STUDIES OF SIMULATED PROSTHETIC VISION

该项目的长期目标是阐明通过假体部分恢复视力的盲人的视觉表现。已有报道称，通过在视皮层植入电极或通过术中视网膜刺激，盲人体内会产生磷烯(局部光点或光斑)。在这个项目中，在与视网膜和皮质假体研究团队的密切合作下，膦将被模拟为对正常视力的受试者的斑点状光刺激。每个模拟的磷化氢代表一个固定的电极，因此必须稳定在视野中：它随着观察者的凝视方向移动。在这个项目中，这将通过眼动补偿来实现，要么是双浦肯野眼镜仪中的散焦面具，受试者通过它观察监视器屏幕-面具上的小开口充当荧光素--或者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继者)。模拟的磷烯将以阵列的形式呈现，最初具有较小的(16-100)个，然后具有较大的(144-400)个，最后具有较大的(最多1,024)个磷烯数，并且具有各种布局：“视网膜”，即最小失真，和“皮质”，即根据条纹皮质投影图变换。在这些有视力的受试者中，将评估重建不规则皮质磷光图的策略。该项目将解决对假体视觉至关重要的问题：特定的视觉任务需要多少个磷烯，以什么间距和构型？面具中的不规则性和扭曲，以及丢失的膦元素会有什么影响？是否会发生图像稳定导致的褪色？是否可以通过眼球运动来防止；如果不是，还有什么其他方法有效？是否可以在较少(4-8)灰度级的情况下执行任务？具有代表性的视觉任务-字母识别、阅读、物体识别、眼手协调以及通过虚拟和真实迷宫的移动-将被执行。任务将由计算机生成，但在第四年和第五年将包括来自头戴式广域摄像机的实时输入。

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.