Fang Xiaoyun, Sakaguchi Hirokazu, Fujikado Takashi, Osanai Makoto, Ikuno Yasushi, Kamei Motohiro, Ohji Masahito, Yagi Tetsuya, Tano Yasuo
Department of Ophthalmology E-7, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Graefes Arch Clin Exp Ophthalmol. 2006 Mar;244(3):364-75. doi: 10.1007/s00417-005-0073-9. Epub 2005 Aug 4.
To determine the safety and efficacy of transsclerally placed intrapapillary wire microelectrodes implanted chronically into the optic nerve head of rabbit eyes.
Four platinum wire microelectrodes were passed through the sclera and implanted into the optic nerve head of five rabbit eyes for 4-6 months. Color fundus photography, fluorescein angiography, electroretinograms (ERGs), and visually evoked potentials (VEPs) were used to monitor the retina. Electrically evoked potentials (EEPs) were elicited by bipolar electrical stimulation of the optic nerve axons by different combinations of the four electrodes immediately after the implantation and at 1-month intervals thereafter. The effects of the chronic implantation of the electrodes on the morphology of the optic nerve were evaluated by histological and immunohistochemical examinations at 4 and 6 months after the implantation.
All of the electrodes remained stable in the implanted sites throughout the post-implantation period, except for one electrode that had pulled out of the optic nerve head at 1 month after implantation. No intraocular infection, inflammation, or vitreoretinal proliferation was observed in any eye. EEPs could be elicited from each pair of electrodes at all testing times. The mean threshold currents (charge densities) to evoke EEPs increased from 19.3 +/- 9.2 microA (6.0 +/- 2.9 microC/cm2) on the implantation day to 78.8 +/- 31.9 microA (24.6 +/- 10.0 microC/cm2) at 1 month after implantation, but did not change significantly thereafter. The implicit time and amplitude of the a- and b-waves of the ERGs and of P1 of the VEPs did not change significantly throughout the post-implantation period. Histological evaluation of the optic nerve head revealed slight tissue encapsulations surrounding the electrode and increased expression of glial fibrillary acidic protein near the surface of the optic nerve.
Implantation of transscleral intrapapillary microelectrodes appears to be safe and effective. These findings indicate that the implantation of microelectrodes in the optic nerve head should be considered for an optic nerve-based prosthesis.
确定经巩膜植入兔眼视神经乳头的经乳头线微电极长期植入的安全性和有效性。
将四根铂丝微电极穿过巩膜并植入五只兔眼的视神经乳头中4至6个月。使用彩色眼底照相、荧光素血管造影、视网膜电图（ERG）和视觉诱发电位（VEP）来监测视网膜。在植入后立即以及此后每隔1个月，通过四个电极的不同组合对视神经轴突进行双极电刺激来引出电诱发反应（EEP）。在植入后4个月和6个月，通过组织学和免疫组织化学检查评估电极长期植入对视神经形态的影响。
在植入后的整个时期内，除了一根电极在植入后1个月从视神经乳头中拔出外，所有电极在植入部位均保持稳定。在任何一只眼中均未观察到眼内感染、炎症或玻璃体视网膜增殖。在所有测试时间，每对电极均可引出EEP。诱发EEP的平均阈值电流（电荷密度）从植入当天的19.3±9.2微安（6.0±2.9微库仑/平方厘米）增加到植入后1个月的78.8±31.9微安（24.6±10.0微库仑/平方厘米），但此后没有显著变化。在植入后的整个时期内，ERG的a波和b波以及VEP的P1波的潜伏期和振幅均无显著变化。视神经乳头的组织学评估显示电极周围有轻微的组织包囊，并且视神经表面附近的胶质纤维酸性蛋白表达增加。
经巩膜经乳头微电极植入似乎是安全有效的。这些发现表明，对于基于视神经的假体，应考虑在视神经乳头中植入微电极。
