[Surgical treatment of paralytic lagophthalmos]

Enhanced Ionic Polymer-Metal Composites with Nanocomposite Electrodes for Restoring Eyelid Movement of Patients with Ptosis

The present study aims to use enhanced ionic polymer-metal composites (IPMC) as an artificial muscle (a soft-active actuator) to restore eyelid movement of patients with ptosis. The previous eyelid movement mechanisms contained drawbacks, specifically in the lower eyelid. We used finite element analysis (FEA) to find the optimal mechanism among two different models (A and B). In addition to common electrodes of IPMC (gold and platinum), the bovine serum albumin (BSA) and microcrystalline cellulose (MCC) polymers, with optimal weight percentages of carbon nanotube (CNT) nanofiller, were also utilized as non-metallic electrodes to improve the efficiency of the IPMC actuator. In both models, IPMC with nanocomposite electrodes had higher efficiency as compared to the metallic electrodes. In model A, which moved eyelids indirectly, IPMC with MCC-CNT electrode generated a higher force (25.4%) and less stress (5.9 times) as compared to IPMC with BSA-CNT electrode. However, the use of model A (even with IPMCs) with nanocomposite electrodes can have limitations such as possible malposition issues in the eyelids (especially lower). IPMC with MCC-CNT nanocomposite electrode under model B, which moved eyelids directly, was the most efficient option to restore eyelid movement. It led to higher displacements and lower mechanical stress damage as compared to the BSA-CNT. This finding may provide surgeons with valuable data to open a window in the treatment of patients with ptosis.

Infrared-based blink-detecting glasses for facial pacing: toward a bionic blink

IMPORTANCE Facial paralysis remains one of the most challenging conditions to effectively manage, often causing life-altering deficits in both function and appearance. Facial rehabilitation via pacing and robotic technology has great yet unmet potential. A critical first step toward reanimating symmetrical facial movement in cases of unilateral paralysis is the detection of healthy movement to use as a trigger for stimulated movement. OBJECTIVE To test a blink detection system that can be attached to standard eyeglasses and used as part of a closed-loop facial pacing system. DESIGN, SETTING, AND PARTICIPANTS Standard safety glasses were equipped with an infrared (IR) emitter-detector unit, oriented horizontally across the palpebral fissure, creating a monitored IR beam that became interrupted when the eyelids closed, and were tested in 24 healthy volunteers from a tertiary care facial nerve center community. MAIN OUTCOMES AND MEASURES Video-quantified blinking was compared with both IR sensor signal magnitude and rate of change in healthy participants with their gaze in repose, while they shifted their gaze from central to far-peripheral positions, and during the production of particular facial expressions. RESULTS Blink detection based on signal magnitude achieved 100% sensitivity in forward gaze but generated false detections on downward gaze. Calculations of peak rate of signal change (first derivative) typically distinguished blinks from gaze-related eyelid movements. During forward gaze, 87% of detected blink events were true positives, 11% were false positives, and 2% were false negatives. Of the 11% false positives, 6% were associated with partial eyelid closures. During gaze changes, false blink detection occurred 6% of the time during lateral eye movements, 10% of the time during upward movements, 47% of the time during downward movements, and 6% of the time for movements from an upward or downward gaze back to the primary gaze. Facial expressions disrupted sensor output if they caused substantial squinting or shifted the glasses. CONCLUSIONS AND RELEVANCE Our blink detection system provides a reliable, noninvasive indication of eyelid closure using an invisible light beam passing in front of the eye. Future versions will aim to mitigate detection errors by using multiple IR emitter-detector units mounted on glasses, and alternative frame designs may reduce shifting of the sensors relative to the eye during facial movements.

A new gyro-based method for quantifying eyelid motion

PURPOSE

We present an innovative method to quantify the eyeblink by using a miniature gyroscopic sensor (gyro), which is applied on the upper eyelid. Electrical Stimulation (ES) of the facial nerve is a promising technology to treat dysfunctional eyelid closure following facial paralysis. We used the new gyro-based method to evaluate the biomechanics of both the spontaneous and the ES-induced eyeblink, and to identify the best ES protocol.


METHODS

During blinking, eyelids rotate about the axis passing through the eye canthi, thus we propose to use a gyro for measuring the angular velocity of the upper eyelid (ωe  ). The angular displacement of the eyelid (θe  ) was calculated by integrating the ωe signal. Two indices were derived from θe: 1) the eyelid angular displacement during eye closure (C), calculated as the peak value of θe ; 2) the eyelid closure duration (D), calculated as the time interval between zero signal and the peak value of θe. In a healthy volunteer we used this method to quantify both the spontaneous eyeblink and the blinks elicited by different ES patterns.


RESULTS

For the spontaneous eyeblink, indices C = 14.0 ± 1.8° and D = 94.0 ± 10.8 ms were computed. By comparing C and D indices for spontaneous and ES cases, trains of 10 pulses with a frequency ranging from 200 Hz to 400 Hz proved to induce the most effective and natural-like eyeblinks.


CONCLUSIONS

The new gyro-based method proved to be a valuable tool to provide dynamic and real-time quantification of eyelid motions. It could be particularly useful for evaluating the effective and natural-like eyeblink restoration provided by ES.

Surface electromyography recording of spontaneous eyeblinks: applications in neuroprosthetics

OBJECTIVE

We are designing an implantable neuroprosthesis for the treatment of unilateral facial paralysis. The envisioned biomimetic device paces artificial blinks in the paretic eyelid when activity in the healthy orbicularis oculi (orbicularis) muscle is detected. The present article focuses on electromyography (EMG)-based eyeblink detection.

STUDY DESIGN

A pilot clinical study was performed in healthy volunteers who were intended to represent individuals with facial paralysis. Spontaneous eyeblinks were detected by a surface EMG recording. Blink detection accuracy was tested at rest and during voluntary smiling and chewing.

SETTING

Fifteen participants were asked to wear surface recording electrodes on the left side of their face, detecting the orbicularis oculi, the masseter, and the zygomatic muscle EMG activity.

SUBJECTS AND METHODS

Participants were asked to look ahead, voluntarily smile, and chew according to an experimental protocol. Custom software was designed with the purpose of selectively filtering the multichannel EMG recordings and triggering a digital output.

RESULTS

The software filter allowed elimination of spurious artificial eyeblinks and thus increased the accuracy of the EMG recording apparatus for the spontaneous blinking.

CONCLUSION

Orbicularis oculi EMG recording worked as a real-time eyeblink-detecting system. Moreover, the multichannel EMG recording coupled to a proper digital signal processing was very effective in specifically detecting the spontaneous blinking during other facial muscle activities. With regard to closed-loop biomimetic devices for the pacing of the eyeblink, the EMG signal represents a valid option for the recording side.

A closed-loop stimulation system supplemented with motoneurone dynamic sensitivity replicates natural eye blinks

OBJECTIVE

The authors are designing an implantable device that will electrically stimulate a paretic eyelid when electrodes implanted into the contralateral healthy orbicularis oculi muscle detect a spontaneous blink activity. As a novelty, the stimulation pattern includes the dynamic sensitivity of motor units, thus obtaining complete eyelid closure, tailored on the kinematics of the natural eye blink.

STUDY DESIGN

A preliminary study was performed on 10 healthy subjects, to observe, first, the kinematics of their natural eye blink and, second, the eye blink stimulated by a dynamic vs nondynamic pattern.

SETTING

A microaccelerometer taped onto the left upper eyelid detected its kinematics. A dedicated LabView software built up and triggered the stimulation pattern. A webcam recorded the behavioral effect.

SUBJECTS AND METHODS

The kinematics of spontaneous eye blinks was detected. Then, an epicutaneous stimulation of the facial nerve branch for the left orbicularis oculi muscle was performed on the same subjects. Muscle recruitment curves were studied, and acceleration of the bionic blink was measured and compared with the natural one.

RESULTS

Kinematics of the natural eyelid is highly variable within subjects. The stimulation pattern frequency was set case by case in order to obtain the desired eyelid acceleration of the contralateral eye. A custom-fit dynamic stimulation leads to a symmetrical natural-like eye blink.

CONCLUSIONS

By adding the dynamic pulse, the authors were able to tailor a bionic eye blink, which was hardly distinguishable from the subject's natural one.