the eye

• Need to know structure of the eye

  
• What is the main focus of today's video?

  The structure of the eye and the iris reflex
• What does a cross section of the eye allow us to see?


  It shows the internal structures of the eye
• What is the first structure that light hits when entering the eye?

  The cornea
• Why is the cornea transparent?


  To allow all light to pass through
• How does the cornea obtain oxygen?


  Oxygen diffuses into it from the outside air
• What is the function of the cornea?


  To refract or bend light
• What is the iris?


  The colored part of the eye that controls pupil size
• What is the pupil?


  A gap in the middle of the iris that allows light to pass through
• How does the lens differ from the cornea?


  The lens can change its shape to control light refraction
• What is the role of the retina?


  To receive light and convert it into neural signals
• What are cone cells sensitive to?


  Color of light
• Why can't we see colors in low light conditions?

  Because only rod cells are active in low light
• What is the fovea?


  A special spot on the retina full of cone cells
• What is the function of the optic nerve?


  To transmit impulses from the receptor cells to the brain
• What happens to the pupil in bright light conditions?


  The pupil constricts to allow less light in
• What is the purpose of the iris reflex?


  To protect the retina from damage due to bright light
• What are the two types of muscles in the iris?

  Circular muscles and radial muscles
• How do circular muscles affect the pupil size in bright light?

  They contract, making the pupil smaller
• What happens to the radial muscles in bright light conditions?

  They relax to allow the circular muscles to contract
• What occurs in low light conditions regarding the pupil size?


  The circular muscles relax and the radial muscles contract
• What are the key structures of the eye and their functions?

  • Cornea: Transparent, refracts light, obtains oxygen from air
  • Iris: Colored part, controls pupil size
  • Pupil: Gap allowing light to pass through
  • Lens: Refracts light, changes shape for focus
  • Retina: Contains receptor cells (cone and rod cells)
  • Fovea: Spot for clear vision, full of cone cells
  • Optic nerve: Transmits impulses to the brain
• What are the processes involved in the iris reflex?


  • In bright light:
  • Pupil constricts (smaller)
  • Circular muscles contract, radial muscles relax
  • In low light:
  • Pupil dilates (larger)
  • Circular muscles relax, radial muscles contract
• What is the scientific name for short sightedness?

  myopia
• what happens in a short sighted persons eye?

  the light is refracted too much and the image is formed before it meets the retina
• how do you fix short sightedness?


  with convex lenses that refract the rays outwards so the image isnt refracted too much
• what is the scientific name for long sightedness?


  hyperopia
• What happens to an eye when it has hyperopia?


  the rays aren’t refracted enough and therefore the image forms behind the retina
• how do you fix long sightedness?

  convex glasses as they refract the rays inwards so they meet at the retina
• What is accomidation?


  the process of changing the shape of the lense to focus on nearby or distant objects
• how does the eye adapt to see near objects?


  cilliary muscle contracts, suspensory ligament relaxes, the lense thickens so the light rays are refracted more strongly
• how does the eye adapt to see far away objects?


  cilliary muscle relaxes, suspensory ligament tightens, lense goes thin so light is refracted less
• Why do older people find it harder to focus on close objects?

  the lense hardens making accomidation more difficult
• what is the cause for myopia?


  a lense that is too curved or a particularly long eyeball
• what is the cause for hyperopia?


  a lense that is too flat/thin or a particularly short eyeball
• how can surgery treat myopia?


  reducing the thickness of the cornea so it refracts the light less strongly