NBEO Ocular Anatomy Posterior Segment (Post Seg) and Cranial Nerves Practice Test

Uncrossed fibers come from the temporal retina and stay on the same side, heading to the LGN layers that represent the ipsilateral eye. In the LGN, inputs from each eye are segregated into alternating layers. The layers that receive input from the ipsilateral eye are the ones carrying the uncrossed signal, typically layers 2, 3, and 5. Layers 1, 4, and 6 receive input from the contralateral eye (the crossed fibers from the nasal retina). So uncrossed fibers do not synapse in the first layer; they synapse in layers 2, 3, and 5. The layer that does not receive uncrossed input is the first layer.