How your eyelids coordinate every blink, over 15,000 times per day

Most people blink an average of 15,000 times per day without ever thinking about it. Blinking the eyelids is a crucial activity that we take for granted until something goes wrong – it keeps the front of the eye clean, moist, and protected.

Losing that autonomic function can lead to irritation, vision problems, and worse.

A new study maps the muscle activity of the eyelid that powers a blink, and shows it is more coordinated and flexible than once thought.

The research comes from the UCLA Samueli School of Engineering and the David Geffen School of Medicine at UCLA.

The team combined engineering tools with clinical expertise to study how the eyelids actually move in real time.

Mechanical aspects of eyelid blinks

The partnership between the engineering and medical teams at UCLA began with a shared goal of improving patient outcomes for those with impaired eyelid function.

By combining motion analysis technology with surgical expertise, they could study both the mechanical and clinical aspects of blinking in unprecedented detail.

This cross-disciplinary approach allowed the researchers to design experiments that captured the muscle activity and movement patterns with both precision and medical relevance.

The findings can be applied directly to device development, bridging the gap between laboratory research and real-world patient care.

Why blinking matters

Adults blink many times per minute, a pattern that supports clear vision and also shifts with attention and task demands.

Each blink spreads the tear film, a multi-layer fluid that includes mucus, water, and oil, across the cornea to keep the surface smooth and comfortable.

When eyelid control falters, people can develop exposure of the eye, pain, and eventually loss of sight, which is why surgeons and engineers look for ways to restore closure.

This study focuses on how the eyelid muscle behaves during different kinds of closure so that future devices can copy the correct patterns.

An eyelid muscle with sections

The orbicularis oculi is a ring-shaped muscle around the eye that closes the lids, and the research paper shows it does not fire as one simple unit.

Instead, segments around the eyelid activate in distinct sequences depending on the action, and those sequences shape the path that the lids travel.

Researchers tracked five behaviors: spontaneous blinks, voluntary blinks, reflex blinks to protect the eye, soft closures, and hard squeezes.

The team found two-dimensional motion signatures for each type and tied those signatures to where and when the muscle became active.

Mapping the eyelid blinks

To capture the fine details, the group used electromyography (EMG) with tiny wires in the eyelid, and high-speed motion capture of reflective markers along the lid margin.

Recordings from healthy volunteers showed that medial segments often lead the way during routine eyelid blinks, while reflex blinks trigger near-simultaneous activation across the muscle.

Two features stood out in the kinematics: an early inward pull at blink onset for everyday blinks, and a brief overshoot that follows rapid protective blinks.

Those patterns support the idea that different blinks serve different purposes, from wetting and pumping tears to shielding the cornea from quick threats.

From motion to mechanism

The team’s data linked higher overall activation to faster, fuller protective blinks and showed that slower, softer closures rely on sustained activity with a different spatial bias.

The researchers also reported strong correlations between local activation and local shortening along the lid, which supports the segmental control model.

That model helps explain how the eyelid can wet the eye efficiently with small, frequent blinks and still slam shut quickly when danger approaches.

It also offers measurable targets for clinicians who evaluate eyelid disorders and recovery after nerve injury.

Moving toward assistive tech

The study pointed to design rules for a neuroprosthesis, a device that stimulates nerves or muscles to restore movement, and that can assist blinking in those with facial paralysis.

Prior reviews showed that electrical stimulation can elicit lid closure in people and discussed timing, pulse trains, and electrode placement, yet no portable system is currently available in clinical use.

Armed with maps of which segments should activate first and how strongly, engineers can move beyond single-channel approaches that close the lids all at once.

Segment-specific stimulation could better reproduce natural wetting blinks instead of only fast, protective snaps. This matters for comfort and vision across a full day.

Why this matters in the real-world

Segmental control means a future device may need several small electrodes across the pretarsal region, rather than one large contact.

It also suggests that sensing on the healthy side could trigger properly timed stimulation on the affected side within tight windows that mimic natural physiology.

Because tear spreading depends on motion paths as well as speed, reproducing the early inward pull seen in routine blinks may be essential for eye health.

These insights give surgeons and rehabilitation teams a technical blueprint to assess eyelid motion and to personalize therapy.

The study is published in the journal Proceedings of the National Academy of Sciences.

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