Eyelid Closure Analysis
All patients underwent video recording with the use of a high-resolution commercially available video camera (Panasonic HC-V770; Osaka, Japan) to capture the eyelid positions at a sampling rate of 30 frames per second. Patients were seated at the slit lamp with their head position verified and were assessed in three different lighting conditions – in regular examination room lighting, under examination with the glare source of an indirect ophthalmoscope (at 2000 lux on both eyes from 5 feet), and in dim lighting. They were given separate tasks during each lighting condition in which blink dynamics were assessed – a quiescent state that consisted of focusing on a fixation target, and two conversation states during which the facial features were in substantial motion. These two conversation states were termed “pleasant” and “unpleasant” lines of questioning (see The upper and lower eyelid positions captured from each frame of the videos were then input into custom software developed by Visage Technologies (Diskettgatan 11A, SE-583 35; Linköping, Sweden), which fit a feature template to the facial features in each frame, including the upper and lower lids of each eye, as shown in Eyelid closure parameter analysis. (The derivation of eyelid closure amplitude and duration from the eyelid aperture time course is illustrated in Examples of the onset times and amplitude estimates for each eyelid closure are plotted as the line graph in From these calculations, the number of eyelid closures and the median amplitudes, durations, and velocities in each viewing condition and study phase were then presented for statistical analysis to determine the significant effect of the CBD intervention.