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General mcqs Flashcards

1
Q

which bones make up the medial wall of the orbit

A

maxilla, lacrimal, ethmoidal, sphenoid

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2
Q

what nerves pass through the superior orbital fissure

A

lacrimal nerve

frontal nerve

trochelar nerve

superior branch of the oculor motor nerve

superior branch of the opthalmic vein

nasocillary nerve

inferior branch of oculomotor nerve

inferior branch of opthalmic vein

abducens nerve

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3
Q

which nerves that travel within the sof pass within the common tendinous ring

A
  • snia

superior division of the oculomotor nerve

nasocillary nerve

inferior branch of the oculomotor nerve

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4
Q

which nerves that travel within the superior orbital fissure rtravel outside the ctr

A

lacrimal

frontal

trochlea

superior branch of opthalmic vein

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5
Q

list the contents of the annulus of zinn

A
  • oc- optic canal, optic nerve and opthalmic artery
  • so- superior divison of the oculomotor nerve
  • n- nasocillary nerve
  • io- inferior divison of oculomotor nerve
  • a- abducens nerve
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6
Q

which of the paranasal sinuses are most vunreable to blow out fractures and why

A

ethmoid and maxillary sinuses - the inferior wall seperating the orbit from the maxillary sinus

and medial walls seperating the orbit from the ethmoidal sinus are very thin

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7
Q

what are the four anterior foramen

A

superiororbtial formanen - supraorbital nerve

infraorbital formane - infraorbital nerve

zygomaticofacial foramen- zygomaticofacial nerve

zygomaticotemporal foramen - zygomaticotemporal nerve

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8
Q

where would you expect to see a lesion in a patient presenting with a left homonymous heminaipoia

A

right optic tract

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9
Q

where would you expect to see a lesion in a patient presening with a bitemporal hemianopia

A
  • optic chiasm
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10
Q

where woulod you expect to see a lesion in a patient presenting with a right homonymous inferior quadrantopia

A

left parietal optic radiation

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11
Q

where would you expect too see a lesion in a patient with a left homonymous hemianopia with macular sparing

A

right visual cortex

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12
Q

what are the four parts of the optic nerve and which of them has the longest course

A
  • intraocular
  • intraorbital
  • intracananicular
  • intracranial

the longest portion is the intraorbial part which is around 25mm- 30mm long

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13
Q

what are the main differences between the magnocellular and parvocellular pathways

A

magnocellular

larger cells
faster conduction
involves heavily myleinated parasol retinal ganglion cells

involved in

motion

depth perception

high contrast vision

corresponds to 10% of nerve fibres

parvocellular

  • smaller cells

slower conduction

involves midget retinal ganglion cells which are less heavily myleinated

involved in -
colour vision
fine high resoloution vision

low contrast vision

corresponds to 90% of the nerve fibres

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14
Q

describe the 6 layers of the lgn in terms of their input (i.e. laterality and visual input)

A

contralateral- 1, 4 , 6

ipsilateral - 2 , 3 , 5

magnocellular - 1 and 2

parvoceullar - 4 and 6

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15
Q

what is the main constituent of aqeuous humour

A

water

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16
Q

what structures produces aqeuous humour

A

non pigmented epithelium of the pars plicata

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17
Q

what is gonioscopy and what is it used to measure

A

angle of the anterior chamber

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18
Q

what avascular structures are nourished by the aqueous humour

A
  • lens , zonules , anterior virteous
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19
Q

what is the normal introcular presssure approxiamtley in mmhg

A

10-21mmhg

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20
Q

describes the conventional route of aqueous drainage

A
  • aqueous produced in the non - pigmented epithelium of the pars plicata of the cillary body

drains anterioly around the iris edge and drains via the conventional route

(90%)
- drains through trabecular meshwork in the angle of the anterior chamber

  • flows into the canal of schlemm and the episcleral veins
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21
Q

describe the unconventional route of aqueous drainage

A

aqueous is produced in the non - pigmented epithelium of the pars plicata of the cillary body

drains anterioly around the iris edge and then drains through

10% via the uncoventional route - drains through the anterior face of the cillary body and iris root and passes into the cillary muscle and suprachoroidal space

from there it is drained by uveal and scleral veins

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22
Q

why does the cornea have a higher refractive in the mamillian eye compared to the crystaline lens

A

the 2 main factors

higher difference in refractive index of the air/tear film interface compared to the aqueous/ lens interface

  • smaller radius of curvature of corneal surface compared to the lens (cornea is more curved than the lens)
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23
Q

describe the main adaptations of the cornea to maintain transparency

A
  • avascular

smooth epithelium

regular arrangement of the collagen in stroma

maintained in a state of relative dehydration by the corneal endothelium

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24
Q

name the 5 corneal layers

A
  • corenal epithelium
  • bowmans layer
  • stroma
  • descements membrane
  • corneal endothelium
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25
Q

which corneal layer is responsible for regulating the state of hydration of the corneal stroma - what happens when this fails - what conditons affect the corneal layer

A

endothelium

failure leads to corneal odema and loss of transparenc

this may happen in conditions like fucks endotheliel dystrophy

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26
Q

the corneal endothelium has epithelilel cells - explain this dichotomy

A
  • epitheliel cells refers to cells that lie on a basemement membrane
  • since the corneal endotheliel cells have a basement membrane (descements) they are said to be of the epitheliel cell type
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27
Q

what are the components of the accomodation reflex

A
  • miosis
  • increase in lens thickness (due to cllary muscle contraction and slackening of the zonular fibres)
  • convergecne of the eyes
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28
Q

list 5 causes of cataracts besides age

A
  • trauma and surgery
  • diabetes
  • steroids
  • radiation
  • genetic predispositon
  • congential- rubella
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29
Q

where is the virteous base most strongly attached to the retina

A

ora serrata - virteous base

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30
Q

describe the consituent layers of the anterior lamellae

A
  • anterior lamellae

skin and obicularis

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31
Q

describe the layers of the posterior lamellae

A
  • tarsus and conj
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32
Q

what is the main function of the obicularis oculi

A

orbital portion - volountary clouse of the lids

palpebral portion - volountary and involountary lid closure

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33
Q

a facial nerve palsy can lead to blindness - how can this happen

A

failure of obicularis/muscles can cause lagopathlamos (incomplete closure of the eyelid) exposure keratopathy and corneal ulceration

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34
Q

how is the levator palpabrae superioris different from mullers muscle

A

lps is a skeletal muscle and innervated by cn iii

mullers muscle is a smooth muscle innervated by the sympathetic nervous system

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35
Q

what is a chalazion

A
  • blocked meibomian gland

- mainstay of treatment is conservative - warm compress and lid hygeine

36
Q

how can entropian and an ectropian lead to blindness

A

entropian - eyelashes rubbing against cornea and corneal scarring (e.g. in a trachoma)

ectropian - exposure keratopathy

37
Q

what are the three main parts of conjuctiva

A

tarsal, forniceal and bulbar

38
Q

what are the three main germinal cell layers which layers are involved in the development of the eye

A
  • ectoderm, mesoderm , endoderm

only ectodermal and mesodermal layers contribute to ocular devlopment

39
Q

which of the secondary brain vesciles are the eyes derived from

A
  • diencephalon
40
Q

describe the formation of the lens placode and the lens vesicle

A
  • as the optic vesicle develops as an outpoutching of the diencephalon - and overlying surface ectoderm is induced to devlop into the lens placode - the lens placode and the optic vesicle then start to simultaneously invaginate - until the lens placode seperates from the surface of the lens vesicle while the optic vesicle becomes the optic cup
41
Q

how does the retina form the optic cup which germinal cell layer is it derived from

A
  • the thick inner layer of the optic cup develops into the neurosensory retina whilst the thinner outer layer devlops into the retinal pigmented epithelium - in between these two layers is the subretinal space

the retina develops from the neuroectoderm

42
Q

what is the hyaloid artery and where does it travel

A

in the fetal eye the hyaloid artery provides blood supply to the retina as well as supporting the development of the lens - it travels through choridal fissure and enters the eye as the optic disc where it travels forward through the virteous (hyaloid canal) towards the lens

43
Q

what is colomboma

A

a coloboma is (usually a inferonasal) defect in ocular structures such as the iris , cillary body , retina , choroid and optic disc

it results from a failure of closure of the choroidal fissure

44
Q

what are the three main types of amblyopia and the causes for each

A

strabismic - squint with a dominant eye and a supressed eye

deprivational - congential catarcats capillary haemngioas obstructing visual axis

refractive - large difference in refractive errors between the two eyes

45
Q

what are the three layers of tear film

A
  • lipid layer
  • aqueous layer
  • mucinous layer
46
Q

what is the function of the lipid layer

A
  • limits evaporation of the aqueous component
47
Q

what is the oily layer produced by

A

the meibomian glands, the glands of moll and ziess

48
Q

what is the aqueous layer produced by

A

lacrimal and acessory glands

49
Q

what is the function of the aqeuous layer

A
  • nourishes , hydrates and immune defense
50
Q

what is the function of the muscinous layer

A
  • lubricates aids an even distribution of tears
51
Q

what is the muscinous layer produced by

A

conjuctival goblet cells

52
Q

the nasolacrimal duct drains into what structure

A

inferior meatus

53
Q

what is dacrocytsis

A
  • infection of the lacrimal sac
54
Q

sesnroy innervation to the lacrimal gland is via which nerve

A
  • lacrimal nerve
55
Q

with reference to the parasympathetic supply of the lacrimal land , the preganglionic fibres travel along which nerve

A

greater petrosal nerve

56
Q

what nerve is part of the symapathetic supply

A

the deep petrosal nerve

57
Q

what are the consituents of circle of wilis

A

internal carotid artery

anterior cerebral artery

anterior communicating artery

posterior cerebral arteyr

posterior communicating artery

58
Q

where do the dural venous sinuses lie in the brain - where do they receive blood from and where do they drain

A
  • they recieve layers from the endosteal and meningeal layers of the brain
  • drain blood from the cerebral veins as well as the csf into the internal jugular veins
59
Q

how can infection around the danger zone lead ro opthalmoparesis (paralysis of the eom)

A
  • infection can travel along the valveless venous system and spread to the carvenous sinus - this can affect cranial nerve 3 and 4 and 6 which all lie within the stryucture and thus lead to complete opthalmoparesis
60
Q

how can internal carotid artery dissection lead to a horners sybdrome

A

postganglionic sympathetic fibres travel along the ica an ica dessection can therefore lead to a third order postganglionic horners

61
Q

what forms the blood retinal barrier

A

zona occludens/ tight junctions between endotheliel cells of cra capillaries

zona occludens/ tight junctions between cells of retinal pigmented epithelium

tight junctions - multiprotein complexes which form a scaffolding between the endotheliel cells of the central retinal artery capillaries and between cells of the retinal pigmented epithelium to form the zona occludentes

62
Q

which branches of the opthalmic artery is the choroidal circulation dervied from

A

cillary arteries - long , short and anterior

63
Q

in which retinal layer do the phototeceptor cell bodies lie

A
  • outer nuclear layer
64
Q

what is meant by on and off bipolar cells

A

on bioplar cells - depolarised by light

off bipolar crells - hyperpolarised by light

65
Q

which axons from the optic nerve

describe the myleination of these axons in terms of where it starts and the glial cell responsible for it

A

ganglion cell axons form the optic nerve

they are unmyleinated within the retina

and become myleinated by oligdodendrocytes as they travel past the lamina cribrosa in the sclera

66
Q

describe how layer 2 of the lgn would recieve its input from a photoreceptor

A
  • layer 2 - ipislateral eye , magnocellular pathway, parasol retinal ganglion cell

layer 2 of the lgn recieves magnocellular input from the ipsilaeral eye - therefore parasol retinal gagnlion cells in the ipsilateral eye are involved and send their signals down their axons which travel via the optic nerve past the optic chiasm and synapse at the ipsilateral lgn in layer 2

67
Q

describe the posterior pole

A
  • lies temporal to the optic disc and is cone dominated

posterior pole is where the fovea and macular lie - high acuity vision , central vision and therefore much higher cone density

68
Q

what structure forms the anterior boundary of the neuroal retina

A

ora serrata - the neural retina is thinest hear but firmly adherent

inner membrane is virteous and outer boundary is bruchs membrane

69
Q

what is the anatomical structure which forms the boundary between myleinated and unmyleimated retinal ganglion cell axons

A
  • the lamina cribosa , a fenestrated (mesh- like) network of fibres in the sclera at the optic disc
70
Q

what are the photopigmenrs responsible for phototransuction in the outer segments of the photoreceptor cells called

A
  • opsins
71
Q

how many different types of cone photoreceptors are there

A

3 types of opsins with spectral sensitivities of varying wavelenghts corresponding to different parts of the colour spectrum

short wavelength (blue)

medium wavelength (green)

long wavelength (red)

72
Q

what might be the clinical consequce of having fewer types of photoreceptors

A

inidivduals with muted or absent types of any of the three types of cones above devlop colour blindness and have diffciulty distingushing between particular coloiurs

73
Q

what happens after a photon is absorbed by a opsin in phototransduction

A

results in hyperpolarisation of the cell and cessation of glutamate release

74
Q

what bones make up the inferior wall

A

paletine , maxilla , inferior

75
Q

what are the contents of the sof

A

lacrimal, frontal , trochlear , superior division of the oculomotor nerve , nasocillary nerve , inferior division of the oculomotor nerve , abducens nerve

76
Q

which nerves passes through the sof within the ctr

A

superior division of the oculomotor nerve

nasocillary nerve

inferior division of the oculomotor nerve

abducens nerve

77
Q

what nerves of the sof pass outside the ctr

A

lacimal, frontal , trochlear

78
Q

what nerves pass through the sof within the ctr most superiorly

A

superior division of the oculomotor nerve

79
Q

which of the paranasal sinuses is the most common transmission of infection in orbital cellulitis

A

ethmoid

80
Q

which veins are drained into the conventional route

A
  • episcleral veins
81
Q

what is the trabecular meshwork formed from

A

the trabecular meshwork is formed of three fenestrated layers

82
Q

what is aqueous humour produced by

A

the non - pigmented epithelium of the pars plicata of the cillary body

83
Q

what embryological layer does not contribute towards the development of the eye

A
  • endoderm
84
Q

what structure in the eye develops from mesoderm

A
  • choroid
85
Q

what struture develops from surface ectoderm

A
  • the lens

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