Term
What forms the roof of the orbit? |
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Definition
Orbital plate of frontal bone Lesser wing of sphenoid |
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Term
| Where does the lacrimal gland lie? |
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Definition
•Lacrimal gland lies in the fossa for the lacrimal gland in the anterolateral part of the roof |
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Term
Roof separates what from the orbit? |
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Definition
The anterior cranial fossa |
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Term
•Where does the optic canal lie and what does it connect? |
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Definition
•Optic canal lies at the extreme posterior end of the roof. It connects the orbit to the middle cranial fossa |
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Term
•What forms the floor of the orbit? |
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Definition
•Floor is formed by the following: –orbital surface of maxilla –anterolaterally by the zygomatic bone –palatine bone posteriorly –infraorbital groove & canal |
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Term
| What forms the floor of the orbit? |
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Definition
•Floor is formed by the following: –orbital surface of maxilla –anterolaterally by the zygomatic bone –palatine bone posteriorly –infraorbital groove & canal |
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Term
•What is the location of the inferior orbital fissure and what does it connect? |
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Definition
•Inferior orbital fissure lies between the floor and lateral wall & connects orbit & infratemporal fossa |
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Term
•What makes up the medial wall of the orbit? |
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Definition
•Medial wall is formed by the following bones –Frontal process of the maxilla & maxillary process of frontal –Lacrimal bone which has a groove and crest –Orbital plate of ethmoid bone (paper thin) –Sphenoid |
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Term
| What are the 2 foramina in the medial wall of the orbit? |
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Definition
| Posterior ethmoid foramen and anterior ethmoid foramen |
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Term
•What makes up the lateral wall of the orbit? |
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Definition
•Lateral wall is formed by the following bones: –Greater wing of the sphenoid –Orbital surface of the zygomatic bone |
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Term
•What lies between the roof and lateral wall of the orbit? |
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Definition
•Between the roof and lateral wall lies the superior orbital fissure |
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Term
•What forms the apex of the orbit? |
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Definition
·Apex is formed by the optic canal (in the lesser wing of the sphenoid) |
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Term
•What forms the base of the orbit? |
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Definition
·Base is the orbital margin |
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Term
•What covers the bony orbit? |
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Definition
•The bony orbit is covered by the orbital periosteum (periorbita) |
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Term
| What are the contents of the orbit |
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Definition
•Contents of the orbit: •Eyeball •Fascial sheath of the eyeball which surrounds the eyeball (Tenons capsule or fascia bulbi) •Muscles of the orbit- 4 recti, 2 oblique, 1 levator palpebrae superioris •Nerves: –Optic N –Oculomotor N- –Trochlear N –Abducent N –Ophthalmic N branches -Lacrimal, Frontal, Nasociliary –Sympathetic nerves –Ciliary ganglion •Vessels : Ophthalmic A & its branches • Ophthalmic veins- Superior & Inferior • Lacrimal gland • Orbital fat. |
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Term
•What is the frontal nerve and its branches? |
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Definition
•It enters the orbit through the superior orbital fissure. It runs forwards above the levator palpebrae superioris. Frontal gives the following branches: –Supraorbital –Supratrochlear |
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Term
•What is related to the lacrimal nerve along its course? |
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Definition
•It enters the orbit through superior orbital fissure. It runs above the lateral rectus to reach the lacrimal gland. It receives postganglionic parasympathetic fibres from the pterygopalatine ganglion through the zygomatic nerve and supplies the lacrimal gland. It ends in the lateral part of the upper eyelid as palpebral branch |
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Term
•What is the nasociliary nerve and its branches? |
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Definition
•It is a branch of the ophthalmic nerve. It enters the orbit through the superior orbital fissure. It crosses above the optic nerve from lateral to medial side behind the ophthalmic artery and vein. It reaches the medial wall of the orbit between the superior oblique and medial rectus. It ends by dividing into anterior ethmoidal and infratrochlear nerve. •Nasociliary gives the following branches –Sensory connection to the ciliary ganglion –Long ciliary nerves –Posterior ethmoidal nerve –Anterior ethmoidal nerve –Infratrochlear nerve |
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Term
•What is the ciliary ganglion? |
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Definition
•It is a peripheral parasympathetic ganglion situated near the apex of the orbit between the optic nerve and lateral rectus muscle. It has sensory, sympathetic and parasympathetic fibers in it. But only parasympathetic fibers relay in the ganglion. |
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Term
•The ciliary ganglion receives parasympathetic fibers from? |
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Definition
•It receives its parasympathetic fibers through the following route: –Preganglionic fibers: • Edinger westphal nucleus in the midbrain -> oculomotor nerve -> Inferior division -> nerve to inferior oblique -> ciliary ganglion –The postganglionic fibers pass through the short ciliary nerves and supply the ciliaris muscle and sphincter puplillae. |
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Term
•What does the ciliaris muscle and sphincter pupillae do? |
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Definition
• Both these muscles are smooth muscles & help in accommodation: • Ciliaris muscle ( in the ciliary body) contracts and relaxes the suspensory ligament of the lens thereby allowing the lens to become more convex. • Sphincter pupillae present in the iris helps the iris to become small. • These two actions help to focus the nearby objects (Accomodation). Both of them are supplied by the parasympathetic fibers from the ciliary ganglion. |
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Term
•What are the sympathetic fibers and sensory fibers passing through the cilliary ganglion? |
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Definition
•Some sympathetic fibers passing through the long ciliary nerves pass through the ciliary ganglion but are not relayed in this. Similarly some Sensory fibers pass through this ganglion without relaying to the nasociliary nerve. –It contains only the cell bodies of the parasympathetic neurons. |
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Term
•How does the ophthalmic artery begin and what is its course? |
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Definition
•It arises from the internal carotid artery and passes through the optic canal along with the optic nerve •It lies lateral to the optic nerve •It crosses above the optic nerve from the lateral to the medial side between the superior ophthalmic vein in front and the Nasociliary nerve behind. •It reaches the medial wall of the orbit and terminates by dividing into supratrochlear and dorsal nasal arteries |
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Term
•What are the branches of the ophthalmic artery? |
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Definition
•It gives the following branches: –Central artery of Retina which is an end artery, runs in the optic nerve –Posterior ciliary arteries –Muscular branches –Posterior ethmoidal artery –Anterior ethmoidal artery –Lacrimal artery –Supraorbital artery –Supratrochlear artery –Dorsal nasal artery |
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Term
•The blockage of which artery will cause total blindness? |
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Definition
•Clinical correlation: blockage of the central artery of retina results in total blindness. |
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Term
•What veins are located in the orbit? |
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Definition
•There are two ophthalmic veins: –Superior ophthalmic –Inferior ophthalmic •Both of them open into the cavernous sinus |
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Term
•What is the lacrimal apparatus? |
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Definition
•Lacrimal gland •Lacus lacrimalis •Lacrimal canaliculi •Lacrimal sac •Nasolacrimal duct |
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Term
•What is the lacrimal gland? |
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Definition
•It is a serous gland secreting tears or lacrimal fluid •It is located in the Lacrimal fossa on the anterosuperolateral part of the orbit •It has two parts- Larger Orbital part and smaller Palpebral part •The two parts are separated by the lateral border of the Levator palpebrae superioris and are continuous with each other lateral to the muscle. •Orbital part lies between the lacrimal fossa and the levator palpebrae superioris •Palpebral part lies between the levator palpebrae superioris and the conjunctiva •There are 8-20 ducts issued from the palpebral part and they open into the superior conjunctival fornix. |
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Term
•What is the blood supply of the lacrimal gland? |
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Definition
•Blood supply: lacrimal branch of the ophthalmic artery |
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Term
•What is the nerve supply of the lacrimal gland? |
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Definition
•Nerve supply: Parasympathetic pathway: (secretomotor) •Lacrimatory nucleus (in the pons) → Facial N → Greater superficial petrosal nerve → Nerve of the pterygoid canal (Vidian N) → Pterygopalatine ganglion (sphenopalatine ganglion) •Postganglionic fibers: Pterygopalatine ganglion → Communicating branch to the maxillary N → Zygomatic N → communicating branch → Lacrimal N → Lacrimal gland |
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Term
•What are the layers of the eyelid? |
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Definition
•Following layers – from superficial to deep - Skin, superficial fascia, Muscle layer, Tarsal plate, Tarsal glands, Palpebral conjunctiva |
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Term
•What are the muscles of the eye? |
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Definition
–Levator palpebrae superioris –Superior oblique –Inferior oblique –Superior rectus –Inferior rectus –Medial rectus –Lateral rectus |
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Term
•What are the recti muscles? |
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Definition
•All the four recti arise from the common tendinous ring and are inserted approximately 6mm posterior to the sclerocorneal junction. • Remember this mnemonic: –SO4, LR6 and AR3 –SO4: superior oblique by the 4th cranial, Trochlear nerve –LR6: lateral rectus by the 6th cranial, Abducent nerve –All the rest: by the 3rd cranial, Oculomotor nerve |
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Term
•What is the levator palpebrae superioris? |
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Definition
•It arises from the lesser wing of the sphenoid bone •It is inserted into the upper eyelid and skin. –It raises the upper eyelid. It is antagonistic to orbicularis oculi. |
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Term
•What is the smooth muscle attached to the tarsal plate called? |
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Definition
•The smooth muscle attached to the tarsal plate of the upper eyelid is called the superior tarsal muscle (muller’s muscle) and it is supplied by the sympathetic nerves. |
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Term
•What are two causes of ptosis and what muscles are affected? |
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Definition
–Therefore in Horner’s syndrome there is ptosis with retention of the palpebral fold due to the paralysis of the superior tarsal muscle. –Paralysis of the levator palpebrae superioris causes ptosis with obliteration of the palpebral fold |
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Term
•What is the superior oblique? |
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Definition
•Arises from near the apex of the orbit superior to the common tendinous ring. It is inserted into the posterolateral quadrant on the superior aspect of the eyeball •It hooks around the trochlea. It is supplied by the trochlear nerve |
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Term
•What is the inferior oblique? |
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Definition
•Arises from the anteromedial part of the floor of the orbit. •It is inserted into the posterolateral quadrant on the inferior aspect of the eyeball. It is supplied by the inferior division of the oculomotor nerve. |
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Term
•What is the inferior oblique? |
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Definition
•Arises from the anteromedial part of the floor of the orbit. •It is inserted into the posterolateral quadrant on the inferior aspect of the eyeball. It is supplied by the inferior division of the oculomotor nerve. |
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Term
•What are the movements of the eye by its extrinsic muscles? |
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Definition
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Term
•When do the muscles of the eyeball bring about only one movement? |
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Definition
•The A-P axis of the eyeball is 23 degrees medial to the axis of the orbit. The muscles acting on the eye ball bring about simple action only when the two axes lie at the same plane. If not, the contraction of the muscle brings about combined movements of the eye ball. |
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Term
•What are the three axes of the eyeball and what are the movements associated with each? |
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Definition
•The movements take place around 3 primary axes which pass through the centre of movement at right angle to each other. •Vertical axis- around which the centre of the cornea & visual axis moves laterally ( abduction) or medially (adduction). •2. Transverse axis- around which the centre of the cornea moves up(elevation) or down ( depression) •3. Anteroposterior axis- around which so-called “wheel rotation” takes place, better defined as intorsion or extorsion as the twelve 0' clock on the cornea moves nasally (intorsion) or temporally (extorsion). |
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Term
•Why do the superior and inferior rectus muscles have three actions each? |
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Definition
•Superior and inferior rectus muscles lie in the long axis of the orbit and not in the long axis of the eyeball. –The long axis of the eyeball is not in the long axis of the orbit. The orbit looks forwards and laterally while the eyeball looks directly forwards. This is responsible for the superior and inferior recti muscles to cross 3 axes as they pass from the common tendinous ring to the eyeball. Therefore each of these muscles has 3 actions. |
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Term
•What is the movement of the superior rectus muscle? |
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Definition
•Superior rectus: It crosses a horizontal axis therefore it elevates the eyeball, crosses the vertical axis therefore adducts, and it also crosses the anteroposterior axis which brings about intorsion of the eyeball. |
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Term
•What are the actions of the inferior rectus muscle? |
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Definition
•Inferior rectus also has 3 actions: depression, adduction and extorsion. |
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Term
•What are the actions of the medial rectus muscle? |
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Definition
•Medial rectus: crosses only one axis and has only one action. It adducts the eyeball towards the median plane. |
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Term
•What are the actions of the lateral rectus muscle? |
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Definition
•Lateral rectus: crosses only one axis and has only one action. It abducts the eyeball away from the median plane. |
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Term
•What is the action of the superior oblique muscle? |
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Definition
•Superior oblique: has 3 actions because of the peculiarity of its insertion. –It lifts the back of the eyeball which results in the depression of the front of the eyeball. It also intorts (medially rotates) the eyeball because it crosses the anteroposterior axis. It pulls the posterior part of the eyeball medially and thus the anterior part of the eyeball turns laterally (abduction) |
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Term
•What are the actions of the inferior oblique muscle? |
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Definition
•Inferior oblique: also has 3 actions because of the peculiarity of its insertion. –It depresses the back of the eyeball which results in the elevation of the front of the eyeball. It extorts the eyeball and abducts. |
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Term
•What are the muscles involved in pure elevation? |
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Definition
•In pure elevation two muscles contract: –Superior rectus: elevation and intorsion and adduction –Inferior oblique: elevation and extorsion and abduction –Opposite torsion movements of these two muscles get cancelled and it results in pure elevation. |
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Term
•What muscles are involved in pure depression? |
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Definition
–Inferior rectus: depression and extorsion –Superior oblique: depression and intorsion. Torsion movements of these two muscles get cancelled and it results in pure depression. |
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Term
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Definition
•Synergists are those muscles which cancel the unwanted movement of another muscle. In this case superior oblique acts like a synergist and cancels the unwanted extorsion of the inferior rectus muscle. |
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Term
•How does one test the superior rectus muscle? |
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Definition
•Superior rectus: it lies in the long axis of the eyeball when the eyeball is abducted. Therefore it has only one action on the abducted eye. That is elevation. •Therefore the subject is asked to look upwards and laterally to test for the superior rectus muscle. –Look at finger at the side of the forehead (temples) |
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Term
•How does one test the inferior rectus muscle? |
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Definition
•Inferior rectus: it lies in the long axis of the eyeball when the eyeball is abducted. Therefore it has only one action on the abducted eye. That is depression. –Therefore the subject is asked to look downwards and laterally to test for the inferior rectus muscle. –Look at finger at the zygomatic |
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Term
•How does one test the superior oblique muscle? |
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Definition
•Superior oblique: it lies in the long axis of the eyeball when the eyeball is adducted. Therefore it has only one action on the adducted eye. That is depression. –So, this muscle is tested by asking the patient to look at the tip of the nose. |
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Term
•How does one test the inferior oblique muscle? |
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Definition
•Inferior oblique: the same description is applicable to this muscle also. –So, the muscle is tested by asking the patient to look upwards and medially. –Look at the finger between the eyebrows |
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Term
•How does one test the inferior oblique muscle? |
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Definition
•Inferior oblique: the same description as the superior oblique applicable to this muscle also. –So, the muscle is tested by asking the patient to look upwards and medially. –Look at the finger between the eyebrows |
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Term
•How does one test the medial rectus muscle? |
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Definition
•Medial rectus: subject is asked to adduct the eye –Look at the finger at the bridge of the nose |
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Term
•How does one test the lateral rectus muscle? |
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Definition
•Lateral rectus: subject is asked to abduct the eye |
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Term
•What is the cheating muscle? |
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Definition
•Clinical: Superior oblique is copying muscle. In trochlear nerve palsy, diplopia occurs on looking downwards! The eyeball rolls upwards when an attempt is made to steal a look into the neighbor’s answers !!! |
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