eye and eye movements Flashcards
what are the facial bones of the orbit ? what are the neurovasculaure that it contains
facial zygomatic lacrimal maxillary sphenoid ethmoid
- maxillary N. (changes to infra orbital N. in pteryogpalatine fossa)
- infraorbital A.
- zygomatic N. (of V2)
what bone is usually most affected in a orbital blow out fracture ? what side effects will occur?
- fracture of the orbital wall caused by indirect trauma causes a “blowout” medially and inferiorly affecting the maxillary bone. the maxillary break causes orbital contents to leak into the maxillary sinus and become entrapped
- symptoms: globe ptosis (descending eyeball), diplopia, exopthalamos
optical axis vs orbital axis
the optical exes (axes of gaze) are parallel to each, while the orbital axis make a 45 degree angle with each other do to the medial wall extending father from the lateral wall and exposing more of the lateral eye
function and innervation of levator palpebrae superiorsis M.
CN- 3 oculomotor
Fxn: elevated eyelid
function and innervation of superior oblique M.
CN-4 trochlear N.
Fxn: eye intorsion, depression, and abduction
function and innervation of inferior oblique ?
CN 3- oculomotor N.
Fxn: eye extorsion, elevation, abduction
function and innervation of superior rectus M.
CN 3- oculomotor N.
FXN: eye intorsion, elevation, and adduction
function and innervation of inferior rectus M.
CN 3 - oculomotor N.
FXN- eye extorsion, depression, and adduction
function and innervation of medial rectus M.
CN- 3 Oculomotor N.
FXN: eye adduction
function and innervation of lateral rectus M.
CN- 6 Abducens N.
FXN: eye abduction
eye muscles become fixated and trapped, unable to perform function, when ?
the axes of gaze is perpendicular to the muscle fiber direction
when the eye is abducted by lateral rectus, only __ muscles can elevate and depress the eye. when the eye is adducted by medial rectus only the ___ muscles can elevate and depress the eye. why is this important/
- rectus muscles (superior and inferior rectus)
- oblique muscles (superior and inferior oblique muscles)
* important for when considering H testing
where is the trigeminal cave
behind the orbit, lateral to the cavernous sinus. is the place where the trigeminal N. splits into V1, V2, V3
what nerve gives rise to the supraorbital and supratrochlear N.
trigeminal N. –> opthalmic N. (V1) –> frontal N.
-frontal N. wlll split into the 2 branches supratrochlear N. (medially) and supraorbital N. (laterally)
what are the 3 terminal branches of opthalmic N. (v1)
- splits in the orbit into
1. nasociliary N.
2. frontal N.
3. lacrimal N.
what are the branches off the nasocilary N. and what are there functions
- infratrochlear N.
- anterior ethmoidal N. (goes to nasal cavity mucosa )
- posterior ethmoidal N. (goes to nasal cavity mucosa)
- long ciliary N. (carries sensory to cornea, and SNS to dilator muscle )
- short ciliary N. (carries carries sensory to cornea and PNS too constrictor M. and SNS to Dilator M )
oculomotor N. supplies most of the eye muscles except 2. what muscles are innervated bu the superior branch ? inferior branch ?
superior: levator palpibrae superiorus M.. ; superior rectus M.
inferior : inferior oblique M. ; inferior rectus M. ; medial rectus M.
what makes up the common ring in the orbit? what nerves go through the common tendinous ring in the orbit
*made of all 4 rectus muscles
- oculomotor n. (inferior and superior divison) (CN3)
- nasociliary N.
- abducens N. (CN 6)
- optic N. (CN 2) (with central retinal A.)
**CN 2, 3, 6 and nasociliary (off V1 , off CN5)
[ trochlear n. ; frontal n. ; lacrimal n. DO NOT ]
a lesion causing trochlear palsy would cause what side effects
- affects superior oblique M.
- head will tilt away from affected side to compensate for decreased intorsion, and double vision will be worsened with downward gaze
a lesion causing abducen palsy would cause what side effects
- affects lateral rectus M.
- cannot look laterally with the affected eye
a lesion causing oculomotor palsy would have what side effects (possibly due to posterior cerebellar A. / posterior communicating A./ superior cerebellar A. aneurysm)
-affects superior/inferior/medial rectus M. and levator palpibrae M.
- affected eye will look down and out
- complete ptosis (from no eyelid opening)
- pupil dilation (from loss of PNS to pupil)
what is horner syndrome
loss of sympathetic innervation to eye.
- contriction of pupils (miosis)
- incoplete ptosis
- skin redness / warmth (vasodilation)
- no sweating (anyhydrosis)
what supplies the tarsus muscles in the orbit and what is there function
SNS fibers (traveling with CN 3 superior branch) to keep eyelid open
*CN3 uses levator palpibrae superioris to open eyelid, and SNS stimulation helps keep it open
what is the pathway that allows for the pupillary light reflex to occur
- optic n. allows sight of the light and sends afferent fibers back to the (olivary) pretectal nucleus
- cells from the pretecal nucleus will synapse in the edinger westphal nucleus , where PNS fibers join on CN 3
- presynaptic PNS fibers will travel on CN3 to synapse on the ciliary ganglion
- postsynaptic PNS fibers will send motor innervation to pupillary constrictor muscle
* consenual response in other eye = double constriction
what is the pathway that allows for the corneal reflex to occur
- ciliary fibers from V1 of CN 5 will send afferent fibers to the trigeminal nucleus
- cells from the trigeminal nucleus will send cells to the facial nucleus
- facial N. send efferent motor innervation to orbiculares occuli M. to close eye
what are the 3 layers of the eyeball and what parts of the eye do they contain
- fibrous layer (outer)
- cornea
- sclera - vascular layer (middle)
- choroid
- ciliary body
- iris
3, inner layer
-retina
T/F
neuroretina makes optic nerve which is covered in all 3 meningeal layers because it is an extension from the brain
true
what is a subjunctival hemorrhage? what can cause this?
- rupturing of vasculature below the bulbar conjunctiva (on the sclera) layer in the eye leading to bloody appearance of eyeball
- can be caused by an increased in pressure such as sneezing, coughing, or val salva maneuver
causes of complete vs partial ptosis
complete
-lesion on facial N. that leads to levator palpebral superioris M. that opens the eyelid
partial
-lesion on T1 or branches that lead to the SNS innervation of the superior tarsal M. (of muller) that maintains an open eye
what is papilledema
- buldging optic disc (blind spot of eye)
- caused by increased intracranial pressure that can potentially compresses optic N.
- emergent!! must find source of pressure to save optic nerve
what arteries anatamose in the head coming from opthalmic A.
- ethmoidal A.s ( from ophthalmic a.) – sphenopalatine A. (from maxillary a.)
- supraorbital A. (from opthalmic A.) – superficial temporal A. (from external carotid a.
- lacrimal A. (from opthalmic a.) – middle meningeal artery (from maxillary A.)
- supratrochlear A. (from opthalmic A.) —- angular A. (from facial A.)
what happens if there is an occlusion of the central retinal A. in the eye
- CRA supplies the retina
- slow occlusion can allow enough time for other anastomoses to continue to supply retina
- sudden occlusion will result in blindness due to the lack of an anastomeses with central retinal A. (it is an end artery )
superior opthalmic Vein drains into what structure? why is this important?
drains into the cavernous sinus therefore can cause spread of infection inside brain if gets infected
(comes from angular V. off of Facial V. off of internal jugular vein)
contrast central retinal V. occlusion vs. central retinal A. occlusion
artery
- “pale with red spot”
- cause: atherosclorisis, or embolism (clot)
- white retina, cherry red macula
- veins and arteries = attenuated
vein
- “ketchup”
- cause: hardening of central retinal A. or HTN of central A. will cause CRV compression
- leads to hemorrhage and dilated veins
describe the pathway of tears from the lacrimal gland
-CN7 stimulates lacrimal tear production. when the eye blinks the tears spread across eye to medial aspect and get vacuumed into the lacrimal canaliculi by the puncta. the canaliculi drains into the lacrimal sac. the orbiculariis oculi M-( palpebral part) will contract and open the lacrimal sac to initate draining into the lacrimal duct. the lacrimal duct leads to the inferior meatus of nose which causes a runny nose !
what is the ciliary body? how does it function to separate the chambers of the eye?
- ciliary body = ciliary processes + ciliary muscles
- ciliary process produces aqueous humor that fills the anterior and posterior chambers of the eye
- anterior chamber : between cornea and iris/pupil
- posterior chamber: between iris/pupil and lens/ciliary body
- aqueous humor nourishes the lens!
what drains aqueous humor from the anterior chamber of the eye? what can happen if this gets blocked ?
- the scleral venous sinus (canal of Schlemm) drains aqueous humor
- blocked of this sinus can cause glaucoma due to increased intraocular pressure
what is hyphema
rupturing and hemorrhage of blood vessels in the anterior chamber, between the cornea and Iris/pupil
*causes by trauma
describe the process of lens accommodation
- in eye accommodation, the eye medially converges, pupil constricts, and lens becomes round due to PNS stimulation on short ciliary N.
- contraction of ciliary M. reduced size of ciliary body and loosens the tension of the zonular suspensory ligaments connecting the ciliary muscle to the lens of the eye. the loss of tension causes lens to return to shape and become round for near vision
**when the ciliary M. receives innervation to relax. it will stretch the ciliary bodies back out, increase tension of zonular ligaments and flatten lens which supports far vision
