Vision

• Visual Receptors

  • RODS
  • CONES
• Optic Disc

  Area where the optic nerve leaves the eye and where the retinal vessels enter the eye, visual receptors are absent, called the BLIND SPOT
• Cones


  • Much greater acuity
  • Responsible for vision in bright light or photopic vision
  • Receptors for color vision
  • Contain pigments called iodopsin
• All types of neurons in the retina

  Converge and leave the eye as the OPTIC NERVE
• Rods

  • Extremely sensitive to light
  • Receptors for night vision or scotopic vision
  • Contain photosensitive pigment called rhodopsin or visual purple
• Retina

  Composed of ten layers of cells, outermost layer is the layer of rods and cones (visual receptors)
• Extraocular Muscles

  • LATERAL RECTUS - eyeball abduction
  • MEDIAL RECTUS - eyeball adduction
  • SUPERIOR RECTUS and INFERIOR OBLIQUE - eyeball elevation
  • INFERIOR RECTUS and SUPERIOR OBLIQUE - eyeball depression
• Fovea Centralis


  Area where visual acuity is greatest (high concentration of visual receptors)
• Parts of the eye

  • VISION
  • CORNEA
  • ANTERIOR CHAMBER
  • LENS
  • POSTERIOR CHAMBER
  • RETINA
  • OPTIC NERVE
  • OCCIPITAL LOBE (VISUAL CENTER)
• Layers of Retina

  • 4 Types of Neurons
  • Bipolar cells
  • Ganglion cells
  • Horizontal cells
  • Amacrine cells
• Reflexes

  1. Pupillary light reflex

  2. Consensual light reflex

  3. Accommodation

  4. Dark adaptation

  5. Light adaptation
• Common Eye Problems

  • Vit. A deficiency
  • Strabismus (squint)
  • Astigmatism
  • Cataract
  • Defects of the image