Neuroanatomy, Optic Tract

Excerpt

The optic tract is a bundle of nerve fibers that serves to carry visual information from the optic chiasm to the left and right lateral geniculate bodies as a part of the visual pathway. The visual pathway refers to the series of cells and synapses that transmit visual signals from the environment to the brain for processing. This pathway begins with light striking the specialized nerve cells of the retina, which convert photons of light into electrochemical signals. Neural signals travel primarily through the retinal layers to the optic nerve (cranial nerve II, or CN II), optic chiasm, optic tract, lateral geniculate bodies, and visual cortex in the brain’s occipital lobe. Each optic tract carries one-half of the visual field, consisting of afferent (sensory) information from temporal hemi-retinal fibers ipsilaterally and nasal hemi-retinal fibers contralaterally. The left optic tract is responsible for the right visual field, and the right optic tract corresponds to the left visual field. Both optic tracts serve as clinically relevant structures in the evaluation of visual deficits, particularly in cases of homonymous hemianopsia. Lesions may impact other physiologic processes dependent on visual input to one or both optic tracts, including pupillary light reflex, accommodation reflex, and circadian rhythms. The neuroanatomy of the optic tract is relevant in cases of stroke, infiltrative tumors, encephalitis, multiple sclerosis, congenital anomalies of the brain development or function, and neurosurgery.