The eye

• Structure and function of the cornea

  Transparent outer covering of the eye

  Refracts light entering the eye
• Structure and function of the iris

  Pigmented ring

  Controls the size of the pupil to alter how much light enters the eye
• What is the pupil?

  The opening in the center of the iris that allows light to enter the eye.
• Function of the lens

  Refracts light, focusing it onto the retina
• What is the function of the ciliary muscles and the suspensory ligaments?

  Change the shape of the lens to focus light onto the retina
• Structure and function of the retina

  Light sensitive layer composed of rod and cone cells.

  Converts light energy into neural signals which are sent to the brain via the optic nerve.
• What are rod cells?

  Cells in the retina that are sensitive to low light density
• What are cone cells?

  Cells found in the retina that are sensitive to high light intensity and can detect different colours
• What is the function of the optic nerve?

  Transmits nerve impulses to the brain from the retina
• Why is the iris reflex important?

  It prevents bright light from damaging the retina
• Causes of long-sightedness?

  Eyeball is too short

  Lens is less elastic (age related)
• How is long-sightedness treated?

  Using a convex lens in glasses or contacts

  Laser eye surgery
• What are the causes of short-sightedness?


  Eyeball is too long

  Lens is too thick and too rounded
• How is short-sightedness treated?

  Using a concave lens in glasses or contacts

  Laser eye surgery
• What are cataracts?

  Clouding of the lens in the eye.
• How are cataracts treated?

  The clouded lens is exchanged for a synthetic lens during surgery
• Cause of colour-blindness

  Damage to cone cells in the retina