Extraocular muscles

EXTRAOCULAR MUSCLES

IMPORTANT LANDMARKS

CONTENTS OF ORBIT

Eyeball

Fascia bulbi

Muscles

Vessels

Nerves

Lacrimal gland

Orbital fat

EXTRAOCULAR MUSCLES

Voluntary muscles

Involuntary muscles

Extraocularmuscles

LPS Recti muscles Oblique muscles

Superior tarsal muscle Inferior tarsal muscle Orbitalis muscle

• ANNULUS OF ZINN -

common tendinous ring

• Attachments

• Forms a muscle cone

RECTI MUSCLES - origin

Medial Rectus

Lateral Rectus

Superior Rectus

Inferior Rectus

RECTI MUSCLES - origin

RECTI MUSCLES - Insertion

Inserted into sclera

In front of equator

• Distance from cornea

MR = 5.5mm IR = 6.5mm LR = 6.9mm SR = 7.7mm

5mm

6 mm

8 mm

7 mm

Superior Oblique

SUPERIOR OBLIQUE - origin

SUPERIOR OBLIQUE – Insertion

Behind the equator on sclera in posterosuperiorquadrant, between the superior and lateral rectus

Inferior Oblique

INFERIOR OBLIQUE - origin

INFERIOR OBLIQUE – Insertion

Behind the equator on sclera in posterior quadrant, between the superior and lateral rectus

Three cranial nerves

3. Trochlear nerve2. Abducent nerve1. Oculomotor nerve

Superior obliqueLateral rectus 1. Superior rectus2. Medial rectus3. Inferior rectos

4. Inferior oblique5. Levator pelpebrae

NERVE SUPPLY OF EOM

ACTION OF INDIVIDUAL MUSCLES

Adduction-MR

Abduction-LR

In Abducted eye Elevation-SR Depression-IR

In Adducted eye Elevation-IO Depression-SO

MOVEMENTS-DUCTIONS

Elevation

Depression Abduction

Adduction Intorsion

Extorsion

• Elevation & Depression – Around the transverse axis

• Adduction & Abduction – Around the vertical axis

• Intortion & Extortion – Around the anteroposterior axis

drepression

elevation

1.Primary position

MOVEMENTS-VERSIONS (CONJUGATE)

Convergence (simultaneous movement nasally)

Divergence (simultaneous temporal movement)

MOVEMENTS-VERGENCE

DUCTIONS - MUSCLES PRODUCING

• Elevation – Superior rectus & Inferior oblique

• Depression – Inferior rectus & Superior oblique

• Intortion – Superior rectus & Superior oblique

• Extorsion – Inferior rectus & Inferior oblique

• Adduction – Medial ,Superior & Inferior recti

• Abduction – Lateral rectus, Superior & Inferior oblique

RECTI -Adduct

OBLIQUES –Abduct

SUPERIORS – Intort

INFERIORS -Extort

Levator palpebrae superioris

LEVATOR PALPEBRAE SUPERIORIS - Origin

Undersurface of

lesser wing of

sphenoid

• Upper lamina : Skin of upper eyelid

• Middle lamina: Superior tarsus(Muller’s)

• Lower lamina: Superior conjunctival fornix

LEVATOR PALPEBRAE SUPERIORIS - Insertion

Nerve Supply :

Voluntary part – Oculomotor Nerve

Involuntary part – Sympathetics

Action : Elevation of upper eye lid

LEVATOR PALPEBRAE SUPERIORIS

CINICAL TESTING

Abnormal deviation of eyeball is known as Squint (Strabismus)

Damage to Abducent nerve - Medial Squint

Damage to Occulomotor nerve - Lateral Squint and Ptosis-Dropping of Eyelid

Damage to Trochlear nerve - diplopiawhile looking downwards

Medial Squint

Lateral Squint and Ptosis

PTOSIS

Drooping of upper eyelid

• Complete ptosis

• Partial ptosis