Spontaneous blinking in healthy persons: an optoelectronic study of eyelid motion

Purpose: To develop a method for the non-invasive detection and quantification of eyelid movements during spontaneous blinking. Methods: Spontaneous eyelid movements were monitored using an optoelectronic motion analyzer with passive markers in a younger group aged 20-30 years (13 men, 12 women) and in an older group over 50 years (10 men and nine women). Blink rate, eyelid displacement as a percentage of maximum excursion, and maximum eyelid velocity in closing and opening were calculated. Results: Spontaneous blink rate was significantly larger in women than in men (19 vs 11 blinks per minute); older women blinked more frequently than younger women. On average, young men closed the eyes completely (or almost completely) 44% of times, whereas the eyelid closure of young and older women was more frequently between 51 and 75% of the maximum excursion. Older men rarely closed completely and showed a similar frequency of blinks with up to 25%, 50% and 75% of maximum excursion. During eyelid closure and opening, the maximum velocity reduced with age: older subjects moved their eyelids approximately 80-70% slower than younger subjects. In all subjects, closing was performed 40-47% faster than opening; women moved faster than men. Eyelid displacement was greater in young than in older subjects. Conclusions: The method used in this study allowed the non-invasive detection of eyelid movements during spontaneous blinking, providing a set of descriptive and kinematic data. The method could also be used to assess blink characteristics in patients with movement disorders, without invasive or time-consuming procedures.