The Retina and Central Visual Pathways

Question 1

Label the following fundoscopic image of the retina

Answer 1

Question 2

What is the name given to the painless temporary loss of vision that is sometimes described as a “black curtain over vision”?

What can cause this?

Answer 2

Amaurosis Fugax

Occlusion of the central retinal artery or opthalmic artery

Question 3

Draw a labelled diagram of the visual pathway including visual fields.

Answer 3

Question 4

Nasal fields of vision are detected by which fibres?

Answer 4

Temporal fibres

Question 5

Temporal fields of vision are detected by which fibres?

Answer 5

Nasal fibres

Question 6

Superior fields are picked up by which fibres?

Answer 6

Inferior fibres

Question 7

Inferior fields are picked up by which fibres?

Answer 7

Superior fibres

Question 8

Superior radiations pass through which lobe of the brain?

Answer 8

Parietal lobe

Question 9

Inferior radiations pass though which lobe of the brain?

Answer 9

Temporal lobe

Question 10

Where is the primary visual cortex found?

Answer 10

Occipital lobe

Question 11

With regard to nasal fibres, what is important about the optic chiasm?

Answer 11

The nasal fibres decussate there

Question 12

Do temporal fibres run ipsilateral or contralateral?

Answer 12

Ipsilateral

Question 13

The optic tract runs lateral to which structure?

Answer 13

Lateral Geniculate Nucleus

Question 14

Visual field defects are named based on what?

Answer 14

They are named based on the area of visual loss and not the site of the lesion

Question 15

A lesion before the optic chiasm will produce which type of visual field defect?

Give two examples

Answer 15

Unilateral, ipsilateral

e.g. central scotoma, monocular vision loss

Question 16

A lesion at or after the optic chiasm will produce which type of visual field defect?

Give an example.

Answer 16

Bilateral

e.g. Bitemporal hemianopia (lesion at optic chiasm)

Question 17

A lesion after the optic chiasm will produce which type of visual field defect?

Give examples.

Answer 17

Bilateral and contralateral

e.g. Contralateral homonymous hemianopia

Contralateral superior quadrantopia

Contralateral inferior quadrantopia

Contralateral homonymous hemianopia with macular sparing

Question 18

What conditions might cause monocular blindness due to damage to the optic nerve?

(for both children and for middle aged individuals)

Answer 18

Children: Glioma or Retinoblastoma

Middle aged adults: Optic sheath meningiomas

Question 19

Bitemporal hemianopia is also known as what?

Which conditions cause this visual field defect?

Answer 19

Tunnel vision

Anything causing enlargement of the pituitary gland or anterior communicating artery

Question 20

In a left homonomous hemianopia, on which side will the patient have the lesion and where?

What is the most common cause of this visual field defect?

Answer 20

Right optic tract

Vascular changes (e.g. stroke)

Neoplasia and trauma can also cause this

Question 21

Explain the anatomical basis behind macular sparing.

Answer 21

Occipital lobe has a duel blood supply

• Posterior cerebral artery
• Middle cerebral artery

In a stroke affecting the PCA, the MCA occipital pole will continue to supply and therefore spare macular function

Question 22

Draw out the pupillary light reflex pathway for light entering the left eye. Label the CNs and nuclei involved.

Answer 22

Question 23

Where does CN II (Optic nerve) synapse in the pupillary light reflex?

Which structure do neurones arising from here then go onto supply bilaterally?

Answer 23

In the pretectal area (nucleus)

Edinger Westphal nucleus

Question 24

The accomodation reflex if required for what?

Answer 24

Near vision

Focusing on things close to us

Question 25

What are the "three C's" of the accomodation reflex? Which muscles are each of these carried out by?

Answer 25

**C**onvergence - medial rectus Pupillary **C**onstriction - constrictor pupillae **C**onvexity of the lens - ciliary muscle

Question 26

Image analysis is required to complete the accomodation reflex, what structure is necessary in order to achieve this?

Answer 26

Cerebral cortex

Question 27

Through what nucleus does the accomodation reflex travel to reach the visual cortex?

Answer 27

The lateral geniculate nucleus

Question 29

In which part of the retina are cones particularly common?

Answer 29

The macula

Question 30

Which part of the retina is rich in rods? What is particularly special about rods?

Answer 30

Peripheral retina They work well in low light (more sensitive at night)

Question 31

Does the optic disc contain photoreceptors?

Answer 31

No, it represents the "blind spot"

Question 32

The lateral genicular nucleus projects to which lobe?

Answer 32

Occipital lobe

Question 33

A patient has a tumour arising from the right cavernous sinus and invading medially towards the optic chiasm. Which visual field defect might this result in?

Answer 33

Right nasal hemianopia If the tumour erodes medially, it will destroy fibres from the temporal retina of the right eye which subserves the nasal field of the right eye.

Question 34

Destruction of the optic tract is rare. What would nne the consequence of compression of the right optic tract?

Answer 34

Left homonymous hemianopia without macula sparing -No macula sparing as that is a feature of vascular lesions of the occipital lobe

Question 35

Homonymous superior qudrantanopia is most commonmly seen in lesions to which part of the visual pathway?

Answer 35

Meyer's loop (inferior optic radiation) This contains fibres from the contralateral superior quarter of the field. "Pie in the sky" defect

Question 36

Photoreceptor cells synapse with which retinal cell type predominantly?

Answer 36

Bipolar cells ## Footnote *Can be thought of as the first order sensory neurones of the visual system*

Question 37

Internuclear opthalmoplegia can be caused by damage to which pathway?

Answer 37

Medial longitudinal fasciculus

Question 38

A trauma patient is found to have had a bleed in the region of the left thalamus, including the lateral geniculate nucleus. Which visual signs might they display?

Answer 38

Right homonymous hemianopia * Input from the left optic tract* * Information for the right half of the visual field*

Question 39

Where is the tumour in the image located? Side: Lobe:

Answer 39

Side: Right Lobe: Temporal

Question 40

A 62 year old male with a lesion in the right temporal lobe presents with a **left superior homonymous quadrantanopia** or "pie in the sky" defect. Why? (3)

Answer 40

Left visual field subserved by the right hemisphere. (horizontal plane defect) The upper halves of the visual fields is carried in the temporal lobes, specifically in Meyer's loop. (vertical plane defect) A right temporal lobe lesion can lead to a homomymous loss of left upper field.