The Orbit And Eye Flashcards
What is the palpebral portion of the orbicularis oculi muscle?
Extends from the medial to the lateral palpebral ligament Functions in gentle closing of the eyelid
What is the lacrimal portion of the orbicularis oculi?
Extends from the posterior lacrimal crest to the tarsal plates of the lids and lacrimal sac Increases amount of lid contact to the surface of the eyeball and dilates the lacrimal sac
What innervates the levator palpebrae superioris muscle?
GSE fibers of CN III
What are the 5 layers of the eyelid?
Skin Subcutaneous tissue Muscular layer containing the orbicularis oculi, levator palpebrae superioris and tarsal muscle Palpebral fascia Conjunctiva
What is the tarsal muscle of Muller innervated by?
Postganglionic sympathetic fibers Preganglionic fibers originating at the level of T1
Destruction of the oculomotor nerve or one of its branches to the levator palpebrae superioris can result in what?
Paralysis of the LPS and complete ptosis
What is Horner’s syndrome?*
Usually involves paralysis of the tarsal muscle Results in slight ptosis Leads to miosis (pupillary constriction due to paralysis of the dilator pupillae muscle), enopthalmos (due to paralysis of the orbitalis muscle of Muller which has a slight protrusion function), Anhidrosis and blushing of the skin on the face may also be present Interruption of pupillary dilation pathway can result in this
Which structures are involved in draining tears from the surface of the eye?
Lacrimal gland, lacrimal duct, lacrimal canaliculi, lacrimal sac and nasolacrimal duct
What is the lacrimal gland?
An oval shaped gland resting in the lacrimal fossa of the orbit It’s secretions (tears) keep the surface of the cornea moist
What are lacrimal canaliculi?
Small L shaped tubes that have an opening called the lacrimal punctum which forms the apex of the lacrimal papilla Drain tears from the surface of teh eyeball to the superolateral aspect of the lacrimal sac via a common sinus (sinus of Maier) Lacerations of the canaliculi require prompt surgical attention
What is the lacrimal sac?
An elongated tear dropped shaped membranous sac located between the anterior and posterior lacrimal crest Receives lacrimal canaliculi superolateral and is continuous with the nasolacrimal duct inferiorly
Describe the parasympathetic innervation to the lacrimal gland
The superior salivatory nucleus sends preganglionic fibers via CN VII, greater superficial petrosal and vidian nerve to the sphenopalatine/pterygopalatine ganglion where they synapse Postganglionic fibers course to the lacrimal gland via the maxillary, zygomatic and lacrimal nerves
Explain sympathetic innervation to the lacrimal gland
Postganglionic fibers from the superior cervical ganglion travel along the internal carotid plexus and give rise to the deep petrosal nerve which fuses with the greater petrosal to form the Vidian N Fibers course through the pterygopalatine ganglion without synapsing and distribute to the lacrimal gland via maxillary, zygomatic and lacrimal nerve route
What is traumatic optic neuropathy?
Intracanalicular portion of the optic nerve is vulnerable to ischemia secondary to orbital fracture Relatively low incidence to head trauma but has a direct impact on the optic nerve, opthalamic A and vascular supply to the retina via the central retinal artery
Blow out fractures of the floor of the orbit may by due to what?
Trauma to the front of the eyeball or a depressed fracture of the zygomatic bone which is displaced medially
What do blow out fractures cause?
Herniation of the certain orbital structures (such as the periorbita, the inferior oblique and inferior rectus muscles, or the orbital fat pad) into the maxillary sinus
In which direction are those with a blow out fracture not able to move their eyes?
Won’t be able to move their eye to the side of injury
What is a Le Forte type I fracture?
Transverse fracture of the maxillae just above the alveolar processes Moveable upper dental arch with some teeth missing
What is a Le Forte type II fracture?
Pyramidal shaped fracture of the maxillae usually involving part of the medial margin of one of the orbits
What is a Le Forte type III fracture/craniofacial dysfunction?
Extensive transverse fractures of the face involving many facial bones and both orbits (panda bear appearance-two black eyes and swollen lower face) Basically the face has been separated from the base of the skull
What innervates the extra-ocular muscles?
All innervated by the oculomotor nerve except the superior oblique (IV) and lateral rectus (VI) SO4, LR6 and remainder 3
What is the periorbita continuous with?
Endosteal dura
What occurs with paralysis of the superior rectus M?
Inability to abduct and elevate the affected eye
What occurs with paralysis of the medial rectus?
Inability to adduct the affected eye
What occurs with paralysis of the inferior rectus?
Inability to abduct and depress the affected eye
What occurs with paralysis of the inferior oblique?
Inability to adduct and elevate the affected eye
What occurs with paralysis of the superior oblique?
Inability to adduct and depress the affected eye
What occurs with paralysis of the lateral rectus?
Inability to abduct the affected eye
Increased intracranial pressure may compress the abducens nerve and result in what?
Paralysis of the lateral rectus muscle
What causes hydrocephaly and what CN problems does it cause?
Congenital Causes compression of the VI nerve (may occur secondary to increase in intracranial pressure) Results in a sundown gaze
What are the cardinal signs of gaze?
Clinical test of extraocular muscle function of both eyes simultaneously Looking straight up and down are not cardinal positions
What is the chief/main sensory nerve of the eye?
Nasociliary N (opthalamic division of CN V)
What are the motor nerves of the orbit?
Oculomotor, trochlear and abducens
What does paralysis of the oculomotor nerve result in (nerve palsy)?
External strabismus, complete ptosis, dilated and unreactive pupils
What does paralysis of the trochlear nerve result in (trochlear nerve palsy)?
Inability to adduct and depress the affected eye Pt tends to tilt his head away from the affected eye
What occurs with with paralysis of the abducens nerve?
Inability to abduct the affected eye Diplopia due to internal strabismus
Describe direct and consensual corneal reflexes
Stimulus: lightly touching the cornea -> Receptors: naked nerve endings in the cornea -> Afferent fibers: nasociliary nerve, especially long ciliary nerves -> Sensory nucleus: descending nucleus of V -> Motor nucleus: facial nucleus -> Efferent fibers: facial nerve -> Effector: orbicularis oculi muscle -> Response: blinking (both direct and consensual)
What are the afferent and efferent fibers of the corneal reflex?
Afferent: nasociliary N (V) Efferent: zygomatic branch of VII
What is the main blood supply to the orbit?
Opthalamic artery
What are the branches of the opthalamic artery?
Supraorbital, posterior ethmoidal, anterior ethmoidal, lacrimal and short ciliary arteries
Which artery is the chief blood supply to the retina?
Central retinal artery
What arteries supply the optic nerve?
Posterior ciliary and central retinal arteries which are branches of the ophthalmic A
What is hyphema?
Presence of blood in the anterior chamber of the eyeball usually due to trauma and rupture of the great arterial circle of the iris A serous medical emergency Involves the arterial circle of the iris
What is subconjuctival hemorrhage?
Usually due to a rupture of the deep pericorneal plexus The bleeding is restricted to the subconjuctival tissue or bulbar fascia
What is conjunctivitis?
Brick red inflammation or irritation of the conjunctiva It is more noticeable at the fornices When touched the reddens does not fade and the vessels are movable Involves the superficial pericorneal plexus
What are the ciliary muscles?
Circularly arranged smooth muscle fibers innervated by postganglionic parasympathetic axons from the ciliary ganglion When stimulated they decrease the tension on the ciliary zonula fibers and allow the lens to thicken for near vision
What is the direct light reflex?
Elicited by shining a light in an eye As a result there is ipsilateral pupillary construction which is mediated at the level of the brainstem via parasympathetics Pretectum is a critical link
What is the consensual light reflex?
Shining a bright light in one eye will result in pupillary constriction of the contralateral eye Posterior commissure involved
What is accommodation?
Gaze and vision to view objects in the near field of vision Initiated in the cerebral cortex and medicated by the oculomotor nerve Originates in the frontal eye field of the frontal lobe and projects to the midbrain Involves Edinger-Westphal and oculomotor nuclei
What are the three responses of the triad of accommodation?
Convergence of vision due to bilateral constriction of the medial rectus muscles Pupillary constriction due to contraction of the sphincter pupillae muscles Thickening of the lens due to relaxation of the ciliary zonula fibers by the ciliary muscles
Which components of the triad of accommodation are mediated by the parasympathetic component of CN III?
Pupillary constriction and thickening of the lens
What is Argyll-Robertson pupil?
A result of syphilis infection Clinically the pupils are unreactive to light but constrict during accommodation probably due to the destruction of the pretectum (important in light reflex but not accommodation)
What is Holmes-Adie pupil (or tonic Adie pupil)?
Benign condition which may be due to a lesion of the ciliary ganglion Slow constriction upon convergence Parasympathomimetic drugs constrict the tonic pupil (which will have no effect on normal pupils) Common in young adult females
What is papilledema?
Due to increased intracranial pressure which restricts venous return from the retina Results in edema of the optic disc
What is the pathway for the light reflex?
