OBJECTIVEDirectly excited the denervated orbicularis oculi muscle (OOM) by electric current on rabbits, to induce efficient eyelid closure, and seek the optimal sites for such excitation that can produce efficient eyelid closure with the minimal excitating current in the least channel.

METHODSBilateral peripheral facial paralysis model on 20 healthy NewZealand rabbits (40 sides) were prepared. Exciting current was designed for two-way rectangular pulse, 35 Hz frequency and 0.2ms pulse width. The current intensity could be adjusted between 0 and 2.5 mA. Middle of upper-orbit (A), outer orbital rim (B), and middle of lower-orbit (C) sites were located around the OOM. Each site underwent parallel muscle fiber excitation by 2.5 and 5 mm distance dual-electrode respectively, additional dual-electrodes were also placed in A- B and A- C positions. All resulted in a total of 8 different exciting methods, and were labeled A2.5, A5.0, B2.5, B5.0, C2.5, C5.0, AB and AC. Then the current was adjusted to achieve efficient eyelid closure. The minimal current intensity needed was regarded as threshold value.

RESULTSAll efficient eyelid closure occurrence rates of 8 methods were compared with combined χ(2) test and showed significant difference. A crossed χ(2) test showed the rates of C2.5, C5.0, and AC was significant lower than the highest methods. Except 3 methods above, the mean threshold values of remain 5 methods were compared with ANOVA test and showed significant difference. Further Fisher's LSD test showed B2.5 had the lowest mean value, was significant lower than A2.5 and AB, P < 0.001, and had no significant difference with A5.0 and B5.0, P > 0.05. A5.0's mean value was significant lower than A2.5's, P < 0.05.

METHODSB2.5, B5.0 and A5.0 were more likely to achieve a perfect closure.

CONCLUSIONSMiddle of supraorbital margin (A) and outer orbital rim (B) are the ideal sites for electric excitation. Exciting the two sites can sufficiently induce the contraction of denervated OOM, leading to high efficient eyelid closure occurrence rates, more perfect closure meanwhile with lower threshold current value, which are priority options.