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The visual system consists of the optical components in the anterior segment, the phototransducers in the posterior segment, and the transmission pathways and higher processing centers in the central nervous system (CNS). The optical components include the cornea, aqueous humor, and lens. Light passes through the cornea, aqueous humor, lens, and vitreous and is focused accurately on the retina. The posterior segment includes the vitreous body and the retina, where the process of converting light into neural signals, called transduction occurs. In the CNS, the neural components include the optic nerves, optic tracts, optic radiations, the visual cortex, and a variety of nuclei within the brain. After initial visual processing in the retina, neural signals then pass through the optic nerves and tracts to central structures where more elaborate processing occurs and where information from other senses is integrated with those from the visual pathways. Finally, the oculomotor system—the efferent limb of the visual system—is responsible for maintaining eye position and executing eye movements. Each of these structures and their interconnections develop in the embryonic and early life through an inter-coordinated process involving neurotropisms of individual axons and active signaling by the components of the visual system. |
