Orbit of the Eye- Gilland

Question 1

What are the 3 general functions of the orbit?

Answer 1

Protects the eye - bony orbit, eyelids, lacrimal apparatus (mechanism for draining the tears); ocular adnexa, is a term that refers to accessory structures of the eyes

Provides a stable platform for the precise eye movements that are necessary for clear vision - extraocular muscles, orbital fascia, orbital fat; it is really easy to disrupt clear vision; if the two eyes are not centered on the same object in space or if the eyes are not both able to move in the same direction at the same time or if the eyes don’t converge correctly as you go closer to an object you get double vision; eye problems could occur through problems with eye muscles or tumor development in orbit

Provides passage for neurovascular structures serving the face - pathways for ophthalmic artery and vein (BV supply and drain orbital structures but also anastomose with BV such as the facial vein and arterial branches out there), branches of V1 and V2; a way for nerves and blood vessels to use orbit as a transit system for connections between face and deep structures

The frontal nerve passes right through the orbit (innervating nothing in the orbit, biggest nerve in orbit) innervating right above your eye and includes the branch that goes all the way to the top of your head to give the V1 dermatome

V2 (maxillary nerve) gives a little bit of innervation to orbital structures but mostly rides forward in the floor of the orbit and emerges out as the infraorbital nerve

Question 2

Slide 4

Answer 2

• the orbit from the front is shaped kind of like a pyramid
• the apex is deep to the back of the orbit
• base of the pyramid is at the margins of the orbit

If we divide the orbit sagittally we will have a lateral and medial half

the orbital cavity whose roof is made up of the frontal bone; its floor is the roof of the maxillary sinus; most of that is a thin sheet of maxillary bone

the lateral wall consists first of a thickened rim that continues posteriorly as the zygomatic arch; the most posterior part of the lateral wall is the greater wing of the sphenoid

the medial wall sits in relation mainly to the ethmoid air cells in the nasal cavity; it has two bones: ethmoid (a thin sheet of bone; if you poke a hole in it you go right through the ethmoid air cells) and lacrimal bone which forms the broad area of the medial wall

posterior part of the medial wall is comprised of lesser wing of the sphenoid

Question 3

Orbital Foramina

Answer 3

lots of opening associated with the orbit

• straight into the orbit is the optic canal for the optic nerve and ophthalmic artery to go through
• just lateral to that is the superior orbital fissure where CN III, IV, V1, and VI gain access to the orbit; it is also an opening directly in btw the lesser and greater wings of the sphenoid
• the floor of the orbit in back is continuous with superior orbital fissure is called the inferior orbital fissure; it is above the pterygopalatine fossa which is a space behind and below the orbit and behind the maxillary sinus; it is continued forward by the infraorbital groove with infraorbital artery and nerve running in that groove; they emerge out front just below the rim of the orbit through the infraorbital foramen; if you dig just deep enough under the levator labii superioris muscle on the face dissection you would have found a big bundle of nerve fiber-infraorbital nerve

an interesting open in the anterior medial part of the orbit that goes down is the nasolacrimal canal whose opening is bounded by the lacrimal bone and parts of the maxilla, that’s the bony canal that will have the nasolacrimal duct and is the passage for draining tears out of the orbit

above the eye is usually just a notch or foramen (supraorbital notch/foramen) where the supraorbital comes out of the orbit and extends up through the scalp to the top of the head; sometimes it ossifies around the nerve and BV and becomes a supraorbital foramen

over laterally is a small zygomatic foramina where branches of V1 and V2 escape out of to give you some of the sensory innervation out on the side of the face in front of the temporal region

medially in the orbit there are some ethmoid foramina for branches of V1 and nasociliary part of V1 along with ethmoidal arteries passing in through the ethmoidal air cells and continuing on out into the nasal region

Question 4

Relationships of the orbit relative to its neighbors

Answer 4

-superiorly (above the orbit) through its roof is the anterior cranial fossa and frontal sinus (frontal bone is hollow)

Medially – ethmoid bones that surround the upper part of the Nasal Cavity near the midline and Ethmoid Sinuses; made up of thin sheets of bone and there are 3 ethmoid air cells whose sinus is the same as frontal maxillary, etc.

Inferiorly –
Maxillary Sinus

Laterally -
Zygomatic-Frontal Buttress (very strong bone) and immediately behind that is Temporal Fossa with the temporalis muscle

Question 5

Pathways to and from the orbit

Answer 5

The Superior Orbital Fissure and Optic Foramen (in apex of orbit) lead to the Middle Cranial Fossa and Cavernous Sinus (main drainage area for the ophthalmic veins); when you’re looking forward when trying to follow the V1 division and the CN III forward that’s where you’re passing and right there is the cavernous sinus

The posterior part of the Inferior Orbital Fissure leads to the Pterygopalatine Fossa (is where branches of maxillary nerve and artery find a nice spot where they can be distributed everywhere in frontal part of the head, so there will be BV and nerve fibers coming up from pterygopalatine fossa into the orbit through the infraorbital fissure

The anterior part of Inferior Orbital Fissure Leads to the Infratemporal Fossa (the deep area where you will get to the back side of the maxillary sinus where you will see the maxillary artery disappearing into the pterygopalatine fossa and right above that is the infraorbital fissure

Question 6

Appreciating the differences in the walls of the orbit

Answer 6

roof made up of frontal bone and side wall largely made up of zygomatic and the greater wing of the sphenoid are pretty STRONG

in contrast the medial wall is largely made up of the large plate of the ethmoid bone is very WEAK; this part is called the lamina papyracea(which is thin like a piece of paper)

the floor which is roof of the maxillary sinus is also very thin (WEAK)

medial and inferior walls can be damaged by trauma to the eye

Question 7

CT imaging of “Blowout” fracture of orbital floor

Answer 7

saw the contents of the orbit being pushed down into the maxillary sinus

• someone could have thrown a baseball into the eye
• there is no air in the orbit and so when you push something in the orbit something gots to give in this case it was the orbital floor

Question 8

Blow-out of medial orbital wall

Answer 8

• pt is able to look ahead and to the right
• the right eye is not moving left and so it looks like the medial rectus (make you look leftward with your right eye) is not working; medial wall of the orbit is gone and contents of the orbit have been pushed into the ethmoid air cells

that medial rectus muscle which is probably hooked onto the sharp bony fragments in there

Question 9

Superficial Orbital and Ocular Structures

Answer 9

superior and inferior palpebrae (eyelids)

the space in between them is the palpebral fissure; so when you blink you eliminate this fissure momentarily

cilia (eyelashes)

supercilium (hairs of eyebrows, everything above the cilia)

tarsal: broad plate of each eyelid

just above the eye is the supratarsal region

the lineup is the superior palpebral sulcus

conjunctiva: transparent layer over the white eye; has bulbar (on eye) and palpebral (on eyelids); does not cover the cornea

Fornix is the junction btw bulbar and palpebral of the conjunctiva

cornea is the clear covering of the pupil and iris

sclera: deep to the conjunctiva is the whitening of the eye; thick connective tissue covering of the eye itself

limbus is the junction between the sclera and cornea

bulbar conjunctiva is continuous with the outer layer of the cornea at the limbus

Question 10

Blowout occurs because

Answer 10

the eyeball itself is unbelievably strong; blowout occurs only when you have a sharp object going into it

Question 11

Innervation of Ocular structures

Answer 11

Cornea is AVASCULAR but is supplied by the liquid structures behind it and does repair itself well (cadaver cornea used in cornea transplant); thus is its so important to protect the cornea with eyelids and the ability to flood tears across it

Conjunctiva, and especially, Cornea are richly innervated by V1 (mechanosensory and pain fibers from V1)

Closure of eyelids is by VII- innervated muscles: orbicularis oculi

V-VII blink reflex is crucial for protection of cornea; trigeminal/facial blink reflex

Question 12

abrasion, laceration, drying and inflammation of the cornea results in

Answer 12

result in temporary and often permanent loss of the visual function of the eye

Question 13

Orbicularis oculi muscle

Answer 13

• has an outer orbital portion and a palpebral portion
• both origin and insertion is the medial palpebral ligament

these are muscles NECESSARY AND SUFFICIENT TO CLOSE THE EYES

lateral palpebral ligament lies deep to the muscle

The palpebral portions of orbicularis oculi are responsible for eyelid closure during normal blinking (in which there is slight retraction of the eyeball)

The orbital portions of orbicularis oculi are responsible for tight eyelid closure; skin of your cheek moves upward and the skin of forehead moves downward

Question 14

Palpebral Structures

Answer 14

Anterior palpebral surface, covered by thinnest skin of the body

Palpebral part of orbicularis oculi

Lev. Palp. Sup. (striated muscle that opens the eye)

Superior Tarsal Muscle (smooth muscles of Mueller); found as you follow Lev. Palp. Sup. into the eyelid which continues as smooth to be this muscle; are tonically active and are present to make eyelid perfectly shaped to your eyeball; when you lose PS innervation of this muscle, your eyelids droop

tarsal plate is a connective tissue structure

Palpebral Conjunctiva is epithelial covering on the inner surface of the eyelid

tarsal glands are embedded in and around the tarsal plate

palpebral rim of the eyelid

Roots of eyelashes (cilia) surrounded by ciliary sebaceous glands

Infection of the ciliary glands is called a “sty”.

Question 15

Deep surface of the eyelid: Tarsal glands

Answer 15

-generate a hydrophobic, lipid-rich secretion that forms a surface film on the lacrimal fluid and helps prevents lacrimal fluid (eery fluid) overflow at the rim

Blockage and infection results in a tarsal chalazion

Openings of excretory ducts at palpebral rim;

Question 16

Lacrimal Gland

Answer 16

take away the skin and the orbicularis oculi you could dissect in the upper lateral part of the eyelid and discover the lacrimal gland

it is outside and deep to the levator palpebrae superioris that opens your eye
it has ducts that dump tears into the conjunctival space

the tears are all put into the conjunctival space superolaterally and they’re spread downward and medially by gravity and partly by capillary action and partly by blinking and movements of the eye

if we take the eye out and look inside the orbit there is the lacrimal gland in the upper lateral part of the eye and coming towards we’ll see lacrimal nerve which is a branch of the V1 and lacrimal artery

the innervation of lacrimal glands is not from V1 except as a hitchhiking pathway

we’ll see later that the pterygopalatine ganglion in the pterygopalatine fossa provides PS innervation to the lacrimal gland

so in the end it is part of the facial nerve PS system

located superolaterally in orbit, partially divided into superficial and deep parts by tendon of Lev. Palp. Sup.

excretory ducts pour lacrimal fluid into conjunctival space

Question 17

Medial Angle (canthus) of the Eye

Answer 17

the tears from superolaterally to inferomedially and they end up in the medial angle of the eye called the lacrimal lake

The “Lacrimal Lake” is bounded by the semilunar fold and the medial palpebral commissure, and contains the a little elevation called caruncle. (last branch of the facial artery was the angular artery because it ends up terminating in the medial angle of the eye)

Tears collect in the lacrimal lake and there is a little hole there on top of the two papilia, one on the upper and one on the lower a couple mm away from the medial angle of the eye called Puncta

Lacrimal fluid is wicked into the Puncta of the Lacrimal Papillae; they wick up the tears through capillary action and taking them into the nasolacrimal system; so as the fluid goes through the Puncta of the Lacrimal Papillae it enters into the Superior and Inferior Lacrimal Ducts (AKA canaliculi) which leads to the structure inside the nasolacrimal canal (lacrimal sac)

Question 18

Lacrimal duct (the lacrimal system dumps into the nasal system)

Answer 18

lacrimal duct extends down through the nasolacrimal canal and into the nasal cavity

this is a cut away to show tears enter the Puncta goes through the canaliculi down through the lacrimal sac and gets dumped here which is the inferior meatus in the nasal cavity

Question 19

Parasympathetic secretomotor innervation of the lacrimal gland

Answer 19

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—>

Zygomatic branch of V2—>

Communicating branch to lacrimal nerve (V1 )

just know that facial nerve gets innervated to the pterygopalatine ganglion which sends its fibers up in a curious path up into V2 along the zygomatic nerve and then there’s a communicating branch along the lateral wall of the orbit to the lacrimal nerve (V1 fibers) and follows them into the lacrimal gland to provide secretomotor PS innervation

Question 20

Sensory Innervation and Vascular Supply of Eye and Orbit: What are the 3 main branches that separate before entry into the orbit?

Answer 20

Afferent Nerve Supply to the Orbit Ophthalmic Nerve - V1 (first division of trigeminal)

frontal, nasociliary, lacrimal

All 3 send cutaneous branches to face (that emerges around the front of the orbit whether it is the top of the head or ones that comes out the eyes above and below) but only nasociliary and lacrimal (innervate anything in the orbit) provide significant innervation to orbital structures

so the frontal nerve does not innervate any orbital structures; just pases through the orbit

lacrimal nerve is part of the pathway to the lacrimal gland

branching occurs before the nerve makes into the supraorbital fissure into the orbit

Following the pathway, V1 enters makes a big branch above the eye (frontal) which then divides into more laterally branch which emerges as the supraorbital nerve and more medially goes right above the medial corner of the eye superiorly called the supratrochlear nerve

trochlear is the pulley that the superior oblique eye muscle runs through; so anything that we talked about as trochlear means that we are in this region: pulley is located superiorly and medially at the margin of the orbit but the supratrochlear nerve is a branch of frontal that comes out and innervates the skin above that region

so both supratrochlear and supraorbital are essentially branches that are only going to come out onto the skin of the face all the way to the top of the head

the lacrimal nerve runs along the supero-lateral side of the orbit and heads towards the lacrimal gland; its motor to the lacrimal gland only because it carries hitchhiking PS fibers but then it is also sensory as it sends fibers along the skin that is lateral to the eye; that frontal nerve really runs up the supero-medial side of the orbit; lacrimal nerve

the nasociliary branch; the naso part means that there is going to be branches that go into the nasal cavity and provides sensory innervation in there; key word is the ciliary; the ciliary structure is what holds your lens in place; and there is a ganglion in your orbit called the ciliary ganglion which innervates some of the ciliary muscle; so the nasociliary nerve gives off short and long ciliary branches which provide sensory innervation to the eyeball proper (long ciliary nerves) and even up in the front to the cornea; nasociliary sends a branch to the ciliary ganglion and sends branches to the eyeball and then moves over over medially giving off branches not concerned with the orbit such as the posterior and anterior ethmoidal nerve that go in and supply sensory innervation to ethmoid air cells and one branch continues as the infratrochlear nerve which gives cutaneous innervation to parts of the inferior eyelid and inferior parts of the conjunctiva and the anterior ethmoidal nerve continues down and eventually becomes the external nasal nerve and that’s the nasal part of nasociliary nerve; it is only the ciliary branches that are innervating the eyeball even to the front (cornea)

Question 21

Vascular Supply of Eye and Orbit

Answer 21

• in front of the orbit is the angular branch of the facial artery
• behind the orbit is the maxillary artery sending branches into the medial parts of the floor of the orbit

Major blood supply to orbit (retina and choroidal parts of the eyeball as well the extraocular muscles) is the ophthalmic artery, the first large branch off the internal carotid; lift up the optic nerve and right next to it is the internal carotid that well cut and you see an artery coming off of the ICA and travel with the optic nerve through the optic canal; that is the ophthalmic artery; use the superior oblique and trochlear muscle for orientation; so as you follow the ophthalmic artery, it passes through the optic canal and it usually does something interesting; it starts out underneath the optic nerve and then it slides out laterally and usually it bends medially by passing over the optic nerve to get over to the medial part of the orbit, sometimes it passes under the optic nerve (variable); as it goes from lateral to medial it gives off a whole series of branches before it runs parallel to the nasociliary nerve; the critical branches come off in the neck; branches of the ophthalmic nerve include lacrimal nerve which pairs with the lacrimal artery that innervates lacrimal gland; anterior ciliary artery comes off the lacrimal artery and goes to the front of the eyeball, Main stem of OA passes superior and medial to ON which is supraorbital artery which does not supply eyeball proper

cannot see macroscopically: as the OA is running underneath the optic nerve it sends a branch right into the optic nerve which is the Central a. of Retina and right after that it gives off a tiny branch that goes right up to the eye and penetrates around the optic nerve into the sclera of the eyeball called Post. Ciliary aa.

Post. Ciliary aa. enters the eyeball in a circle surrounding the optic nerve; there are two sets of the Post. Ciliary aa.; Short Posterior Ciliary arteries go immediately into the vascular bed of the choroidal layer and they branch out and become part of the choroidal capillary bed; Long Posterior Ciliary Arteries enter and run all the way forward and then branch up towards the front of the eyeball towards the ora serrata

Again up in the front are the anterior ciliary arteries, one came off of the lacrimal artery and the others will come off BV that are supplying the eye muscles themselves (Extraocular muscles give branches into the ciliary region as anterior ciliary arteries)

Minor supply from external carotid via facial and maxillary arteries

Angular artery (from facial)
Supplies superficial part of medial orbital region

Infraorbital artery (from maxillary)
Supplies part of orbital floor

Question 22

What is the only real supply of the neural retina?

Answer 22

central retinal artery and vein

if you block this blood flow in this artery, in approximately a minute the eye vision in that eye stops

Question 23

Cross section of optic nerve

Answer 23

• optic nerve is surrounded by dura mater
• right in the middle is the central retinal artery and vein and because this is part of the brain surrounded by dura that’s increased CSF pressure is dangerous for visual function because the little clear space will increase pressure within the optic nerve which can slow down or stop blood in the Central artery/vein of the retina with increased CSF through the spinal fluid

Question 24

Venous drainage of eye and orbit

Answer 24

In the whole region of the choroid we have venous drainage that is drained by the vorticose veins NOT the Central Retinal vein; vorticose veins get collected together and dump into the superior and inferior ophthalmic veins

there’s usually a big venous branch superiorly (superior ophthalmic vein) and inferiorly (inferior ophthalmic vein) which comes together and form a singular ophthalmic vein in the back of the orbit (although they don’t always come together)

that then dumps in to the cavernous sinus; sometimes it superior and inferior ophthalmic veins dumping in cavernous sinus separately

central vein of retina, into ophthalmic or directly to CS

we have more superficial veins (supraorbital v., angular v. which are part of the facial vein draining down; they are connected with an anastomosis to the ophthalmic veins); the other region of draining is from the inferior ophthalmic vein down into the pterygoid plexus which is down in the infratemporal fossa and as it goes posteriorly it gradally joins the maxillary vein

this is why this is always described as a dangerous zone (upper eyelid, nose, and upper lip; don’t pop pimples in nose or lips); Connections between facial and ophthalmic venous channels provide routes for superficial infections to spread to deep structures, especially, cavernous sinus

Question 25

Smooth muscles of the eye and their autonomic control

What is all this ciliary stuff?

Autonomic control of pupil aperture: smooth muscles in iris

Answer 25

smooth muscles properly in the eye itself (we’ve already discussed those in the upper and lower eyelid)

• they are controls by PS and S systems
• look at the eyeball and peel everything until its naked choroidal area
• yellow are posterior ciliary nerve coming forward; then we see the great marginal structure which is the ciliary apparatus and more central to that is the iris with pupillary muscles

cross-section from right to left shows the lens, iris, and ciliary apparatus; within the iris there is a band of circular muscle shown near the opening of the iris called the Sphincter Pupillae

Sphincter Pupillae:
when contracted, CONSTRICTS the iris (Constricts the pupil opening) in response to:
-bright LIGHT (pupillary light response)
-near viewing (pupillary near response) AKA looking up in the distance or looking near

Sph. Pup. contraction is controlled by PARASYMPATHETIC pathways of CN III via Edinger-Westphal nucleus and will go to the ciliary ganglion (III, short ciliary nerves) which will send up branches in the choroidal layer and run into the iris getting to these smooth muscle cells

They are another set of muscles that run in opposite orientation; they are radially oriented to the iris where they will run near the pupil opening to where the iris is attached to the ciliary apparatus. They are called Dilator Pupillae.

Dilator Pupillae:
Dilates the iris (opens up the pupil opening) in response to SYMPATHETIC activation via postganglionic fibers of Superior Cervical Ganglion (internal carotid plexus, long and short ciliary nerves). This is part of the Oculosympathetic pathways that also target palpebral smooth muscles (in tarsals) and orbital arteries.

all these arteries (branches of OV) are also receiving sympathetic innervation for vasoconstriction

next muscle is concerned with controlling the lens of the eye but we first need to talk about refractive elements of the eye

Question 26

Refractive Elements in the Eye

Answer 26

• those that can bend light that is headed to the retina
• From physics, the degree of refraction at an interface depends on the difference of refractive index of the two media and the curvature of the interface.

-We measure the refractive power of the eye in diopters.
Of the total 60 diopters refractive power of the (young, healthy) eye, and of that 60 most of it is not occuring at the lens but at the cornea because air and cornea have radically different refractive indices and the surfaces is nicely curved; the cornea provides c.40 diopters (2/3 of refractive power)

the rest of the refractive power is with the lens of the eye which has a curved front surface in contact with the aqueous humor and curved back surface with the vitreous body; so refraction can occur at both of those surface; we change the curvature of the lens to give us more or lesser refractive power

Modifying the curvature of the front and back surfaces of the lens provide a means of fine-tuning the refractive power, and hence, the focal length of the eye

Question 27

Accomodation for Near Vision

Answer 27

Your eye at rest is looking at the distance. The lens is at flat as it can be. As you look from distant to close, the lens get thicker to shorten the focal length.

The resting eye with flat lens focuses:
-parallel rays from distant objects onto the retina
combination of the cornea and flat lens focuses the distant objects perfectly on the retina

-diverging rays from near objects behind the retina
their diverging rays are not bent enough and so they focus behind the retina and are blurry

The accommodated eye focuses (lens has become thickened and now has stronger refractive power):
-diverging rays from near objects onto the retina;
the change in the thickness (increase) in the lens to change the focal length (shorten) for closer objects that’s the accommodation

Question 28

The Crystalline Lens - a deformable, variable-focus optical element

Answer 28

the lens itself is a deformable, variable, optical element

Made of spiralling layers yielding 3D gradients of refractive indices that correct for spherical and chromatic aberration

At REST (side view of lens is flat due to a sac around it; and this capsule is being pulled outwards away from the center of the lens is what flattens the lens) by the ciliary apparatus/muscle) centrifugal tension is high, lens is flattened, refraction is MINIMAL. The origin of all that pulling force is just the turgor of your eyeball itself.

When you reduce the force pulling away from the center of the lens the lens thickens up. During ACCOMMODATION centrifugal tension is reduced, lens is thickened, refraction is MAXIMAL. The whole trick of looking for close vision is to use your ciliary muscle to resist this outward pull from the whole turgor pressure of the eyeball, pull against that thereby reduce the pull on the lens itself. When you reduce the outward pull of the capsule on the lens, the lens thicken up which allows for sharper curvature and focuses for near vision.

Question 29

Ciliary Muscle

Answer 29

is a great big ring of muscle (bigger than sphincter or dilator pupillae) which are all under PS control except for radial fibers of the dilator pupillae which is sympathetic control

• iris attaches to the ciliary body which gives off fibers that attach to the lens called Zonule Fibers, aka, Suspensory Ligament of the lens
• At rest there is a lot of pressure pulling those eyeballs outward. The big ciliary muscle when it contracts it pulls inwards and forwards which relaxes the force of the Zonule fibers allowing the lens to thicken up and have a closer or SHORTER FOCAL length due to INCREASED REFRACTION.
• regulates refractive power of the lens: parasympathetic activation results in Accomodation, i.e., more diopters of refraction for closer visual focal length

Contains meridional, radial and circular smooth fibers

Contraction of the ciliary muscle moves the ciliary body forward and towards the optical axis, thereby decreasing tension in the suspensory ligament, resulting in lens thickening and increased refraction.

Question 30

The “Near Reflex” or “Near Triad” for Close Vision

Answer 30

this accommodation is part of this Near Reflex; im looking at the distant and now im going to shift and look close

During a shift of view from a distant to a nearby object:

1 - eyes converge (medial recti, III)
2 - pupils constrict (sphincter pupillae, IIIps; E-W, Cil.Gang.)
3 - lenses thicken (ciliary muscle, IIIps; E-W, Cil.Gang.)

this automatically happens every time you look from distant to near

Question 31

Autonomic Innervation of the Iris and Ciliary Body

Answer 31

• midbrain with oculomotor nucleus
• we start with E-W nucleus and the fibers run out of the CN III and there is an inferior division of the CN III which goes to the striated muscles in the lower orbit; the PS fibers follow that because it leads them right near to the ciliary ganglion; these fibers synapse in ciliary ganglion (a PS ganglion) whose fibers travel through the short ciliary nerves and then pass up towards the front of the eye to get to the iris and the ciliary body

the sympathetics which are going to the dilator pupillae originate in the superior cervical ganglion; their input was from the thoracic spinal ganglion; postganglionic fibers joins the internal carotid plexus and then jumps off as the IC is right behind the orbit in the cavernous sinus, sympathetic fibers jump off of IC and go right in to join the maxillary nerve and they then travel in and some of them pass right through the ciliary ganglion and of course those synapse while other travel on sensory branches of the ophthalmic nerve; sensory branches go into the eye and the ones from the ciliary ganglion are the short ciliary nerves and the ones that are just direct branches of the nasociliary branch of the ophthalmic nerve are the long ciliary nerves

so the distinction is that the only ones that carry PS fibers are the SHORT ciliary fibers because they go directly from the ganglion to the eyeball; long ciliary nerves are long trigeminal sensory fibers, especially the ones for the cornea that will give you screaming pain when you scratch the cornea; also sympathetic fibers that are going to BV and muscles of the eyelid and the dilator pupillae

the similar fibers are on the short ciliary nerve; they are not solely postganglionic PS, they also have the trigeminal sensory fibers and sympathetics

what is unique about the short ciliary nerves is that they are the only pathway for PS to get up into the eye to get to the sphincter pupillae and the ciliary muscle

you want to get the balance of those and realize how much more force it takes to manipulate the lens; of the cells in the ciliary ganglion, about 5% of them innervate the sphincter pupillae to close your eyelids, 95% of them innervate the ciliary muscle to allow relaxation of the tension on the sensory ligaments of the lens

when you eyes are tired you have fatigued the ciliary muscle which allows to lower the tension on the lens allowing for thickening of lens for near view

Question 32

Horner’s Syndrome – interruption of sympathetic supply to the head

Answer 32

Classic Triad

• drooping eyelids (partial ptosis or pseudo-ptosis) of both the upper and lower eyelid due to the tarsal muscles having no innervation (usually due to damage of the cervical sympathetic trunk, tumor in neck, etc.)
• contracted pupil (meiosis)
• lack of thermal sweating (anhydrosis)

Other signs

• sunken globe (enophthalmos)
• narrow palpebral fissure
• vasodilatation

ON THE AFFECTED SIDE

Question 33

The external ocular signs of Horner’s Syndrome can vary in degree and require close inspection

Answer 33

on the affected side, Loss of tone in the palpebral smooth muscles results in:

• drooping eyelid ( partial ptosis)
• narrowing of the palpebral fissure
• Loss of tone in the dilator pupillae results in:
• contracted pupil (meiosis)

First, compare left and right pupil size and then compare the eyelids and fissure.

The first is considered partial ptosis because you can open eyes still, it’s just the upper and lower eyelid droops. Complete/full ptosis is part of the Down and out syndrome where the oculomotor nerve has been damaged.

Question 34

Eye movements and extraocular muscle functions:

What are the 3 basic types of eye movements?

Answer 34

Horizontal eye movements (looking left and right) - rotations about a vertical axis through the center of the eye:

• Abduction is rotation away from the median plane (movement in temporal direction)
• Adduction is rotation towards the median plane (movement in nasal direction)

Vertical eye movements (looking up or down) - rotations about a horizontal axis through the center of the eye in a frontal plane:

• Elevation is rotation of gaze superiorly
• Depression is rotation of gaze inferiorly

Torsional eye movements - rotations about a horizontal axis through the center of the eye in a parasagital plane. The gaze direction is not altered, rather the eye rotates about the gaze axis.

• Extorsion is rotation that displaces the 12 O’clock position of the eye laterally
• Intorsion is rotation that displaces the 12 O’clock position of the eye medially

So there 3 axis of rotation

Question 35

Apex of Orbit and Origin of Extraocular Muscles from the Common Tendinous Ring

Answer 35

There are 6 extraocular muscles. 4 are straight muscles (recti) and 2 are oblique.

Most of them originate in the back of the eye. Need to think about the origin and insertion of each muscle in relation to the geometry of orbit.

At the back of the eye you have the common tendinous ring. All of the EM except the inferior oblique originate on or around this common tendinous ring and this ring surrounds the optic nerve in the back of the orbit.

The 3 branches of the ophthalmic nerve, lacrimal branch of trigeminal nerve, CN III, IV, and VI pass through the superior orbital fissure along with being met by ophthalmic artery coming through the optic canal and the veins leaving through the inferior orbital fissure to get to the cavernous sinus.

The main thing is that the INFERIOR OBLIQUE muscle DOES NOT originate on or around the common tendinous ring. It originates from the front of the orbit medially.

Question 36

The insertions of extraocular muscle

Answer 36

The rectus muscles become tendinous that insert into the sclera:

• lateral rectus
• medial rectus
• inferior rectus
• superior rectus

Obliques insert in two patches on the back of the orbit:
-superior oblique: goes over the top of the eye and inserts in the back; good for looking down
-inferior oblique: goes under the bottom of the eye and inserts on the back of the orbit; good for looking up
Their insertions into the back is very important because when you pull the back of the eye down, the front of the eye goes up and when you pull the back of the eye up, the front of the eye goes down (looking up and down).

Question 37

When an infant or child is born with double vision

Answer 37

quite often the problem is that one or more eye muscles did not insert in exactly the right spot, you can surgically put the muscle in the right place

you fix it by cutting one of the insertions, moving it, and stitching it

Question 38

Orbit dissection viewed from above

from the left orbit

Answer 38

LPS: levator palpebrae superioris
striated muscle that opens the eyelid and is the ONLY muscle that OPENS your EYE; innervated by the oculomotor nerve; it goes forward into the lid and has no direct connection to the eye

-below LPS is the superior rectus which comes from apex and inserts onto the upper part of eye; the from the under side of the eye we have the superior oblique muscle running forward to the trochlea , so the oblique tendon runs through it and over the eye and inserts behind the center of the eye from the posterior position

trochlea is a FIBROELASTIC pulley

inferior oblique starts medially in front of the eye swings under the eye to insert in the back of the eye

Question 39

Eye in primary position

Answer 39

The geometry of the orbit determines how those origins and insertion will end up moving the eye.

You can define the medial wall of the orbit which runs along the ethmoid bone and a lateral wall. It forms a lovely cone with the eyeball as the center.

The middle of the eyeball is about 45 degree off the median plane. The eye looks straight ahead. compare the middle of the orbit with the gaze axis when looking straightforward and it has a difference of about 23 degrees.

When the muscles are now put it, we realize that the superior rectus and the inferior rectus, they are lined up according to the center of the orbit NOT the direction of gaze (center of looking). The obliques are also not lined up with the direction of gaze either. So we have 4 muscles none of which are lined up very well with your eye.

The lateral and medial rectus just turn your eye left/right/horizontally. We have to see how the superior/inferior rectus/oblique are moving the eye when the eye is at a funny angle to the orbit.

You start with the eye in primary position looking straight forward. You are 23 degrees off the pulling direction of the SR and 50 degrees off the pulling direction of SO.

Question 40

In primary position to look straight upwards requires what two muscles at the same time?

Answer 40

superior rectus and inferior oblique

the combination of the two of them; each of them want to look up but one wants to adduct and the other wants to abduct, one wants to intort and the other wants to extort

when you combine the SR and IO together everything other than the elevation cancel out

Question 41

In primary position to look straight DOWNWARDS requires what two muscles at the same time?

Answer 41

superior oblique and inferior rectus

Question 42

How are you able to isolate the muscles that are looking up on the H-test?

Answer 42

ask the patient to look to the right and then up
-when the eye is abducted the right eye is looking to the right and the SO is perfectly line up and IO is at right angle to the gaze angle so it will be ineffective

the only muscle when my right eye is abducted that will help me look up is my SR

my left eye which is adducted, the only muscle that can efficiently help me look up is my inferior oblique

Question 43

How are you able to isolate the 12 extraocular muscles on the H-Test?

Answer 43

Look Right (LR, MR), Look Up (SR, IO), Look Down (IR, SO)

For looking up: abducted (rectus) vs. adducted eye (oblique)

Look left (MR, LR), Look Up (IO, SR), Look Down (SO, IR)

Question 44

Eye position in cranial nerve lesions

Answer 44

Mutually antagonistic/synergistic “tonus” actions of eye muscles are required to maintain the eye in the primary position

The deviation of a “relaxed” eye from the primary position due to loss of action of a muscle gives the appearance of a “reversal” of each of the muscles actions, i.e., deviations opposite to it’s normal vertical, horizontal and torsional actions. This is due to the activity of the remaining functional muscles of the orbit.

Question 45

CN III innervates what extraocular muscles?

Answer 45

SR
IR
MR
IO
actions are:
-elevation (SR, IO)
-depression (IR)
-adduction (MR, SR, IR)
-abduction (IO) 
-intorsion (SR)
-extorsion (IO, IR)

Question 46

With a CN III lesion, the resting eye position is?

Answer 46

• depressed
• abducted

AKA Down and Out

SO4 and LR6 are working and those are its functions respectively

Question 47

CN IV innervates what extraocular muscles?

Answer 47

SO
actions are:
-depression
-abduction
-intorsion

Question 48

With a CN IV lesion, the resting eye position is?

Answer 48

• elevated
• adducted
• extorted

Up and In, but mainly Head Tilt OPPOSITE/AWAY the site of nonfunctional muscle

Question 49

CN VI innervates what extraocular muscles?

Answer 49

LR

action is: abduction

Question 50

With a CN VI lesion, the resting eye position is?

Answer 50

-adducted

adducted eye

Question 51

What are the characteristic signs of unilateral oculomotor nerve palsy?

Answer 51

Ptosis (drooping) of the upper eyelid, due to lack of action of the levator palpebrae superioris

Dilation of the pupil due to loss of sphincter pupillae function

Depressed and abducted resting eye position due to the IVth and VIth nerve eye muscles acting unopposed

Hence the term “down and out syndrome”

Question 52

Another IIIrd nerve palsy - Berry Aneurysm

Answer 52

The most common and feared cause of an isolated pupil-involving acute third nerve palsy is compression by an enlarging intracranial aneurysm.

Isolated third cranial nerve palsies may be caused by compressive intracranial aneurysms located at the junction of the internal carotid and posterior communicating arteries or, less commonly, at the apex of the basilar artery or its junction with the superior cerebellar or posterior cerebral arteries.

Question 53

Right IVth nerve palsy

Answer 53

Two main actions of the superior oblique are to depress and medially rotate the eye

The axially rotated eye position may be compensated for by tilting the head away from the direction of the non-functional SO muscle