Orbit Flashcards
•Prevention of drying of the cornea is a major function of CN__________ and _________.
V AND VII
*If the surface of the eye dries out, even for a day or two, the cornea will be completely destroyed. That’s why dry eye is an important clinical condition.
•CN III, IV, VI are centrally placed in the head around the _____________ sinus, so any issues like double vision constitute an immediate medical emergency.
cavernous
Functions of the Orbit
- Protects the eye
- Provides a stable platform for the precise eye movements that are necessary for clear vision
- Provides passage for neurovascular structures serving the face
The very back of the orbit is called the __________.
apex.
What travels through the optic canal?
CN II and the ophthalmic artery
What travels through the superior orbital fissure?
CNS III, IV, V1, VI, ophthalmic vein
Does the frontal nerve inenrvate anything in the orbit?
No. Just passes through
Conjunctiva, and especially, Cornea are richly innervated by __________
V1
Closure of eyelids is by ________- innervated muscles
VII
The cornea is ____________ (avascular/vascular).
Avascular
*But can be transplanted and even harvested from cadavers for transplants
The oblicularis oculi muscle originates from the _________, circles around the eye and then comes back to insert onto the _______________.
medial palpebral ligament; medial palpebral ligament
Levator palpebrae superioris is the striated muscle that opens eye; it is innervated by __________. Deep to that is the ____________, which is actually a smooth muscle that allows the eyelid to fit to the curvature of the eye.
CN III; superior tarsal muscle
NOTE: Because it is smooth muscle, the superior tarsal muscle has sympathetic innervation from the ANS
Infection of the ciliary glands is called a ____________
“sty”.
____________generate a hydrophobic, lipid-rich secretion that forms a surface film on the lacrimal fluid and helps prevents lacrimal fluid overflow at the rim.
Tarsal glands
Blockage and infection of the tarsal glands results in a __________.
tarsal chalazion
The lacrimal gland is divided into superficial and deep portions by a sheet of tissue, the tendon of the______________. The gland has excretory ducts that dump tears into the conjunctival space, superior-laterally.
levator palpebrae superioris
The lacrimal nerve is a branch of ___________ and lacrimal artery is a branch of the __________. Both supply to lacrimal gland, which receives autonomic parasympathetic innervation.
CN V1; ophthalmic artery.
The puncta also lead into the superior and inferior _____________, which drain into the lacrimal sac.
lacrimal ducts
The lacrimal sac drains into the ___________, which opens up into the ___________ of the nasal cavity.
nasolacrimal duct; inferior meatus
What is the flow of the drainage of tears?
Drainage of tears: From lacrimal gland-> conjunctiva, across surface of cornea-> punta-> superior and inferior lacrimal ducts-> nasolacrimal sac-> nasolacrimal duct-> nasal cavity.
That’s how your nose runs when you cry.
Parasympathetic secretomotor innervation of the lacrimal gland
- Lacrimal subdivision of superior salivatory nucleus in caudal pons
- Facial nerve in temporal bone
- Greater petrosal nerve out of temporal bone into pterygoid canal
- Into pterygopalatine fossa to synapse with cells of pterygopalatine ganglion
5. Zygomatic branch of V2
6. Communicating branch to lacrimal nerve (V1 )
_____________ is a branch of CN VII that provides parasympathetic innervation to the lacrimal gland, for tear production.
The greater petrosal nerve
The anterior ethmoidal nerve continues downward to provide cutaneous innervation to the __________.
tip of the nose
_____________also gives rise to the nerve to the ciliary ganglion, and the long ciliary nerves, which enter the eyeball proper.
Nasociliary nerve
Major blood supply to orbit is the ophthalmic artery, the first large branch off the _____________.
internal carotid artery
The ophthalmic artery originates right under _________as it passes through the optic canal. It comes in at the apex of the orbit, but its main course is along the medal side of the orbit. It terminates as the __________ and ______________
CN II; supratrochlear artery; dorsal nasal artery.
The first big branch of the ophthalmic artery is on the lateral aspect of the orbit, ____________. It supplies the lacrimal gland and sends a branch toward the front of the eyeball, the anterior ciliary artery, which supplies the vascular layers of the eye.
the lacrimal artery.
•The ophthalmic artery also sends a tiny artery right into the optic nerve itself, called the _______________. It is most important because it’s the only source of blood supply to the retina.
central artery of the retina
__________ are also branches of the ophthalmic that pass behind the optic nerve and run to the back of the eyeball, bringing blood to the vascular layers of the eye and choroid of the eye.
•The posterior ciliary arteries
Damage to the central artery to the retina is mainly caused by?
•high CSF pressure, which squeezes the optic nerve.
•_______________supply the choroid, which is a big vascular backing to the neural layer. The blood vessels within the neural layer are strictly branches of the central retinal artery.
The long and short posterior ciliary arteries
•Blood is drained from the choroidal layer via the ____________.
vorticose veins
*These all eventually drain into the ophthalmic vein, which passes into the cavernous sinus.
_____________is a connection between the ophthalmic vein and the facial vein.
Suprorbital vein
•Angular vein drains down into the___________
facial vein.
The inferior ophthalmic vein drains down into _____________ within the infratemporal fossa, eventually forming the maxillary vein.
pterygoid plexus
•Sphinctor pupillae or constrictor pupillae- constricts the iris in response to:
- Pupillary light response
- Pupillary near response
Sphintor Pupillae. contraction is controlled by Parasympathetic pathways via _____________ and _________.
E-W nucleus & ciliary ganglion (III, via short ciliary nerves)
Dilator pupillae dilates the iris in response to Sympathetic activation via ______________.
Superior Cervical Ganglion (carotid plexus, long & short ciliary nerves).
When you talk about the eye’s ability to bend light you use the term ________.
diopters.
*The total refractive power in a young person’s eye is about 60 diopters.
What are the two refractive elements of the eye?
Cornea
Lens
. The lens has interfaces with the ____________ on the front and the _________ in the back.
aqueous humor; vitreous humor
The degree of refraction at an interface depends on…
The difference of refractive index of the two media and the curvature of the interface.
The degree of refraction determines the __________of the optical system.
focal length
*Sometimes this can’t be controlled (i.e in cataracts- lens is opaque)
Accommodation
Changing the curvative of the lens so that you can look at close objects; in the accommodated eye the lens is big and flat.
Parallel= distant
Diverging= near (needs to be accomodated)
What muscle regulates refractive power of the lens: parasympathetic activation results in Accomodation?
Ciliary muscle
*When muscle contracts, it allows the lins to thicken.
The “Near Reflex” or “Near Triad” for Close Vision
During a shift of view from a distant to a nearby object:
1 - eyes converge (medial recti, III)
2 - pupils constrict (sphinter pupillae, IIIps; E-W, Cil.Gang.)
3 - lenses thicken (ciliary muscle, IIIps; E-W, Cil.Gang.)
•Ciliary ganglion is tiny parasympathetic ganglion in the orbit.
- Dangling off of the_____________ branch of V1
nasociliary
Horner’s Syndrome
Classic Triad
- drooping eyelids (partial ptosis or pseudo-ptosis)
- contracted pupil (meiosis)
- lack of thermal sweating (anhydrosis)
*Results from loss of sympathetics
What nerve is the only pathway for parasympathetics to get to the Schinter pupillae and ciliary muscles?
Short ciliary nerve
•All extraocular muscles, except__________, originate from the common tendinous ring
IO
Inferior oblique doesn’t originate from the common tendinous ring. It originates from the_____________
medial wall of the orbit
•Sometimes children are born with ____________ (double vision because the insertion of eye muscles in one eye doesn’t match the other)
strabismus
The fascial system around the eyeball is called ___________. The muscle insertions have to pass through this fascia.
Tenon’s capsule.
You use two different muscles to look straight up:
•Superior rectus
•Inferior oblique
*This is the same for inferior rectus and superior oblique in the depression of the eye
•When you’re checking a patient you want to separate the different actions using the H test
