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General mcqs Flashcards

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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
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
endothelium failure leads to corneal odema and loss of transparenc this may happen in conditions like fucks endotheliel dystrophy
26
the corneal endothelium has epithelilel cells - explain this dichotomy
- 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
27
what are the components of the accomodation reflex
- miosis - increase in lens thickness (due to cllary muscle contraction and slackening of the zonular fibres) - convergecne of the eyes
28
list 5 causes of cataracts besides age
- trauma and surgery - diabetes - steroids - radiation - genetic predispositon - congential- rubella
29
where is the virteous base most strongly attached to the retina
ora serrata - virteous base
30
describe the consituent layers of the anterior lamellae
- anterior lamellae skin and obicularis
31
describe the layers of the posterior lamellae
- tarsus and conj
32
what is the main function of the obicularis oculi
orbital portion - volountary clouse of the lids palpebral portion - volountary and involountary lid closure
33
a facial nerve palsy can lead to blindness - how can this happen
failure of obicularis/muscles can cause lagopathlamos (incomplete closure of the eyelid) exposure keratopathy and corneal ulceration
34
how is the levator palpabrae superioris different from mullers muscle
lps is a skeletal muscle and innervated by cn iii mullers muscle is a smooth muscle innervated by the sympathetic nervous system
35
what is a chalazion
- blocked meibomian gland | - mainstay of treatment is conservative - warm compress and lid hygeine
36
how can entropian and an ectropian lead to blindness
entropian - eyelashes rubbing against cornea and corneal scarring (e.g. in a trachoma) ectropian - exposure keratopathy
37
what are the three main parts of conjuctiva
tarsal, forniceal and bulbar
38
what are the three main germinal cell layers which layers are involved in the development of the eye
- ectoderm, mesoderm , endoderm only ectodermal and mesodermal layers contribute to ocular devlopment
39
which of the secondary brain vesciles are the eyes derived from
- diencephalon
40
describe the formation of the lens placode and the lens vesicle
- 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
how does the retina form the optic cup which germinal cell layer is it derived from
- 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
what is the hyaloid artery and where does it travel
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
what is colomboma
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
what are the three main types of amblyopia and the causes for each
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
what are the three layers of tear film
- lipid layer - aqueous layer - mucinous layer
46
what is the function of the lipid layer
- limits evaporation of the aqueous component
47
what is the oily layer produced by
the meibomian glands, the glands of moll and ziess
48
what is the aqueous layer produced by
lacrimal and acessory glands
49
what is the function of the aqeuous layer
- nourishes , hydrates and immune defense
50
what is the function of the muscinous layer
- lubricates aids an even distribution of tears
51
what is the muscinous layer produced by
conjuctival goblet cells
52
the nasolacrimal duct drains into what structure
inferior meatus
53
what is dacrocytsis
- infection of the lacrimal sac
54
sesnroy innervation to the lacrimal gland is via which nerve
- lacrimal nerve
55
with reference to the parasympathetic supply of the lacrimal land , the preganglionic fibres travel along which nerve
greater petrosal nerve
56
what nerve is part of the symapathetic supply
the deep petrosal nerve
57
what are the consituents of circle of wilis
internal carotid artery anterior cerebral artery anterior communicating artery posterior cerebral arteyr posterior communicating artery
58
where do the dural venous sinuses lie in the brain - where do they receive blood from and where do they drain
- 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
how can infection around the danger zone lead ro opthalmoparesis (paralysis of the eom)
- 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
how can internal carotid artery dissection lead to a horners sybdrome
postganglionic sympathetic fibres travel along the ica an ica dessection can therefore lead to a third order postganglionic horners
61
what forms the blood retinal barrier
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
which branches of the opthalmic artery is the choroidal circulation dervied from
cillary arteries - long , short and anterior
63
in which retinal layer do the phototeceptor cell bodies lie
- outer nuclear layer
64
what is meant by on and off bipolar cells
on bioplar cells - depolarised by light off bipolar crells - hyperpolarised by light
65
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
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
describe how layer 2 of the lgn would recieve its input from a photoreceptor
- 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
describe the posterior pole
- 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
what structure forms the anterior boundary of the neuroal retina
ora serrata - the neural retina is thinest hear but firmly adherent inner membrane is virteous and outer boundary is bruchs membrane
69
what is the anatomical structure which forms the boundary between myleinated and unmyleimated retinal ganglion cell axons
- the lamina cribosa , a fenestrated (mesh- like) network of fibres in the sclera at the optic disc
70
what are the photopigmenrs responsible for phototransuction in the outer segments of the photoreceptor cells called
- opsins
71
how many different types of cone photoreceptors are there
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
what might be the clinical consequce of having fewer types of photoreceptors
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
what happens after a photon is absorbed by a opsin in phototransduction
results in hyperpolarisation of the cell and cessation of glutamate release
74
what bones make up the inferior wall
paletine , maxilla , inferior
75
what are the contents of the sof
lacrimal, frontal , trochlear , superior division of the oculomotor nerve , nasocillary nerve , inferior division of the oculomotor nerve , abducens nerve
76
which nerves passes through the sof within the ctr
superior division of the oculomotor nerve nasocillary nerve inferior division of the oculomotor nerve abducens nerve
77
what nerves of the sof pass outside the ctr
lacimal, frontal , trochlear
78
what nerves pass through the sof within the ctr most superiorly
superior division of the oculomotor nerve
79
which of the paranasal sinuses is the most common transmission of infection in orbital cellulitis
ethmoid
80
which veins are drained into the conventional route
- episcleral veins
81
what is the trabecular meshwork formed from
the trabecular meshwork is formed of three fenestrated layers
82
what is aqueous humour produced by
the non - pigmented epithelium of the pars plicata of the cillary body
83
what embryological layer does not contribute towards the development of the eye
- endoderm
84
what structure in the eye develops from mesoderm
- choroid
85
what struture develops from surface ectoderm
- the lens

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