Artificial Muscles Can Restore Blinking, Save Vision
The simple act of blinking is necessary to maintain healthy eyes and vision, yet thousands of people lose that ability each year due to stroke, combat-related injuries, surgery, or nerve damage. Now surgeons have shown that artificial muscles can restore the ability to blink, a development that could not only save people’s vision but ultimately have other applications as well.
The study, which was conducted by researchers at the University of California (UC) Davis Medical Center, involved a technique that uses electrode leads and silicon polymers and is “the first-wave use of artificial muscles in any biological system,” according to Travis Tollefson, a facial plastic surgeon in the University of California Davis Department of Otolaryngology - Head and Neck Surgery.
In the study, Tollefson and his team were looking to develop the protocol and device design for implanting electroactive polymer artificial muscle (EPAM) in humans to reproducibly create a long-lasting blink of the eyelid. Electroactive polymers act like human muscles because they can expand and contract in response to voltage input. When a current is applied, the outer layer of the three-layered artificial muscle pulls together, which expands the artificial muscle. When the charge is stopped, the muscle contracts, blinking the eye. The artificial muscle was developed by engineers at SRI International of Palo Alto, California.
Blinking is critical because it helps keep the eyes moist, it protects the eyes against incoming threats, and it helps cleanse the eye of allergens, such as dust and pollen, and other foreign objects. Without the lubrication that blinking helps to provide, the eyes are soon at risk of developing corneal ulcers that can cause blindness. Thus people who have lost the ability to blink are at great risk of damage to their eyes and vision.
Blinking is controlled by a cranial nerve, and in most people who have permanent eyelid paralysis, this nerve has been damaged. Current techniques to treat eyelid paralysis involve either taking a muscle from the leg and transplanting it into the face or suturing a tiny gold weight inside the eyelid. The former procedure requires extensive, prolonged surgery and is not suitable for elderly or medically compromised patients.
The latter procedure is successful in more than 90 percent of cases, but blinking of the treated eye is slower than the opposite eye and the weight can cause problems for some patients when they sleep. Up to 5,000 people undergo the gold weight procedure each year in the United States and could benefit from the artificial muscle approach.
In the University of California Davis study, the researchers used an eyelid sling device to create an eyelid blink when actuated by an artificial muscle. They conducted their experiments in cadavers and found that they were able to achieve an acceptable result. Their success may then allow the creation of a realistic and functional eyelid blink that mimics the normal blink.
The study’s authors note that a similar system could be used to develop artificial muscles to control other parts of the body. Craig Senders, MD, UC Davis otolaryngologist, noted that “For people with other types of paralysis, the use of artificial muscles could someday mean regaining the ability to smile or control the bladder.” For now, the use of artificial muscles to help restore blinking and thus save vision is being refined on cadavers and animal models for eventual use in patients, hopefully within five years.
University of California Davis news release, Jan. 18, 2010