the eye

• what is the sclera?

  the tough supporting wall of the eye
• what is the cornea?

  the cornea is the transparent outer layer found at the front of the eye. it refracts (bends) light into the eye
• what is the iris?

  the iris contains muscles that allow it to control the diameter of the pupil (the hole in the middle) and therefore how much light enters the eye
• what is the lens?


  the lens focuses the light onto the retina (which contains receptors cells sensitive to light intensity and colour)
• how is the shape of the lens controlled?

  Ciliary muscles & suspensory ligaments
• what is the optic nerve?

  the optic nerve carries impulses from the receptors on the retina to the brain
• what does the iris reflex do?

  adjusts the eye to bright light as bright light can damage the retina so you have a reflex to protect it
• what happens when light receptors detect a very bright light?

  a reflex is triggered which makes the pupil smaller, the circular muscles in the iris contract and the radial muscles relax - reducing the amount of light which can enter the eye
• what happens when the eye is in dim light?

  the pupil becomes bigger. the radial muscles contract and the circular muscles relax, making the pupil wider
• what is accommodation?


  its when the eye focuses light by changing the shape of the lens
• how does the eye focus to look at nearby objects?

  1. ciliary muscles contract which slackens the suspensory ligaments
  2. lens becomes more curved
  3. this increases the amount by which it refracts light
• how does the eye look at distant objects?

  1. ciliary muscles relax which allow the suspensory ligaments to pull tight
  2. this makes the lens less curved
  3. refracts light by a smaller amount
• what are long sighted people unable to focus on?

  they are unable to focus on nearby objects
• what is the medical term for long sightedness?

  hyperopia
• when does longsightedness occur?

  • occurs when the lens is the wrong shape and doesn’t refract light
  • images of near objects are brought into focus behind the retina
  • use a convex lens to correct it
• what is a convex lens?

  a lens which curves outwards to correct the shape of the lens
• how do convex lens help longsightedness?

  the lens refracts the light rays so they can focus on the retina
• what are short sighted people unable to focus on?

  they are unable to focus on distant objects
• when does short sighted occur?

  1. occurs when the lens is the wrong shape and refracts the light too much
  2. images of distant objects are brought unto focus in front of the retina
  3. use a concave lens to correct it
• what’s a concave lens?


  a lens which curves inwards to correct the light rays that focus on the retina
• what is the medical terms or short sighted ness?

  myopia
• treatments for vision defects

  • contact lens
  • laser eye surgery
  • replacement eye surgery
• a doctor shines a light onto the eyes of an unconcious man to check wether or not his brain is functioning. suggest how a doctor can tell this


  if the brain is functioning, the persons pupil should become smaller when the doctor shines the light into their eye, as the iris reflex should be triggered (the brain controls the size of the pupil)
• describe how information about light entering the eye is passed to the brain

  information is sent using impulses via the optic nerve
• label the eye

  ..

  A) suspensory ligament

  B) cornea

  C) iris

  D) pupil

  E) lens

  F) ciliary muscles

  G) sclera

  H) retina

  I) optic nerve