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

To develop a method for the non-invasive detection and quantification of eyelid movements during spontaneous blinking.

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.

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.

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.