eye

• What is the eye?

  A sense organ containing receptors sensitive to light intensity and colour.
• What is hyperopia?


  Long slightness - defect where people cannot focus on near objects.
• What is myopia?


  Short sightedness - defect where people cannot focus on far objects.
• What are the parts of the eye?

  • Lens
  • Cornea
  • Iris
  • Suspensory ligaments
  • Ciliary muscles
  • Optic nerve
  • Retina
  • Sclera
• What is the function of the lens?

  Changing the thickness to focus the light rays on the retina.
• What is the function of the cornea?

  Refracting light rays entering the eye.
• What is the function of the iris?

  To cause the pupil to change size.
• What is the function of the suspensory ligaments?

  Connect the ciliary muscles to the lens.
• What is the function of the ciliary muscles?

  To contract and relax to change the thickness of the lens during accommodation.
• What is accommodation?


  The process of changing the shape of the lens to focus on near/distant objects.
• What is the function of the optic nerve?

  Contains sensory neurones that transmits to impulses to the brain, where the image is processed and perceived.
• What is the function of the retina?

  Contains receptors to detects the light intensity and colour and to generate electrical impluses.
• What is the function of the sclera?

  To protect the surface of the eye.
• How does the eye focus on far object?

  • The ciliary muscles relax
  • So there is a larger diameter
  • Suspensory ligaments tighten
  • Lens is pulled thin and refracts light less
  • Light rays are focused on the retina
• How does the eye focus on a near object?

  • The ciliary muscles contract
  • So there is a smaller diameter
  • Suspensory ligaments loosen
  • Lens is thickened and refracts light more
  • Light rays are focused on the retina
• What are the characteristics of myopia?


  • lens too thick
  • eyeball too long
  • light rays focused in front of the retina
• What are the characteristics of hyperopia?


  • lens cannot be thickened
  • eyeball to short
  • light rays focused behind the retina
• How is myopia treated?

  • Using a concave (diverging) lens to refract light rays outwards
  • Light rays focused on the retina
• How is hyperopia treated?

  • Using a convex (converging) lens to refract the light rays inwards
  • Light rays focused on the retina
• How does the eye respond to dim light?

  The radial muscles contract causing dilation of the pupil.
• How does the eye respond in bright light?

  The circular muscles respond causing constriction of the pupil.