Chow Alan Y, Pardue Machelle T, Perlman Jay I, Ball Sherry L, Chow Vincent Y, Hetling John R, Peyman Gholam A, Liang Chanping, Stubbs Evan B, Peachey Neal S
Optobionics Corporation, Wheaton, IL 60187, USA.
J Rehabil Res Dev. 2002 May-Jun;39(3):313-21.
Selective degeneration of the retinal photoreceptor layers underlies blindness in retinitis pigmentosa (RP) and other inherited retinal disorders. Because there are no therapies for these patients, we are evaluating the possibility that electrical stimulation delivered to the subretinal space by a microphotodiode array (MPA) could replace, in some aspect, the function of diseased photoreceptors. Early MPA prototypes utilized gold as the electrode material, which gradually dissolved during the postoperative period following subretinal implantation. Here we present the results obtained when different MPA materials were used. Semiconductor-based silicon MPAs (2 mm in diameter; 50 microm in thickness), incorporating iridium/iridium oxide (IrOx) or platinum (Pt) electrodes, were implanted into the subretinal space of the right eye of normal cats with the use of vitreoretinal surgical techniques. Indirect ophthalmoscopy, fundus photography, ganzfeld electroretinography, and histology were used for the evaluation of the implanted retinas postoperatively. Infrared (IR) stimulation was used to isolate electrical responses generated by the MPA. The unimplanted left eyes were used for control purposes. After the implantation surgery, subretinal MPAs retained a stable position in the subretinal space. Up to 12 months after surgery, there was little change in the magnitude of the electrical response of IrOx- and Pt-based MPAs to a standard IR light stimulus. Overlying the implant, there was a near-complete loss of the outer retinal layer, which is likely to reflect obstruction of choroidal nourishment to these layers by the solid disk implant. In addition, the inner retinal layers showed variable disorganization. Away from the implant, the retina displayed a normal appearance. In comparison to electroretinograms (ERGs) obtained from unimplanted eyes, responses recorded from implanted eyes had a normal waveform but were slightly smaller in amplitude. These results indicate that IrOx and Pt improve implant electrode durability and that implants incorporating these materials into the electrode layer do not induce panretinal abnormalities.
视网膜色素变性（RP）和其他遗传性视网膜疾病导致失明的根本原因是视网膜光感受器层的选择性退化。由于这些患者目前尚无治疗方法，我们正在评估通过微光电二极管阵列（MPA）向视网膜下间隙传递电刺激在某些方面替代患病光感受器功能的可能性。早期的MPA原型使用金作为电极材料，在视网膜下植入后的术后阶段会逐渐溶解。在此，我们展示了使用不同MPA材料时所获得的结果。采用玻璃体视网膜手术技术，将基于半导体的硅MPA（直径2毫米；厚度50微米），其电极采用铱/氧化铱（IrOx）或铂（Pt），植入正常猫右眼的视网膜下间隙。术后使用间接检眼镜、眼底摄影、全视野视网膜电图和组织学检查来评估植入的视网膜。使用红外（IR）刺激来分离由MPA产生的电反应。未植入的左眼用作对照。植入手术后，视网膜下MPA在视网膜下间隙中保持稳定位置。术后长达12个月，基于IrOx和Pt的MPA对标准IR光刺激的电反应幅度几乎没有变化。在植入物上方，外层视网膜几乎完全缺失，这可能反映了固体盘状植入物对这些层脉络膜营养供应的阻碍。此外，内层视网膜层显示出不同程度的紊乱。在远离植入物的地方，视网膜外观正常。与未植入眼获得的视网膜电图（ERG）相比，植入眼记录的反应波形正常，但幅度略小。这些结果表明，IrOx和Pt提高了植入电极的耐久性，并且将这些材料纳入电极层的植入物不会诱发全视网膜异常。
