The Eye

• 1. Pupil - opening in eye, allows light to pass the back of the eyeball
  2. Iris - ring-shaped muscle that controls the size of the pupil
  3. Cornea - clear, protective layer in front of the eye that refracts light to the pupil
  4. Aqueous humour - clear, watery fluid between the sclera and lens that provides nutrients (for eye health)
• 1. Lens - transparent flexible tissue that refracts the light towards the back of the eye
  2. Ciliary muscles - muscles that change shape of the lens to adjust the focus
  3. Vitreous humour - cloudy, jelly-like substance that maintains the shape of the eyeball
  4. Retina - layer at the back of the eye that contains light sensitive cells
  5. Optic nerve - transmits information from retina to the brain for analysis
• How does the eye work

  1. Light rays entering the eye are refracted by the cornea

  • Amount of light is limited by pupilsize that is adjusted by the Iris

  1. Rays that move through the lens refracting again

  • Lens adjusts its focal length via muscles that stretch it thin or relax it is wider

  1. Light rays cross over in the eye cavity and form a smaller, inverted image or retina
  2. Sensors in the retina turns the image into electrical signals which goes via the optic nerve to the brain
  3. Brain translates the signal, turns it upright and interprets it
• The Retina

  • Robs: detect low levels of light, so they can be used for night vision
  • Cones: less sensitive to light than rods, but can see colour
• Colour Blindness

  • Is when one/more of the colour cone cells are absent, not working, or detect a different colour than normal
• Accommodation

  • Process where ciliary muscles change the shape if the eye lens to focus on distant or nearby objects
  • Changing the focal length of the lens to allow the image to focus on the retina
  • To be able to see object clearly, the focus point for the light rays must be exactly on the retina
  • Focusing problems occur when the lens can’t focus the light on the retina
• Hyperopia

  Description: aka farsightedness bc a person can see objects clearly but near objects are blurry

  Problem: light from nearby objects focuses behind the retina

  Solution: convergent lens
• Myopia

  Description: aka nearsightedness bc a person can see near objects clearly. Far objects are blurry

  Problem: Light from far objects focuses in the front of the retina

  Solution: divergent lens