Eye

• Cornea function

  refracts light (bends it as enters the eye)
• Iris function

  controls how much light enters the pupil
• Lens function

  further refracts light to focus onto the retina
• Retina

  contains light receptors
• Optic nerve function


  carries impulses between the eye and the brain
• What are the two light receptor cells?

  rods and cones
• Which light receptor cell is more sensetive?

  rods
• Where does light pass through to what?

  eyeball to retina
• What are the three types of cone cells which produce colour vision?


  Short, long, and medium
• What type of action controls the amount of light entering the eye?

  Reflex action
• What controls the pupil's size changes in response to dim or bright or dim light?

  muscles of the iris
• How does the eye respond to dim light?

  • radial muscles contract
  • circular muscles relax
  • pupil dilates
• How does the eye respond to bright light?

  • radial muscles relax
  • circular muscles contract
  • pupil contracts
• What is Myopia?

  short sightedness
• What is Hhyperopia?

  long sightedness
• What are causes of myopia?

  • the eyeball being elongated- so that the distance between the lens and the retina is too big
  • the lens being too thick and curved-so that light is focused in the front of the retina
• What is a treatment special for myopia?

  placing a concave lens in front of the eye
• What are causes of hyperopia?

  • the eyeball being too short- so the distance between the lens and retina is too small
  • a loss of elasticity in the lens- meaning it can't become thick enough to focus
• What is a treatment for hyperopia?

  putting a convex lens in front of the eye
• What are two treatment methods that can be used for both myopia and hyperopia?

  Laser eye surgery and replacement lenses
• What does laser eye surgery do?

  reshapes cornea. more commonly used for myopia
• What are replacement lenses and how do they work?

  artificial lenses are implanted and placed in front of the original lens through a small cut in the cornea to connect an eye deflect.
• cornea

  protects the surface of the eye
• Retina

  senses light
• suspensory ligaments

  holds the lens in place
• sclera

  tough, protective coat
• iris

  regulates amount of light entering the eye
• pupil

  opening to allow light through
• lens


  focuses light on retina
• ciliary muscles

  changes the shape of the lens
• optic nerve 


  transmits impulses to the brain
• How does the eye focus on near ojects?

  Ciliary muscles contract, suspensory ligaments loosen, lens becomes thicker and curved. This allows light to be bent more.
• How does the eye focus on distant objects?

  Ciliary muscles relax, suspensory ligaments tighten, lens becomes thin and flat. This allows the light rays to be bent less.
• Accomodation


  The changing of the shape of the lens to view distant or near objects
• Where does the focus point always need to be?

  On the retina
• What happens to the light rays in myeopia

  Light rays are bent too much
• What happens to the light rays in hyperopia?

  Light rays are bent too little
• Where is the focsl point in myopia?

  In front of the retina
• Where is the focal point in hyperopia?

  Behind the retina