Stroke, injury, trigeminal neuralgia, and a number of other diseases can cause problems with the blink reflex. This frustrating and debilitating condition is currently addressed by embedding a weight into the eyelid to use gravity to bring it down, or by performing a muscle transplant, which is rarely done. Because these approaches have substantial side effects, researchers from University of California Davis Medical Center and SRI International have been working on an artificial eyelid muscle mechanism. In the latest issue of Archives of Facial Plastic Surgery the team is describing the development of a electroactive polymer artificial muscle (EPAM) based system that has yet to be tried on humans, but is showing promise in the lab.
From UC Davis Health System:
Using cadavers, the surgeons inserted a sling made of muscle fascia or implantable fabric around the eye. Small titanium screws secured the eyelid sling to the small bones of the eye. The sling was attached to a battery-operated artificial muscle. The artificial muscle device and battery were into a natural hollow or fossa at the temple to disguise its presence.
Senders and Tollefson found that the force and stroke required to close the eyelid with the sling were well within the attainable range of the artificial muscle. This capability may allow the creation of a realistic and functional eyelid blink that is symmetric and synchronous with the normal, functioning blink. A similar system also could give children born with facial paralysis a smile.
The three-layered artificial muscle was developed by engineers at SRI International of Palo Alto, Calif., in the 1990s. Inside is a piece of soft acrylic or silicon layered with carbon grease. When a current is applied, electrostatic attractions causes the outer layers to pull together and squash the soft center. This motion expands the artificial muscle. The muscle contracts when the charge is removed and flattens the shape of the sling, blinking the eye. When the charge is reactivated, the muscle relaxes and the soft center reverts back to its original shape.
An implanted battery source similar to those used in cochlear implants would power the artificial muscle.
For patients who have one functioning eyelid, a sensor wire threaded over the normal eyelid could detect the natural blink impulse and fire the artificial muscle at the same time. Among patients lacking control of either eyelid, an electronic pacemaker similar to those used to regulate heartbeats could blink the eye at a steady rate, and be deactivated by a magnetic switch.
The researchers are now refining the technique on cadavers and animal modes. They estimate the technology will be available for patients within the next five years.
Abstract in Archives of Facial Plastic Surgery: Force Requirements for Artificial Muscle to Create an Eyelid Blink With Eyelid Sling
Press statement from UC Davis Health System: Artificial muscles restore ability to blink, save eyesight…