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Vision System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Aaron P. Batista and George D. Stetten
All of this preprocessing by the retina is essential because the optic nerve constitutes a bottleneck. Evolution’s solution to the need to transmit visual information from the retina to the brain through that narrow pipeline is retinal data compression, a high-acuity fovea, and a moveable sensor. e two optic nerves, from the le and right eyes, join at the optic chiasm, forming a hemidecussation, meaning that half the axons cross while the rest proceed uncrossed. e resulting two bundles of axons leaving the chiasm are called the optic tracts. e le optic tract contains only axons from the le half of each retina. Since the images are reversed by the lens, this represents the right side of the visual eld. e division between the right and le optic tracts basically splits the retina down the middle, although there is a vertical strip of the visual eld that runs through the fovea that is represented in both hemispheres. is overlap accounts for the fact that occipital strokes and trauma oen spare the fovea. e segregation of sensory information into the contralateral hemispheres corresponds to the general organization of sensory and motor centers in the brain: the right hemisphere controls the le half of the body, and vice versa.
Central nervous system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The inferior orbital fissure is situated between the greater wing of sphenoid and the maxilla at the junction of the lateral wall and floor. It transmits the maxillary branch of the trigeminal nerve and the infraorbital artery. The optic foramen or canal, which is situated at the apex of the orbit in the sphenoid bone, transmits the optic nerve and the ophthalmic artery. The optic nerves from both eyeballs intercommunicate at the optic chiasma, which is situated in the middle cranial fossa anterior to the sella turcica. The optic tract then passes posteriorly through the lateral geniculate bodies to the visual cortex in the occipital lobe of the cerebrum.
Bridging Fashion Design and Color Effects
Published in Marcelo M. Soares, Francisco Rebelo, Ergonomics in Design Methods & Techniques, 2016
From the retina, visual information passes to the optic nerve, joining in the optic chiasma. Here, the images are organized in a way that the information that one or both eyes see in the left side of the sight is directed to the left half of the brain, and vice versa.
Tutorial: Theoretical Considerations When Planning Research on Human Factors in Lighting
Published in LEUKOS, 2019
Vision starts in the eye and requires light. Photoreceptors in the outer layer of the retina—the well-known rods and cones—absorb light particles and transduce photic information to neural signals that travel to the optic chiasm via the optic nerve. The retina consists of multiple layers of neurons that are tightly interconnected. These interconnections are the means through which light processing starts immediately, including, for instance, contrast detection, color processing, and very quick adaptation to local and ambient light levels. Typically such processing continues deeper in the brain, but the initiation in the retina implies that, rather than transferring direct pixel-based information like a digital camera, the optic nerve transports preprocessed light information, having already converted individual photoreceptor inputs into, for instance, light- and color channel–based data and accentuating color and light contrasts (both spatial and temporal), which are important for fast downstream (deeper in the brain) detection of, for instance, borders and shapes; that is, object detection. From there, light information takes different routes into the brain. The pathway mainly responsible for vision is that from the optic chiasm, via the lateral geniculate nucleus to the visual cortex. Once the signals reach the cortex, we become consciously aware of them; in other words, we see.