Eye Orbit Flashcards
Where is the sclera normal visible
normally visible between iris and lower lid
not visible above iris
caruncle
tears accumulate here
in medial canthus
three V1 branches
frontal: forehead and scalp
lacrimal: sensory to gland, upper eyelid
nasociliary: medial orbit, upper nose
^all somatic sensory
lateral/medial canthus
where eyelids meet
only ___ provides sensory info to the eyeball
only NASOCILIARY N. provides sensory info to the eyeball
V2 supplies (inferior/superior?) eyelid
V2 supplies INFERIOR eyelid
the frontal n. branches into which nerves
supraorbital n.
supratrochlear n.
the nasociliary n. branches into which nerves
ant/post ethmoidal n.s
infratrochlear n.
orbicularis occuli m. have 2 parts
orbital parts: on bone itself
palpebral parts: on eyelid itself
innervated by facial n.
insertion point of orbicularis oculi m.
medial palpebral ligament
pushes tears medially to accumulate in lacrimal lake
tarsal plates
inert tissue, not many vessels
- support for eyelids
- anchors tarsal m.
- contains tarsal glands
input must touch ___ to trigger blink reflex
cornea
felt via CN V1 (nasociliary n.)
blink reflex - motor response is via
CN VII
to orbicularis oculi, palpebral part
blink reflex - sensory input
n. and stimulus
CN V1 - touch cornea
CN II - visual threat/bright light
CN VIII - sudden sounds >50-60 dB
6 bones of orbit
frontal sphenoid GW/LW ethmoid lacrimal maxilla zygomatic
lamina papyracea
“paper-thin bone”
orbital plate of ethmoid bone, has air cells
orbital blowout fractures
can be toward medial side or inferiorly (twd maxillary sinuses)
- diplopia
- infraorbital n. damage
- infections
How can hydrocephalus lead to papilledema?
high CSF pressure (hydrocephalus) –> impedes venous drainage –> pressure on optic disc causes bulging —> papilledema
usually bilateral
(unilateral –> ocular pathology)
6 extraocular m. of eye that move eyeball
superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique
which extraocular m. elevates the upper eyelid?
levator palpebrae superioris
recti m. of eye insert ____ to equator
recti m. of eye insert ANTERIOR to equator
oblique m. of eye insert _____ to the equator
oblique m. of eye insert POSTERIOR to the equator
CN III supplies which extraocular m.?
superior rectus inferior rectus medial rectus inferior oblique levator palpebrae superioris
CN IV supplies which extraocular m.?
superior oblique m.
LR6SO4
CN VI supplies which extraocular m.?
lateral rectus m.
LR6SO4
adduction of eye
medial rectus
aBduction of eye
lateral rectus
elevation + adduction of eye
superior rectus
depression + adduction of eye
inferior rectus
which m. compensate for adduction of superior/inferior rectus m.?
superior oblique/inferior oblique
depression + aBduction
superior oblique
elevation + aBduction
inferior oblique
m. required to look straight down
inferior rectus + superior oblique
m. required to look straight up
superior rectus + inferior oblique
4 smooth muscles (intra and extraocular) are controlled by ANS
parasympathetic: ciliary m. and sphincter pupillae m.
sympathetic: dilator pupillae m. and superior tarsal m.
causes of slow pupillary constriction
- brainstem damage (to parasympathetic nucleus)
- CN III compression (epidural hematoma, squished against petrous temporal bone)
- depressants (barbiturates)
- untreated syphilis
temporal retina
receiving light from midline
fibers do NOT cross at optic chiasm
most go to motor cortex (some to midbrain pretectal nucleus –> Edinger-Westphal nucleus –> ciliary ganglion –> pupillary constriction)
nasal retina
receiving light more laterally
fibers decussate at optic chiasm
most go to motor cortex (some to midbrain pretectal nucleus –> Edinger-Westphal nucleus –> ciliary ganglion –> pupillary constriction)
how does ciliary m. accommodate for near vision?
ciliary m. contracts –> loosens lens zonules –> lens rounds up
What input is needed to cause lens flattening?
lens default shape is FLAT
NO sympathetic input is needed to cause lens flattening, zolular tension is sufficient
presbyopia
diminished ability of the lens to become round
need reading glasses
mydriasis
pupil dilation
superior tarsal (Muller’s) m.
SMOOTH muscle, in tarsal plates
helps pull eyelid up
damage –> ptosis
left abducent nerve palsy
abducent n. affected (at risk w/ cavernous sinus pathology)
–> lateral rectus m. affected –> eye pulled medially by medial rectus
left oculomotor nerve palsy
- all extraocular m. affected EXCEPT superior orbital and lateral rectus
- pupil dilation (lost parasymp to sphincter pupillae)
- ptosis (lost LPS)
ptosis could be due to loss of which m.
superior tarsal (Muller’s) m.
OR
levator palpebrae superioris
bitemporal hemianopsia
could be due to compression of optic chiasm
fibers from nasal retina can’t decussate
results in bilateral half vision (vision lost on LATERAL) sides
tear production is controlled by ______ fibers via CN ___
tear production is controlled by secretomotor fibers via CN VII
glands responsible for tear production
- lacrimal glands
- meibomian glands
- conjunctival glands (goblet cells)
all controlled by CN VII
path of tear drainage
tears accumulate in lacrimal lake –> thru superior/inferior punctum –> lacrimal canaliculi –> lacrimal sac –> lacrimal duct –> inferior turbinate
meibomian (tarsal) glands
visible thru palpebral conjunctiva
specialized sebaceous gland (oil surface layer for tear film)
lipids seal lid margin (holds tear film in place
waterproofs lids when closed
reduces evaporation from deeper, aqueous tear film layer (from lacrimal gland)
punctual plugs
tx for dry eye
prevents evaporation of tears
mucus layer of tear film produced via
conjunctival glands (goblet cells)
aqueous layer of tear film produced via
lacrimal gland
lipid layer of tear film produced via
meibomian glands
tear film functions
flushes debris
protects cornea from drying
provides O2 and nutrients to cornea
contains antibacterial enzymes (lysozyme)
ptosis (via superior tarsal damage) + constriction of pupil
possibly caused by ________
Horner Syndrome
What gives rise to anterior meningeal a.s?
ethmoidal a.s go through ant/post ethmoidal foramina –> become anterior meningeal a.s
Middle meningeal a. anastomoses w/ _____ a. to contribute to ICA/ECA anastomoses
Middle meningeal a. anastomoses w/ LACRIMAL a. to contribute to ICA/ECA anastomoses
Which vessels supply INNER aspect of retina?
central a. of retina (goes thru optic disk and branches)
br. of ophthalmic a.
When looking through funduscope, optic disc is always on ____ side of the eye
When looking through funduscope, optic disc is always on MEDIAL side of the eye
Which vessels supply OUTER aspect of retina?
short posterior ciliary a.
form choriocapillaris (cluster of vessels, very dense –> red eye in pics)
choroid
the pigmented vascular layer of the eyeball between the retina and the sclera.
Which vessels supply anterior eye of retina?
long posterior ciliary arteries
what contributes to risk of spreading infections on face to cavernous sinus
superior/inferior ophthalmic v. are continuous w/ v. that supply face
(angular v. and facial v.)
infections can work their way back to the cavernous sinus
which n. is just deep to the periorbita?
frontal n. (largest V1 branch)
which m. is just deep to frontal n.?
levator palpebrae superioris m.
which m. is just deep to levator palpebrae superioris?
superior rectus m.
