EYE (HOMEOSTASIS)

• Accommodation


  The process of changing the shape of the lens to focus on near or distant objects
• Structures of the eye

  • Retina
  • Optic nerve
  • Sclera
  • Cornea
  • Iris
  • Ciliary muscles
  • Suspensory ligaments
• To focus on a near object

  Ciliary muscles contract, suspensory ligaments loosen, lens becomes thicker and refracts light rays strongly
• To focus on a distant object

  Ciliary muscles relax, suspensory ligaments are pulled tight, lens becomes thinner and only slightly refracts light rays
• Two common defects of the eyes are myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina
• Students should be able to interpret ray diagrams, showing these two common defects of the eye and demonstrate how spectacle lenses correct them