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

Ocular Anatomy & Clinical Correlations Flashcards

(61 cards)

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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
which orbital wall contains the thinnest portion? what is called?
the medial wall. in particular, the * **lamina pryracea**: ethmoid bone that overlies ethmoid sinus * **posteriormedial maxillary bone**
26
what is the lamina papyracea? why is it clinically significant?
* 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
what are "trap door" fractures? which population is susceptible?
_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
what physical exam findings may be indicative of an orbital fracture? why?
* 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
what is the work-up in a suspected obital fracture?
**CT with contrast of face & orbit**
30
what neurovascuature exit the skull via the _superior orbital fissure_?
* **CN III - VI** (V = V1, opthalmic division of trigeminal nerve) * sympathetic fibers * opthalmic vein
31
which neurovasculature exits the skull via the _optic canal_?
* CN II * opthalmic artery * central retinal vein
32
which neurovasculature exits the skull via the _inferior orbital fissure_?
* CN V - V2 (maxillary division of trigeminal nerve) inferior opthalmic vein
33
where do the opthalmic vein & artery exit the skull?
* vein - superior orbital fissure * artery - optic canal
34
list the cranial nerves that exit through the * superior orbital fissure * optical canal * inferior orbital fissure
* superior orbital fissure: III-IV, V = V1 (opthalmic division of V) * optic canal: II * inferior orbital fissure: V2 (maxillary division of V)
35
how do branches of the trigeminal nerve exit the skull?
* V1 (opthalmic division) - superior orbital fissure * V2 (maxillary divsion) - inferior orbital fissure
36
37
which parts of the ocular region do the carotids perfuse?
* internal carotid - majority of eye * external carotid - eyelids / conjunctiva
38
which cranial nerves innervate the extra-ocular muscles?
III (oculomotor) IV (trochlear) VI (abducens)
39
CN III controls which extra-ocular muscles / actions?
* medial rectus → **adduction** * superior rectus → **elevation,** adduction, inorsion * inferior rectus → **depression**, adduction, extorsion * inferior oblique → **extorsion,** abduction, depression
40
CN III innervates muscles that all share what motion? what is the exception?
adduction exception is the inferior oblique, which abducts
41
CN IV controls which extra-ocular muscles / actions?
superior oblique: intorsion, elevation, abduction
42
CN VI controls what extra-ocular muscles / actions?
lateral rectus - abduction
43
which extra-ocular muscles abduct the eye?
lateral rectus (VI) the obliques - superior oblique (VI), inferior oblique (III)
44
which extra-ocular muscles elevate the eye?
* superior rectus (III) * superior oblique (VI)
45
which extra-ocular muscles depress the eye?
* the inferior rectus (III) * inferior olique (III)
46
which extra-ocular muscles adduct the eye?
all the rectuses execpt for the lateral rectus
47
which extra-ocular muscles & nerves deviate the eye to the * temporal side * nasal side
* temporal - lateral rectus (CN VI) * nasal - medial rectus (CN III)
48
describe the presentation of an _oculomotor nerve palsy_ that damages **somatic fibers**
**"down and out" gaze** **ptosis**
49
describe the presentation of an _oculmotor nerve palsy_ that damages **autonomic fibers**?
**mydriasis / diminished pupillary reflex** **loss of accomodation**
50
in which part of the oculomotor nerve (CN III) are _somatic_ vs _autonomic_ fibers carried?
* somatic = central * autnomic = peripheral.
51
what are the most common causes of a oculomotor (III) nerve palsy?
* microvascular disease - HTN, DM * external compression * PCOM or SCA aneurysm * uncal herniation * neoplasm
52
what is a "blown" pupil? what medical management does it necessitate? why?
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
internuclear opthalmoplegia * definition * cause * presentation
* 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
contrast the presentation of a CN VII LMN lesion to a CN VII UMN lesion
* LMN: paralysis of * forehead * ipsilateral face * UMN: paralysis of * contralateral lower face
55
which type of facial nerve palsy will _spare the forehead_? why?
an upper motor neuron lesion because UMN innervation to the forehead is bilateral, whereas LMN innervation is unilateral
56
facial nerve palsy * causes * treatment * prognosis
* causes: idiopathic = bell's palsy (m/c), lyme disease, HSV (ramsay hunt) * treatment: * systemic - **corticosteroids** * eye - **lubricants\*** * prognosis: gradual recovery
57
horner syndrome * definition * cause * presentation
* definition: sympathetic denervation of face * cause: ipsilateral sympathetic trunk damage * presenation: * **miosis\*** * **ptosis** * **anihidrosis - absence of sweating**
58
what is the consensual light reflex?
bilateral pupillary constriction even if light is shined only in one eye
59
what are _argyll robertson pupils_ ? what can cause them?
working accomodation but NO pupillary reaction (no constriction on light) ​**a/w neurosyphilis**
60
what is marcus gun pupil? what can cause it?
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
what is the _ocular_ treatment for facial nerve palsy?
lubricating drops

SURG - Neuro III (4 decks)

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