Anatomy and Physiology of Vision II

Question 1

Which is larger? nasal retina or temporal retina?

Answer 1

Nasal retina is larger than temporal retina

Question 2

What is the fovea’s diameter?

Answer 2

1.5 mm

Question 3

What makes resolution high in the fovea?

Answer 3

1- Anatomical structure
2- Receptor/ganglia ratio
3- types of photoreceptors

Question 4

What makes the anatomy of the fovea special for visual resolution?

Answer 4

Few anatomical structures impede the passage of light
a- fovea is avascular
b- contains only receptors with few vascular cells
c-ganglion axons divert AROUND the fovea

Question 5

What kind of receptor has higher density in the fovea? what is its ratio to ganglion cells?

Answer 5

Cons, 1:1

Question 6

What kind of vision do rods produce? In what light conditions?

Answer 6

Monochromatic vision, in dim light

“where”

Question 7

What kind of vision do cons produce? In what light conditions?

Answer 7

Colour vision, in bright light
visual acuity
“What”

Question 8

What is the ratio of photoreceptors to ganglion cells in average for the retina? the reinal periphery? Fovea?

Answer 8

137:1, 1000:1, 1:1

Question 9

What is the main change associated with macular degeneration?

Answer 9

Aging changes in RPE

accumulation of metabolic debris at the layer of Bruch’s membrane —> Drusen

Question 10

What pathology is associated with late stage macular degeneration?

Answer 10

Subretinal fibrosis

- photoreceptors are dead, but the periphery vision is not affected

Question 11

What is the role of the retinal pigment epithelium (RPE)?

Answer 11

Provide suitable ionic and metabolic conditions for the rods and cons

Question 12

What conditions cause possible damage to the optic nerve?

Answer 12

Glaucoma, optic neuritis, ischemia, inflammation, and compression

Question 13

What 3 areas in the brain receive visual input?

Answer 13

Suprachiasmatic nucleus of the hypothalamus, lateral geniculate body of the thalamus, and pretectal region of the brain.

Question 14

Where is the pretectal region of the brain located?

Answer 14

Anterior to the superior colliculus (pretectal nucleus and Edinger Westphal nucleus)

Question 15

What is the main function of the pretectal region and its nuclei?

Answer 15

Drives the Pupillary light reflex

Question 16

Where does the image from the top visual field get delivered?

Answer 16

To the thalamus, through the loop of Meyer’s, and to the occipital region (all contralateral)

Question 17

Where does the image from the lower visual field get delivered?

Answer 17

To the thalamus, and directly to the occipital region

Question 18

What is the name of the axons carrying visual information from lateral geniculate body to the occipital lobe?

Answer 18

Geniculocalacarine axons

Question 19

What kind of lesion does a visual field loss respecting the horizontal midline suggest?

Answer 19

An optic disc (nerve)/retinal lesion (one or both eyes)

Question 20

What kind of lesion does a visual field loss respecting the vertical midline suggest?

Answer 20

A neurologic lesion (often both eyes)

Question 21

What kind of visual loss does a lesion to the right optic nerve produce?

Answer 21

Loss of vision in the right eye

Question 22

What kind of visual loss does a lesion to the optic chiasm (pituitary tumour) produce?

Answer 22

Bytemporal hemianopsia

Question 23

What kind of visual loss does a lesion to the right optic tract produce?

Answer 23

Left homonymous hemianopsia

Question 24

What kind of visual loss does a lesion to the left myers loop produce?

Answer 24

Right homonymous superior quadrantanopsia (pie in the sky)

Question 25

What kind of visual loss does a lesion to the left geniculocalcarine axons produce?

Answer 25

Right homonymous heminaopsia

Question 26

What kind of visual loss does a lesion to the right occipital lobe produce?

Answer 26

Left homonymous heminanopsia sparing the macula

Question 27

What kind of visual loss does a lesion to the right optic nerve close to the optic chiasm produce?

Answer 27

Junctional scotoma

Question 28

Where does the visual association area lie?

Answer 28

Surrounds the primary visual area (para-calcarine fissue area) and occupies the occipital lobe

Question 29

What percentage of the optic nerve, tract, and geniculocalcarine axons represents the fovea?

Answer 29

50%

Question 30

What cortex area represents the fovea?

Answer 30

Posterior one half of the calcarine fissure