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2.15, 2.16 and 2.17 Structure and Function of the Eye and Defects of the…
2.15, 2.16 and 2.17 Structure and Function of the Eye and Defects of the Eye and their Treatment
Intro
They are adapted to allow the eye to change its shape in order to focus on near or distant objects (a process called accommodation), and to dim light
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Structures
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Retina
The retina contains rod cells and cone cells, each of which convert light to nerve impulses destined for the brain
Rod cells are more sensitive to light so they are better for seeing in low light, whereas cone cells allow colour vision
When light hits this, the cells are stimulated. Impulses are sent to the brain, which interprets the information to create an image
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Iris
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In bright light, the circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damage to the retina
In dim light, the circular muscles relax and the radial muscles contract to make the pupil larger- so more light can enter to create a better image
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Lens
Transparent, curved surface on the front of the eye
The lens, like the cornea, reflects light onto the retina
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