Evaluation of the Hall-effect sensor for determination of eyelid closure in vivo.

A small device to detect eyelid closure was designed on the basis of a Hall-effect sensor. Accurate sensing of normal eyelid closure is required to develop a prosthetic eyelid closure device for patients with paralyzed orbicularis oculi muscles. In this study, six rabbits had the sensors surgically implanted. A Hall-effect sensor, a small device that measures magnetic fields, was implanted in the inferior eyelid near the ciliary margin. An opposing magnet was implanted in the upper eyelid. Thus, as the eyelid closes, the output of the Hall-effect sensor will increase. This output voltage was monitored weekly. During the first 5 weeks the output of the Hall-effect sensor decreased slightly but then reached a steady state for the duration of the experiment. This study suggests that the Hall-effect sensor could be used to detect normal eyelid closure in an implantable facial reanimation device.