Vergence amplitudes with random-dot stereograms.

Random-dot stereograms were found to be capable of producing fusional vergence amplitudes in the absence of monocular contours. These vergence amplitudes are not an artefact of monocular contours provided by the target borders or test instrument and are comparable in range to vergence amplitudes measured clinically with second degree fusion targets in an amblyoscope. We conclude that diplopia of monocularly recognisable contours is not necessary for producing fusional vergence amplitudes.