Eyes

• myopia


  short-sightedness
• hyperopia


  long sightedness
• hyperopia details


  1)lens is either wrong shape or eyeball is too short

  2) images brought to focus behind retina

  3)use glasses with convex lens to correct it

  4)convex lens refracts more light so they focus more on retina
• myopia / short-sightedness

  1)occurs when lens is wrong shape or eyeball is too long

  2)images brought to focus infront of retina

  3) use glasses with concave lens to correct this, so light rays frefracted less, and onto retina
• look at near objects


  1. The ciliary muscles contract, which slackens the suspensory ligaments

  2. The lens becomes fat (more curved)

  3. This increases the amount by which it refracts light
• look at distant objects


  1. The ciliary muscles relax, which allows the suspensory ligaments to pull tight

  2. This makes the lens go thin (less curved)

  3. So it refracts light by a smaller amount
• in bright light


  -Circular muscles contract

  -Radial muscles relax

  -Pupil constricts
• in dim light


  -Circular muscles relax

  -Radial muscles contract

  -Pupil dilates
• treatments for vision defects

  -Contact lenses

  -laser eye surgery -replacement lens surgery
• ciliary muscles


  muscles which relax or contract and alter the shape of the lens
• the sclera


  white part of the eye
• the retina


  Light sensitive layer of the eye; contains rods and cones
• the iris


  a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening