The eye

• what is the conjunctiva?

  • lubricates and protects the surface of the eye
• what is the Sclera?

  • tough outer layer that protects the eye
• what is the cornea?

  • refracts light into the eye - transparent and no blood vessels - oxygen diffuses in from outer surface
• what is the iris?

  • controls diameter of pupil = how much light enters the eye
• what is the lens?

  • focuses light onto retina - covered in rods and cones
  • rods = more sensitive in dim light can't sense colour
  • cones = sensitive to colours - aren't good in dim light - lots in fovea and retina
• what is the optic nerve?

  • carries impulses from receptors to brain
• what happens when you look at distant objects?

  • ciliary muscles = relax
  • suspensory ligaments = tighten
  • lens goes thin
  • refracts small amount of light
• what happens when you look at near distance objects?

  • ciliary muscles = contract
  • suspensory ligaments = slacken
  • lens become more fat
  • increased amount of refracted light
• how do short sighted people find it hard to focus onto distant objects?

  • cornea/lens bends too much light or too long of an eyeball
  • distant objects images are brought into focus in front of retina
• how do long sighted people find it hard to focus onto near objects?

  • cornea/lens doesn't bend enough light or eyeball too short
  • images of near objects brought in focus behind the retina