I know of at least one exception: in adult Xenopus laevis (African clawed frog) retinal ganglion cell (RGC) axons from the nasal retina cross at the optic chiasm while temporal RGC axons do not cross. Interestingly, however, this is not the case in Xenopus tadpoles whose RGC axons are completely crossed. It also happens to be the case that the eyes of the tadpole are positioned on the side of the head and they move to point forward during metamorphosis. This explains the arrangement of the projections because the tadpole's eyes would not have overlapping visual fields and thus would not be capable of stereoscopic vision. I think it is generally the case that predator animals tend to have eyes that point forward and have 3D vision (useful for chasing down lunch) while prey animals have eyes on the sides of their heads which allows for a wider field of view (useful to avoid becoming lunch). Because frogs move up the food chain when they go from tadpole to adult, it makes sense for their visual system to switch from one mode to the other.
Last edited by Brent Richards (30th Jan 2012 15:00:37)