Interocular suppression produced by rivalry stimuli: a comparison of normal and abnormal binocular vision

This study compares interocular suppression in subjects with early strabismus and/or anisometropia with binocular rivalry suppression in subjects with normal binocular vision. A psychophysical test-probe paradigm was used to measure the changes in luminance-increment detection thresholds associated with periods of phenomenal suppression. In subjects with normal binocular vision, rivalry suppression induced by viewing orthogonally oriented grating pairs produced a distinctive wavelength-dependent change in visual sensitivity; specifically, there was a greater reduction in sensitivity for short (e.g., 450 nm) vs. middle or long wavelength stimuli (e.g., 560 nm). In contrast, subjects with abnormal binocular vision, regardless of the type of early abnormal visual experience, showed more reduction in sensitivity for a 560-nm stimulus than for the short-wavelength, 450-nm stimulus. Moreover, the pattern of sensitivity change in subjects with abnormal binocular vision was the same for suppression induced by either rivalry stimuli or stimuli that would normally promote fusion. The results clearly indicate that interocular suppression in subjects with abnormal binocular vision is qualitatively different from normal binocular rivalry. Evidently, the processes that mediate binocular rivalry are very susceptible to environmental influences during early vision development and can be disrupted easily.