Bilateral visual projections exist in non-teleost bony fish and predate the emergence of tetrapods

Dating the ipsilateral visual pathway

In primates, visual connections are bilateral: Each eye sends neural connections to both sides of the brain. Vigouroux et al. looked at the evolutionary underpinnings of the bilateral visual system. A close look at the connections between the retina and the brain in a variety of fish species representing a span of evolutionary divergence revealed that contralateral connections seem to be universal. The ipsilateral connections, which add to the contralateral connections to form a bilateral visual system, arrived later in evolution but before the transition to land-dwelling animals.

Science , this issue p. 150