Eye

Inferior Rectus

- depression - secondary: aBduction and lateral rotation - ocular motor nerve, inferior branch (CN III)

Superior Oblique

- depression and aBduction - secondary: medial rotation - trochlear nerve (CN IV)

Superior Rectus

- elevation - secondary: aDduction and medial rotation - ocular motor nerve, superior branch (CN III)

Inferior Oblique

- elevation and aBduction - secondary: lateral rotation - ocular motor nerve, inferior branch (CN III)

Common Tendinous Ring

- inside: abducens (CN VI), nasociliary (CN V-1), oculomotor (CN III), optic nerve (CN II), ophthalmic artery - outside: trochlear (CN IV), ophthalmic vein, lacrimal nerve, frontal nerve

Greater Petrosal Nerve

- parasympathetic branch of the facial nerve - innervation to the lacrimal gland

Following endarterectomy on the right common carotid, a patient is found to be blind in the right eye. It appears that a small thrombus embolized during surgery and lodged in the artery supplying the optic nerve. What artery would be blocked? Central artery of the retina Infraorbital Lacrimal Nasociliary Supraorbital

The correct answer is: Central artery of the retina The central artery of the retina is a branch of the ophthalmic artery. It is the sole blood supply to the retina; it has no significant collateral circulation and blockage of this vessel leads to blindness. The branches of this artery are what you view during a fundoscopic exam. The infraorbital artery is a branch of the maxillary artery. It comes through the infraorbital foramen, inferior to the eye. It supplies the maxillary sinus, the maxillary incisors, canine and premolar teeth, and the skin of the cheek below the orbit. The supraorbital artery is another branch of the ophthalmic artery. It comes through the supraorbital foramen or notch and supplies blood to the muscles, skin and fascia of the forehead. The lacrimal artery is a branch of the ophthalmic artery that supplies the lacrimal gland. The nasociliary artery doesn't exist, but there is a nasociliary nerve (the third and lowest branch of the ophthalmic division) that travels with the continuation of the ophthalmic artery.

The extraocular muscle that does not originate at or near the apex of the orbit is the: Inferior oblique Inferior rectus Levator palpebrae superioris Superior oblique Superior rectus

The correct answer is: Inferior oblique The inferior oblique muscle does not originate at the apex of the orbit. It takes origin from the floor of the orbit, lateral to the lacrimal groove. The inferior rectus and superior rectus muscles take origin from the common tendinous ring at the apex of the orbit. The levator palpebrae superioris takes origin from the apex of the orbit above the optic canal. The superior oblique muscle takes origin from the apex of the orbit, above the optic canal.

Lateral Rectus

- aBduction - abducens nerve (CN VI)

Medial Rectus

- aDduction - ocular motor nerve (CN III)

You are asked to check the integrity of the trochlear nerve in the right eye of a patient. Starting with the eyes directed straight ahead, you would have the patient look: Inward, toward the nose and downward Inward, toward the nose and upward Toward the nose in a horizontal plane Laterally in a horizontal plane Outward, away from the nose and downward Outward, away from the nose and upward

The correct answer is: Inward, toward the nose and downward To understand this question, you need to understand how the motions of the eye are tested. Since the actions of the extraocular muscles are complex, it is necessary to turn the eye to a position where a single action of each muscle predominates when evaluating the individual muscles. To test the superior and inferior recti, a patient needs to turn the eye outward approximately 25 degrees. At this postion, the superior rectus will simply act to raise the eye, and the inferior rectus will lower the eye. To test the superior and inferior obliques, a patient needs to turn the eye inward approximately 50 degrees. When the eye is in this position, the superior oblique muscle will act to lower the eye, and the inferior oblique will act to raise the eye. So, now that you understand how to the test the eye, you have to decide which muscle is innervated by the trochlear nerve. And that's the superior oblique. So, to test this muscle, the eye needs to turn inward (toward the nose) and downward. What nerves innervate the other muscles? The abducens nerve (CN VI) innervates the lateral rectus muscle. The oculomotor nerve (CN III) innervates the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles.

An adolescent boy suffers from severe acne. As is often the case he frequently squeezed the pimples on his face. He subsequently develops a fever and deteriorates into a confused mental state and drowsiness. He is taken to his physician and after several tests a diagnosis of cavernous sinus infection and thrombosis is made. The route of entry to the cavernous sinus from the face was most likely the: Carotid artery Mastoid emissary vein Middle meningeal artery Ophthalmic vein Parietal emissary vein

The correct answer is: Ophthalmic vein The ophthalmic veins are continuous with the facial vein and the pterygoid plexus of veins. These veins drain the face toward the cavernous sinus. They are valveless, so infections from the face can drain into the cavernous sinus. Besides causing fever and confusion, thrombotic congestion and edema in the cavernous sinus can compress the nerves that traverse that space to exit through the superior orbital fissure(CN III, CN IV, CN V1, and CN VI). This can affect the function of the ocular muscles, so one symptom of a cavernous sinus infection might be an inability to perform different eye movements. The carotid artery and middle meningeal artery would not be the source of the infections. Infections do not tend to enter through arterial circulation. Remember--the common carotid is the major source of blood to the head and neck, and the middle meningeal artery is the branch of the maxillary artery that supplies blood to the dura. The emissary veins are valveless veins of the scalp. These veins can carry blood from the scalp to the dural venous sinuses or in the reverse direction depending on blood pressure. These veins may carry infectious materials from the scalp into the dural venous sinuses, but they are not important for carrying infections to the cavernous sinus.

If a person is taking a sympathetic blocking agent, what would you notice in her or his eyes? Dry eyes and inability to accommodate for reading Enophthalmos and teary eyes (III) Exophthalmos and dilated pupil Ptosis and constricted pupil Wide open eyes and loss of depth perception (IV)

The correct answer is: Ptosis and constricted pupil To understand this question, it's important to look at all the different choices and determine which ones fit with a sympathetic block. First, the lacrimal gland is innervated parasympathetically, so a sympathetic blocker should have no effect on eye secretions. Accomodation is also a function of the parasympathetic nervous system; it should not be altered by a sympathetic blocker. Enophthalmos is the name for the eye sinking into its orbit. A sympathetic block does cause enophthalmos, due to the paralysis of a smooth muscle in the floor of the orbit. Exophthalmos is the opposite of enophthalmos--it is the protrusion of the eye from the orbit. You would not see exophthalmos with a sympathetic blockade. Sympathetic nerves allow the eye to dilate--if you blocked these nerves, the eye would constrict. A sympathetic blocker would also cause ptosis--it would paralyze the superior tarsal muscle, which holds the lids up involuntarily and receives sympathetic innervation. Finally, the sympathetic blocker should not affect depth perception. If you put all of these things together, answer choice D is the correct one. If it helps to remember, taking a sympathetic blocking agent will lead to similar symptoms in the head and neck as Horner's syndrome, a disease characterized by a loss of sympathetic innervation to the head and neck.

What would the examining physician notice in the eye of a person who has taken a sympathetic blocking agent? Exophthalmos and dilated iris Enophthalmos and dry eye Dry eye and inability to accommodate for reading Wide open eyelids and loss of depth perception What would the examining physician notice in the eye of a person who has taken a sympathetic blocking agent? Exophthalmos and dilated iris Enophthalmos and dry eye Dry eye and inability to accommodate for reading Wide open eyelids and loss of depth perception Ptosis and miosis (pin-point pupil)

The correct answer is: Ptosis and miosis (pin-point iris) Start this question out by thinking about what a sympathetic blocker would do to the pupil of the eye. Since sympathetic nerves allow the pupil to dilate, a sympathetic blocker would stop the eye from dilating and make the pupil constrict. Now think about the other issues. First, remember that sympathetic nerves innervate the superior tarsal muscle, which elevates the eyelids. If there is a problem with the regional sympathetics (as is the case with Horner's syndrome), the superior tarsal muscle will be paralyzed, and the eyelid will droop (ptosis). If the sympathetic nervous system is inhibited, sweating will cease, and you will observe the eye sinking back into the orbit. Accomodation is not mediated by the sympathetic system; accomodation is a function of parasympathetic nerve so this should not be affected. Finally, the lacrimal gland is innervated by parasympathetics, so there should not be a major change in eye secretions after a sympathetic blocker. Putting all of these factors together, answer choice E is the only one that fits!

Starting from a position gazing straight ahead, to direct the gaze downward, the inferior rectus muscle must be active along with the: Superior oblique Inferior oblique Medial rectus Lateral rectus Superior rectus

The correct answer is: Superior Oblique The inferior rectus muscle depresses the eye and medially rotates it. So, to direct the gaze downward, you want to find a muscle that will depress the eye while counterbalancing the medial rotation with lateral rotation. And, the superior oblique, innervated by the trochlear nerve (CN IV), does just that--it depresses the eye while laterally rotating it. The inferior oblique muscle laterally rotates the eye and elevates the eye. The medial rectus adducts the eye--it does not raise or lower the eye. The lateral rectus abducts the eye--it also does not raise or lower the eye. Finally, the superior rectus elevates the eye and draws it medially.

The ducts of the lacrimal gland open into the: Superior fornix of the conjunctiva Inferior fornix of the conjunctiva Lacrimal puncta Lacrimal canaliculi Lacrimal lake

The correct answer is: Superior fornix of the conjunctiva Lacrimal fluid is produced by the lacrimal gland, which lies in a fossa in the superolateral part of each orbit. The fluid from this gland enters the conjunctival sac through up to 12 lacrimal ducts that open into the superior conjunctival fornix. The tears then flow to the medial angle of the eye and collect in the lacrimal lake. The lacrimal papilla are small elevations on the eyelids, found near the lacrimal lake. These papillae have small openings called the lacrimal puncta; tears flow from the lacrimal lake into these puncta. From there, the lacrimal fluid goes into small canniliculi which drain the fluid into the lacrimal sac. The lacrimal sac continues on as the nasolacrimal duct and drains tears into the inferior nasal meatus. Take a look at Netter Plate 77 and try to follow the path of tears from the lacrimal gland to the inferior meatus!

During a physical examination it is noted that a patient has ptosis. What muscle must be paralyzed? Orbicularis oculi, lacrimal part Orbicularis oculi, palpebral part Stapedius Superior oblique Superior tarsal (smooth muscle portion of levator palpebrae)

The correct answer is: Superior tarsal The superior tarsal muscle is a smooth muscle which is sympathetically innervated. It is an involuntary muscle that elevates the eyelid. It is innervated by the cervical sympathetic trunk, and this muscle's functioning provides a good indication of the integrity of the cervical sympathetic trunk. If the cervical sympathetic trunk has been damaged, a patient will have ptosis, a droopy eyelid. Orbicularis oculi is innervated by the facial nerve. If this muscle is paralyzed, the problem won't be a droopy eyelid--instead, the patient won't be able to close the eyelid. This is why patients with Bell's palsy are prescribed lubricating eye drops--if they can't close the eyelid, they may be at risk for corneal irritation. Stapedius is another muscle innervated by the facial nerve -- it serves to dampen the vibrations of the stapes and the tympanic membrane. Finally, the superior oblique muscle depresses the eyeball and turns it laterally. It does not affect the eyelid.

If a person looking inward towards their nose is unable to look down, which nerve may be injured? Abducens (CN VI) Inferior division of oculomotor (III) Optic (II) Superior division of oculomotor (III) Trochlear (IV)

The correct answer is: Trochlear (IV) To understand this question, you need to understand how to evaluate the muscles of the eye. Since the actions of the extraocular muscles are complex, it is necessary to turn the eye to a position where a single action of each muscle predominates. To isolate the superior and inferior recti, the patient needs to turn the eye outward by approximately 25 degrees. This places the superior rectus in position to raise the eye and the inferior rectus in position to lower the eye. Turning the eye inward approximately 50 degrees places the inferior oblique in position to raise the eye and the superior oblique in position to lower the eye. The medial and lateral recti are the easy muscles -- they may be checked while the eye is staring straight ahead since they have simple planar actions So, this patient is looking inward, which means that the obliques are being tested. The patient can't look downward, which shows that the superior oblique is not functional. This is the only muscle innervated by the trochlear nerve (CN IV). Abducens (CN VI) innervates the lateral rectus muscle, which is tested by asking the patient to move the eye outward. The inferior division of the oculomotor nerve innervates inferior rectus, inferior oblique, and medial rectus. The superior branch of the oculomotor nerve innervates levator palpebrae superioris and superior rectus muscles. Finally, the optic nerve (CN II) provides the special sense of vision, and it is not tested in the eye-movement tests.

You have a patient with a drooping right eyelid. You suspect Horner's syndrome. Which of the following signs on the right side would confirm this diagnosis? Constricted pupil Dry eye (lack of tears) Exophthalmos Pale, blanched face Sweaty face

The correct answer is: constricted pupil Horner's syndrome is a disorder involving damage to the sympathetic trunk in the neck. This means that the sympathetics of the head will be disrupted. This causes a variety of very characteristic symptoms, including a constricted pupil. Remember--sympathetic nerves innervate the dilator pupillae muscle. This muscle allows the eye to dilate. If these sympathetic nerves are lost, the pupil will contract. Several of the other listed symptoms are the opposite of what you would expect with Horner's syndrome. Exophthalmos is the protrusion of the eye, but in Horner's syndome the eye sinks in, possibly due to the paralysis of a smooth muscle in the floor of the orbit. The face does not become blanched and sweaty with Horner's syndrome--instead, it becomes red and dry. Without the sympathetic nerve supply, the vasculature of the face cannot constrict. So, the arterioles in the patient's face are vasodilated, making the face red. Sympathetic nerves also innervate sweat glands; if these nerves are interrupted, the patient will not sweat and the face will appear very dry. Finally, the lacrimal gland is innervated by parasympathetics, not sympathetics. So, Horner's syndrome should produce no appreciable changes in tearing. Make sure to know the different symptoms and signs of Horner's syndrome!

The outermost layer of the optic nerve sheath is a continuation of the: Arachnoid membrane Meningeal dura Periosteal dura Pia mater Retina

The correct answer is: meningeal dura The optic nerve comes off the base of the brain and passes through the optic canal. As it leaves the brain, it still retains all of the meningeal layer coverings. So, it is covered by meningeal dura, arachnoid membrane, and pia mater. This is significant, because an increase in intracranial pressure will increase the pressure in the subarachnoid space. This may squeeze the optic nerve and make the optic nerve bulge into the eye, a condition known as papilledema. The periosteal dura is the layer of periosteum covering the internal surface of the calvaria. The retina is the inner layer of the eyeball which receives and absorbs visual light rays.

You are examining a patient who has a pituitary tumor involving the cavernous sinus. While doing a preliminary eye exam, you suspect the right abducens nerve of the patient has been damaged by the tumor. In which direction would you have the patient turn his right eye to confirm the defect? Inward Outward Downward Down and out Down and in Upward Up and out Up and in

The correct answer is: outward To understand this question, you need to understand how the motions of the eye are tested. Since the actions of the extraocular muscles are complex, it is necessary to turn the eye to a position where a single action of each muscle predominates when evaluating the individual muscles. For the superior and inferior recti, turning the eye outward (abduction) by approximately 25 degrees places the superior rectus in position to raise the eye and the inferior rectus to lower the eye. Similarly, turning the eye inward (adduction) approximately 50 degrees places the inferior oblique in position to raise the eye and the superior oblique to lower the eye. The medial and lateral recti may be checked while the eye is staring straight ahead since they have simple planar actions. In this case, you're interested in testing an "easy" muscle. Since the lesion appears to be in the abducens, which innervates the lateral rectus muscle, you could just ask the patient to turn the eye outward. If the patient could not do this, it would confirm that there was a lesion in the abducens nerve, since the muscle responsible for lateral movement of the eye would be paralyzed. Also remember--a tumor in the cavernous sinus could affect many nerves. The oculomotor nerve (CN III), trochlear (CN IV), ophthalmic division of trigeminal (CN V1), and abducens (CN VI) all pass through the cavernous sinus.

The inner lining of the eyelid is called the: Orbital septum Palpebral conjunctiva Periorbita Sclera Tarsal plate

The correct answer is: palpebral conjunctiva The palpebral conjunctiva is the thin membrane that lines the eyelid. It is continuous with the bulbar conjunctiva which lines the eyeball. The orbital septum is a weak membrane that spans from the tarsal plates to the margins of the orbit where it becomes continuous with the periosteum. It contains orbital fat and can limit the spread of infection in the orbit. The periorbita is the periosteum lining covering the bones forming the orbit. The sclera is the outer fibrous layer of the eyeball. Finally, the tarsal plate is a thin, cardboard-like layer of connective tissue in the eyelids which forms the "skeleton" of the eyelids.

You are testing the extraocular muscles and their innervation in a patient who periodically experiences double vision. When you ask him to turn his right eye inward toward his nose and look downward he is able to look inward, but not down. Which nerve is most likely involved? Abducens Nasociliary Oculomotor, inferior division Oculomotor, superior division Trochlear

The correct answer is: trochlear To understand this question, you need to understand how the motions of the eye are tested. Since the actions of the extraocular muscles are complex, it is necessary to turn the eye to a position where a single action of each muscle predominates when evaluating the individual muscles. A key principle for muscle testing is: if a muscle has two actions and you perform one of those two, then it can't perform its other action. Superior and inferior recti turn the eye in and up or in and down. Superior and inferior oblique turn the eye out and down or out and up. So, if you turn your eye in (with the superior and inferior rectus as well as medial rectus), then only superior and inferior oblique can move the eye down or up (because the superior and inferior recti are already shortened by turning the eye in - they can't shorten any more). Similarly, if you turn the gaze out (with the obliques and lateral rectus) then only superior and inferior rectus can turn the eye up or down. In this case, the patient has the eye turned inward, so the doctor must be testing the oblique muscles. The superior oblique muscle is the muscle that lowers the eye when it is turned inward. Since the patient can't do this, the superior oblique must not be functioning, and this muscle is innervated by the trochlear nerve. Abducens (CN VI) innervates the lateral rectus muscle, which is not involved in the eye test. The nasociliary nerve comes from the ophthalmic division of the trigeminal nerve (V1). It is a sensory nerve to the eyeball that also carries some sympathetic fibers. The inferior division of the oculomotor nerve innervates inferior rectus, inferior oblique, and medial rectus. All of these muscles appear to be functioning. Finally, the superior division of the oculomotor nerve innervates levator palpebrae superioris and superior rectus. These are not the muscles that appear to be malfunctioning.