• The visually evoked response (VER) caused by the horizontal sinusoidal movement of a display consisting of a checkerboard with 15-minute checks of relatively low contrast oscillating at 6.3 Hz is itself sinusoidal with a frequency of 12.6 Hz. When viewed binocularly, the VER is 25% to 30% greater in amplitude than the sum of the amplitudes for monocular viewing. This binocular facilitation may be a VER correlate of normal binocular single vision. It is lost in small-angle esotropes and in normals whose binocular function is disturbed by a vertical prism placed over one eye. Characteristic curves relating VER amplitude and phase angle to frequency of oscillation of the checkerboard display suggest that two "systems" carry information to the visual cortex: a long and a short latency system. In amblyopia, the long latency system may be selectively impaired.
Srebro R. The Visually Evoked ResponseBinocular Facilitation and Failure When Binocular Vision Is Disturbed. Arch Ophthalmol. 1978;96(5):839-844. doi:10.1001/archopht.1978.03910050445009