Exam 4 Orbit Flashcards
1
Q
Orbit
- Apex
- Base
- Superior border
- Inferior border
- Medial border
- Lateral border
A
- Apex: Lesser wing of sphenoid
- Contains optic foramen/canal
- Base: Orbital margin (rim)
- Contains supraorbital foramen, Infraorbital foramen
- Superior border: Frontal lobe and lesser wing of sphenoid
- Inferior border: Maxilla, zygomatic, and palantine bones
- Contains inferior orbital fissure, maxillary sinus
- Medial border: Ethmoid, maxilla, lacrimal, and sphenoid bones
- Contains ethmoid air cells, anterior/posterior ethmoidal foramina, nasolacrimal canal
- Lateral border: Zygomatic bone and greater wing of sphenoid
- Contains superior orbital fissure
2
Q
In a blow out fracture or persistent infection, which parts of the orbital are most susceptible to damage and why?
A
- Medial wall and floor because they are the thinnest aspects of the orbital.
3
Q
Lacrimal gland
- Where is it located?
- Where does it secrete tears?
- What makes up this space?
- What path do tears take when they drain?
A
- Located in superolateral aspect of the orbit
- Secretes tears into conjunctival sac
- Made up of palpebral conjunctiva and bulbar conjunctiva
- Pathway: Tears swept medially by blinking of eyelids
- Drain into punctum on medial aspect of eyelid
- Drain from punctum to nasolacrimal duct that opens into the nasal cavity
- Drains into nasal cavity under the inferior concha on the lateral wall.
4
Q
Tarsal plates
- How are they anchored to orbital margin?
- What is the function of the tarsal glands?
A
- Anchored by medial and lateral palpebral ligaments
- Tarsal glands secrete fatty substance that prevents eyelids from sticking together when they are closed.
5
Q
Levator palpebrae superioris muscle
- Action
- Innervation
- Blood Supply
A
- Action: Raises upper eyelid
- Innervation: Oculomotor (CN III)
- Blood Supply: Ophthalmic artery
6
Q
Superior tarsal muscle
- Action
- Innervation
- What can happen from a lesion of the nerve supplying this muscle?
A
- Action: Maintins tone of the eyelid (involuntary muscle back up for when levator palpebrae superioris is fatigued or damaged).
- Innervation: Sympathetic fibers traveling with frontal nerve
- Ptosis can occur from lesion of superior cervical ganglion (or Horner’s syndrome)
- Horner’s Syndrome: disruption of sympathetics to eye and area around eye
7
Q
Rectus muscles
- Origin
- Attachment
- Action
- Innervation
- Blood Supply
A
- ALL rectus muscles originate from common tendinous ring
- ALL rectus muscles attach to anterior 1/2 of eyeball
-
Superior Rectus
- Action: Elevates, adducts, medially rotates eyeball
- Innervation: Oculomotor (CN III)
- Blood Supply: Ophthalmic artery
-
Inferior Rectus
- Action: Depresses, adducts, laterally rotates eyeball
- Innervation: Oculomotor (CN III)
- Blood Supply: Ophthalmic artery
-
Lateral Rectus
- Action: Abducts eyeball
- Innervation: Abducent (CN VI)
- Blood Supply: Ophthalmic artery
-
Medial Rectus
- Action: Adducts eyeball
- Innervation: Oculomotor (CN III)
- Blood Supply: Ophthalmic artery
8
Q
Oblique Muscles
- Origin
- Attachment
- Action
- Innervation
- Blood Supply
A
- Both attach to posterior 1/2 of eyeball
-
Superior Oblique:
- Origin: Body of sphenoid
- Action: Abducts, depresses, and medially rotates eyeball
- Innervation: Trochlear (CN IV)
- Blood Supply: Ophthalmic artery
-
Inferior Oblique:
- Origin: Anterior floor of orbit lateral to nasolacrimel canal
- Action: Abducts, elevates, and laterally rotates eyeball
- Innervation: Oculomotor (CN III)
- Blood Supply: Ophthalmic artery
9
Q
Movements of the eye
Which muscles perform what action?
A
- Abduction: Lateral rectus
- Adduction: Medial rectus
- Elevation: Superior rectus, inferior oblique
- Depression: Inferior rectus, superior oblique
- Intortion (rotate eye toward nose): Superior oblique and superior rectus
- Extortion (rotate eye away from nose): Inferior oblique and inferior rectus
10
Q
Assessing the action of complementary muscle pairs of extraocular muscles and testing the integrity of the cranial nerves.
- What must the visual axis be aligned with for each muscle?
- How do you test each muscle?
A
Visual axis must be aligned with Line of Pull of muscle being tested.
Test for lesion of CN III unless stated otherwise.
- Testing Lateral and Medial Rectus:
- Eye in level forward gaze
- Lateral Rectus: Abduct eye (test for CN VI lesion)
- Medial Rectus: Adduct eye
- Testing Superior and Inferior Rectus:
- Pupil abducted 22.5˚ from midsagittal plane
- Superior Rectus: Abduct and look up
- Inferior Rectus: Abduct and look down
- Testing Superior and Inferior Oblique:
- Visually axis maximally adducted (cross-eye)
- Superior Oblique: Adduct and look down (testing for CN IV lesion)
- Inferior Oblique: Adduct and look up
- Since superior and inferior obliques also intort/extort respectively, CN IV lesion would cause inferior oblique to be unopposed, resulting in diplopia (double vision) with extortion
- Characteristic head tilt to decrease double vision
11
Q
What composes each layer of the eye?
- External fibrous layer
- Middle vascular layer
- Internal retinal layer
A
- External fibroud layer
- Sclera: posterior 5/6 of eye; opaque
- Cornea: anterior 1/6 of eye; transparent
- Middle vascular layer
- Choroid: adherent to retina and terminates at ciliary body
- Ciliary body: connects choroid to iris
- Ciliary muscle: parasympathetic innervation; contracts to change thickness of lens
- Iris: contractile colored diaphragm anterior to lens
- Sphincter pupillae: parasympathetic; constricts pupil
- Dilator pupillae: sympathetic; dilates pupil
- Internal retinal layer:
- Optic disc: where optic nerve enters eye, blind spot (no receptors, just fibers)
- Macula lutea: Contains fovea centralis (most acute area of vision)
12
Q
What are the refractive media light must pass through before reaching retina?
A
- Cornea: Transparent and avascular (long healing periods for abrasions)
- Continuous with sclera at sclerocorneal junction
- Aqueous humor: Clear watery fluid in anterior & posterior chambers of eyeball
- Made by ciliary processes
- Drained through iridio-corneal angle to circular venous canal of Schlemm
- Lens: Transparent biconvex structure within transparent capsule
- Curvature altered by contraction of suspensory ligament of lens (off ciliary bodies)
- Accommodation is reflex that allows us to view objects a short distance away from eye
- Vitreous body: Jelly-like matrix filling space b/w lens and retina
- Not continually replaced
- “Floaters” are cellular debris from vitreous body
13
Q
What can clinically happen in relation to the lens if:
- CN III is damaged?
- There is a loss of transparency?
A
- If CN III is damaged, muscles responsible for accommodation cannot contract and thus accommodation is lost.
- Loss of transparency = cataracts
14
Q
Branches of ophthalmic artery and what they supply
A
- Lacrimal artery: supplies lacrimal gland
- Central artery of retina: supplies retina
- Ciliary arteries: supply structures within the eyeball
- Supraorbital artery: exits orbit via supraorbital notch
- Anterior and posterior ethmoidal arteries: supply ethmoid air cells and nasal cavity
- Dorsal nasal artery: supplies dorsum of nose
- Supratrochlear artery: terminal branch of ophthalmic artery
15
Q
- What are they veins of the orbit?
- Where to they exit the orbit?
- What do they drain into?
A
- Superior and inferior ophthalmic veins
- Arise form supraorbital and angular veins
- Pass trhough superior orbital fissure
- Drain into cavernous sinus
- Central vein of retina
- Travels with central artery of retina
- Drains into cavernous sinus
