orbit and extra-ocular muscles

DR. SUSHRUT AHALE

ORBIT AND EXTAOCULAR

MUSCLES

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

zygomaticIt 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

sphenoid

Lacrimal fossa for lacrimal sac.

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

sphenoid

Thickest and strongest

Lateral 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

Extraocular 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 Obliques – Superior & Inferior3. Elevator of upper eyelid – Levator palpebrae

superioris.

Involuntary Muscles:

1. Superior tarsal muscle – Deeper part of levator palpebrae superioris

2. Inferior tarsal muscle3. Orbicularis muscle

Extraocular Muscles

Extraocular Muscles

Extraocular Muscles: Origin

4 Recti originate from a common tendinous ring (the annulus of Zinn) which is attached at the apex of the orbit encircling the optic foramina and the medial part of the superior orbital fissure.

SO: arises from the body of sphenoid bone above and medial to the optic foramen

IO: arises by a round tendon from a shallow depression on the orbital plate of maxilla

Extraocular Muscles: Origin

Common annular tendinous ring

Extraocular Muscles: Origin

Superior ObliqueLevator palpebrae superioris

Medial Rectus

Lateral Rectus

Superior Rectus

Inferior RectusInferior Oblique

Extraocular 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 superior and lateral recti.

Inferior Oblique – Behind the equator on sclera in inferolateral posterior quadrant, between the recti superior and lateralis.

Blood Supply:

2 muscular arteries from the ophthalmic arteryThe medial (larger) branch supplies the MR, IR

and IO muscles.The lateral (smaller) branch supplies the LR,

SR, SO and levator palpebrae muscles.Anterior ciliary arteries (usually 7) from the

above arteries.Veins correspond to the arteries and empty into

the superior and inferior ophthalmic veins.

Nerve Supply:

Superior, Inferior & Medial Recti; Levator palpebrae superioris and Inferior Oblique Muscles are supplied by Oculomotor (III cranial) Nerve

Nerve Supply:

Trochlear (IV cranial) nerve supplies Superior Oblique [SO4]

Nerve Supply:

Abducent (VI cranial) nerve supplies Lateral Rectus [LR6]

Levator Palpebrae Superioris: Origin: Orbital surface of lesser wing of

sphenoid bone, anterosuperior to optic canal.

Insertion: Splits into two laminas Superior lamina (voluntary) to the skin of

upper eyelid & anterior surface of superior tarsal plate

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

Nerve Supply: Oculomotor nerve (voluntary part); Sympathetic (involuntary part, ie Muller’s muscle)

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

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

Both the obliques are attached behind the equator and thus, cause opposite movement of the eyeball in the vertical axis.

Actions of Oblique Muscles:

Superior Oblique: : Intortion

Inferior Oblique : Extortion

Anteroposterior axis

Actions of Oblique Muscles:

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

Vertical axis

Extraocular muscles actions:

Movements of Eyeball:

MUSCLE NERVE SUPPLY

ACTIONS

SUPERIOR RECTUS

Oculomotor Adduction, Elevation, Intorsion SIN

INFERIOR RECTUS

Oculomotor Adduction, Depression, Extorsion

RAD

MEDIAL RECTUS

Oculomotor Adduction RADLATERAL RECTUS Abducent LR6 Abduction

SUPERIOR OBLIQUE Trochlear SO4 Abduction,

Depression, Intorsion

SIN

INFERIOR OBLIQUE

Oculomotor Abduction, Elevation, Extorsion

Applied Anatomy:

Abnormal deviation of the is known as Squint (Strabismus).

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

Damage to Oculomotor nerve (3Ds) leads to paralysis of all muscles of eye except Superior Oblique and Lateral Rectus leading to Divergent Squint, Diplopia and Ptosis- Drooping of Eyelid.

Damage to Trochlear nerve cause paralysis of Superior Oblique muscle causing diplopia while looking downwards.

Medial Squint

Divergent Squint and Ptosis -Drooping 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

Orbicularis muscle which supports the eyeball• Loss of sweating (anhydrosis) due to damage to sympathetic

fibers to the sweat glands• Loss of ciliospinal reflex

Horner’s syndrome