Orbit & Eye Flashcards
What is in the bony orbit?
Zygomatic, ethmoid, maxillary, frontal, lacrimal, palatine
What is a “blowout” fracture?
result in bleeding into maxillary sinus; may entrap inferior rectus (restricted upward gaze) or inferior oblique muscle and/or lacerate the infraorbital n. (sensory loss on lower eyelid & maxilla)
What is a medial orbital fracture? What does in impact?
impact the ethmoid»_space; sphenoid sinus; can entrap
medial rectus (restricted lateral gaze)
What are the structures of the eyelids?
Skin, loose CT, muscular layer, tarofascial layer, conjunctiva
What lubricates the eye?
Lacrimal gland along with accessory lacrimal glands
The lacrimal gland’s innervation is…
GSA, GVE parasympathetics via CN VII, and GVE sympathetics via T1-T4
Where is the collecting apparatus situated?
Medial canthus
What does sympathetics control in the eye?
Blood
What does parasympathetics control in the eye?
Secretion
Injury to parasympathetics -> dry eye
The suspensory ligament of Lockwood…
Holds eyeball inside eye
What are the internal structure of the eye?
- Fibrous layer
- Vascular layer
- Nervous layer
What is the fibrous layer continuous with?
Dura
What does the fibrous layer make up?
Sclera
What is the sclera?
Covers 5/6 of the eye, opaque, lamina cribrosa, major attachment of eye muscles
What is continuous with the sclera?
Cornea, transparent
What does the vascular layer make up?
Choroid
What is the choroid continuous with?
Arachnoid + pia
What is the choroid?
Covers about 5/6 of the eye, has the optic nerve within
If we block scleral venous sinus, what can occur?
Glaucoma
Where is the ciliary body?
Vascular layer
What is the ciliary body?
- from ora serrata to scleral spur
- ciliary process and zonular fibers
- secretes aqueous humor
- ciliary muscle
- scleral venous sinus
- anterior and posterior chambers
How is the lens anchored?
Zonular fibers
What is lens?
- found at the junction of the anterior and posterior compartments
- anterior surface contacts the iris
- posterior surface contacts the vitreous body
- ciliary processes and zonular fibers
- cataract
The action of ciliary muscle when relaxed is…
Big opening, tight zonula fibers, lens is flat & skinny
The action of ciliary muscle when contracted is…
Small opening, slack zonula fibers, lens is rounded & fat
What is within the iris?
Sphincter pupillae (CN III)
Dilator pupillae (sympathetics, T1-T4)
What is the function of the iris?
Split into anterior & posterior compartments
Pupil is…
Empty!
When are dilator pupillae most active?
Scared, sympathetics, dark room
When are constrictor pupillae most active?
Surrounded by light
What is in the nervous layer?
Retina, macula layer, optic disc
What does the retina contain?
- contains pigmented epithelium and photoreceptive cells
- neural and non neural parts
- from ora serrata to optic disc
What is macula layer?
- an area of the retina with a high concentration of photoreceptors
- fovea centralis - area of highest visual acuity, a tea cup-like depression
What is optic disc?
- where optic nerve fibers leave the eye
- no photoreceptors here = blind spot
- entry/exit of the central retinal vessels
If the macula is flattened, what occurs?
Papilledema
What is the vitreous body?
gel-like mass that fills the posterior chamber
functions in refraction of light and maintains the shape of the globe
hyaloid canal
What is the vascular supply of the eye?
Ophthalmic artery
What are the branches of the ophthalmic artery?
- central artery of the retina
- muscular
- ciliary
- lacrimal
- supraorbital
- anterior and posterior ethmoidal
- meningeal
- supratrochlear and dorsal nasal
What is amaurosis fugax?
Vision loss in one eye, fleeting blindness
Sign of impending stroke
What is the venous drainage of the eye?
- Superior ophthalmic vein
- Inferior ophthalmic vein
- Infraorbital vein
- Central vein of the retina
All drain into cavernous sinus -> pterygoid plexus
What is the sensory innervation of the eye?
CN V1 (ophthalmic nerve)
- Nasociliary
- Frontal nerve
- Lacrimal nerve
CN V2 (maxillary nerve)
- infraorbital & zygomatic
What is present within corneal reflex?
CN V -> trigeminal ganglion -> close eye -> orbicularis oculi -> CN VII
The ciliary ganglion is a …
Parasympathetic ganglion
What does the ciliary ganglion contain?
Cell bodies that innervates the intrinsic eye muscles
What are the three roots of the ciliary ganglion?
- Sensory - returning sensory information from the eye; CN V1
- Sympathetic - from internal carotid plexus via ophthalmic artery or CN III; supplies the dilator pupillae
- Motor - contains preganglionic axons from CN III to sphincter pupillae and ciliary muscles
Postganglionic sympathetic axons….
- arise from the superior cervical ganglion and travel along the cavernous plexus
- reach the orbit on ophthalmic artery, CN III or CN V
- traverse the ciliary ganglion without synapse
- Innervate the dilator pupillae muscle and superior tarsal muscle
What occurs when paralysis of dilator pupillae occurs?
Miosis
What occurs when paralysis of superior tarsal muscle?
Mild ptosis
What are the muscles of the eye innervated by?
Oculomotor nerve (CN III), trochlear nerve (IV), abducens nerve (VI)
Key points of the oculomotor nerve in the eye
- arises from: cavernous sinus:
- through the supraorbital fissure
- divides into: parasympathetic root to ciliary ganglion
If anisocoria occurs in the dark…
Sympathetics injury
If anisocoria occurs in the light…
CN III injury
What are the extraocular muscles?
- a common tendinous ring is derived from the orbital fascia
- neurovascular structures and the common tendinous ring
What is levator palpebrae?
- arises from the roof of the orbit and attaches to the upper eyelid, associated with superior tarsal muscle
- Innervation: CN III
Compressive injury of CN III?
PCOM aneurysm, abscess
* a painful and complete oculomotor palsy that involves the pupil is most often an aneurysm
* compressive injuries can affect the pupil but spare eye movements (because of the superficial location of the GVE axons in CN III)
Ischemic injury of CN III?
- can spare GVE axons
- a painless oculomotor palsy that spares the pupil is most often microvascular
