Eye

• The eye is a sense organ
• The retina contains receptor cells that are sensitive to the brightness and colour of light
• The optic nerve carries impulses from the retina to the brain
• The sclera forms a tough outer layer , with a transparent region at the front called the cornea
• The cornea is a transparent region at the front of the eye
• The iris controls the size of the pupil and the amount of light reaching the retina
• The ciliary muscles and suspensory ligaments change shape to focus light onto the retina
• Accommodation is the process of changing the shape of the lens to focus on near or distant objects
• What does the eye do to focus on a near object?

  The ciliary muscles contract - The suspensory ligaments loosen - The lens becomes thicker and refracts light rays strongly

  
• What does the eye do to focus on a distant object?

  The ciliary muscles relax - The suspensory ligaments tighten- The lens becomes thinner and refracts light rays slightly

  
• Two common defects of the eye are myopia (short sightedness) and hyperopia (long sightedness)
• Myopia and Hyperopia occur when rays of light do not focus on the retina
• Myopia and hyperopia are generally treated with spectacle lenses
• New technologies that are used to treat eye defects include - contact lenses , laser surgery and replacement eye lenses
• Laser eye surgery is used to change the shape of the cornea
• When your eyes are exposed to bright light , your pupils automatically become smaller - they do this to protect the cornea from damage
• Complete the diagram of the eye below

  A) Cornea

  B) Suspensory Ligament

  C) Optic Nerve

  D) Retina

  E) Sclera

  F) Lens

  G) Ciliary Muscle

  H) Pupil

  I) Iris