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neurology > Vision lectures > Flashcards

Vision lectures Flashcards

1
Q

what is refraction?

A

when light rays bend to form a sharp image on the retina

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2
Q

what is accommodation?

A

the changes occurring in both eyes as it changes focus from a distant to a close object

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3
Q

what causes refractive errors?

A

when there is a mismatch between how much we bend light rays in each eye

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4
Q

what are the refractive media in the eyeball?

A

cornea
aqueous humor
lens
vitreous humor

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5
Q

what does the eye need to do when an object is closer to you to maintain a clear image on the retina?

A

needs to bend light rays more

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6
Q

what 3 processes occur simultaneously that comprise accommodation?

A

lens changes shape to become more spherical and thicker
pupil constricts
eyes converge

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7
Q

how does the lens thicken during accommodation?

A 
1/ ciliary muscle contracts making the ciliary body bulge
space in the middle decreases
suspensory ligaments become lax
lens is no longer under stretch
lens becomes thicker
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8
Q

what muscle causes the pupil to constrict?

A

sphincter pupillae

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9
Q

what branch of the autonomic nervous system innervates the sphincter pupillae?

A

parasympathetic

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10
Q

where is the sphincter pupillae located?

A

around the border of the pupil

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11
Q

what muscles are responsible for the eyes converging during accommodation?

A

medial rectus muscles

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12
Q

what is myopia?

A

short sightedness

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13
Q

what is hyperopia?

A

long sightedness

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14
Q

what is astigmatism?

A

non spherical curvature of cornea (or lens)

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15
Q

what is presbyopia?

A

long sightedness of old age

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16
Q

what is the most common cause of myopia?

A

eyeball too long

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17
Q

what are symptoms of myopia?

A

divergent squint in infants

headaches, complain of not being able to see blackboards/distant objects

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18
Q

how is myopia corrected?

A

bending power is decreased using biconcave lenses:
spectacles
contact lenses
laser eye surgery

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19
Q

what is the most common cause of hyperopia?

A

eyeball too short or cornea + lens too flat

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20
Q

what objects appear hazy in astigmatism?

A

both close and distant objects

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21
Q

why does the chance of developing long sightedness increase with old age?

A

lens gets less mobile/elastic so when the ciliary muscle contracts it is not as capable of changing shape as it was before

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22
Q

what is phototransduction?

A

conversion of light energy to an electrochemical response by photoreceptors

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23
Q

what do rods and cones have to do in order to illicit an electrochemical response?

A

activate optic nerve neurons (generate an action potential)

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24
Q

what visual pigment is integrated in the lamellae of rods?

A

rhodopsin

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25
Q

what visual pigments are integrated in the lamellae of cones?

A

opsins S, M and L

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26
Q

what type of protein is rhodopsin?

A

integral transmembrane helical protein

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27
Q

what is the chromophore of rhodopsin formed from?

A

vitamin A

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28
Q

what happens when light forms on the 11-cis retinal?

A

it isomerises to all trans retinal

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29
Q

what happens to photoreceptors in the dark?

A

the are kept depolarised by open sodium/calcium channels

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30
Q

what happens in the phototransduction cascade when the Na+ channels close?

A

there is RELATIVE hyperpolarisation of photoreceptor cells

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31
Q

how are the photoreceptor cells truly hyperpoolarised?

A

flux of Ca+ ions to the synapse with bipolar cell, which ultimately stimulates the retinal cell

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32
Q

what will happen in any condition that affects vitamin A absorption?

A

vision will be affected, possibly leading to blindness. there will also be abnormal conjunctiva and corneal epithelium

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33
Q

what can corneal melting lead to?

A

future opacification of the cornea

34
Q

what is the function of the intrinsic ocular muscles?

A

control pupil diameter and helps alter lens curvature to enable us to see near objects

35
Q

what is the function of the extrinsic muscles of the eye?

A

they move the eye

36
Q

what are the 4 straight muscles of the eye?

A

medial rectus
lateral rectus
inferior rectus
superior rectus

37
Q

what are the 2 oblique muscles of the eye?

A

superior oblique

inferior oblique

38
Q

where do the recti muscles arise from?

A

the apex of the orbit from an annular fibrous ring

39
Q

where does the superior oblique muscle arise from?

A

the roof of the orbit posteriorly

40
Q

where does the inferior oblique muscle arise from?

A

floor of the orbit anteriorly

41
Q

what muscle elevates the eyelid?

A

levator palpebrae superioris

42
Q

where does the LPS lie?

A

above the superior rectus

43
Q

what nerve supplies everything except the superior orbit and the lateral rectus muscle?

A

oculomotor nerve

44
Q

what does the trochlear nerve supply?

A

superior orbit

45
Q

what does the abductent nerve supply?

A

lateral rectus

46
Q

where does the LPS muscle originate?

A

roof of orbit

47
Q

where do all recti muscles originate from?

A

tendinous ring

48
Q

where does the superior oblique originate from?

A

lesser wing of sphenoid

49
Q

where does the inferior oblique originate from?

A

medial part of orbit floor

50
Q

where do both oblique muscles of the eye insert?

A

sclera posteriorly

51
Q

where do all rectus muscles insert?

A

sclera anteriorly

52
Q

what is the action of the superior rectus?

A

elevation when abducted

intorsion when adducted

53
Q

what is the action of the inferior rectus?

A

depression when abducted

extorsion when adducted

54
Q

what is the action of the superior oblique?

A

depression when adducted
intorsion
abduction

55
Q

what is the action of the inferior oblique?

A

elevation when adducted
extorsion
abduction

56
Q

what are some signs of right third nerve palsy?

A

drooping eyelid

eye only able to move laterally and slightly downwards

57
Q

what are some signs of left fourth nerve palsy?

A

eye moves up when adducted

58
Q

what are some signs of abducent nerve palsy?

A

eye being adducted

eye not able to abduct

59
Q

what is the medical term for a squint?

A

strabismus

60
Q

what is esotropia?

A

manifest convergent squint

61
Q

what is exotropia?

A

manifest divergent squint

62
Q

what is ambylopia?

A

“lazy eye” where brain supresses the image of one eye leading to poor vision in that eye without any pathology

63
Q

what is diplopia?

A

double vision which usually occurs in squints occuring as a result of nerve palsies

64
Q

what is your visual field?

A

everything you see with one eye including the periphery

65
Q

where do all nerve fibres from the eye pass through?

A

the optic nerve and then to the optic chiasma

66
Q

where do fibres from the optic tract synapse?

A

lateral geniculate body of the thalamus

67
Q

what kind of nerve fibres does the optic tract contain?

A

fibres from the temporal half of the ipslateral eye and nasal fibres from the contralateral eye

68
Q

where is the primary visual cortex?

A

occipital lobe

69
Q

what does the right visual cortex see?

A

left half of the visual field and vice versa

70
Q

what would you expect to happen if the right optic nerve is damaged?

A

blindness in one eye

71
Q

what would you expect to happen if the optic chiasma was disrupted in the middle?

A

bitemporal hemianopia (blindness)

72
Q

what would you expect to happen if the right optic tract was damaged

A

left sides of both eyes will be blind

73
Q

what would you expect to happen if the right optic radiation was damaged?

A

contralateral homonymous hemianopia

74
Q

what are the 3 intrinsic eye muscles?

A

ciliaris muscle
constrictor pupillae
dilator pupillae

75
Q

what are the ciliaris and constrictor pupillae muscles innervated by?

A

cranial nerve 3 (parasympathetic)

76
Q

what is the dilator pupillae innervated by?

A

plexus around blood vessels (sympathetic)

77
Q

where do fibres destined to activate the pupillary reflex travel to?

A

midbrain - to the edinger westphal nucleus of both sides

78
Q

what is the clinical term for when both pupils are different sizes?

A

anisocoria

79
Q

what are the steps in pupillary constriction?

A

EWN > preganglionic parasympathetic fibres pass through 3rd CN into orbit > parasympathetic fibres go to and synapse in the ciliary ganglion > postganglionic fibres go through short ciliary nerves to constrictor pupillae
all of this leads to pupillary constriction of both sides

80
Q

what can cause an abnormal/absent pupillary reflex?

A

diseases of the retina - detachment/degenerations or dystrophies
any abnormality of the afferent limb centre/efferent limb of the reflex
diseases of the optic nerve - optic neuritis
diseases of the 3rd cranial nerve

81
Q

what is horners syndrome?

A

anisocoria due to damage to the sympathetic innervation to the pupil

neurology (29 decks)

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