Retina and central visual pathways

Question 1

Describe the layers of the back of the eye. (5)

Answer 1

From the outer layer in:
Choroid layer
Pigmented layer 
Photoreceptive layer (rods and cones)
Horizontal and bipolar cell layer 
Axon layer of ganglionic cell axons to the optic nerve.

Question 2

Describe the functions of these eye structures: (4)
Pigmented layer 
Photoreceptors cells 
Horizontal cells 
Bipolar cells

Answer 2

Pigmented layer - Stops glare
Photoreceptor cells - rods and cones - colour and black/white vision
Horizontal cells - enhance edges and contrast
Bipolar cells - primary neurones that communicate with ganglion.

Question 3

What four things can you look for on fundoscopy? (4)

Answer 3

Retinopathies, vascular occlusion, macula degeneration, papilloedema.

Question 4

Describe the three key facts needed to work out which quarter of the retina ends up where. (3)

Answer 4

Right side of the retina - right tract.
Nasal fibres decussate.
Inferior fibres - inferior radiation.

Question 5

Describe the path of the impulses of the image of Marcus naked seen in the lower nasal visual field of the right eye. (7)

Answer 5

Upper, temporal, right Retina 
Right optic nerve 
Optic chiasm
Right optic tract 
Right  lateral geniculate ganglion
Right superior radiation
Primary visual cortex.

Question 6

Describe the path of the impulse of the image of a cute doggo seen in the lower temporal visual field of the right eye. (7)

Answer 6

Upper, nasal quadrant of the right retina 
Right optic nerve 
Optic chiasm 
Left optic tract
Left lateral geniculate ganglion
Left superior radiation 
Primary visual cortex

Question 7

Describe the path of the impulse of the image of a flying pig seen in the upper temporal visual field of the left eye. (7)

Answer 7

Lower, nasal quadrant of the left retina 
Left optic nerve 
Optic chiasm 
Right optic tract
Right lateral geniculate ganglion 
Right inferior radiation 
Primary visual cortex.

Question 8

Describe the path of the impulse of the image of a donut in the sky seen in the upper nasal visual field of the left eye. (7)

Answer 8

Lower temporal quadrant of the left retina 
Left optic nerve 
Optic chiasm 
Left optic tract
Left lateral geniculate ganglion 
Left inferior radiation 
Primary visual cortex.

Question 9

Describe the lesion that results in monocular vision. (1)

Answer 9

Lesion of the optic nerve

Question 10

Describe the visual defect that would occur with a lesion of the left inferior radiation. (4)

Answer 10

Homonymous, right sided, superior quadrantinopia of both visual fields.

Question 11

Describe the visual defect that would occur with a lesion of the left superior radiation. (4)

Answer 11

Homonymous, right sided, inferior quadrantinopia of both visual fields.

Question 12

Describe the visual defect that would occur with a lesion of the right superior radiation. (4)

Answer 12

Homonymous, left sided, inferior quadrantinopia of both visual fields.

Question 13

Describe the visual defect that would occur with a lesion of the right inferior radiation. (4)

Answer 13

Homonymous, left sided, superior quadrantinopia of both visual fields.

Question 14

Describe the visual field defect seen in a lesion of the optic chiasm. (2)

Answer 14

Bitemporal hemianopia.

Question 15

Describe the location of the lesion that occurs with a left sided homonymous hemianopia as a visual field defect. (2)

Answer 15

Left optic tract.

Question 16

Describe the visual field defect that would occur following a lesion of the right optic tract. (3)

Answer 16

Right sided, homonymous hemianopia.

Question 17

Describe the anatomical location of the optic radiation. (4)

Answer 17

Inferior radiation - Meyer’s loop - temporal lobe

Superior radiation - Beum’s loop - parietal lobe.

Question 18

Describe why macular sparing defect can occur. (5)

Answer 18

The occipital lobe (containing the primary visual cortex) has a duel blood supply from the posterior and middle cerebral arteries. If a stroke of the posterior cerebral artery occurs, Homonymous hemianopia occurs, but because the middle cerebral artery supplies the macula, the macula will be spared.