Effect of binocular rivalry suppression on initial ocular following responses.

To study the effect of binocular rivalry (BR) suppression on the ocular following response (OFR), we recorded the OFR in both the suppressed and the dominant phases of BR. The BR was established using stationary horizontal/vertical grating patterns presented on two PC monitors. Once a subjective image of a vertical or horizontal grating pattern was perceived, subjects pressed a button to trigger an onset of brief horizontal movement (750 ms) of the vertical grating pattern and an offset of the horizontal pattern. The OFRs were recorded using a scleral search coil system at 1 kHz. The OFRs from the suppressed phases were significantly reduced compared to those from the dominant phases. The OFRs were asymmetrical to temporalward and nasalward motion in most conditions. We suggest that asymmetry of OFRs under the incomplete BR conditions may be a reflection of imbalance binocular inputs and processing in the visual system similar to asymmetrical optokinetic nystagmus in strabismic subjects. The latency of the OFR in deeper suppressed conditions was prolonged, suggesting that the interaction of BR and OFR may occur at multiple stages including an early stage of the visual processing. The OFR may have the potential for objective measurement of BR suppression in clinical evaluation of binocular function.