The eye

• What is the function of the cornea?

  Refracts light as it enters eye
• What is the function of the iris?

  Controls how much light enters the pupil
• What is the purpose of the lens?

  • Further refracts light to focus it on retina
• What is the function of the retina?

  Contains light receptors
• What is the function of the optic nerve?

  Carries impulses between the eye and the brain
• What is the function of the sclera?

  Tough white outer layer that protects eye from injury
• What is accommodation?

  Process of changing shape of lens to focus on near/distant objects
• What is the term for long sightedness?

  Hyperopia
• What is the term for short sightedness?

  Myopia
• What is the problem in a long sighted eye?

  • Point where light rays come together is BEHIND eye, not on retina
  • Light receptors pick up individual rays of light and not the focus point of light
  • Leads to unclear image formed on the retina
• What is the problem in a short sighted eye

  • Light rays are refracted too strongly so come together BEFORE retina
  • Retina picks up on individual rays and not focal point
  • Sends an unclear image as electrical impulse to brain
• What are ways eye defects can be treated?

  • Glasses
  • Contact Lenses (hard/soft)
  • Laser eye surgery
  • Lens replacement
• What is a convex lens and what defect does it treat?

  Convex lens: converging lens Defect treated: hyperopia (farsightedness)
• How does a convex lens work?

  • Converges light rays inwards before lens refracts the light on retina
• What is a concave lens and what defect does it treat?

  Concave lens: diverging lens

  Treats: Myopia
• How does a concave lens work?

  • Diverges rays so they are refracted away from centre point of eyes
  • Rays are then refracted inwards onto retina by cornea and lens
• How dies light enter the eye?

  1. First, the light is refracted by the cornea.
  2. Then it travels through the pupil.
  3. Then it gets further refracted by the lens.
  4. Finally it gets focused on the retina.
• What holds the lens in place?

  • Suspensory ligaments
  • Cilliary muscles