Caspi Avi, Zivotofsky Ari Z
Department of Applied Physics, Jerusalem College of Technology-Lev Academic Center, Jerusalem, Israel; Second Sight Medical Products, Inc., Sylmar, CA United States.
Brain Science Program, Bar Ilan University, Ramat Gan, Israel.
Vision Res. 2015 Mar;108:77-84. doi: 10.1016/j.visres.2015.01.006. Epub 2015 Jan 29.
There are presently several ongoing clinical trials to provide usable sight to profoundly visually impaired patients by means of electrical stimulation of the retina. Some of the blind patients implanted with retinal prosthesis reported un-patterned perception and yet benefit from the device in many activities of daily living, seemingly because they adopt active scanning strategies. The aim of the present work is to evaluate if and under what conditions a measured visual acuity level is truly an indication that the brain perceived a patterned image from the electrical stimulation of the visual prosthesis. Sighted subjects used a pixelized simulator in which they perceived either a low resolution sub-sampling of the original image ("normal mode"--patterned vision) or an image that was solely a function of the brightness and size of the original image ("brightness mode"--no patterned vision). Results show that subjects were able to adopt a head scanning strategy that enabled acuity beyond the resolution set by a static view of the stimulus. In brightness mode, i.e. without patterned vision, most subjects achieved a measurable acuity level better than the limit set by the geometrical resolution of the entire array but worse than the limit set by the distance between neighboring simulated pixels. In normal mode all subject achieved acuity level that is better than the geometrical resolution of the simulated pixels. Thus, visual acuity levels comparable with the electrodes/pixels resolution implies that the patient perceives an image with spatial patterns.
目前有几项正在进行的临床试验，旨在通过视网膜电刺激为严重视力受损患者提供可用视力。一些植入视网膜假体的盲人患者报告有非图案化的感知，但在许多日常生活活动中仍从该设备中受益，这似乎是因为他们采用了主动扫描策略。本研究的目的是评估在何种条件下，测量到的视力水平能真正表明大脑从视觉假体的电刺激中感知到了有图案的图像。有视力的受试者使用了一个像素化模拟器，在模拟器中，他们要么感知到原始图像的低分辨率子采样（“正常模式”——有图案视觉），要么感知到仅取决于原始图像亮度和大小的图像（“亮度模式”——无图案视觉）。结果表明，受试者能够采用头部扫描策略，使视力超过刺激静态视图所设定的分辨率。在亮度模式下，即无图案视觉时，大多数受试者达到了可测量的视力水平，该水平优于整个阵列几何分辨率所设定的极限，但低于相邻模拟像素之间距离所设定的极限。在正常模式下，所有受试者达到的视力水平均优于模拟像素的几何分辨率。因此，与电极/像素分辨率相当的视力水平意味着患者感知到了具有空间图案的图像。
