness Scale

7. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)
Subjects reported in at 1 AM.
Study began twelve hours later
Study involved flying a 4.5 hour sortie. Flight performance was measured by deviations from assigned heading, altitude, and speed.
Subjective fatigue measures were taken before and after the sortie

8. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)
Performance continually decreased until the next to last flight segment, but then decreased after that until the end
Subjective fatigue measures indicated a significant change in fatigue
Blink rate, blink duration, long closure rate, blink amplitude, and saccade rate were all significantly correlated with error

9. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)

10. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)
Stepwise regression was used to determine what EOG measures predicted performance
Blink amplitude fit R2 = 0.36
Blink amplitude & long closure rate R2= 0.54
Blink amplitude, long closure rate, & blink duration R2=0.61
Adding saccade velocity, saccade rate, and peak saccade velocity did not increase R2

11. Electrooculographic and performance indices of fatigue during simulated flight (Morris et al., 1996)

12. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
N = 156 (all diagnosed with narcolepsy)
Used electronic infrared pupillograph
All recordings done in darkness
Subject fixated on a lighted distant target.
Headrest and lid crutch employed

13. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Pupillary size of the narcoleptic state was calculated as a percentage of the pupillary diameter in the alert state
When patient was alert, pupils were large and constant in size (5.5 to 8.5 mm)

14. Authors developed a classification system for levels of wakefulness
Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Authors developed a classification system for levels of wakefulness
Level 1 – pupils at maximum size, pupillary waves virtually absent.
Subject is alert, well rested, and in an efficient state.
Environment is stimulating

15. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

16. Level 2 – pupils are slightly smaller.
Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Level 2 – pupils are slightly smaller.
Low-amplitude waves of short duration
Subject is still alert, but sharpness is fading and the mind may briefly wander
Subjects enter this stage when in a peaceful environment and when inactive

17. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

18. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Level 3 – mild eyelid droop, pupils are at 85% of their diameter in level 1
Subjects likely had inadequate sleep the night before.
Subjects are irritable and concentration is reduced.
Subjects are tired but deny drowsiness
Alertness is easily obtained if the environment becomes stimulating.

19. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

20. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Level 4 – eyelids droop, pupillary diameter is approximately 75% of the size in level 1
Pupillary waves are of medium and high amplitude and medium duration
Subjects admit that they are drowsy and would like a nap

21. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

22. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

23. Level 5 – severe eyelid droop and eyelid closure mmost of the time.
Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Level 5 – severe eyelid droop and eyelid closure mmost of the time.
Pupil diameter is approximately 55% of its alert size
Waves are medium to high amplitude and medium duration
Major effort is required for the subject to stay awake

24. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

25. Sleep was divided into two levels based on pupillography.
Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Sleep was divided into two levels based on pupillography.
Level 1 Sleep – pupil diameter was 45% of the size in wakefulness level 1.
Wave amplitude is reduced and less rhythmic
Virtually no low-amplitude waves of short duration

26. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

27. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)
Level 2 Sleep – pupil diameter is 35% of that found in level 1 wakefulness
Some high amplitude pupillary waves

28. Pupil Size and Spontaneous Pupillary Waves Associated with Alertness, Drowsiness, and Sleep (Yoss et al., 1970)

29. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)
Pupillary recordings were made with an infrared video device that used the “dark pupil system”
Stanford Sleepiness Scale (SSS) used for subjective fatigue measurements

30. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)
All subjects wore an actigraph on his/her wrist to record hand movement for 24 hours before the study
Subjects were instructed to sleep at home the night before the study and avoid any activity the next day
Each subject completed the SSS and pupillography in the morning.

31. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)
At 11 PM, subjects reported to the lab where they spent the night reading or watching TV.
The next morning, the SSS and pupillography were administered

32. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)
Actigraph recordings indicated that all subjects had slept the night prior to the study.
Pupil size was relatively stable during alertness
After the night of sleep deprivation, pupil size was found to vary with a tendency to decrease
Median value for alertness using the SSS was 2 before sleep deprivation and 6 after
SSS scores and pupillary diameter were correlated (r = -0.51, p = 0.028)

33. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)

34. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)
First to demonstrate a correlation between pupillary parameters and subjective evaluations of the subject’s state of vigilance
Authors were able to assign an absolute number value for fatigue.
Cumulative variability for fatigue - mean 79.8  65
Cumulative variability for alertness - mean  7.1
Cumulative variability never rose about 25 in alertness

35. Pupillography as an Objective Indicator of Fatigue (Morad, 2000)

36. Effect of Sleep Deprivation on Saccades and Eyelid Blinking (Crevtis, 2003)
N = 21 (medical students working overnight shift)
Subjects performed their normal job duties of monitoring patients in the sleep disorder lab
Researchers used infrared oculography to collect data for both horizontal and vertical eye movements before and after the subject’s night shift.

37. Effect of Sleep Deprivation on Saccades and Eyelid Blinking (Crevtis, 2003)
Subjects were seated in a dark room in front of a computer screen
Reflexive saccades, voluntary prosaccades, and antisaccade tasks were executed
Reflexive saccades – follow target as quickly as possible
Voluntary prosaccades – look toward target as indicated by arrow
Antisaccade – Look in the opposite direction of the arrow

38. Effect of Sleep Deprivation on Saccades and Eyelid Blinking (Crevtis, 2003)
Results for saccadic latencies were mixed
Reflexive saccade task – 25% of the subjects had slower latencies after sleep deprivation
Voluntary prosaccade – 10% of the subjects had slower latencies after sleep deprivation, but 25% were faster
Antisaccade – 15% of the subjects were slower, but 15% of the subjects were faster after sleep deprivation

39. Effect of Sleep Deprivation on Saccades and Eyelid Blinking (Crevtis, 2003)
Blink rate was significantly higher in the morning after sleep deprivation
True for reflexive saccade, voluntary prosaccade, and antisaccade tasks

40. PERCLOS System
A measure of the proportion of time that the eyes are closed over a one minute period
Reflects slow eyelid closure rather than blinks
Drowsiness criterion of the eyes – greater than 80% closed
PERCLOS measures the proportion of the time in a minute that the eyes meet the 80% closure criterion

41. PERCLOS System
N = 14
Used actigraph to screen subjects for one week prior to the study
For the study, subjects were sleep deprived for 42 hours
A variety of fatigue-tracking equipment was used (eye blink, brain wave activity, head movements)

42. PERCLOS System
Every 4 hours subjects were required to perform an hour long test battery and complete a survey about mood and alertness
PERCLOS was used for eye ratings.
Video camera, TV, and video monitor were used.
Scorers manually tracked eyelid movements
Eye closure was based on the percentage of pupil/iris coverage. Blinks were ignored.

43. PERCLOS System

44. PERCLOS System Results:
PERCLOS correlated more highly with performance measure decrements than the subject’s own rating of their sleepiness
Bout-to-bout and minute-to-minute coherence for lapse duration for eye ratings of PERCLOS were well above the average coherence for lapse duration for all other technologies (r =  0.10)