retina


ret·i·na

noun \ˈre-tə-nə, ˈret-nə\

: the sensitive tissue at the back of the eye that receives images and sends signals to the brain about what is seen

plural retinas or ret·i·nae \-ˌnē, -ˌnī\

Full Definition of RETINA

:  the sensory membrane that lines the eye, is composed of several layers including one containing the rods and cones, and functions as the immediate instrument of vision by receiving the image formed by the lens and converting it into chemical and nervous signals which reach the brain by way of the optic nerve — see eye illustration

Origin of RETINA

Middle English rethina, from Medieval Latin retina, probably from Latin rete net
First Known Use: 14th century

ret·i·na

noun \ˈret-ən-ə, ˈret-nə\   (Medical Dictionary)
plural retinas also ret·i·nae \-ən-ˌē\

Medical Definition of RETINA

: the sensory membrane that lines most of the large posterior chamber of the vertebrate eye, is composed of several layers including one containing the rods and cones, and functions as the immediate instrument of vision by receiving the image formed by the lens and converting it into chemical and nervous signals which reach the brain by way of the optic nerve

Illustration of RETINA

retina

noun    (Concise Encyclopedia)

Layer of nerve tissue covering the back two-thirds of the eyeball. Light focused onto the retina by the lens of the eye stimulates two types of light-sensitive cells: rods, which are sensitive to low light levels, and cones, which provide detailed vision and colour perception. Chemical changes in these cells trigger nerve impulses, which are assembled by complex connections among retinal nerves into a pattern to be carried through the optic nerve to the visual centres of the brain. Disorders affecting the retina or the macula in its centre decrease vision and can cause blindness. See also detached retina; macular degeneration.

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