Visual Pathway

Question 1

Define visual field

Answer 1

everything you see with one eye

Question 2

List the 4 basic steps in the visual pathway.

Answer 2

1. Signal exits eye via optic nerve.
2. Medial fibers from each eye cross over at optic chiasma.
3. Signal continues along optic tract to
4. Continues via optic radiation to primary visual cortex in the occipital lobe.

Question 3

What occurs at the point of the optic chiasma

Answer 3

Nasal fibres cross to the opposite sides

Question 4

Where does the optic tract synapse

Answer 4

At the lateral geniculate body in the thalamus

Question 5

Which nerve fibers are found in the optic tract?

Answer 5

1. Lateral (temporal) fibers from the ipsilateral eye.

2. Medial (nasal) fibers from the contralateral eye.

Question 6

Where are the lateral geniculate nuclei located?

Answer 6

In the thalamus.

Question 7

Where is optic radiation located?

Answer 7

In cerebral white matter.

Question 8

Why does the right visual cortex see the left half of the visual field?

Answer 8

Because the lateral half of the retina receives input from the medial (nasal) fibers of the contralateral (right) eye.

Question 9

What happens if an optic nerve is damaged before it reaches the chiasma?

Answer 9

1. Total loss of depth perception.

2. Loss of peripheral vision on ipsilateral side.

Question 10

What happens if the optic chiasma is cut?

Answer 10

1. Medial (nasal fibers) from each eye are damaged.
2. Loss of lateral (temporal) field of vision
3. Medial (nasal) is field of vision is unaffected.

Question 11

What happens to vision after a stroke affecting the left visual cortex?

Answer 11

Blindness in right half of visual field.

Question 12

What happens if neural damage occurs beyond the optic chiasma (tract, thalamus or visual cortex)?

Answer 12

Loss of part or all of the image from the contralateral visual field.

Question 13

Define and describe nyctalopia.

Answer 13

Night blindness is a condition in which rod function is compromised, impairing ability to drive safely at night.

Question 14

What is the most common cause of nyctalopia. How is it treated.

Answer 14

Prolonged vitamin A deficiency, leading to rod degeneration. If administered early, may be treated with supplements.

Question 15

Define and describe retinitis pigmentosa.

Answer 15

1. A group of degenerative retinal diseases that destroy rods.
2. Occurs when pigment epithelial cells are unable to recycle tips of rods as they slough off.