Eye and Eye Movements Flashcards
What bones form the orbit?
Frontal Ethmoid Sphneoid (greater wing) Zygomatic Lacrimal Maxillary
Draw the anatomical relationship of the paranasal sinuses - frontal, ethmoid and maxillary sinuses
REfer to drawings
What happens if you get an infection in the ethmoid sinuses?
Infection can erode to the orbits and cause optic neuritis
Orbital Blow out fractures:
Fracture of the orbital walls caused by indirect trauma
Usually occurs medially and inferiorly involving the maxillary bone
Contents of the orbit may prolapse and entrapped in the maxillary sinus
Clinical: diplopia, globe ptosis, exophthalmos (protrusion of eyeball)
Describe the position of the orbital globe
Medial walls are parallel but lateral walls are right angles to each other , causing the axes of the orbit to diverge at 45 degrees while the axes of gaze are parallel
Draw out the different movements of the pupil and their axis
Refer to drawings
Draw the schematic for remembring EOM actions:
Refer to drawings
How would you clinically test the EOMs?
H test, Superior/inferior rectus and obliques are tested through actions opposite their actions
So to test Inferior/superior Oblique: Adduct the eye (since these are abductors)
To test the superior/inferior rectus: Abduct the eye
How do you discriminate between muscle and nerve dysfunction?
Trap one muscle and test the muscle doing opposite the movement. Trapping means the visual gaze axis is perpendicular to muscle fiber direction
Long ciliary N. and short ciliary N. innervation:
Sensation to cornea and sympathetic to dilator pupilae
Short ciliary carries parasympathetic fibers to dilator pupillae
Long ciliary carries … fibers
Short Ciliary carries …. Fibers
Sympathetic to dilator pupilae
parasympathetic to sphincter pupilae
Which nerves go through the superior orbital fissure?
What is the tendinous ring? Which nerves go through it?
Lacrimal, frontal and trochlear. Do NOT pass through the tendinous ring
Formed by the rectus muscles. Oculomotor, Abducens, Nasociliary (also passes through the superior orbital fissure)
*OAN passes through both
Optic nerve passes through ….
Tendinous ring and optic canal
Draw the sympathetic pathway of eye movement:
REfer to drawings
What do the sympathetic fibers of the external carotid plexus innervate?
Salivary glands, sweat glands, blood vessels (vasoconstriction)
What comes off the internal carotid plexus:
Deep petrosal N. (sympathetic). Joins greater petrosal N. (parasympathetic) to form the N. of the pterygoid canal. Sympathetic fibers join the parasympathetic pterygopalatine ganglion to the blood vessels
How is the eye sympathetically innervated?
From the Internal carotid plexus, sympathetic fibers jump on to nerves that will get them where they wanna go.
Via ciliary ganglion (parasympathetic) then short ciliary N. > dilator pupilae (do sympathetic stuff!)
Via the nasociliary N. > dilator pupilae.
Via the Superior root of CN III then > superior tarsal muscle (keep eyes open!)
Horner’s syndrome:
Cause
Clinical
Damage to the sympathetic innervation of the head and neck. No sympathetics = parasympathetics take over.
Constricted pupil, ptosis (eyes staying shut), anhydrosis (no sweat), vasodilation leading to flushing of skin,
Draw the parasympathetic pathway of eye movement:
Refer to drawings
Describe parasympathetic innervation to the eye:
From parasympathetic root of the Ciliary ganglion > Synapse at ciliary ganglion > post synaptic parasympathetic travels to the sphincter pupilae and ciliary muscle to constrict the pupil
Trochlear palsy:
Superior oblique paralysis. Eye is laterally rotated.
Patient presents with eye tilted away from affected side. Diplopia worse on downward gaze.
Abducens palsy:
Cannot look laterally with affected eye
Oculomotor Palsy:
Eye is down and out due to loss of ocular muscle innervation. SO and LR are still intact.
Complete ptosis due to loss of innervation to LPS
Pupil dilation due to loss of parasympathetic innervation to pupil (Oculomotor carries parasympathetics)
Explain the pupillary light reflex:
4 neuron pathway. Light sensed by CN II (sensory) and will synapse to pretectal nucleus > pretactal nucleus cells synapse to Edinger-Westphal nucleus > Preganglionic parasympathetic neurons travel with CN III (motor portion) and will synapse to ciliary ganglion > postganglionic parasympathetic neurons synapse in the pupillary constrictor muscle and constrict the pupil
Explain the corneal reflex:
Corneal receptor detect touch and irritation > travel in CN V and synapse in trigeminal sensory nucleus or spinal trigeminal nucleus > cells at the TSN project to facial nucleus > neuron in facial nerve will cause eye to blink
Layers of the eyeball:
Fibrous (sclera and cornea)
Vascular (choroid - full of blood vessels, ciliary body and iris)
Inner (retina)
Draw the cross section of the optic nerve and its contents:
Refer to drawings
Difference between Levator Palpebrae superioris and Lateral Tarsal muscle:
Lateral tarsal muscle keeps the eye open. Innervated by sympathetic nerve fibers
Characteristics of bacterial vs. viral conjunctivitis
Bacterial: crusty eyes, discharge
Viral: Red with no discharge
Subconjunctival hemorrhage:
Rupture of eye vessel between the sclera and bulbar conjunctiva
Can happen whenever you increase your interabdominal pressure (like blowing your nose)
Complete ptosis:
Complete closure of eye
Paralysis of the levator palpebrae superioris due to damage of CN III or one of its branches.
Tarsal ptosis:
Paralysis of the tarsal muscle. Somewhat close eyes.
Innervated by postganglionic sympathetic fibers (from T1 level)
Horner’s usually due to Tarsal muscle paralysis due to sympathetic nerve damage
Papilledema
Caused by increased intracranial pressure (ICP) in the subarachnoid space and pushing on the optic disc.
Emergent as cause of increased ICP needs to be determined.
Where do the arteries supplying the eye branch from?
Internal carotid artery
Anastomosis of eye arteries:
Supraorbital A. anastomose with Superficial temporal A.
Supratrochlear A. anastomose with Angular
Lacrimal anastomose with middle meningeal
Ethmoidal anastomose with sphenopalatine
Draw the arteries of the eye
Refer to drawings
Importance of anastomosis:
Blood flow keeps going despite occlusion.
If ophthalmic a. is blocked, anastomosis takes care of the blood flow by supplying the central retinal artery
Central retinal artery:
Sole blood supply to the eye (no anastomose). Occlusion will cause organ death
Venous supply to the eye:
Superior and inferior ophthalmic vein can drain infections in the face to the cavernous sinus and cause meningitis.
Central retinal vein occlusion:
Cause
Clinical
Hardening of the CRA and HTN in CRA can compress the CRV
Hemorrhages and dilated veins
Central Retinal Artery occlusion
Cause
Clinical
Artherosclerosis, embolism
Retinal appears white. Cherry red spot. Veins and arteries attenuated
What is the lacrimal apparatus?
Consists of the lacrimal gland, lacrimal canaliculi, lacrimal sac and nasolacrimal duct
Draw the lacrimal apparatus
Refer to drawings
Drainage of tears:
Lacrimal gland > lacrimal canaliculi > puncta “wick” the tear into the lacrimal sac > through the nasolacrimal duct > inferior nasal meatus
Lacrimal part of the orbicularis oculi
Attaches to the lateral side lacrimal sac, opening it up when you blink and suck it down the lacrimal aparatus
Draw the parasympathetic innervation of the lacrimal gland
REfer to drawings
Describe the process of tear production:
Greater petrosal N.(parasympathetics from CN VII) and deep petrosal n. form the N. of the pterygoid canal > Parasympathetic fibers synapse to the pterygopalatine ganglion > fibers travel with v2 > zygomaticotemporal n. and its communicating branch to get to lacrimal n. > synapse at lacrimal gland
Only lesions on this pathway can affect tear production. Trigeminal nerve is just a highway.
Four eye chamber:
Ciliary body
Ciliary process
Anterior chamber
Posterior chamber
Describe the flow of the aqueous humor:
Ciliary process secrete the aqueous humor > posterior chamber >anterior chamber > flow into the scleral venous sinus (Schlemm’s canal)
Draw the flow of the aqueous humor
Refer to drawings
Glaucoma:
Cause
Blockage of the Schlemm’s canal leading to increased pressure
Hyphema
Cause
Clinical
Rupture of blood vessels that supply the anterior chamber
Ciliary body mechanics (effect on lens)
Contraction of ciliary muscles decreases the size of the ciliary body
Reduces the tension on the suspensory ligament and lens becomes more rounded (for near vision)
2 types of conjunctiva:
Palpebral (lines inner most part of the eyelid)
Bulbar (ocular) conjunctiva (lines the outermost part of the eyeball
