Development of an implantable epiretinal vision prosthesis with integrated image acquisition (OPTOEPIRET)

在德国，约有10，000人患有视网膜色素变性。目前还没有治疗这种疾病的方法，这种疾病会慢慢导致失明。百分之七的失明是由这种疾病引起的。将入射光转化为电脉冲的光感受器（视锥细胞和视杆细胞）正在逐渐死亡。尽管光感受器被破坏，但从视网膜神经细胞到大脑的连接部分仍然起作用。因此，通过电刺激视网膜神经细胞，可以产生动作电位，该动作电位经由神经纤维传递到视觉皮层并被处理成光学感知。世界各地的研究人员都在研究基于电刺激的视网膜假体。这些方法在刺激电极的放置上不同。在最复杂的方法中，刺激电极被放置在视网膜上或视网膜下。当今用于人类的植入物的共同点是，由于电极阵列的尺寸小，因此只能刺激视网膜的小区域。因此，视野非常小，仅相当于约9°。用这些系统不能实现外围识别的恢复。然而，视网膜的周边功能对于房间中的自主运动是必不可少的。这种能力首先在视网膜色素变性患者中消失。然而，在视网膜前途径中，刺激阵列的直径的增加仍然是可能的，并且通过这种增加视野，视网膜下途径将由于视网膜分离或进一步手术并发症的危险而非常有限。在OPTOEPIRET提案中，视网膜前入路将通过将眼睛透镜产生的图像集成到视网膜上的视网膜前记录来扩展。为此，将开发基于薄柔性聚酰亚胺基板的直径约为12 mm（其对应于约40°的视野）的柔性刺激阵列。该基板的背面面向眼睛透镜。将集成变薄且因此柔性的相机芯片，其具有与刺激电极相同数量的光电二极管。光电二极管阵列现在将记录通常落在视网膜上的晶状体产生的图像。集成CMOS电路将该光学信息转换为适当的刺激脉冲，该刺激脉冲被转发到基板前侧上的电极。通过这种方法，将不需要外部图像处理。

In Germany about 10,000 people are suffering from Retinitis Pigmentosa. No treatment for this disease slowly leading to blindness is established. Seven percent of all blindness is caused by this disease. The photoreceptors (cones and rods) which convert the incoming light into electrical pulses are dying off gradually. Despite of the destroyed photoreceptors the connections from retinal nerve cells to the brain are partly still functioning. Therefore by electrically stimulating retinal nerve cells action potentials can be generated that are transmitted via nerve fibers to the visual cortex and processed to optical perceptions. Researchers are worldwide working on retinal prostheses based on electrical stimulation. These approaches differ in the placement of the stimulation electrodes. In the most sophisticated approaches the stimulation electrodes are placed epiretinally or subretinally. Implants that are used in humans today have in common that due to the small size of the electrode array only a small area of the retina can be stimulated. So the field of vision is very small and corresponds to only about 9°. The recovery of the peripheral recognition cannot be achieved with these systems. However the peripheral function of the retina is indispensable for autonomous movement in rooms. This capacity is dropped out first in retinitis pigmentosa patients. Whereas in the epiretinal approach an increase of the diameter of the stimulation array is still possible and by this an increase of the visual field, the subretinal approach will be very limited due to the danger of separation of the retina or further surgery complications. Within the proposal OPTOEPIRET the epiretinal approach will be extended by an integrated epiretinal recording of the image produced by the eye lens onto the retina. For this a flexible stimulation array with a diameter of about 12 mm (which corresponds to a visual field of about 40°) based on a thin flexible polyimide substrate will be developed. The backside of this substrate is faced to the eye lens. Thinned and therefore flexible camera-chips will be integrated having the same number of photodiodes as there are stimulation electrodes. The photodiode-array will now record the image produced by the eye-lens that would normally fall onto the retina. Integrated CMOS-circuitry converts this optical information in appropriate stimulation pulses that are forwarded to the electrodes on the front side of the substrate. By this approach no external image processing will be necessary.