Human Eye Notes

Human Eye Structure

  • The human eye is analogous to a camera.
  • Light enters through the pupil, is focused by the lens, and forms an image on the retina.

Key Parts of the Eye

  • Cornea: Clear covering, protects the eye; helps focus light.
  • Pupil: Central hole; size adjusts based on light levels.
  • Iris: Colored part, controls light entry by adjusting pupil size.
  • Lens: Transparent structure; a converging lens that alters shape for focusing.
  • Retina: Contains light-sensing nerve cells:
    • Rods: Detect black and white.
    • Cones: Detect colors (red, blue, green).
  • Optic Nerve: Sends visual signals from the retina to the brain.

Vision Process

  • Light must reach the retina for vision.
  • The brain interprets images, flipping the inverted image from the retina.
  • Squinting adjusts lens shape for clearer focus.

Vision Deficiencies

  • Myopia (nearsightedness): Image falls short of the retina; corrected with a diverging (concave) lens.
  • Hyperopia (farsightedness): Image forms beyond the retina; corrected with a converging (convex) lens.

Eye Health Applications

  • Laser Eye Surgery: Reshaping the cornea to reduce dependence on corrective lenses.
  • Cataracts: Clouding of the lens with age; surgery removed cloudy lens to restore vision.

Blind Spot

  • Area where the optic nerve meets the retina; lacks rods and cones.

Color Blindness

  • Defects in one or more cones can cause color blindness; most commonly red-green, linked to X chromosome.