eye

• myopia


  Shortsighted.
• hyperopia


  farsighted
• what causes myopia

  eyeball is too long; focal point is in front of the retina
• what causes hyperopia

  eyeball is too short; focal point is behind retina
• how to fix myopia

  concave lens
• how to fix hyperopia

  convex lens
• alternatives to glasses

  Contact lenses, laser eye surgery and replacement lens surgery.
• screla

  white of the eye
• Cornea


  the transparent layer forming the front of the eye - focuses light onto retina
• lens


  Focuses light onto retina
• ciliary muscle and Suspensory ligaments. 


  controls the shape of the lens for fine focusing
• pupil


  middle of eye where light enters
• iris

  muscles that control the size of pupil by constricting or dilating
• cones

  detect colour of light
• rods


  detects light intensity
• optic nerve


  neurone carries impulses from the eye to the brain
• In dim light the pupil

  dilates
• in bright light the pupil

  constricts
• To make pupil dialate

  circular muscles relax

  radial muscles contract
• To make pupil constrict

  circular muscles contract

  radial muscles relax
• Why does the pupil constrict and dialate?

  to focus the object on the retina and protect it from receving too much light.
• Constricting pupil

  Circular

  Contract

  Radial

  Relax
• When we look at distant objects the ciliary muscle relaxes pulling the suspensory ligaments constrict thinning the lens.
• When we look at an object close up the ciliary muscle contracts causing the suspensory ligaments to become slack allowing the lens to bulge outwards making it more convex.
• how does the nervous system detects and responds to a torch being shone into the eye.

  Photoreceptors in the retina detect a change in light. A sensory neurone sends an impulse. The impulse is passed to a relay neuron in the brain. An impulse is sent along a motor neuron to the muscles in the iris. The circular muscles in the iris contract The pupil reduces in size
• Close object Ciliary muscles

  Contract

  Suspensory ligaments

  Slacken

  Lens

  Lanky
• suspensory ligaments


  A ring of fibres that connect ciliary muscles to the lens
• Accomodation


  The process where the eye focuses on objects