Vision and Optic Pathway

Question 1

What is the consequence of a lesion to the optic nerve?

Answer 1

Monocular vision loss (loss of complete visual field of one eye)

Question 2

What is the consequence of a lesion to the optic chasm?

Answer 2

Bitemporal Hemianopia (loss of nasal retina fibers from both eyes- loss of temporal visual field in both eyes)

Question 3

What is the consequence of a lesion to the optic tract?

Answer 3

Contralateral Homonymous Hemianopia (loss of contralateral visual field in both eyes)

Question 4

What is the consequence of a lesion to the meyer loop?

Answer 4

Contralateral superior quadrantanopia (affect fibers from upper portion of contralateral visual field from both eyes)

Question 5

What is the consequence of a lesion to the optic radiations?

Answer 5

Contralateral inferior quadrantanopia (affect fibers from lower portion of contralateral visual field from both eyes)

Question 6

What is the consequence of a lesion to the primary visual cortex?

Answer 6

Contralateral Homonymous Hemianopia (loss of contralateral visual field in both eyes)

Question 7

Describe the Visual Pathway

Answer 7

Visual stimuli is detected by photoreceptor cells in the retina and synapses on bipolar cells.

Retinal Ganglion cells leave the eye as the optic nerve through the optic canal to optic chiasm. Temporal retinal fibers stay ipsilateral.

At the optic chiasm, nasal retinal fibres decussate and form the optic tract together with the temporal retinal fibres

Optic tract carries visual stimulus to LGN of the thalamus

where information is then carried to the primary visual cortex at calcarine sulcus in the occipital lobe via optic radiations (in temporal and parietal lobes)