ORBIT

EXTRAOCCULAR MUSCLES

Dr.B.B.Gosai

Bony Orbit

Seven bones make up the bony orbit: Frontal Zygomatic Maxillary Ethmoidal Sphenoid Lacrimal Palatine

Bony Orbit

ROOF:The orbital roof

formed from both the orbital plate of the frontal bone and the lesser wing of the sphenoid bone. Above the roof is cranial cavity.

Contains: Lacrimal fossa for lacrimal gland

FLOOR:The floor of the orbit

is formed from three bones and related to maxillary sinus:

Maxillary Palatine Orbital plate of the

zygomatic

It contains:Infraorbital grooveAttachment of Inferior

oblique muscle

Bony Orbit

MEDIAL WALL of the orbit is formed from four bones and related to lateral wall of nose: Frontal process of the

maxillary Lacrimal Orbital plate of the

ethmoidal Lesser wing of the

sphenoidLacrimal fossa for

lacrimal sac.

LATERAL WALL: Formed from two bones: Zygomatic Greater wing of the

sphenoidThickest and strongestLateral orbital

tubercle (Whitnall’s tubercle) for attachment of lateral check ligament

Orbital Foramina

The optic foramen: Transmit Optic nerve and Ophthalmic artery

The supraorbital foramen, or notch: transmit supraorbital nerve and vessels

The zygomatic foramen: Transmit Zygomatic nerve

Infraorbital canal: Transmit Infraorbital nerve and vessels

Superior orbital fissure: Transmit occulomotor nerve, trochlear nerve, abducent nerve, Branches of Ophthalmic nerve, Ophthalmic veins

Inferior orbital fissure: Maxillary nerve

Structures passing through superior orbital fissure

Extra ocular Muscles in the orbit

Extraocular Muscles

The four recti and two oblique muscles

All are supplied by oculomotor nerve III except superior oblique (Trochlear N) and lateral rectus (Abducent N)

Voluntary Muscles:1. Four Recti – Superior, inferior, medial and

lateral.2. Two Oblique – Superior & inferior.3. Elevator of upper eyelid – Levator palpebrae

superioris.Involuntary Muscles:1. Superior tarsal muscle – Deeper part of levator

palpebrae superioris2. Inferior tarsal muscle3. Orbitalis muscle

Extra ocular Muscles in the Orbit

Extra ocular Muscles

Extra ocular Muscles:Origin

Common annular tendinous ring

Extra ocular Muscles:Origin

Superior ObliqueLevator palpebrae superioris

Medial Rectus

Lateral Rectus

Superior Rectus

Inferior RectusInferior Oblique

Levator Palpebrae Superioris Origin: Orbital surface of lesser

wing of sphenoid bone, anterosuperior to optic canal.

Insertion: Splits in two lamina Superior lamina (voluntary) to Skin

of upper eyelid & anterior surface of superior tarsal plate

Inferior lamina (Muller’s muscle)(involuntary) to upper margin of superior tarsus (superior tarsal or muller’s muscle) & superior conjunctival fornix

Nerve Supply: Oculomotor nerve (voluntary part); Sympathetic (involuntary part)

Action: Elevation of upper eyelid. Damage to oculomotor nerve lead

to paralysis of this muscle and leads to ptosis.

Even damage to sympathetic fibers in Horner’s syndrome leads to partial ptosis due to paralysis of Muller’s muscle.

Extra ocular MusclesInsertion: on the sclera

Recti – on sclera in front of equator; distance from cornea – SR = 7.7mm, LR = 6.9mm. IR = 6.5mm; MR = 5.5mm.Superior Oblique – Behind the equator on sclera in superolateral posterior quadrant, between the recti superior and lateralis.Inferior Oblique: - Behind the equator on sclera in inferolateral posterior quadrant, between the recti superior and lateralis.

Nerve Supply:

Abducent (VI cranial) nerve supplies lateral rectus

Nerve Supply:

Trochlear (IV cranial) nerve supplies superior oblique

Nerve Supply Superior, Inferior & Medial Recti; Levator

palpebrae superioris and Inferior Oblique Muscles are supplied by Oculomotor ( III cranial) Nerve

Movements of Eyeball Along vertical axis : Lateral rotation (Abduction) & Medial

rotation (Adduction) Along Transverse axis: Elevation & Depression Along anteroposterior axis: Intortion (cornea moves

medially from 12 O'clock position) & Extortion (cornea moves laterally from 12 O'clock position)

Actions of Recti Muscles

Actions of Recti Muscles

Superior rectus: Elevation; Adduction; Intortion

Inferior rectus: Depression; Adduction; Extortion

Medial rectus: Adduction;

Lateral rectus: Abduction;

Actions of Oblique Muscles

Superior Oblique: : Depression,Abduction,Intortion

Inferior Oblique : Elevation,Abduction,Extortion

Actions of Oblique Muscles

Superior Oblique: : Intortion

Inferior Oblique : Extortion

Anteroposterior axis

Actions of Oblique Muscles

Both oblique muscles pulls posterolateral quadrant anteromedially; thus abduct the eyeball.

Vertical axis

Recti muscles: straight muscles•Superior rectus: oculomotor nerve

•Adduction, elevation, intorsion

•Inferior rectus: oculomotor nerve•Adduction, depression, extorsion

•Medial rectus: oculomotor nerve•Adduction

•Lateral rectus: abducent nerve•Abduction

•Superior oblique: trochlear nerve•Abduction, depression, intorsion

•Inferior oblique: oculomotor nerve•Abduction, elevation, extorsion

Movements of Eyeball

Applied AnatomyAbnormal deviation of eyeball is known as

Squint (Strabismus).

Paralysis of Lateral rectus due to damage to Abducent nerve leads to Medial Squint.

Damage to Occulomotor nerve leads to paralysis of all muscles of eye except Superior oblique and lateral rectus leading to Lateral Squint and Ptosis-Dropping of Eyelid.

Damage to Trochlear nerve cause paralysis of superior oblique muscle causing diplopia while looking downwards.

Medial Squint

Lateral Squint and Ptosis -Dropping of Eyelid.

Superior Oblique

Inferior Oblique

Superior rectus

Inferior rectus

Medial rectus

Lateral rectus

• Causes: interruption of sympathetic pathway like multiple sclerosis, syringomyelia, traction of stellate ganglion by cervical rib, ganglion metastatic lesion.

• Signs:• Constriction of pupil (miosis) due to paralysis of dilator

pupillae• Slight drooping of eyelid (ptosis) due to paralysis of

Muller’s muscle (Part of Levator palpebrae superioris)• Enophthalmos (Retraction of eyeball) due to paralysis of

Orbitalis muscle which support the eyeball• Loss of sweating (anhydrosis) damage to sympathetic

fibers to sweat glands• Loss of ciliospinal reflex

Horner’s syndrome