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Learning Objectives

Learning Objectives . Can you label a diagram of the eye and explain the function of each part? How does the eye focus on near and distant objects, and respond to changes in light intensity?. Petr Novák, Wikipedia. Watch the video clip.

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Learning Objectives

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  1. Learning Objectives • Can you label a diagram of the eye and explain the function of each part? • How does the eye focus on near and distant objects, and respond to changes in light intensity? Petr Novák, Wikipedia

  2. Watch the video clip • http://www.bbc.co.uk/learningzone/clips/the-human-eye/1626.html

  3. Complete these activities to learn more about your eyes Iris reflex • Print this slide and look at the picture of the hat with your right eye while covering your left eye. • Move the image closer to your face until the rabbit disappears. • Look in a mirror at the size of your pupils. • Get a friend to shine a torch in your eyes and see how the pupil changes. Find your blind spot • Hold a pencil vertically at arms length. • Focus on an object in the distance in line with the pencil. • Close your left eye. If the pencil jumps to the side then your left eye is dominant. If not try the same with the right. Find your dominant eye

  4. Structure of the eye Suspensory Ligament Sclera Retina Ciliary Muscle Vitreous Humour Pupil Fovea Cornea Optic Nerve Aqueous Humour Iris Blind Spot Choroid

  5. Functions of each part of the eye

  6. Rods and cones • Rod cells work well in dim light but can only see black and white. • The cones only work in bright light. • There are three types of cone cells, red, green and blue.

  7. How do you see? • The image is refracted, first by the cornea and then by the lens.

  8. How do you see? • The image is refracted, first by the cornea and then by the lens.

  9. The Iris • The iris can change the size of the pupil. • This means it controls the amount of light entering the eye. • It does this using circular and radial muscles. Pupil Iris

  10. The Iris • The iris can change the size of the pupil. • This means it controls the amount of light entering the eye. • It does this using circular and radial muscles. • Dim Light • Circular muscles relax. • Radial muscles contract. • Pupils dilate. • Bright Light • Circular muscles contract. • Radial muscles relax. • Pupils constrict. Pupil Iris

  11. How do your eyes focus? • Humans can focus on near or distant objects, but not both at the same time. The lens has to change shape. • This is called accommodation. • This is controlled by the ciliary muscles and the suspensory ligaments.

  12. Accommodation Focusing on a distant object. • Ciliary muscles relax. • Suspensory ligaments tighten. • Lens is pulled thin. Focusing on a close object. • Ciliary muscles contract. • Suspensory ligaments slacken. • Lens becomes fatter.

  13. Problems with vision • Red-green colour blindness is an inherited condition. They do not have certain specialised cells in the retina. • Click hereto take the Ishihara colour blind test. • People with long sight cannot see close things clearly. • People with short sight cannot see things in the distance.

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