the eye

• what are the receptors of the eye sensitive to?

  • light intensity
  • colour
• describe the structure & function of the retina

  • light-sensitive layer found at the back of the eye
  • contains receptor cells which are sensitive to light intensity & colour
  • light stimulates the retinal cells, resulting in impulses being sent to the brain
• describe the structure & function of the optic nerve

  • connects the eye and the brain
  • carries impulses from the receptors on the retina to the brain
• describe the structure & function of the sclera

  • tough supporting wall of the eye
  • protects its internal structures
• describe the structure & function of the cornea

  • curved transparent outer layer found at the front of the eye
  • refracts light into the eye
• describe the structure & function of the iris

  • contains circular muscles & radial muscles that allow it to control the size of the pupil
  • controls how much light enters the eye
• describe the structure & function of the ciliary muscles & suspensory ligaments

  • control the shape of the lens
• A - ciliary muscle

  B - suspensory ligaments

  C - pupil

  E - cornea

  F - lens

  H - retina

  K/L - optic nerve

  M - sclera

  
• how does the iris alter the size of the pupil in bright light?

  • circular muscles contract
  • radial muscles relax
  • this makes the pupil smaller (to avoid retinal damage)
• how does the iris alter the size of the pupil in dim light?

  • circular muscles relax
  • radial muscles contract
  • this makes the pupil larger (so more light enters)
• how does the eye focus on a nearby object?

  • ciliary muscles contract to have a smaller diameter
  • suspensory ligaments loosen
  • lens becomes more thicker & more curved - light rays are refracted more strongly
  • light rays focus on retina
• how does the eye focus on a faraway object?

  • ciliary muscles relax
  • suspensory ligaments tighten
  • lens becomes thinner - light rays are refracted weakly
• what is accommodation?

  alteration of the lenses shape in order to focus on near or distant objects
• what is myopia?

  • shortsighted
  • lens is too curved and refracts light too much
  • as a result, light is focused in front of the retina
• how is myopia treated?

  • concave lenses
  • they spread out light rays so that they are focused on the retina

  
• what is hyperopia?

  • longsighted
  • lens is too flat and light is focused behind the retina
• how is hyperopia treated?

  • convex lenses
  • refract light rays more
  • light rays focus on retina
• what are some new technologies that treat eye defects?

  • hard & soft contact lenses
  • laser surgery which changes the shape of the cornea
  • replacement lens surgery