Eye and Eye movements Flashcards
What are the bones of the orbit?
St Louis Zoo Makes Entrance Passes Free
Sphenoid
Lacrimal
Zygomatic
Maxillary
Ethmoid
Palatine
Frontal
What passes through the superior orbital fissure?
CNs 3, 4, V1, and 6
opthalamic Vs
What passes through the optic canal?
optin n
opthalamic A
What passes through the infraorbital fissure?
infraorbital A, zygomatic N (branch of maxillary N = V2)
What are the major paranasal sinuses to know?
Frontal = sup to orbit
ethmoid = medial to orbit
maxillary = inf to orbit
How do orbital blow out fractures usually occur and what can happen because of them?
usually occurs medial and inferiorly involving the maxillary bone (sometimes ethmoid)
blood and other orbital contents can prolapse –> go to maxillary sinus
can get iplopia, globe ptosis, exophthalmos
How is the eye positioned in relation to the orbit?
medial walls of orbit are parallel and in line w/ gaze
lateral walls are at right angles
axes of orbit diverge at 45 degree angles
(lateral side of eyeball is more exposed)
What are intorsion and extorsion and upon what axis do they occur?
intorsion = medial rotation
extorsion = lateral rotation
on AP axis
What extraocular Ms are innervated by what nerves?
SO4 LR6
occulomotor (CN III) –> levator palpebrae superioris, IO, SR, IR, MR
Trochlear N (CN IV) –> superior oblique
Abducent N (6) –> Lateral rectus
What is the action of superior oblique m?
(out and down)
abducts
depresses
medially rotates eye
What is the action of inferior oblique m?
laterally rotates
elevates
abducts
What occurs to elevation and depression when the eye is abducted by lateral rectus?
only rectus ms can produce elevation and depression
(so looking out and up tests SR, looking out and down tests IR)
What happens to elevation and depression during adduction by medial rectus?
only the oblique muscles can produce elevation and depression
(looking in and up tests IO, looking in and down tests SO)
What are the branches of V1 (opthalmic n) in the orbit?
first breaks into frontal n, nasociliary n, and lacrimal n
lacrimal n –> lacrimal gland
frontal –> supratrochlear and supraorbital n
nasociliary n –> posterior ethmoidal, anterior ethmoidal, infratrochlear, long ciliary, sensory root of ciliary ganglion
What nerves go through both the superior orbital fissure and the common tendinous n?
superior and inferior divisions of occulomotor n
nasociliary n (branch of V1)
abducent n (CN 6)
What structures go through the superior orbital fissure but not the common tendinous ring?
trochlear n (4)
superior ophthalmic v
frontal n (V1)
lacrimal n (v1)
How do sympathetics get to the eye and what do they innervate?
From T1-T4 –> synapse at superior cervical ganglion
postsynaptic fibers –> to internal carotid plexus –> either on CN 3 or V1 –> either to ciliary ganglion and then short ciliary ns
or on their own to muscles via long ciliary n(5) or CN3
What muscles are innervated by sympathetics in the eye?
Levator palpebrae superioris m
dilator pupilae
super and inf tarsal muscles
How do parasympathetics travel to and within the orbit?
Travel with CN III –> synapse in ciliary ganglion –> short ciliary n to ms
What eye muscles are innervated by PS?
sphincter pupilae
ciliary muscle
What types of fibers are in long ciliary nerves?
general sensory
post-synaptic sympathetics
What type of fibers are in short ciliary nerves?
general sensory
post-synaptic sympathetic
post-synaptic parasympathetic
What eye parts are innervated by general sensory fibers?
choroid
iris
cornea
What occurs in trochlear palsy?
Trochlear n innervates superior oblique m (abducts, depresses, medially rotates)
so eye is stuck laterally rotated –> head tilts away from affected side to compensate
diplopia worse on downward gaze
What occurs in abducens palsy?
CN C innervates lateral rectus m
can’t look laterally w/ affected eye
What are the different types of oculomotor palsy?
down and out eye: loss of occular m innervation, but SO and LR are still intact (I by 4 and 6)
complete ptosis: loss of I to levator palpebrae superioris m
pupil dilation: loss of PS to pupil
What are the 4 steps of the pupillary light reflex?
- light sensed by CN 2 –> synaps in pretectal nucleus
- cells from pretectal nucleus synapse in edinger-westphal nucleus
- presyn PS travel w/ CN 3 –> synapse at ciliary ganglion
- PS neurons go to pupillary constrictor m
What is the corneal reflex?
- receptors in cornea detect touch –> travel in CN V –> synapse in trigeminal sensory nucleus or spinal trigeminal nucleus
- cells from trigeminal nuclei project to facial nucleus
- neuron in facial n will cause eye to blink via tarsal m
What makes up the fibrous layer of the eye?
sclera
cornea
What makes up the vascular layer of the eye?
choroid
ciliary body
iris
What makes up the inner layer of the eye?
retina = optic n, covered w/ meninges until it goes in eye
What are palpebral and bulbar conjuctiva?
palpebral lines innermost part of eyelids
bulbar lines the outermost part of the eyeball
What innervates the superior tarsal m?
sympathetics
keeps eye open
What innervates orbicularis oculi and what does it do?
facial N
closes eye
What is a subconjunctival hemorrhage?
ruptures of vasculature under conjuctiva
see red patches in sclera
What are the conjuctival fornices?
sac btw bulbar and palpebral conjuctiva
What occurs in complete vs partial ptosis?
complete = CN3 lesion, levator palpebrae superioris doesn’t work
partial = sympathetics issue that won’t keep eyelid up via Tarsal muscle, usually horner’s syndrome
What is papilledema?
caused by increased intracranial pressure
see bulging optic disc
What is the macula?
What is the fovea?
macula = center of vision
fovea = area of macula most concentrated by cones
* have blind spot in optic disc
The occlusion of what artery will certainly cause blindness?
central retinal artery
quick occlusion of any orbital a –> most likely blindness
slow occlusion –> enough anastomoses that you will be okay
What are the 3 main endpoints for venous drainage from the eye?
to cavernous sinus
to pterygoid plexus
to facial V and internal jugular
What occurs in central retinal vein occlusion?
hardening of CRA or HTN can compress –> backup of blood and hemorrhages
dilated veins
looks like ketchup on retina
What occurs in central retinal artery occlusion?
retina appears white
cherry red spot = macula
veins and arteries attenuated
What innervates the lacrimal gland?
lacrimal n from CN 5 innervates sensory
PS innervation from greater petrosal n (CN 7)
What does the lacrimal part of orbicularis oculi m do?
contracts –> opends lacrimal sac to hold more tears
What is the general path of tears?
lacrimal gland –> to lacrimal canaliculi –> lacrimal sac –> nasolacrimal duct to nose
if tears overflow lacrimal sac –> cry
How are tears produced?
- greater petrosal n (CN 7) and deep petrosal n from n of pterygoid canal
- PS fibers synapse in pterygopalantine ganglion
- travel w/ V2 then w/ zygomatic branch, communicating branch, then lacrimal n of V1
What is the ciliary body?
circumferential tissue inside the eye composed of ciliary m and ciliary processes
What do ciliary processes do?
secrete aqueous humor –> fills ant and post chambers
What define the anterior and posterior chambers?
part of anterior cavity which is anterior to lens
ant chamber = btw cornea and iris/pupil
post chamber = btw iris/pupil and lens and ciliary body
What can glaucoma in relation to aqueous humor?
schlemm’s canal = how aqueous humor drains out of anterior cavity of eye
blockage of this canal –> increased pressure = glaucoma
What is hyphema?
blood pooled btw cornea and iris
How do the ciliary ms affect vision?
muscles contract –> loosens suspensory L of lens –> lens more round –> near vision
muscles loose –> lens flat –> far vision
