eye

• give components of eye

  • sclera
  • cornea
  • iris
  • pupil
  • lens
  • retina
  • ciliary muscles and suspensory ligaments
  • optic nerve
• describe function of sclera

  supporting wall of eye
• describe function of cornea

  transparent outer layer that refracts light into eye
• describe function of iris

  contains muscles that control size of pupil
• describe function of lens

  refracts light onto retina
• describe function of retina

  contains receptors sensitive to light intensity and colour
• describe function of ciliary muscles and suspensory ligaments

  control size of lens
• describe function of optic nerve

  send impulses from retina to brain
• describe iris reflex to bright light

  1. circular muscle contract
  2. radial muscle relax
  3. pupil constrict
• describe iris reflex to dim light

  1. radial muscle contract
  2. circular muscle relax
  3. pupil dilate
• describe accommodation

  process of changing shape of lens to focus on near or distant objects
• describe process of focusing on near object

  1. ciliary muscle contract
  2. suspensory ligament slacken
  3. lens becomes fatter
  4. light refracted more
• describe process of focusing on distant object

  1. ciliary muscle relax
  2. suspensory ligament tighten
  3. lens becomes thinners
  4. light refracted less
• describe eye defects

  myopia (short sightedness) and hyperopia (long sightedness) where light does not focus on retina
• give treatment to eye defects

  spectacles, contact lenses, laser eye and lens replacement surgery
• describe treatment of spectacles

  myopia - concave to diverge light rays

  hyperopia - convex to converge light rays