Visual Pathway

Question 1

What is the visual pathway from retina to cortex?

Answer 1

3 neuron chain from photoreceptor:

1) Bipolar cells
2) Ganglion cells form optic nerve. Goes to Lateral Geniculate nucleus in thalamus
3) Optic radiation to primary visual cortex

Question 2

What is an outgrowth of the diencephalon?

Answer 2

The optic nerve is an outgrowth of the diencephalon so has meninges covering it to the eyeball

Question 3

What is papillodema?

Answer 3

PAPILOEDEMA = swelling of optic disc
The optic nerve is surrounded by meninges. Incease in CSF pressure can cause the optic nerve to swell.
This compresses the central retinal vein.
Prevents venous drainage.

Question 4

where does the striate cortex lie?

Answer 4

above and below the calcarine sulcus (in occipital lobe)

Question 5

In what optic tract do the does info from the left / right visual fiel run in?

Answer 5

Info from the left visual field runs in the right optic tract to the right hemisphere.

Info from the right visual field runs in the left optic tract to the left hemisphere.

Question 6

What bank of the calcarine sulcus do the upper and lower visual fields go to?

Answer 6

1) Upper visual field goes to LOWER bank of calcarine sulcus.
2) Lower visual field goes to the UPPER bank of the calcarine sulcus

Question 7

Where does info from the centrel of the visual axis go?

Answer 7

Occipital pole

Question 8

Scotoma

Answer 8

localised patch of blindness

Question 9

Anopia

Answer 9

loss of one or more quadrants of the visual field

Question 10

Hemianopia

Answer 10

loss of half of visual field

Question 11

Quadrantanopia

Answer 11

quarter of visual field is lost

Question 12

Homonymous

Answer 12

visual field losses are similar for both sides

Question 13

Heteronymous

Answer 13

Visual field losses are on different sides

Question 14

What lesion can cause monocular blindness?

Answer 14

Optic nerve lesion

Question 15

What lesion can cause Heteronymous Hemianopis?

Answer 15

(loss of left visual field on left eye and right visual field on right eye)

Lesion of optic chiasm

Question 16

What lesion can cause homonymous hemianopia?

Answer 16

(right or left visual field lost on both eyes)

Lesion of optic tract on oposite side of field. E.g if right visual field lost then left optic tract lesion.

Question 17

What lesion can cause central scotoma?

Answer 17

(blindess in centre of visual field)

lesion of occipital pole.

If scotoma elsewhere then lesion will be in optic radiation

Question 18

Where in the thalamus do the optic nerve fibres go?

Answer 18

Lateral Geniculate Nucelus

10% go to midbrain for pupillary light reflex / accomodation reflex

Question 19

If light if shone in the left eye and both pupils constrict what is this?

Answer 19

This is the normal pupillary light relfex.

1) optic nerve detects light
2) synapse with interneurones in the pretectal area.
3) Interneurones synapse with the oculomotor neurones in the edinger westphal nucleus associated with BOTH eyes.
4) Pre-oculomotor neurone synapses with post oculomotor neurone in the ciliary ganglion.
5) innervates eye causing constriction

Question 20

If light is shone in the left eye and only the left eye pupil constricts what is this?

Answer 20

CN 3 (oculomotor lesion)
loss of consensual pupillary light reflex.

The light is being detected by the left optic nerve and transferred via interneurone to EW nucleus. However motor impulse not being relayed to right eye.

Question 21

If light is shone in the left eye and none of the eyes constrict what is this?

Answer 21

CN 2 (optic nerve ) lesion.
Loss of direct pupillary light reflex

Question 22

If light is shone in the left eye and only the right eye constricts what is this?

Answer 22

Lesion of left CN 3 (oculomotor)

Question 23

What 3 things occur when the gaze is transferred from a distant to near object/

Answer 23

1) Accomodation (lens becomes rounded)
2) Pupil constricts (sphincter pupillae)
3) Ocular convergence (medial rectus)