The eye


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The eye

  1. 1. Visual Perception
  2. 2. Sensation & Perception <ul><li>What is sensation? </li></ul><ul><li>The detection or awareness of the presence of a stimulus. </li></ul><ul><li>What is perception? </li></ul><ul><li>The process by which we make sense of the sensations. </li></ul>
  3. 3. Object Agnosia
  4. 4. The visual perception system <ul><li>The network of physiological structures involved in vision, that includes: </li></ul><ul><li>* The eyes, </li></ul><ul><li>* The nervous system pathways that connect the eyes and the brain, and, </li></ul><ul><li>* The areas of the brain that process visual information. </li></ul>
  5. 5. Quick Quiz! <ul><li>Name as many parts of the eye as you can… </li></ul><ul><li>How does light enter the eye?? </li></ul>
  6. 6. The Eye <ul><li>Sense organ for vision </li></ul><ul><li>Major parts include: </li></ul><ul><li>* Cornea </li></ul><ul><li>* Pupil </li></ul><ul><li>* Iris </li></ul><ul><li>* Lens </li></ul><ul><li>* Retina </li></ul>
  7. 7. How Light Enters the eye
  8. 8. Anatomy of the Eye
  9. 9. Cornea <ul><li>The transparent coating which covers the iris and the pupil. </li></ul><ul><li>Together with the help of the lens, the cornea refracts the light onto the retina. </li></ul>
  10. 10. Pupil <ul><li>The black hole in the centre of the eye (not an actual structure!). </li></ul><ul><li>The size of the pupil is controlled by the iris. </li></ul><ul><li>When it is very bright, the pupil is small, </li></ul><ul><li>When it’s dark, the pupil grows bigger to allow more light in. </li></ul>
  11. 11. Iris <ul><li>The coloured part of the eye. </li></ul><ul><li>Tiny muscles inside the iris control the amount of light that enters the eye, through the pupil. </li></ul>
  12. 12. Lens <ul><li>Focuses light onto the retina. </li></ul><ul><li>Ciliary muscles attached to each side of the lens, help change the shape of the lens, according to the distance of the object being viewed. </li></ul><ul><li>Once the light has been refracted onto the retina, the image which hits the retina is upside down! </li></ul>
  13. 13. Retina <ul><li>The retina contains millions of photoreceptors – known as rods and cones, that convert light into electrical impulse which are sent along the optic nerve to the brain. </li></ul>
  14. 14. Activity <ul><li>Cut out ‘The Eye’ and label each of the major components. </li></ul><ul><li>Include the definition of each of the components. </li></ul>
  15. 16. <ul><li>So, light reflected off objects travels in a straight line into the eye through the cornea and the pupil… </li></ul><ul><li>…the light travels through the lens, which focuses it on the back of the eye, projecting an upside-down image onto the retina… </li></ul>
  16. 17. <ul><li>…photoreceptors in the retina translate the image into electrical impulses which travel along the optic nerve and into the brain… </li></ul><ul><li>…the brain makes sense of the signals, and tells us what we can see! </li></ul>
  17. 18. Stages of the Visual Perception System <ul><ul><li>Reception - Structures of the eye capture the light and project it onto the retina </li></ul></ul><ul><ul><li>It is at this stage, the photoreceptors detect and respond to light. </li></ul></ul><ul><ul><li>The two types of photoreceptors are called: Rods and Cones. </li></ul></ul><ul><ul><li>The stage where visual information is received. </li></ul></ul>
  18. 19. Rods and Cones <ul><li>Rods are important for night vision </li></ul><ul><li>Rods are also important for peripheral vision </li></ul><ul><li>Cones are important for daylight vision, visual acuity and colour. </li></ul>
  19. 20. <ul><ul><li>Transduction - Photoreceptors (rods and cones) convert electromagnetic energy (‘light’) into electrochemical energy (‘signals’). </li></ul></ul><ul><ul><li>You can remember transduction as the process by which light energy is translated into signals the brain can understand. </li></ul></ul><ul><li>Transmission - Neural information is sent down the optic nerve towards the primary visual cortex. </li></ul>
  20. 21. <ul><ul><li>Selection - Visual discrimination occurs which breaks down the visual stimulus into different features. This occurs in the photoreceptors and visual cortex (feature detectors) </li></ul></ul><ul><ul><li>Organisation and Interpretation - This is the reassembling of features which is then organised and given meaning by the brain. </li></ul></ul>