Accurate simulation of visual scotomas in normal subjects

A technique has been developed for accurately simulating visual scotomas in subjects with normal vision. To accomplish this, the image of an opaque or partially transmitting mask is stabilized on a fixed region of the subject’s retina, while the image of the visual world that falls everywhere else on the retina moves about in the normal manner controlled by the subject’s eye movements. The mask that produces the scotoma is located in a plane conjugate to the retina and is stabilized by signals from a dual-Purkinje-image eyetracker, while the stimulus image makes two passes through the same optical system, but in opposite directions, thereby arriving at the retina in its original unstabilized state. Artificial scotomas generated in this way can be of any desired size, shape, density, and retinal location. The device promises to be a powerful tool for both basic and clinical research.