A New Gyro-Based Method for Quantifying Eyelid Motion

Abstract

Purpose We present an innovative method to quantify the eyeblink by using a miniature gyroscopic sensor (gyro), which is applied on the upper eyelid. Electrical Stimulation (ES) of the facial nerve is a promising technology to treat dysfunctional eyelid closure following facial paralysis. We used the new gyro-based method to evaluate the biomechanics of both the spontaneous and the ES-induced eyeblink, and to identify the best ES protocol. Methods During blinking, eyelids rotate about the axis passing through the eye canthi, thus we propose to use a gyro for measuring the angular velocity of the upper eyelid (ωe). The angular displacement of the eyelid (θe) was calculated by integrating the ωe signal. Two indices were derived from θe: 1) the eyelid angular displacement during eye closure (C), calculated as the peak value of θe; 2) the eyelid closure duration (D), calculated as the time interval between zero signal and the peak value of θe. In a healthy volunteer we used this method to quantify both the spontaneous eyeblink and the blinks elicited by different ES patterns. Results For the spontaneous eyeblink, indices C = 14.0 ± 1.8° and D = 94.0 ± 10.8 ms were computed. By comparing C and D indices for spontaneous and ES cases, trains of 10 pulses with a frequency ranging from 200 Hz to 400 Hz proved to induce the most effective and natural-like eyeblinks. Conclusions The new gyro-based method proved to be a valuable tool to provide dynamic and realtime quantification of eyelid motions. It could be particularly useful for evaluating the effective and natural-like eyeblink restoration provided by ES.