Two-dimensional video analysis of the upper eyelid motion during spontaneous blinking

PURPOSE:: To validate and to report the results of a new inexpensive video-based method to measure upper eyelid motion during spontaneous blinks. METHODS:: Spontaneous blinks were simultaneously recorded in 21 healthy adult subjects for 5 minutes with magnetic search coil (MSC) and a portable video system (VDS) composed by a commercial high-speed camera coupled to a laptop computer and a blue light-emitting diode. Agreement between the 2 methods was assessed using qualitative comparison of the eyelid motion traces and Bland-Altman plots. RESULTS:: The blink traces registered with both methods were virtually identical. With the either method, the relationship between amplitude and maximum velocity was well fitted by linear regression with mean r values = 0.81 (MSC) and 0.85 (VDS). Bland-Altman plots showed good agreement between methods. The mean ± SE differences of amplitude (0.06 ± 0.17 mm) and maximum velocity (5.0 ± 3.4 mm/s) were not significant. With the VDS, it was also possible to quantify the horizontal component of the blink movements. The amplitude of the horizontal shift of the eyelid during blinks was 40% of the vertical downward phase of the movement. CONCLUSIONS:: Blinking kinematics can be precisely measured using a simple and inexpensive video system suitable for clinical settings.