The Eye

• What is the sclera?

  Tough, supporting wall of the eye
• What is the cornea?

  Transparent layer found at the front of the eye to refract light.
• What is the iris?

  Controls size of the pupil and how much light enters. Also controls colour of the eye
• What is the pupil?

  The opening in the center of the iris that allows light to enter the eye.
• What is the lens?

  Focuses light onto retina
• What is the retina?

  The retina is the light-sensitive layer of tissue at the back of the eye that contains receptor cells.
• How is the shape of the eye controlled?

  By the suspensory ligaments and ciliary muscles
• What is the optic nerve?

  Carries impulses from the retina's receptors to the brain
• What happens in bright light?

  • Circular muscles contract
  • Radial muscles relax
  • Pupil gets smaller
  • Reduces amount of light that can enter
• What happens in dim light?

  • Circular muscles relax
  • Radial muscles contract
  • Pupil gets wider
  • More light can enter
• What is accommodation?

  Changing the shape of the lens to suit what we are looking at
• What happens when you look at nearby objects?

  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens gets fatter
  • More light is refracted
• What happens when you look at far away objects?

  • Ciliary muscles relax
  • Suspensory ligaments tighten
  • Lens gets thinner
  • Less light is refracted
• What is another word for long-sightedness?

  Hyperopia
• What is another word for short-sightedness?

  Myopia
• Why does long-sightedness occur?

  When people are unable to focus on near objects

  • Lens is the wrong shape and doesn't refract enough light
  • Images of near objects are brought into focus behind the retina
• Why does short sightedness occur?

  Short sighted people are unable to focus on distant objects

  • Lens is the wrong shape and refracts the light too much
  • The images of distant objects are brought up in focus in front of the retina
• How can vision defects be treated?

  • Contact lenses
  • Glasses (convex for hyperopia and concave for myopia)
  • Laser eye surgery
  • Replacement lens surgery