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SURG - Neuro III > Ocular Anatomy & Clinical Correlations > Flashcards

Ocular Anatomy & Clinical Correlations Flashcards

1
Q

cornea

  • location
  • components
  • role
A
  • location: ocular surface
  • components: epithelium, stroma, and endothelium
    • stroma = collagen: type I, IV, V
  • role: 70% of light focusing power
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2
Q

lens

  • structure
  • roles
  • clinical relevance
A
  • structure: suspended by zonules to attached to ciliary body
  • role:
    1. 30% of light focusing of the eye
    2. accomodation (via ciliary body attachment)
    3. separates anterior / posterior chambers
  • clinical:
    • hardening thru age = decreased accomodation (presbyopia)
    • clouding thru age = reduce vision (cataract)
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3
Q

how does the lens evolve throughout age structurally and why is this important?

A
  • becomes harder → presbyopia: reduced accomodation
  • becomes cloudy → cataracts: reduced vision
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4
Q

the uvea consists of___?

A

iris

ciliary body

choroid

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5
Q

the ciliary body

  • is part of what eye structure?
  • interacts with what eye structures?
  • has what roles?
A
  • part of: the uvea
  • interacts with: the lens via zonula fibers
  • has what roles:
    1. holds lens in place (via zonula fibers)
    2. accomodation (via zonula fibers)
    3. produces aqeous humor that bathes the anterior chamber
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6
Q

the iris

  • is part of what eye structure?
  • has what role?
A
  • part of: the uvea
  • role: controls pupil size to augment light reaching the retina
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7
Q

the choroid

  • is a part of what eye structure?
  • has what role?
A
  • is a part of the uvea (most posterior)
  • role: highly vascular - provides majority of blood flow to retina
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8
Q

vitreous humor

  • structure
  • clinical significance
A
  • made of:
    • type II collagen
    • hyaluronic acid
    • water
  • clinical: liquefaction throughout age → vitreous detachment → possible retinal tears → possible retinal detachment
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9
Q

the stroma of the cornea is made of what types of collagen?

A
  • type I
  • type IV
  • type V
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10
Q

nasolacrimal duct obstruction in an infant

  • presentation
  • management
A
  • presentation: recurring tearing & discharge
  • management: warm digital massage over duct
    • if not resolved in 12 months → opthalmologist can probe to open
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11
Q

orbital septum

  • definition
  • clinical significance
A
  • definition: fibrous layer running from skull periosteum → eyelids
  • clinical significance: differentiates periorbital from orbital cellulitis
    • periorbital: anterior to septum
    • orbital: posterior to septum
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12
Q

periorbital cellulitis

  • definition
  • incidence
  • presentation
A
  • definition: eyelid infection anterior to orbital septum
  • incidence: more common than orbital cellulitis
  • presentation:
    • NO proptosis
    • NO opthalmoplegia
    • NO vision loss
    • LESS pain with eye movement
  • treatment: oral antibiotics
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13
Q

orbital cellulitis

  • definition
  • cause
  • incidence
  • presentation
  • diagnosis
  • treatment
A
  • definition: inflammation of fat / ocular muscles posterior to orbital septum
  • causes: infectious spread from sinuses - m/c ethmoid sinus
  • incidence: less common than periorbital cellulitis
  • presentation:
    • opthalmoplegia
    • proptosis
    • more pain with eye movement > periorbital
    • possible vision loss
    • conjunctival chemosis*
    • co-existing rhinosinusitis*
  • diagnosis: CT/MRI
  • management: IV antibiotics 3x / week
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14
Q

what are the complications of orbital cellulitis?

A

cavernous sinus thrombosis

meningitis

absesses

vision loss

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15
Q

how does the management of peri-orbital & orbital cellulitis differ?

why?

A

peri-orbital cellulitis: oral Abx

orbital cellulitis: dx w/ CTI/MRI → IV Abx 3x/week

  • orbital celluitis is posterior to the septum, thus must be tx agressively to prevent progress to dangerous complications:
    • cavernous sinus thrombosis
    • meningitis
    • abessess
    • vision loss
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16
Q

orbital cellulitis often co-exists with what other presentation?

why?

A

rhinosinusitis

b/c the cellulitis likely arose from sinus infection - esp ethmoid sinus

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17
Q

what bones comprise the orbital roof?

A

frontal bone

lesser wing of sphenoid

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18
Q

which bones comprise the lateral wall of the orbit?

A

zygomatic bone

greater wing of sphenoid

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19
Q

which bones comprise the orbital floor?

A

maxilla

palatine

zygomatic

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20
Q

what bones comprise the medial wall of the orbit?

A

lacrimal

ethmoid

maxilla

sphenoid

“LEMS”

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21
Q

the sphenoid bone comprises which borders of the orbit?

A
  • the roof - lesser wing
  • the lateral wall - greater wing
  • the medial wall
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22
Q

the zygomatic bone comprises what borders of the floor?

A

floor

lateral wall

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23
Q

the maxilla bone comprises which borders of the orbit?

A

floor

medial wall

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24
Q

which orbital wall is the thickest / strongest?

A

lateral wall

(zygomatic bone & greater wing of sphenoid)

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25
Q

which orbital wall contains the thinnest portion?

what is called?

A

the medial wall. in particular, the

  • lamina pryracea: ethmoid bone that overlies ethmoid sinus
  • posteriormedial maxillary bone
26
Q

what is the lamina papyracea?

why is it clinically significant?

A
  • the portion of the medial wall ovelying the ethmoid sinus
  • is the thinnest part of the orbit, thus prone to fracture from blunt force trauma, which can lead to infections that spread thru the ethmoid sinus:
    • orbital cellulitis
    • proptosis
27
Q

what are “trap door” fractures?

which population is susceptible?

A

orbital fractures to the weakest / thinnest part (lamina papyracea, postermedial maxilla) that result in incarceration & ischemia of introcular contents

younger patients with flexible bones = susceptible

28
Q

what physical exam findings may be indicative of an orbital fracture?

why?

A
  • orbital rim deformity on palpation
  • impaired pupillary response - optic nerve (CN II) compression
  • impaired sensation over maxillary nerve (V2) distribution - compression of infraorbital nerve in infraorbital fissure
  • imapired visual acuity
29
Q

what is the work-up in a suspected obital fracture?

A

CT with contrast of face & orbit

30
Q

what neurovascuature exit the skull via the superior orbital fissure?

A
  • CN III - VI (V = V1, opthalmic division of trigeminal nerve)
  • sympathetic fibers
  • opthalmic vein
31
Q

which neurovasculature exits the skull via the optic canal?

A
  • CN II
  • opthalmic artery
  • central retinal vein
32
Q

which neurovasculature exits the skull via the inferior orbital fissure?

A
  • CN V - V2 (maxillary division of trigeminal nerve) inferior opthalmic vein
33
Q

where do the opthalmic vein & artery exit the skull?

A
  • vein - superior orbital fissure
  • artery - optic canal
34
Q

list the cranial nerves that exit through the

  • superior orbital fissure
  • optical canal
  • inferior orbital fissure
A
  • superior orbital fissure: III-IV, V = V1 (opthalmic division of V)
  • optic canal: II
  • inferior orbital fissure: V2 (maxillary division of V)
35
Q

how do branches of the trigeminal nerve exit the skull?

A
  • V1 (opthalmic division) - superior orbital fissure
  • V2 (maxillary divsion) - inferior orbital fissure
36
Q
A
37
Q

which parts of the ocular region do the carotids perfuse?

A
  • internal carotid - majority of eye
  • external carotid - eyelids / conjunctiva
38
Q

which cranial nerves innervate the extra-ocular muscles?

A

III (oculomotor)

IV (trochlear)

VI (abducens)

39
Q

CN III controls which extra-ocular muscles / actions?

A
  • medial rectus → adduction
  • superior rectus → elevation, adduction, inorsion
  • inferior rectus → depression, adduction, extorsion
  • inferior oblique → extorsion, abduction, depression
40
Q

CN III innervates muscles that all share what motion?

what is the exception?

A

adduction

exception is the inferior oblique, which abducts

41
Q

CN IV controls which extra-ocular muscles / actions?

A

superior oblique: intorsion, elevation, abduction

42
Q

CN VI controls what extra-ocular muscles / actions?

A

lateral rectus - abduction

43
Q

which extra-ocular muscles abduct the eye?

A

lateral rectus (VI)

the obliques - superior oblique (VI), inferior oblique (III)

44
Q

which extra-ocular muscles elevate the eye?

A
  • superior rectus (III)
  • superior oblique (VI)
45
Q

which extra-ocular muscles depress the eye?

A
  • the inferior rectus (III)
  • inferior olique (III)
46
Q

which extra-ocular muscles adduct the eye?

A

all the rectuses execpt for the lateral rectus

47
Q

which extra-ocular muscles & nerves deviate the eye to the

  • temporal side
  • nasal side
A
  • temporal - lateral rectus (CN VI)
  • nasal - medial rectus (CN III)
48
Q

describe the presentation of an oculomotor nerve palsy that damages somatic fibers

A

“down and out” gaze

ptosis

49
Q

describe the presentation of an oculmotor nerve palsy that damages autonomic fibers?

A

mydriasis / diminished pupillary reflex

loss of accomodation

50
Q

in which part of the oculomotor nerve (CN III) are somatic vs autonomic fibers carried?

A
  • somatic = central
  • autnomic = peripheral.
51
Q

what are the most common causes of a oculomotor (III) nerve palsy?

A
  • microvascular disease - HTN, DM
  • external compression
    • PCOM or SCA aneurysm
    • uncal herniation
    • neoplasm
52
Q

what is a “blown” pupil?

what medical management does it necessitate?

why?

A

a dilated pupil (mydriasis)

  • requires emergent CTA / MRA
  • could be indicative of a oculomotor (III) nerve palsy, and thus a PCOM aneurysm, which must be fuled out
53
Q

internuclear opthalmoplegia

  • definition
  • cause
  • presentation
A
  • definition: conjugate horizantal gaze palsy
  • cause: MLF lesion → failure of CN-III to fire → ipsilateral medial rectus paralysis → failed adduction
  • presentation: nystagmus of the eye contralateral to the defect
    • (still from functioning contralateral CN IV)
54
Q

contrast the presentation of a CN VII LMN lesion to a CN VII UMN lesion

A
  • LMN: paralysis of
    • forehead
    • ipsilateral face
  • UMN: paralysis of
    • contralateral lower face
55
Q

which type of facial nerve palsy will spare the forehead?

why?

A

an upper motor neuron lesion

because UMN innervation to the forehead is bilateral, whereas LMN innervation is unilateral

56
Q

facial nerve palsy

  • causes
  • treatment
  • prognosis
A
  • causes: idiopathic = bell’s palsy (m/c), lyme disease, HSV (ramsay hunt)
  • treatment:
    • systemic - corticosteroids
    • eye - lubricants*
  • prognosis: gradual recovery
57
Q

horner syndrome

  • definition
  • cause
  • presentation
A
  • definition: sympathetic denervation of face
  • cause: ipsilateral sympathetic trunk damage
  • presenation:
    • miosis*
    • ptosis
    • anihidrosis - absence of sweating
58
Q

what is the consensual light reflex?

A

bilateral pupillary constriction even if light is shined only in one eye

59
Q

what are argyll robertson pupils ?

what can cause them?

A

working accomodation but NO pupillary reaction (no constriction on light)

​a/w neurosyphilis

60
Q

what is marcus gun pupil?

what can cause it?

A

impaired consensual reflex (no bilateral constriction) when light is shown in one damaged eye

light shining in unaffected eye yields normal reflex

a/w optic neuritis (MS), acute CNS demylination

61
Q

what is the ocular treatment for facial nerve palsy?

A

lubricating drops

SURG - Neuro III (4 decks)

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