Eye Anatomy


Eyes are like windows to the outside world, but their intricacies and functionalities are far more extensive than those of any given glass window. They are able to capture, adjust, and transform light into a chemical code that only the brain can decipher. Each structure of the eye works in accord with the next – refracting, constricting, dilating and chemically reacting to convert patterns of light. This article uses the mammalian eye as a primary model and follows the path that light takes on its journey through the functional eye, detailing the essential components of one of the smallest, yet most complex organs in the body. Many have attempted to emulate its abilities, but even top‐of‐the‐line digital single lens reflex cameras dare not compare with the elegant, efficient design infused in this multifaceted unit of anatomical machinery.

Key Concepts:

  • Accommodation refers to the changing of the shape of the lens as a result of the constriction or relaxation of ciliary muscles, in order to adjust its optical power to see clearly in the near distance. This process is used to bring objects into focus.

  • Eyes are part of the central neuronal system exposed to environmental stimuli. It captures and processes light signals to form discernible images.

  • Phototransduction refers to the process that creates a change in a photoreceptor's membrane potential due to the absorption of a photon by a photopigment molecule.

  • Retina is the outgrowth of the brain composed of multiple types of neurons and supportive cells that converts light signal into electrochemical impulses that are transmitted to the processing centres in the brain to form discernible images.

  • Glial cells are supporting cells of the nervous system. They provide support and protection for neurons by holding them in place, supplying nutrients and oxygen, isolating them from each other and removing the debris of dead neurons.

  • Neurons are a group of cells that can be electrically excited to process and transmit information by electrical and chemical signalling. They are the basic building blocks of the nervous system.

Keywords: eye; vertebrate; human; retina

Figure 1.

Schematic of a vertebrate eye. (a) Basic structures of the vertebrate eye have been colour coded. (b) Magnification of the anterior part of the eye, depicting the structures involved in aqueous humour circulation.

Figure 2.

Schematic view of the organisation of neurons and supportive glial cells in the vertebrate retina. (a) Organisation of retinal neurons within the retina. Six types of neurons are present in the vertebrate retina including rod and cone photoreceptors, bipolar, horizontal, amacrine and ganglion cells. (b) Organisation of retinal glial cells within the retina. Five glial cell types have been found in the vertebrate retina. Astrocytes are present in vascular retinas whereas oligodendrocytes are predominantly present in avascular retinas.



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Zhu, Jie, Zhang, Ellean, and Del Rio‐Tsonis, Katia(Nov 2012) Eye Anatomy. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000108.pub2]