Oculomotor responses during sleep deprivation

Purpose: To evaluate whether oculomotor responses related to the pupillary light reflex and saccadic velocity can identify subjects with sleep deprivation and whether these objective values correlate with subjective feeling of sleepiness.Methods: 11 normal subjects (3M,8F) participated in a 4 day study. During first two days following full night's (8 hours in bed) sleep they underwent baseline evaluation using automated oculomotor tests by FIT 2500 Fatigue Analyzer (Pulse Medical Instruments, Inc., Rockville, MD). Then, following third full night's sleep participants were sleep deprived for 28 hours. Ten measurements of automated oculomotor tests were performed during sleep deprivation period. Visually guided saccadic velocity (SV), initial pupil diameter (PD), pupillary constriction latency (CL), and amplitude of pupil constriction (CA) were assessed using FIT 2500 Fatigue Analyzer. FIT index that expresses the deviation of the ocular parameters from the baseline measurements was calculated. Assessment of correlation of oculomotor parameters with the subjective Stanford sleepiness scale was performed.Results: Oculomotor measures showed a significant increase in CL and calculated FIT index and significant decrease in SV during sleep deprivation. Subjective Stanford score was found to significantly increase over the sleep deprivation period and was significantly positively correlated with FIT index.Conclusion: Evaluation of oculomotor responses, particularly CL and SV together with FIT index might be practical for assessment of an individual's state of alertness or fatigue. Correlation of FIT index to Stanford provides evidence for the potential usefulness of oculomotor functions in the detection of subjective sleepiness states.