High-speed infrared imaging analysis of spontaneous versus reflex blinking

Blinking plays a vital role in protecting the eye and maintaining ocular surface health. Understanding blink behaviour may help identify ocular surface disorders and detect blink abnormalities associated with systemic or neurological conditions. This study assessed the kinematic characteristics of spontaneous blinking versus mechanically evoked reflex blinking and explored their relationship with potentially related ocular surface characteristics. This pilot study used high-speed infrared imaging to capture spontaneous and reflex blinking in 11 participants. A five-minute video recording of spontaneous blinking was captured while participants watched a wildlife documentary. Reflex blinking was evoked by delivering a puff of air into the right eye at random intervals. Blink velocity, completeness and duration were determined using custom semi-automated analysis software. Corneal sensitivity, subbasal corneal nerve morphology, non-invasive tear break-up time and tear meniscus height were also assessed. Spontaneous blinking was less complete than reflex blinking (p = 0.012). Closing-phase velocity was greater for reflex blinking than for spontaneous blinking (p < 0.001), whilst no significant difference was observed for opening-phase velocity (p = 0.164). Closed-phase duration was longer for reflex blinking than for spontaneous blinking (p = 0.023), whereas total blink duration did not differ significantly (p = 0.718). Exploratory analyses suggested potential associations between tear film parameters and blink dynamics. Differences were found in the kinematic characteristics of spontaneous and reflex blinking. Preliminary associations between blink characteristics and ocular surface parameters warrant confirmation in larger studies. High-speed infrared imaging is a promising technique that may be used in the future to better understand how blinking is affected by ocular, systemic and neurological conditions.