Eye

• The cornea refracts light into the eye
• The iris controls how much light enters the pupil
• The lens refracts light to focus it on the retina
• The ciliary muscles and suspensory ligaments alter the shape of the lens, based on how much light is refracted.
• The retina is covered in rods and cones, which detect light

  Rods can't detect colour

  Cones detect colour
• The optic nerve send impulses from the receptors in the eye to the brain
• The eye

  • Cornea
  • Iris
  • Pupil
  • Lens
  • Ciliary muscle
  • Suspensory ligament
  • Retina
  • Optic nerve

  
• To look at distant objects:

  • Ciliary muscles relax
  • Suspensory ligaments contract

  Produces a less rounded shape = light refracted less
• To look at closer objects:

  • Ciliary muscles contract
  • Suspensory ligaments relax

  This produces a rounder shape = light refracted more
• Long Sighted = Lens doesn't refract light enough

  Fixed by a Convex lens (LSCV)

  
• Short sighted = Lens refracts too much

  Fixed by a concave lens (SSCC)

  
• Colour blindness is caused by rods and cones not working correctly.

  Fixed by tinted lense.