Lecture 5-Retina And Central Visual Pathways

Question 1

What do bipolar cells synapse with?

Answer 1

Axons of ganglia which converge to form the optic nerve

Question 2

What does the retinal pigment epithelium prevent?

Answer 2

Excessive refraction by absorbing light as it has melanin

Question 3

What are horizontal cells?

Answer 3

Cells for lateral vision, they prevent receptors next to the point of strongest stimulation from sending signals

Question 4

What is amaurosis fugax?

Answer 4

“Black curtain falling over vision” is indicative of occlusion of central retinal artery

Question 5

Which fibres form the optic chiasm?

Answer 5

Nasal fibres

Question 6

Where does the optic tract run to?

Answer 6

Lateral geniculate nucleus

Question 7

Where do the superior radiations run through?

Answer 7

Parietal lobe

Question 8

Where do the inferior radiations run through?

Answer 8

Temporal lobe

Question 9

Which fibres are responsible for temporal field of vision?

Answer 9

Nasal fibres

Question 10

Which fibres are responsible for nasal field of vision?

Answer 10

Temporal fibres

Question 11

What causes monocular blindness?

Answer 11

Lesion of the optic nerve eg optic nerve glioma or retinoblastoma in children, optic sheath meningiomas in adults

Question 12

What causes bitemporal hemianopia?

Answer 12

Lesion at the optic chiasm

Question 13

What causes left homonomous hemianopia?

Answer 13

Lesion of right optic tract, affecting right temporal and left nasal fibres (stroke common)

Question 14

What causes right homonomous hemianopia?

Answer 14

Lesion of left optic tract

Question 15

Describe the blood supply of the occipital lobe

Answer 15

-Posterior cerebral artery -Middle cerebral artery -> occipital pole

Question 16

Why is there macular sparing in a stroke affecting the posterior cerebral artery?

Answer 16

Middle cerebral artery isn’t damaged and this supplies the occipital pole which represents the macula therefore macular function is spared

Question 17

In the light reflex, where does the afferent optic nerve synapse?

Answer 17

In the pretectal area

Question 18

What are the three Cs of the accommodation reflex?

Answer 18

Convergence (medial rectus)
pupillary Constriction
Convexity of the lens

Question 19

Why is the fovea represented as a thin nerve fibre layer on an optical coherence tomogram (OCT)?

Answer 19

Fewer cells for light to pass through -> high definition

Question 20

What is the medial longitudinal fasciculus?

Answer 20

Tract which connects all extra-ocular muscle nuclei

Question 21

How does the medial longitudinal fasciculus aid in gaze fixation?

Answer 21

MLF receives input from vestibular apparatus and this informs eye muscles about the position of the head in order to be able to fixate gaze

Question 22

How does multiple sclerosis affect the MLF?

Answer 22

Demyelinates white matter (MLF tract) so conduction is slowed down and coordination is impaired