STUDIES OF SIMULATED PROSTHETIC VISION

该项目的长期目标是阐明通过假肢部分恢复视力的盲人的视觉表现。 已经报道了通过在视觉皮层中植入电极或通过术中视网膜刺激在盲人个体中引起的光幻视（光的局部点或斑点）。 在这个项目中，在与视网膜和皮质假体研究小组的密切合作下，光幻视将被模拟为对正常视力受试者的斑点状光刺激。 每个模拟光幻视都代表一个固定的电极，因此必须在视野中保持稳定：它随着观察者的注视方向移动。 在本项目中，这将通过眼动补偿来实现，无论是双浦肯野眼动仪中的散焦掩模，受试者通过其观察监视器屏幕-掩模中的小开口充当光幻视-还是头戴式显示系统（低视力增强系统和两个后续系统）中的虚拟掩模。 模拟的光幻视将以阵列呈现，最初具有小的（16-100），然后具有较大的（144-400），最后具有大的（高达1，024）光幻视数目，并且具有各种布局：“视网膜”，即最小扭曲，和“皮质”，即，根据纹状皮质投影图进行转换。 重建不规则皮质光幻视地图的策略将在这些有视力的受试者中进行评估。 该项目将解决对修复视力至关重要的问题：具体的视觉任务需要多少光幻视，以什么样的间距和配置？ 面具的不规则和扭曲以及缺少光幻视会产生什么影响？ 是否会出现由于图像稳定而导致的褪色;是否可以通过眼球运动来防止;如果不能，还有哪些方法可以使用？ 可以用很少的灰度级（4-8）来执行任务吗？代表性的视觉任务-字母识别，阅读，物体识别，眼手协调，并通过虚拟和真实的迷宫的移动性将被执行。任务将由计算机生成，但在第4年和第5年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.