STUDIES OF SIMULATED PROSTHETIC VISION

该项目的长期目标是阐明通过义肢部分恢复视力的盲人的视觉表现。有报道称，通过在视觉皮层植入电极或通过术中视网膜刺激，可以在盲人体内产生光幻视（局部光点或光点）。在这个项目中，在与视网膜和皮质假体研究团队的狭窄合作下，磷幻视将被模拟成斑点状的光刺激，以刺激正常视力的受试者。每个模拟的光幻灯代表一个固定的电极，因此必须在视野中保持稳定：它随着观察者注视的方向移动。在这个项目中，这将通过眼动补偿来完成，要么是双浦肯野眼动仪中的散焦面具，通过它受试者观察监视器屏幕-面具上的小孔作为磷光片-要么是头戴式显示系统中的虚拟面具（低视力增强系统和两个后续系统）。模拟的磷光体将以阵列呈现，最初是小的（16-100），然后是大的（144-400），最后是大的（多达1024）磷光体数量，并具有各种布局：“视网膜”，即最小扭曲，“皮质”，即根据纹状皮质投影图进行转换。重建不规则皮质磷脑图的策略将在这些视力正常的受试者中进行评估。该项目将解决假肢视觉的关键问题：具体的视觉任务需要多少个磷光体，间距和配置是多少？面具中的不规则和扭曲以及缺失的光幻视有什么影响？是否由于图像稳定而出现褪色；可以通过眼球运动来预防吗？如果不行，还有什么其他方法有效？任务是否可以用较少的（4-8）灰度来完成？具有代表性的视觉任务——字母识别、阅读、物体识别、手眼协调以及通过虚拟和真实迷宫的移动能力——将被执行。任务将由计算机生成，但在四年级和五年级，将包括来自头戴式宽视场摄像机的实时输入。

The long term goal of this project is to elucidate visual performance by blind individuals whose vision is partially restored through a prosthesis. Phosphenes (localized dots or blobs of light) elicited in blind individuals, through implanted electrodes in visual cortex or through intra-operative retinal stimulation, have been reported. In this project, in narrow collaboration with retinal and cortical prosthesis research teams, phosphenes will be simulated as blob-like light stimuli to normally sighted subjects. Each simulated phosphene represents a stationary electrode, and must thus be stabilized in the visual field: It moves with the observer's direction of gaze. In this project, this will be accomplished through eye movement compensation, either of a defocused mask in a dual Purkinje eyetracker through which the subject observes a monitor screen- with small openings in the mask acting as phosphenes-or of a virtual mask in a head-mounted display system (Low Vision Enhancement System and two successors). Simulated phosphenes will be presented in arrays, initially with small (16-100), then with larger (144-400) and finally with large (up to 1,024) phosphene numbers, and with various layouts: "retinal", i.e. minimally distorted, and "cortical", i.e., transformed according to the striate cortical projection map. Strategies for reconstruction of irregular cortical phosphene maps will be evaluated in these sighted subjects. The project will address issues crucial to prosthetic vision: How many phosphenes, in what spacing and configuration, are required for specific vision tasks? What are the effects of irregularities and distortions in the mask, and of missing phosphenes? Does fading due to image stabilization occur; can it be prevented with eye movements; if not, what other methods work? Can tasks be carried out with few (4-8) gray levels? Representative visual tasks-letter recognition, reading, object recognition, eye-hand coordination, and mobility through virtual and real mazes-will be performed. Tasks will be computer-generated, but in years 4 and 5 will include live input from a head-mounted wide-field camera.