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The orbit is a bony cavity that houses the eyeball, extraocular muscles, nerves, blood vessels, and the lacrimal gland.
Out of the 12 pairs of cranial nerves, II, III, IV, VI, and part of V (trigeminal), along with sympathetic fibers, are dedicated to orbital structures.
The orbit serves primarily to protect and support the eyeball.
Each orbit is a pyramidal cavity, one on each side of the nose.
They allow rotatory movements of the eyeball.
The long axis of each orbit passes backward and medially.
The medial walls of both orbits are parallel (2.5 cm apart).
The lateral walls are at right angles to each other.
Contents of the Orbit
Eyeball (anterior one-third of orbit).
Fasciae – Orbital and Bulbar fasciae.
Muscles – Extraocular and intraocular.
Vessels – Ophthalmic artery, superior and inferior ophthalmic veins, and lymphatics.
Nerves – Optic, oculomotor, trochlear, abducent, and branches of ophthalmic and maxillary nerves.
Lacrimal gland.
Orbital fat.
Visual axis: Line through the anterior and posterior poles of the eyeball.
Orbital axis: Line passing through the optic canal and center of orbital base.
The two axes form an angle of 20–25° with each other.
The periorbita is the periosteum of the bony orbit.
It is loosely attached to the bone and easily stripped off.
Posteriorly: Continuous with dura mater and the optic nerve sheath.
Anteriorly: Continuous with periosteum at the orbital margin.
Inferior orbital fissure: Covered by connective tissue containing smooth muscle fibers forming the orbitalis muscle.
Extensions of Orbital Fascia
a. At upper and lower orbital margins → forms orbital septa for eyelids.
b. Sends a process to hold the fibrous pulley of the superior oblique muscle.
c. Another process forms the lacrimal fascia bridging the lacrimal groove.
A thin, loose membranous sheath surrounding the eyeball from the optic nerve to the sclerocorneal junction.
Separated from the sclera by the episcleral space filled with delicate fibrous bands → allows free movement of the eyeball.
Pierced by:
Tendons of extraocular muscles.
Ciliary vessels and nerves near the optic nerve.
Expansions from the Sheath
a. Tubular sheaths for each extraocular muscle.
b. Medial check ligament: Expansion from medial rectus sheath → attached to lacrimal bone.
c. Lateral check ligament: Expansion from lateral rectus sheath → attached to zygomatic bone.
Suspensory Ligament of the Eye (Lockwood’s ligament)
Formed by the union of the sheaths of inferior rectus and inferior oblique muscles with medial and lateral check ligaments.
Acts like a hammock supporting the eyeball from below.
Total: 7 muscles (6 act on the eyeball + 1 elevates the upper eyelid).
Origin: From the common tendinous ring (annulus of Zinn) at the apex of the orbit.
Insertion: Onto the sclera of the eyeball.
Recti Muscles
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Oblique Muscles
5. Superior oblique (passes through trochlea pulley)
6. Inferior oblique (arises from maxilla, below the lacrimal fossa)
Eyelid Muscle
7. Levator palpebrae superioris — raises upper eyelid.
Nerve Supply
Oculomotor nerve (III): all except LR6, SO4
Trochlear nerve (IV): superior oblique
Abducent nerve (VI): lateral rectus
Mnemonic → “LR6 SO4, rest by 3”
| Axis | Movements |
|---|---|
| Transverse | Elevation (up) and depression (down) |
| Vertical | Adduction (medial) and abduction (lateral) |
| Anteroposterior | Intorsion (inward rotation) and extorsion (outward rotation) |
Individual Muscle Actions
Superior rectus → Elevation + Adduction + Intorsion
Inferior rectus → Depression + Adduction + Extorsion
Superior oblique → Depression + Abduction + Intorsion
Inferior oblique → Elevation + Abduction + Extorsion
Medial rectus → Adduction
Lateral rectus → Abduction
Combined Actions
Elevation: Superior rectus + Inferior oblique
Depression: Inferior rectus + Superior oblique
Adduction: Medial, Superior, and Inferior recti
Abduction: Lateral rectus + Both obliques
Intorsion: Superior rectus + Superior oblique
Extorsion: Inferior rectus + Inferior oblique
Conjugate Movements
Coordinated movement of both eyes in the same direction.
Example:
Right gaze → right lateral rectus + left medial rectus.
Left gaze → left lateral rectus + right medial rectus.
Orbitalis Muscle (Müller’s muscle)
Smooth muscle bridging the inferior orbital fissure.
Innervated by sympathetic fibers.
Keeps the eyeball slightly protruded; its paralysis causes sunken eyeball (enophthalmos).
Superior Tarsal Muscle (Müller’s of eyelid)
Smooth muscle aiding levator palpebrae superioris.
Sympathetic nerve supply.
Paralysis → partial ptosis (drooping of upper eyelid).
Inferior Tarsal Muscle
Weak smooth muscle aiding lower eyelid retraction.
Sympathetic fibers.
Paralysis of Oculomotor Nerve (III):
Ptosis (levator paralysis)
Eye deviated down and out (LR & SO unopposed)
Dilated pupil and loss of accommodation.
Trochlear Nerve (IV) Palsy:
Difficulty looking down and in (e.g., reading, descending stairs).
Abducent Nerve (VI) Palsy:
Failure to abduct the eye → Medial squint (convergent strabismus).
Nystagmus:
Involuntary rhythmic eye movements due to cerebellar or vestibular disturbance.
Origin: Cerebral part of the internal carotid artery (near anterior clinoid process).
Entry: Through optic canal with the optic nerve (below and lateral to it).
Course:
Pierces dura → ascends lateral to optic nerve → crosses above it to medial side → runs forward with nasociliary nerve between superior oblique and medial rectus.
Ends at medial angle of eye → divides into supratrochlear and dorsal nasal arteries.
Identify artery crossing above the optic nerve with nasociliary nerve and superior ophthalmic vein.
Locate the central artery of the retina — a vital end artery.
Within Dural Sheath
Central artery of retina — supplies retina; occlusion → sudden blindness.
In the Orbit
Lacrimal artery → lacrimal gland, eyelids, zygomatic branches, recurrent meningeal branch.
Posterior ciliary arteries (long & short) → choroid and iris.
Supraorbital and Supratrochlear arteries → forehead and scalp.
Ethmoidal arteries (anterior & posterior) → ethmoidal sinuses and nasal cavity.
Medial and Lateral Palpebral arteries → eyelids.
Dorsal nasal artery → bridge of nose.
Muscular branches → supply extraocular muscles; give rise to anterior ciliary arteries.
Central artery of retina occlusion → sudden, permanent blindness.
Ophthalmic vein thrombosis may spread infection to the cavernous sinus.
Anastomosis between ophthalmic artery and facial artery (via dorsal nasal branch) maintains collateral circulation between internal and external carotid systems.
Superior Ophthalmic Vein
Accompanies the ophthalmic artery.
Lies above the optic nerve.
Receives tributaries corresponding to the branches of the ophthalmic artery.
Passes through the superior orbital fissure to drain into the cavernous sinus.
Communicates anteriorly with supraorbital and angular veins, forming a link between facial and intracranial veins (important clinical pathway).
Inferior Ophthalmic Vein
Lies below the optic nerve.
Receives tributaries from lacrimal sac, lower orbital muscles, and eyelids.
Drains either into the superior ophthalmic vein or directly into the cavernous sinus.
Also communicates with the pterygoid venous plexus via the inferior orbital fissure.
Lymphatic Drainage
Lymphatics of the orbit drain into preauricular (parotid) lymph nodes.
Origin and Nature
Composed of axons of ganglion cells of the retina (second-order neurons).
Structurally, it is a tract of the brain rather than a true peripheral nerve — lacks a neurilemma and cannot regenerate.
Relations
Crossed superiorly by the ophthalmic artery, nasociliary nerve, and superior ophthalmic vein.
Crossed inferiorly by the nerve to medial rectus.
Surrounded near the eyeball by orbital fat containing ciliary vessels and nerves.
Structure
Contains around 1.2 million myelinated fibers, 53% of which cross in the optic chiasma.
Covered by three meningeal layers continuous with those of the brain.
Infection Spread: Facial and ophthalmic venous connections can transmit infection → cavernous sinus thrombosis.
Optic Neuritis: Pain with eye movement and loss of vision; optic disc may appear normal (retrobulbar neuritis).
Optic Atrophy: Degeneration of the optic nerve, primary or secondary to inflammation or raised intracranial pressure.
Non-regenerative Nature: Due to absence of neurilemma, regeneration is impossible after injury.
Location
Small parasympathetic ganglion near the apex of the orbit, between the optic nerve and lateral rectus tendon.
Roots
Parasympathetic (motor) root:
From the nerve to inferior oblique (branch of oculomotor).
Preganglionic fibers originate in the Edinger–Westphal nucleus.
Postganglionic fibers travel through short ciliary nerves to the sphincter pupillae and ciliaris muscle (for accommodation).
Sensory root:
From nasociliary nerve; conveys sensory fibers from the eyeball.
Fibers do not relay in the ganglion.
Sympathetic root:
From internal carotid plexus (postganglionic fibers from superior cervical ganglion).
Pass through ganglion without relay → supply dilator pupillae and blood vessels of the eye.
Branches
8–10 short ciliary nerves divide into multiple filaments to pierce the sclera near the optic nerve, carrying all three types of fibers.
Course
Arises from the midbrain (interpeduncular fossa).
Passes through the cavernous sinus, divides into superior and inferior divisions, and enters the orbit through the superior orbital fissure.
Branches
Superior division:
Supplies superior rectus and levator palpebrae superioris.
Inferior division:
Supplies medial rectus, inferior rectus, and inferior oblique.
Gives a branch to ciliary ganglion (parasympathetic).
Functional Components
Somatic motor → all extraocular muscles except lateral rectus & superior oblique.
Parasympathetic → to sphincter pupillae and ciliaris via ciliary ganglion.
Clinical Correlation
Lesion → complete ptosis, pupil dilation, eye deviation down and out, and loss of accommodation.
Course
The smallest cranial nerve; the only one emerging from the dorsal aspect of the brainstem.
Passes around the midbrain, through the cavernous sinus, and enters the orbit through the superior orbital fissure.
Supplies the superior oblique muscle.
Functional Component
Somatic motor — controls depression, abduction, and intorsion of the eyeball.
Clinical Correlation
Trochlear nerve palsy → Diplopia (double vision), especially while looking downward and medially, difficulty descending stairs or reading.
Functional Type:
Somatic motor nerve to the lateral rectus muscle of the eye (responsible for abduction).
Nucleus:
Located in the floor of the 4th ventricle in the lower pons, beneath the facial colliculus.
Closely related to the medial longitudinal fasciculus, coordinating conjugate gaze.
Course:
Emerges from lower border of pons, between the pons and medulla.
Ascends upward and forward through the pontine cistern, usually above the anterior inferior cerebellar artery.
Pierces the dura lateral to the dorsum sellae and passes under the petrosphenoidal ligament.
Enters the cavernous sinus, running lateral and then inferolateral to the internal carotid artery.
Enters the orbit through the superior orbital fissure, lying inferolateral to the oculomotor nerve, to supply the lateral rectus muscle.
Clinical Anatomy:
Abducent nerve palsy → paralysis of lateral rectus → failure of abduction of the affected eye.
The eye deviates medially (medial squint), and diplopia (double vision) occurs when looking toward the affected side.
Vulnerable to raised intracranial pressure because of its long intracranial course and sharp bend over the petrous apex.
Nature:
Purely sensory; supplies structures in the orbit, forehead, and scalp.
Divisions and Branches:
Frontal Nerve (largest branch)
Supratrochlear nerve → upper eyelid, conjunctiva, and lower forehead.
Supraorbital nerve → frontal air sinus, upper eyelid, forehead, and scalp up to the vertex.
Nasociliary Nerve
Long ciliary nerves → sensory fibers to eyeball and sympathetic fibers to dilator pupillae.
Branch to ciliary ganglion → sensory root.
Posterior ethmoidal nerve → sphenoidal and posterior ethmoidal air sinuses.
Anterior ethmoidal nerve → middle and anterior ethmoidal sinuses; divides into:
Medial and lateral internal nasal branches (nasal septum and lateral wall).
External nasal branch (skin of ala and tip of nose).
Infratrochlear nerve → both eyelids, side of nose, and lacrimal sac.
Lacrimal Nerve
Supplies the lateral part of upper eyelid and conjunctiva.
Carries secretomotor fibers from the zygomatic nerve (V2) to the lacrimal gland.
Nature:
Purely sensory; supplies midfacial region, upper teeth, and nasal cavity.
Important Branches:
Infraorbital Nerve (continuation of maxillary nerve)
Enters orbit via inferior orbital fissure, runs through infraorbital groove and canal, and emerges via infraorbital foramen.
Branches:
Middle superior alveolar nerve → upper premolar teeth.
Anterior superior alveolar nerve → upper incisor and canine teeth, anterior nasal cavity, and maxillary sinus.
Terminal branches: palpebral, nasal, and labial — supply skin of eyelid, cheek, and upper lip.
Zygomatic Nerve
Branch of maxillary nerve in pterygopalatine fossa.
Enters orbit through lateral part of inferior orbital fissure; divides into:
Zygomaticotemporal nerve → anterior temple skin; gives branch to lacrimal nerve carrying secretomotor fibers to lacrimal gland.
Zygomaticofacial nerve → skin over the prominence of the cheek.
Posterior Superior Alveolar Nerve
Arises in pterygopalatine fossa; supplies molar teeth and maxillary sinus.
Origin
Arise from the internal carotid plexus, which is derived from the superior cervical sympathetic ganglion.
Course and Distribution
To the Dilator Pupillae
Fibers pass through the ophthalmic nerve (V1) → nasociliary nerve → long ciliary nerves.
Supply the dilator pupillae muscle of the iris, responsible for pupil dilation (mydriasis).
Other Sympathetic Pathways to the Orbit
a. Perivascular plexus — surrounds the ophthalmic artery and its branches, providing vasomotor fibers to orbital vessels.
b. Branch via Superior Orbital Fissure — from the internal carotid plexus → joins the ciliary ganglion (passes through without relay).
c. Other Filaments — travel along oculomotor (III), trochlear (IV), abducent (VI), and ophthalmic nerves (V1).
These fibers are vasomotor, supplying blood vessels within the orbit and ocular muscles.
Pupil Dilation (Mydriasis) — via dilator pupillae.
Vasomotor control — constriction of blood vessels in the orbit and eye.
Assists levator palpebrae superioris (through superior tarsal muscle) in elevating the upper eyelid.
Horner’s Syndrome results from interruption of sympathetic fibers:
Ptosis — drooping of upper eyelid (loss of tone in superior tarsal muscle).
Miosis — constricted pupil (unopposed sphincter pupillae).
Anhidrosis — loss of sweating on the affected side of the face.
Enophthalmos — slight sinking of the eyeball due to paralysis of orbitalis muscle.
For Nerve Supply of Extraocular Muscles
→ “LR6 SO4 rest 3”
Lateral rectus (LR) → supplied by 6th nerve (Abducent)
Superior oblique (SO) → supplied by 4th nerve (Trochlear)
Rest of the muscles (Superior rectus, Inferior rectus, Medial rectus, Inferior oblique, Levator palpebrae superioris) → supplied by 3rd nerve (Oculomotor)
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Levator palpebrae superioris is supplied partly by the oculomotor nerve (III) and partly by sympathetic fibers.
Central artery of retina is an end artery — its blockage causes sudden irreversible blindness.
Nerve supply of extraocular muscles: LR6, SO4, and the rest by III nerve.
Edinger–Westphal nucleus provides parasympathetic fibers to ciliaris and constrictor pupillae muscles after relay in the ciliary ganglion.
Elevation and depression of the eyeball occur around a transverse axis.
Adduction and abduction occur around a vertical axis.
Intorsion and extorsion occur around an anteroposterior axis
A hypertensive and diabetic woman with high cholesterol and lipid levels suddenly develops blindness in her right eye.
Question:
What is the likely cause of blindness in this case?
Name other end arteries in the body.
In hypertension, atheromatous (fatty) changes develop in arteries, leading to narrowing and hardening of the vessel wall.
The retina receives its main blood supply from the central artery of the retina, which is an end artery (i.e., it has no significant anastomoses with neighboring vessels).
Occlusion or blockage of this artery causes sudden irreversible blindness in that eye, as there is no alternate blood supply to the inner retinal layers.
Labyrinthine artery → supplies the inner ear.
Coronary arteries → functionally end arteries, despite minor anastomoses.
Central branches of cerebral arteries → supply deep brain structures.
Segmental arteries of kidney and spleen → end arteries supplying independent vascular segments.
Case:
A patient presents with fever, periorbital swelling, chemosis (conjunctival edema), and paralysis of ocular movements on one side.
Explanation:
Infection from the danger area of face (upper lip, nose) can spread through facial → angular → ophthalmic veins into the cavernous sinus.
Inflammation leads to thrombosis of the cavernous sinus, affecting the III, IV, VI, V1, and V2 cranial nerves that pass through or in its wall.
Results in ophthalmoplegia, proptosis, and loss of corneal reflex.
Key Anatomy:
Ophthalmic veins are valveless, allowing retrograde spread of infection.
Case:
A middle-aged person develops ptosis, the eye deviated down and out, and dilated pupil.
Explanation:
Indicates oculomotor nerve (III) paralysis.
Muscles affected: superior, inferior, medial recti, inferior oblique, and levator palpebrae superioris.
Unopposed action of lateral rectus (VI) and superior oblique (IV) causes downward and outward deviation.
Parasympathetic fibers to sphincter pupillae and ciliaris are also paralyzed → pupil dilates and accommodation is lost.
Case:
A patient with head injury complains of double vision when looking sideways.
Explanation:
Indicates abducent (VI) nerve lesion.
Lateral rectus paralyzed → failure of abduction → affected eye turns medially (due to medial rectus).
Commonly affected by raised intracranial pressure, as the nerve has a long intracranial course and a sharp bend over the petrous apex.
Case:
A patient presents with ptosis, miosis, anhidrosis, and slight enophthalmos.
Explanation:
Caused by interruption of sympathetic supply to the orbit.
Affects superior tarsal muscle (ptosis), dilator pupillae (miosis), and orbitalis muscle (enophthalmos).
Often due to lesions of the cervical sympathetic chain or superior cervical ganglion.
Case:
After a blunt injury to the eye, a person shows swelling, diplopia, and infraorbital numbness.
Explanation:
Inferior wall of the orbit (maxilla) is thin → may fracture (blow-out fracture).
Inferior rectus and inferior oblique muscles may get trapped → restricted upward gaze.
Infraorbital nerve injury → sensory loss over cheek and upper lip.
Case:
A young adult complains of pain during eye movement and sudden visual loss.
Explanation:
Inflammation of the optic nerve behind the eyeball (retrobulbar region).
Commonly seen in multiple sclerosis.
The optic disc appears normal initially, but later shows optic atrophy.
1. Name the contents of the orbit.
→ Eyeball, extraocular muscles, nerves, vessels, lacrimal gland, fascial sheaths, and orbital fat.
2. Which are the extraocular muscles?
→ Superior, inferior, medial, and lateral recti; superior and inferior oblique; and levator palpebrae superioris.
3. Name the involuntary muscles of the orbit.
→ Orbitalis, superior tarsal (of eyelid), and inferior tarsal muscles.
4. What is the nerve supply of the extraocular muscles?
→
Oculomotor (III): All except LR & SO.
Trochlear (IV): Superior oblique.
Abducent (VI): Lateral rectus.
Mnemonic — LR6 SO4 rest 3.
5. What is Tenon’s capsule?
→ Fascial sheath of the eyeball that surrounds it from optic nerve to sclerocorneal junction; allows free movement of the eyeball.
6. Name the branches of the ophthalmic artery.
→ Central artery of retina, lacrimal, supraorbital, supratrochlear, ethmoidal, dorsal nasal, posterior ciliary, palpebral, and muscular branches.
7. Which vein connects the facial vein with the cavernous sinus?
→ Superior ophthalmic vein.
8. Name the layers covering the optic nerve.
→ Dura mater, arachnoid mater, and pia mater (continuous with brain coverings).
9. Name the roots of the ciliary ganglion.
→
Parasympathetic: From oculomotor nerve.
Sympathetic: From internal carotid plexus.
Sensory: From nasociliary nerve.
10. Name the branches of the ciliary ganglion.
→ 8–10 short ciliary nerves.
11. What are the parts of the oculomotor nerve?
→ Superior and inferior divisions.
Superior → superior rectus and levator palpebrae superioris.
Inferior → medial, inferior recti, and inferior oblique muscles.
12. Which muscle is supplied by the trochlear nerve?
→ Superior oblique muscle.
13. Which muscle is supplied by the abducent nerve?
→ Lateral rectus muscle.
14. What are the branches of the ophthalmic division of the trigeminal nerve?
→ Frontal, lacrimal, and nasociliary nerves.
15. Which nerves pass through the superior orbital fissure?
→ Oculomotor, trochlear, abducent, ophthalmic division of trigeminal (V1), and sympathetic filaments.
16. What is the function of the sympathetic nerves of the orbit?
→ Pupil dilation (dilator pupillae), vasomotor control, and assistance in eyelid elevation (superior tarsal muscle).
17. What are the effects of injury to the oculomotor nerve?
→ Ptosis, dilated pupil, eye deviated down and out, and loss of accommodation.
18. What are the effects of Horner’s syndrome?
→ Ptosis, miosis, anhidrosis, and enophthalmos due to sympathetic interruption.
19. Which artery is called the end artery of the orbit?
→ Central artery of the retina.
20. Name the bones forming the orbit.
→ Frontal, sphenoid, zygomatic, maxilla, lacrimal, ethmoid, and palatine bones.
1. Which nucleus is related to the ciliary ganglion?
a. Superior salivatory
b. Lacrimatory
c. Inferior salivatory
d. Edinger–Westphal
→ Answer: d. Edinger–Westphal
2. Ophthalmic artery is a branch of which of the following arteries?
a. Internal carotid
b. External carotid
c. Maxillary
d. Vertebral
→ Answer: a. Internal carotid
3. Supraorbital artery is a branch of:
a. Maxillary
b. External carotid
c. Ophthalmic
d. Internal carotid
→ Answer: c. Ophthalmic
4. Which of the following is true about ocular muscles?
a. Medial rectus is supplied by III nerve
b. Superior oblique turns the cornea upward and laterally
c. Inferior oblique arises from medial wall of the orbit
d. Lateral rectus is supplied by IV nerve
→ Answer: a. Medial rectus is supplied by III nerve
5. Which nerve does not traverse the middle part of the superior orbital fissure?
a. Two divisions of III nerve
b. Frontal nerve
c. VI nerve
d. Nasociliary nerve
→ Answer: b. Frontal nerve
6. Which of the following arteries is an end artery?
a. Lacrimal artery
b. Zygomaticotemporal artery
c. Central artery of retina
d. Anterior ethmoidal artery
→ Answer: c. Central artery of retina
1. Name the bones forming the orbit.
→ Frontal, sphenoid, zygomatic, maxilla, lacrimal, ethmoid, and palatine.
2. What is the shape of the orbit?
→ Pyramidal cavity with its apex directed posteriorly and medially.
3. Which structure passes through the optic canal?
→ Optic nerve and ophthalmic artery.
4. Name the contents of the superior orbital fissure.
→ Oculomotor, trochlear, abducent, ophthalmic (V₁) nerves, and sympathetic filaments.
5. What are the extraocular muscles and their nerve supply?
→
Lateral rectus → abducent (VI).
Superior oblique → trochlear (IV).
Rest (superior, inferior, medial recti; inferior oblique; levator palpebrae) → oculomotor (III).
Mnemonic: LR6 SO4, rest 3.
6. What is the fascial sheath of the eyeball?
→ Tenon’s capsule — a fibrous sheath around the eyeball allowing free movement.
7. What is the suspensory ligament of the eyeball?
→ Lockwood’s ligament — formed by inferior rectus and inferior oblique sheaths; supports the eyeball from below.
8. Name the branches of the ophthalmic artery.
→ Central artery of retina, lacrimal, supraorbital, supratrochlear, ethmoidal, dorsal nasal, and palpebral arteries.
9. Which vein connects facial and intracranial venous systems?
→ Superior ophthalmic vein.
10. What are the roots of the ciliary ganglion?
→ Sensory (nasociliary), parasympathetic (oculomotor), and sympathetic (from internal carotid plexus).
11. What is the function of the short ciliary nerves?
→ Carry sensory, parasympathetic, and sympathetic fibers to the eyeball.
12. Which muscle causes abduction of the eye?
→ Lateral rectus.
13. Which muscle depresses and intorts the eye?
→ Superior oblique.
14. What is the function of the orbitalis muscle?
→ Maintains slight protrusion of eyeball; supplied by sympathetic nerves.
15. What happens in Horner’s syndrome?
→ Ptosis, miosis, anhidrosis, and enophthalmos due to sympathetic interruption.
16. What are the effects of oculomotor nerve palsy?
→ Ptosis, eye turned down and out, dilated pupil, and loss of accommodation.
17. What is the cause of sudden blindness in hypertension?
→ Occlusion of the central artery of the retina (end artery).
18. Which nerve carries secretomotor fibers to the lacrimal gland?
→ Zygomatic branch of maxillary nerve → lacrimal nerve.
19. Which cranial nerves are related to the orbit?
→ II (optic), III (oculomotor), IV (trochlear), V₁ (ophthalmic division), and VI (abducent).
20. Name the involuntary muscles in the orbit.
→ Orbitalis, superior tarsal, and inferior tarsal muscles.
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