1. Chapter 12 Review Light and Vision

2. Category: The Eye Give the name and function of the eye part indicated by #3 (the thin layer between #1 and #2). Choroid (coat). Supplies blood to the retina. 1 2 3 4 5 6 7 8

3. What are the secondary light colours? Cyan, yellow, and magenta. They are formed from combining two of the primary light colours. Category: Colour Vision

4. What makes the pupil smaller or bigger? Why? The iris makes the pupil smaller or bigger depending on how much light is present. Small if lots of light; large if a small amount of light. 4 Category: The Eye

5. Which of the following can be corrected using laser eye surgery: myopia, hyperopia, astigmatism, presbyopia? All but presbyopia can be corrected with laser eye surgery. Presbyopia occurs naturally with age, so it cannot be reversed. 5 Category: Vision and Vision Problems

6. What does it mean if someone has myopia? Nearby objects can be seen clearly, but distant objects appear out of focus. (Nearsightedness). 6 Category: Vision and Vision Problems

7. What is the name of the jelly-like substance that fills the eye between the lens and retina and what is its function? Vitreous humour. Helps keep the eye’s shape. 7 Category: The Eye

8. What is a blind spot? Where the optic nerve attaches to the retina. There are no sensory receptors (rods and cones) in this area, therefore no image is produced there. 8 Category: The Eye

9. Explain what changes occur in the eye when you enter a dark room after being out in the bright sunshine. In the bright sunshine, the iris contracts and the pupil is small to regulate the amount of light entering the eye. When you enter a dark room, the iris will dilate (expand) the pupil to allow more light to come in so that you can see better in the dark. It takes a bit of time for the pupil to get to the right size.

10. What is the complementary light colour of magenta? Green, since green and magenta (red + blue) would produce white light. Category: Colour Vision

11. What is normal vision? What is 3/6 vision? What is 10/6 vision? 6/6 - If you are standing 6 meters away, you are able to read the chart (normal vision). 3/6 – You need to stand 3 meters away to read what can normally be read at 6 meters (worse than normal vision). 10/6 – You can stand 10 meters away to read what can normally be read at 6 meters (better than normal vision). 11 Category: Vision and Vision Problems

12. Name one reason why a person might have myopia. Where is the clear image formed in a myopic eye? Their eyeball is too long OR the cornea/lens system refracts light too much. The focused image is formed in front of the retina. 12 Category: Vision and Vision Problems

13. When you combine all three primary colours, what is produced? White light. 13 Category: Colour Vision

14. Category: The Eye What is the name and function of the fluid found between the cornea and lens? Aqueous humour. It supplies oxygen and nutrients to parts of the eye and helps the front of the eye keep its shape.

15. Why is a convex lens used to correct hyperopia? With hyperopia, light rays converge behind the retina so if a convex lens is used the rays will converge at a steeper angle. With the right thickness of lens, the image will then be focused exactly on the retina. 15 Category: Vision and Vision Problems

16. What colour of light would be created if blue light overlaps with green light? Cyan. Category: Colour Vision

17. What is the difference between LASIK and PRK laser eye surgery? In LASIK surgery, a flap of the cornea is cut back and a laser is used to remove some of the cornea underneath. With PRK surgery, no flap is involved. Corneal tissue is removed directly from the eye’s surface. Category: Vision and Vision Problems

18. What three colours are the cones in your retina sensitive to? The cones are sensitive to green, red, and blue light. Category: Colour Vision

19. What chart is used to compare a person’s vision with normal vision? The Snellen Eye Chart. 19 Category: Vision and Vision Problems

20. Why do people start to suffer from presbyopia later on in life? The lens and cornea lose their elasticity so that both nearby and distant objects appear out of focus. 20 Category: Vision and Vision Problems

21. What is the purpose of the sclera? To protect and keep the shape of the eyeball. 21 Category: The Eye

22. What are complementary light colours? Two colours of light that when added together, produce white light. Category: Colour Vision

23. Where is the image produced in the eye and what is its attitude and type? The image is produced on the retina. It is inverted and real (since it is being put on a screen – the retina). 23 Category: The Eye

24. What two eye parts are mainly responsible for focusing light onto the retina? Which of the two does about 80% of the refraction? Cornea and lens. The cornea does most of the refraction. 24 Category: The Eye

25. What colour do we see when light containing only red and green wavelengths enters our eyes? Yellow. Category: Colour Vision

26. What colour would you see if an equal number of red and blue cones in your eyes were activated? Magenta. Category: Colour Vision

27. What is the complementary light colour of blue? Yellow, since blue and yellow (red + green) would produce white light. Category: Colour Vision

28. Category: The Eye Give the name and function of the eye part indicated by #8. Cornea. First part responsible for focusing light onto the retina. Also protects the front of the eye. 1 2 3 4 5 6 7 8

29. What refractive vision problem is often caused by the eye being too short? Where is the clear image formed in this case? Hyperopia (farsightedness). The focused image would be formed behind the retina. 29 Category: Vision and Vision Problems

30. Explain how you focus on distant objects. Include how light rays are entering the eyes. Light rays are coming into the eye nearly parallel. The ciliary muscles relax and the lens gets “thin” so that the image is focused on the retina. 30 Category: The Eye

31. Explain what you would see if you looked at a bright red circle for a long time then looked at a white surface. Why? You would see a cyan circle. Staring at the red circle causes the red cones to tire, so that when you look at a white surface (reflecting all three primary light colours), only the blue and green cones respond – this is seen as cyan. Category: Colour Vision

32. What is astigmatism and what causes it? When the cornea has an irregular curvature (like a football). Light entering the eye is focused on more than one focal point. This causes vision to be blurred at any distance. 32 Category: Vision and Vision Problems

33. What does it mean if someone has a refractive vision problem? One or both of their eyes is unable to focus an image properly onto the retina, so that it appears blurry. 33 Category: Vision and Vision Problems

34. What is red-green colour blindness and why does it occur? The inability to distinguish something red against a green background. This occurs when some of the cones in the retina do not respond properly to the light received. Category: Colour Vision

35. Category: The Eye Give the name and function of the eye part indicated by #4. Optic nerve. Carries nerve signals to the brain. 1 2 3 4 5 6 7 8

36. Explain how you focus on nearby objects. Include how light rays are entering the eyes. Light rays are coming into the eye at an angle. The ciliary muscles contract and the lens gets “fat” so that the image is focused on the retina. 36 Category: The Eye

37. What type of lens is used to correct myopia? Why? A concave lens is used because it diverges light more before it enters the eye so that the image is focused onto the retina. 37 Category: Vision and Vision Problems