Evidence of pericentral stereopsis in random dot VECP

Dynamic random dot patterns generated on a TV screen by a special pattern generator are proven to be adequate stimuli for testing stereopsis. In our experimental set-up we use red-green coded striped or checkered patterns of various size and disparity as stimuli, which are viewed through red-green glasses (anaglyph method). The registration of transient visual evoked cortical potential (VECP) to these random dot stimuli offers objective proof of stereopsis. There is a typical amplitude behavior with maximum amplitudes at medium disparities. By recording the specific stereo VECP while masking the central retinal areas stepwise (artificial central scotoma) we can objectively show intact stereopsis of corresponding pericentral retinal areas. This peripheral stereopsis is demonstrable in the VECP by central scotomas up to eight degrees.