Visual pathway

visual pathway


The visual pathway is the route by which visual information travels from the eyes to the brain for processing. Here’s a clear breakdown:


1. Components of the Visual Pathway











1. Retina

  • Light is converted into nerve impulses by photoreceptors (rods & cones).

  • Impulses pass through bipolar cells → ganglion cells.

  • Axons of ganglion cells form the optic nerve.

2. Optic Nerve (CN II)

  • Carries signals from each eye to the optic chiasm.

3. Optic Chiasm

  • Fibers from the nasal retina cross to the opposite side.

  • Fibers from the temporal retina remain on the same side.

This crossing ensures that 

left visual field → right brain

right visual field → left brain.

4. Optic Tract

  • Pathway from the optic chiasm to the lateral geniculate body (LGB) of the thalamus.

  • Each tract carries information from the opposite visual field.

5. Lateral Geniculate Body (LGB)

  • Located in the thalamus.

  • Acts as a relay station for visual signals.

6. Optic Radiations (Geniculocalcarine Tract)

Fibers from the LGB spread as:

  • Meyer’s loop (temporal lobe) – carries upper visual field.

  • Parietal lobe fibers – carry lower visual field.

7. Primary Visual Cortex (Area 17, Occipital Lobe)

  • Final destination where visual perception occurs.

Simplified Flow

Retina → Optic Nerve → Optic Chiasm → Optic Tract → LGB → Optic Radiations → Visual Cortex (Occipital Lobe)


Key Clinical Correlation


Lesions along the pathway cause characteristic visual field defects:

1. Optic nerve lesion → Complete blindness in that eye.

2. Optic chiasm lesion (pituitary tumor) → Bitemporal hemianopia.

3. Optic tract lesion → Homonymous hemianopia.

4. Optic radiation lesion (Meyer’s loop) → Quadrantanopia.

5. Occipital lobe lesion → Homonymous hemianopia with macular sparing.


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