Visual Pathway

Question 1

Define visual field

Answer 1

everything you see with one eye

Question 2

What is two visual field tests

Answer 2

Confrontation test - move hands till appears in patients visual field

Automated perimetry - Patients focus on central light on the machine and press joystick when see additional light appear in their periphery

Question 3

What is the purpose of the confrontation and automated perimetry tests

Answer 3

Map out visual field

Question 4

does Visual acuity test your visual field

Answer 4

No, Measures the distance you can read from

Question 5

What is the 4 basic steps in the visual pathway

Answer 5

Optic nerve
Optic chiasma
Optic tract
Optic radiation

Question 6

Where does the optic nerve leave the orbit through

Answer 6

The optic foramen into medial cranial fossa

Question 7

What is the point in the visual pathway were nerves merge together

Answer 7

Optic chiasma

Question 8

What occurs at the point of the optic chiasma

Answer 8

Nasal fibres cross to the opposite sides

Question 9

Where does the optic tract synapse

Answer 9

At the lateral geniculate body in the thalamus

Question 10

What fibres does the optic tract contain

Answer 10

Optic tract contain fibres from the (lateral) temporal half of the ipsilateral eye and the crossed over over nasal fibres from the contralateral eye

Question 11

Where does the optic tract axons synapse

Answer 11

At the lateral geniculate body in the thalamus

Question 12

How does the optic nerves travel through the cerebral hemisphere

Answer 12

As optic radiation

Question 13

Where does the optic radiation travel to

Answer 13

The optic radiation passes behind the internal capsule (retro-lentiform fibres) to reach the primary visual cortex in the occipital lobe

Question 14

What does the primary visual cortex receive from optic radiation

Answer 14

an action potential

Question 15

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

Answer 15

When the nasal fibres cross over at the chiasma

(nasal go to the opposite optic tract and temporal remain in thee same optic tract)

Therefore the left visual field fibres are all traveling in the right optic tract which then sends action potential to the right occipital lobes visual cortex

Question 16

What occurs when the right optic nerve is damaged

Answer 16

Right eye blindness

Question 17

What occurs when the optic chasm is disputed in the middle

Answer 17

Nasal fibres are damaged meaning the temporal field of vision is affected but the nasal field of vision is fine
= Bitemporal hemianopia

Question 18

What is a common cause of bitemporal hemianopia

Answer 18

Pituitary gland enlargement as sits below point of optic chiasma

Question 19

What occurs when the right optic tract is damaged

Answer 19

The left visual field of both sides is lost

Causing contralateral homonymous hemianopia

Question 20

When right optic tracts temporal fibres are damaged what visual field does this affect

Answer 20

Damaged temporal fibres from the right optic tract means nasal field vision from right eye is lost

Question 21

When right optic tracts nasal fibres are damaged what visual field does this affect

Answer 21

Damaged nasal fibres from the right optic tract means temporal visual field from the left eye is lost

Question 22

Why is it “contralateral” homonymous hemianopia

Answer 22

As the damages occurs in one of the optic tact but affects both eyes

Question 23

When visual lesions are symmetrical what does this usually indicate

Answer 23

lesion is occurring in optic tract

Question 24

When either left/right visual field is lost n both eyes, where is the lesion

Answer 24

In the opposite optic tract

Question 25

What occurs when there is optic radiation damage

Answer 25

Contralateral homonymous hemianopia

Question 26

Define hemianopia

Answer 26

The loose of half your field of vision