UCLA researchers decod muscle mechanics with flashing

The blink of an eye seems natural and immediate, but is it true? Without a working eyelid, the eye can become dry, irritated and ultimately lose the ability to see clearly.

Now a team of biomechanical engineers and UCLA ophthalmologists has discovered new details about muscles that control the flashing, offering the path to developing prostheses supporting the blink. Published in the study, it showed that Orbicularis Oculi – a muscle that controls the movement of the eyelid – shrinks in complex patterns, which vary depending on the action and move the eyelid in more than just simple movement up and down.

Scientists studied how this muscle behaves differently in different activities, including spontaneous blinks, quick protective closures and strict closed movements.

“The movement of the eyelid is both more complex and precisely controlled by nervous system Than previously understood – he said that the author of the correspondent, Tyler Clites, assistant to the professor of mechanical and air engineering at Ucla Samueli School of Engineering. “Different parts of the muscle activate in carefully temporary sequences depending on what the eye does. This level of muscle control has never been recorded in the human eyelid. Now, when we have rich information, we can go ahead in the design of neuroprosthesis, which help restore the natural function of the eyelid.”

In experiments with volunteers, scientists looked at five different ways in which the eyes are closing:

• Spontaneous blink: automatic, unaware blink that occurs regularly to keep the eye lubrication
• Voluntary blink: intentional blink, just like if someone is asked to blink at the recommendation
• Reflective blink: Fast, involuntary blinking caused to protect the eye from collision
• Soft closure: a delicate, slow eyelid descent, similar to the beginning of sleep
• Forced closure: deliberate squeezing of the eyelids tightly closed

To register activity in Orbicularis Oculi with high precision, the ophthalmological surgeon put small eyelid wire electrodes. Then the scientists used a system of grabbing movement to track the movement of eyelid in ultrasonic movement. These tools allowed the team to measure subtle differences in eyelid movement, including speed, direction and which part of the muscle initiated the action.

“People may lose the ability to blink due to stroke, tumor, infection or injuries. The condition is painful in a short period and can damage the eyes enough to cause loss of sight,” said study co -author Daniel Rootman, an ophthalmology professor at David Geffen School of Medicine in UCLA and director of the Orbital Center UCLA. “We know that a small electrical impulse can stimulate the muscle orbicularis Oculi to move, but the design of one that works well was elusive. What we have now is a good road map to such a device, including where exactly he places the electrodes, how to replace them, and how strong the pulse should be. These guidelines.

Thanks to this fundamental knowledge about the biomechanics of eyelids, scientists can now work on improving prototype neuroprottese to help people blink.

“Understanding how the eyelid works is crucial for designing the exact pattern of stimulation for prostheses, as well as for diagnostic purposes,” said the first author of the study Jinyoung Kim, a PhD student of mechanical engineering UCLA and a member of the CLITES research group, a group of anatomical engineering in UCLA. “We are more than excited that we can fill this gap and go to work with patients who have face paralysis and help improve their lives.”

Other authors, all from UCLA, are Ashley Shirriff, Jordan Cornwell and Maria Paula Quintero Mutis with plastic and reconstructive surgery; and Ereni Delis and Sophia Wang, both Bachelor Studies Researchers in the Clutes group. Klici also organize joint faculty visits to the Bioengineering Departments in Ucla Samueli and orthopedic surgery at the Geffen School of Medicine.

The research was financed by the National Institutes of Health National Eye Institute.