Parts of the Eye

• Sclera


  Protects and supports eyeball; white, fibrous external layer of eye
• Cornea


  Let light into eye; bends light rays into the eye
• Choroid

  Absorbs scattered light and contains blood vessels
• Iris


  Regulates the amount of light entering the eye
• Pupil


  Opening for light to enter the eye; controlled by the iris
• Ciliary Muscles


  Changes the shape of the lens
• Rods

  Photoreceptors that are sensitive to brightness; allow you to see black and white
• Cones

  Photoreceptors that are sensitive to different wavelengths of light; are either red, green, or blue colours
• Fovea Centralis


  Contains a high density of cones, and provides acute vision
• Retina


  contains photoreceptors
• Lens


  Focusses light rays onto the fovea centralis; controlled by the ciliary muscles
• Optic Nerve


  Transmits sensory information to the brain
• Aqueous Humour


  maintain shape of lens; nourish surrounding cells
• Distance Accommodation

  ciliary muscles relax, suspensory ligaments tighten, lens flatten
• Proximity Accommodation

  ciliary muscles contract, suspensory ligaments loosen, lens round
• Myopia

  eyeball too long; lens round
• Cure for Myopia

  Concave lens
• Hyperopia

  eyeball too short; lens flat
• Cure for Hyperopia

  Convex lens
• Glaucoma

  aqueous humour not drained; pressure in the eye too strong blood vessels rupture
• Cataracts

  clouding of lenses
• Vitreous Humour

  maintain shape of eye
• 3 layers of the Retina

  1. Ganglion layer
  2. Bipolar layer
  3. Photoreceptor layer
• The optic nerve is made up of ganglia cells that carry information from photoreceptor to brain.
• Rods detect light intensity, while cones detect colour.