Lecture on Visual Pathway and Lesions

Overview of Visual Pathway

• Key Components:
  • Occipital Lobe
  • Eyeball
  • Optic Nerve
  • Optic Chiasm
  • Lateral Geniculate Body
  • Optic Tract (also known as Geniculocalcarine Tract)
• Visual Fields:
  • Blue nerve (Left side):
    • Picks up left nasal field
    • Carries information to the lateral geniculate body
    • Synapses with another nerve to carry information to the occipital lobe
  • Blue nerve (Right side):
    • Captures images from the right temporal field
    • Crosses at the optic chiasm
    • Synapses with neurons of the left lateral geniculate body
    • Information carried to occipital lobe
  • Orange Optic Nerve (Left eyeball):
    • Captures left temporal visual field
    • Crosses at optic chiasm
    • Synapses at the right lateral geniculate body
    • Information relayed to occipital lobe
  • Orange Optic Nerve (Right eye):
    • Captures right nasal visual field
    • Relays information to lateral geniculate body
    • Synapses along optic tract to occipital lobe

Effects of Lesions on Vision

• Left Optic Nerve Lesion (A):
  • Blindness in left eye
  • Known as "Left Anopia"
• Optic Chiasm Lesion (B):
  • Caused by pituitary tumors
  • Blindness in temporal visual field of both eyes
  • Known as "Bitemporal Hemianopia"
• Post-Optic Chiasm Lesion (C):
  • Loss of left nasal and right temporal fields
  • Known as "Right Homonymous Hemianopia"
• Nerve Tract Bundle Lesion (D):
  • Causes "Right Homonymous Superior Quadrantanopia"

Eye Structures and Related Conditions

• Optic Disc
  • Location where optic nerve and vessels pass
• Macula
  • Contains "Fovea" (high concentration of cones for high resolution)
  • Damage leads to loss of central vision
• Conditions
  • Central Scotoma/Macular Degeneration:
    • Damage to macula causes loss of central vision
  • Glaucoma and Retinitis Pigmentosa:
    • Preserved macula but loss of peripheral vision (tunnel vision)

Additional Visual Pathway Information

• Midbrain
  • Receives optic nerve information
  • Involved in eye reflexes (blink and light reflex)

This overview provides a basic understanding of the visual pathways and potential implications of lesions along different points of the pathway.