Accommodation

• What is accommodation?


  The ability to change shape of lens to focus on near or distant objects
• What is the lens surrounded by?


  ciliary muscle
• How is the ciliary muscle connected to the lens?


  By fibres called suspensory ligaments
• What happens when the ciliary muscles relax or contract?

  Change in thickness of lens
• What happens when the eye focuses on near objects

  1. ciliary muscles contract 2. suspensory ligaments loosen 3. Lens is thicker
• What happens to the light if the lens is thicker?


  more light waves refracted
• What happens when the eye focuses on distant objects

  1. ciliary muscles relax 2. suspensory ligaments are pulled tight 3. Lens is pulled thin
• What happens to the light if the lens is thinner?


  Less light rays refracted
• What is long sited also called?


  hyperopia
• What does it mean to be long sited?


  Can focus on distant objects, can't focus on nearby objects If the eyeball is too short the light is focused behind retina. The lens could also be less elastic. This means the lens cannot become thick enough to focus on near objects
• How to treat long sited people?


  Glasses with convex lens. Convex lens partially focuses light before it enters eye
• What is short sight also called?


  myopia
• What does it mean to be short sited?

  Can focus on near objects not distant objects. If there eyeballs is too long the light Is focused in front of retina
• How to treat short sited people?


  Glasses with concave lenses. concave lenses partially unfocused light before it enters eye.
• What other lenses do people use?


  contact lenses refract light in same way as glasses
• What is used in replacement of faulty lenses?


  artificial lenses
• What does laser surgery change?


  Shape of cornea to refract light to greater or lesser extent