The Eye

• what is the cornea?

  Transparent outer layer of the eye that refracts light into the eye
• what is the sclera?

  tough, supporting wall
• what is the lens?

  focuses light onto the retina
• what is the retina?

  contains receptor cells sensitive to light intensity and colour
• what is the iris?

  contains muscles that allow it to control the diameter of the pupil to control how much light enters the eye
• what is the optic nerve?

  carries impulses from the receptors on the retina to the brain
• the shape of the lens is controlled by the cilliary muscles and suspensory ligaments
• what happens to the eyes in a dim/dark room?

  1. light receptors in the eye detect dim light
  2. reflex is triggered making pupil larger
  3. radical muscles contract
  4. circular muscles relax
  5. increases the amount of light that can enter eye
• what happens to the eyes in a bright room?

  1. light receptors in the eye detect very bright light
  2. reflex is triggered making pupil smaller
  3. circular muscles contract
  4. radial muscles relax
  5. reduces the amount of light entering the eye
• what happens to the eye when focusing on a distant object?

  1. ciliary muscles relax
  2. suspensory ligaments are pulled tight
  3. lens becomes thin(less curved) and pulled thin and only slightly refracts light rays.
• what happens to the eye when focusing on a near object?

  1. ciliary muscles contract
  2. suspensory ligaments loosen
  3. lens are thicker (more curved)
  4. the lens is then thicker and refracts light rays strongly
• what is the name for long-sighted?

  Hyperopia
• what is the name for shortsighted?

  Myopia
• what is the issue with long sightedness?

  they cannot focus on nearby objects
• what happens during long-sightedness?

  1. lens is the wrong shape and doesn't refract light enough
  2. eyeball is too short = light focused at the point behind retina
• what happens during long-sightedness for old people?

  1. lens becomes less elastic= lens cannot become thick enough to focus on near objects
• how can long sight be treated?

  by using glasses with convex lens
• what is convex lens?

  focuses the light before it enters the eye

  
• what is the issue with short sightedness?

  cannot focus on distant objects
• what happens during short sightedness?

  1. eyeball can be too long = light focuses at the point infront of retina
  2. lens is too thick
• how can short sightedness be treated?

  using glasses with concave lens
• what is concave lens?

  Diverging lens that unfocused the light before it enters the eye

  
• other treatments for abnormal eyes:

  1. contact lenses
  2. glasses
  3. laser surgery = used to change shape of cornea so refraction of light is much greater or lesser
  4. artificial lens to replace original lens