Lecture 23 - vision 2

Question 1

How are fibres located?

Answer 1

Fibres representing one half of the field of view cross over to the opposite side of the brain

Question 2

what type of order do fibres retain in the optic nerve and throughout the visual system?

Answer 2

retinotopic order

Question 3

what do optic nerve fibres enter?

Answer 3

the LGN

Question 4

whats LGN ?

Answer 4

Lateral geniculate nucleus

Question 5

How many layers does the LGN have?

Answer 5

6

Question 6

what are the layers of the LGN?

Answer 6

2 magnocellular layers and

4 parvocellular layers

Question 7

how does the LGN receive input form the eye ?

Answer 7

Alternating layers receive input from alternate eyes

Question 8

what layers of the LGN are ipsilateral?

Answer 8

5 3 2

Question 9

what layers of the LGN are contralateral?

Answer 9

6 4 1

Question 10

where d nerve fibres form the LGN go?

Answer 10

to the visual cortex

Question 11

where do nerve fibres from the LGN synapse?

Answer 11

layer IV of the cortex

Question 12

what is the arrangement of the Cortex ?

Answer 12

each eye contributes to both sides but remain segregated to some degree in primary cortex

Question 13

How is the visual cortex arranged?

Answer 13

in columns

Adjacent columns represent alternate eyes

Question 14

what do simple cells respond too?

Answer 14

Simple cells respond to bars of light of one orientation

Question 15

what kind of regions do simple cells have?

Answer 15

on-off regions

Question 16

facts about complex cells

Answer 16

• orientation selective
• do not have simple on-off fields
• usually binocular

Question 17

Neurones with the same orientation selectivity are arranged in ______

Answer 17

columns

Question 18

Adjacent orientation columns within an ocular dominance column show what?

Answer 18

a gradual shift in orientation across the full range

Question 19

what do you find between ocular dominance columns?

Answer 19

blobs

Question 20

what are blobs?

Answer 20

patches of colour sensitive neurones

Question 21

what are blobs and modules arranged into?

Answer 21

modules

Question 22

what do modules contain?

Answer 22

complete representation of the colour, motion and orientation of a point in the visual field observed using both eyes

Question 23

How many channels can the pathway from the retina to cortex be split into ?

Answer 23

atleast two main channels

Question 24

what happens at the p- channel?

Answer 24

retinal ganglion cells have small receptive fields and analyse detailed form and colour

Question 25

what happens at the m-channel?

Answer 25

retinal ganglion cells have large receptive fields and probably detect motion and large scale detail

Question 26

how many pathways are there in the primary visual cortex?

Answer 26

2

Question 27

what does the dorsal pathway in the higher visual centres subserve?

Answer 27

subserves spatial vision

Question 28

what does the ventral pathway in the higher visual centres subserve?

Answer 28

subserves colour and object vision

Question 29

where can visual disorders occur?

Answer 29

anywhere in the visual pathway

Question 30

name a neural deficit?

Answer 30

Colour blindness, caused by loss of one type of cone

Question 31

whats optic neuropathy?

Answer 31

A Neural deficit, specific to retina; blood vessel damage and regrowth

Question 32

what does glaucoma cause?

Answer 32

Causes thinning of the nerve fibre layer in the retina and gradually results in loss of vision

Question 33

what does untreated glaucoma eventually lead too?

Answer 33

lead to blindness

Question 34

whats a risk factor for glaucoma?

Answer 34

a family history of glaucoma, increasing age and prolonged steroid use.

Question 35

whats AMD?

Answer 35

Age related macula degeneration

Question 36

whats the most commonest cause of registered blindness?

Answer 36

Age related macula degeneration

Question 37

who does AMD affect?

Answer 37

65 years

Question 38

does peripheral vision remain unaltered with AMD ?

Answer 38

yes

Question 39

what does AMD produce?

Answer 39

Produces blurry vision, wavy or distorted lines or a central blind spot.

Question 40

what are the risk factors of AMD?

Answer 40

Risk factors include increasing age, female gender and smoking. The disease may have a genetic component.

Question 41

what is diabetic retinopathy?

Answer 41

Deterioration of the tight junctions of a blood vessel wall causing blockage, exudates hemorrhages and micro aneurysms.

Question 42

Name a common eye disease?

Answer 42

Superior temporal branch retinal vein occlusion

Question 43

what is Superior temporal branch retinal vein occlusion

?

Answer 43

blockage of a retinal vein ?

Question 44

what are predisposing factors of Superior temporal branch retinal vein occlusion
?

Answer 44

1. Increasing age
2. Systemic hypertension
3. Raised Intra ocular pressure and long sighted spectacle corrections.

Question 45

what is Presbyopia ?

Answer 45

when Ages of 40-45 showing difficulties with reading.

Question 46

what are some symptoms of Presbyopia?

Answer 46

holding reading material further from the eyes and blurry distance vision immediately after reading.

Question 47

why does Presbyopia happen?

Answer 47

the lens becoming inelastic making focusing on near objects difficult

Question 48

How can Presbyopia be rectified?

Answer 48

Rectified by the use of bifocals, varifocals, separate reading spectacles or contact lenses.

Question 49

what is cataracts?

Answer 49

Any opacity of the lens.

May present as gradual blurring of the vision, seeing double in one eye or increased sensitivity to glare.

Question 50

when is cataracts more common?

Answer 50

common with increasing age. Excessive unprotected exposure to UV light, smoking, poor nutrition and prolonged steroid.

Question 51

How can cataracts be treated?

Answer 51

Cataracts can be removed surgically by replacing the lens with a clear plastic lens implant.