Describes in brief about extraocular muscles and their applied in ophthalmological medicine and surgery.

1. EXTRAOCULAR
MUSCLES
DR. SHUBHADA NILKANTHE
ANATOMY AND
APPLIED

2. INVOLUNTARY
EXTRA-OCULAR MUSCLES
▸SUPERIOR TARSAL MUSCLE
▸INFERIOR TARSAL MUSCLE
VOLUNTA
RY
▸LPS
▸SUPERIOR RECTUS
▸INFERIOR RECTUS
▸LATERAL RECTUS
▸MEDIAL RECTUS
▸SUPERIOR OBLIQUE
▸INFERIOR OBLIQUE

3. EMBRYOLOGY
▸Prechordal mesenchyme and neural crest cell
▸The extraocular muscles are some of the few periocular tissues that have been shown not to be of neural crest
origin. Recently, they are thought to differentiate in situ from the mesodermal derived mesenchymal tissue which
constitutes the myotomic cells of the preotic mesodermal somites that have shifted cranially.
▸The four rectus muscles and the superior and inferior oblique muscles differentiate from the mesenchyme in the
region of developing eyeball (prechordal mesenchyme).
▸Originally represented as a single mass of mesenchyme, they later separate into distinct muscles, first at their
insertions and later still at their origins.
▸Myoblasts with myofibrills and immature Z bands are distinguishable by the 5th week of gestation.
▸The extraocular muscles appear in approximately the following sequences: lateral rectus, superior rectus and
levator palpebral superioris (week 5), superior oblique and medial rectus (week 6), followed by inferior oblique
and inferior rectus (common primordium).
▸During development, the extraocular muscles become associated with the axons of the general somatic efferent
neurons of cranial nerves III, IV and VI, which innervate these muscles.

4. ▸Recti form muscle cone. From the origin they tend to diverge and then start converging after they cross the
equator and get inserted anterior to equator.
▸Recti have direct path from origin to insertion.
▸Obliques have angular course , do not originate from annulus of zin and get inserted behind the equator .
INTRODUCTION

5. ORIGIN OF RECTI- ANNULUS
▸Connective tissue ring
▸Encircles optic foramen and medial
part of superior orbital fissure
▸Close association of SR and MR
with dural sheath of optic nerve-
causes pain one eye movements in
optic neuritis.

6. COURSE
▸Medial rectus- almost parallel to
saggital plane.
▸Vertical recti- angle of 23 0 with
saggital plane.
▸Lateral rectus makes an angle of 40-
450 with the plane.

7. SPIRAL OF TILLAUX
▸The insertions of the recti, being not equidistant
from the limbus, do not form a circle concentric
with the limbus; rather form a spiral (the spiral of
Tillaux).
▸The lines of insertion of superior and inferior rectus
muscles show marked convexity towards the
limbus and are obliquely placed in such a way that
the lateral end of their insertion line is posteriorly
placed as compared to the medial end.

8. LEVATOR PALPEBRAE SUPERIORIS
ORIGIN Lesser wing of sphenoid bone
INSERTION
Upper lamina ( voulntary ) - anterior surface of superior
tarsal plate, skin of upper eyelid.
Middle lamina ( involuntary ) - superior margin of superior
tarsus ( superior tarsus or muller muscle )
Lower Lamina ( involuntary) - superior conjunctival fornix.
ACTION Elevates superior eyelid
INNERVATION
Voluntary part - oculomotor nerve
Involuntary part - sympathetic plexus around carotid
BLOOD
SUPPLY
Interal carotid -> ophthalmic artery, supraorbital artery

9. LPS CONTD.
▸Originates near the orbital apex , not a
part of the annulus, courses anteriorly
in close contact with the orbital roof
superiorly and SR inferiorly.
▸Fleshy ( horizontal) part of muscle
:40mm
▸aponeurosis (vertical) : 15 mm
▸Change of direction occurs at the level
of superior transverse ligament of
WHITNALL.
▸This acts as a check ligament of LPS
muscle.

10. ▸The connective tissue sheaths enclosing SR and LPS muscles are
fused along their related surfaces.
▸LPS aids in the action of SR in superior gaze.
▸In maximal resection of LPS in ptosis , hypotropia can be induced if
these connections are not severed.
▸Horner’s syndrome i.e. disruption of sympathetic nerve supply can
cause ptosis d/t muller muscle paralysis.
LPS CONTD.

11. SUPERIOR RECTUS
ORIGIN Common tendinous ring ( Annulus of Zinn)
INSERTION
Anterior half of eyeball ( posterior to corneoscleral
junction) 7.7 mm from limbus superiorly
ACTION Elevates, adducts , internally rotates eyeball
INNERVATION Oculomotor nerve
BLOOD
SUPPLY
Supraorbital branch of ophthalmic artery

12. MEDIAL RECTUS
ORIGIN Common tendinous ring
INSERTION
Anterior half of eyeball medially , 5.5 mm posterior to
corneoscleral junction
ACTION Adduction
INNERVATION Oculomotor nerve
BLOOD
SUPPLY
Ophthalmic artery

13. LATERAL RECTUS
ORIGIN Common tendinous ring
INSERTION
Anterior half of the eyeball, 6.9 mm posterior to
corneosclearal junction laterally
ACTION Abduction
INNERVATION Abducens nerve
BLOOD
SUPPLY
Ophthalmic artery

14. ▸Sixth nerve paralysis is one of the
commonest false localizing sign in
cases with raised intracranial
pressure. Its susceptibility to such
damage is due to its long course
and to its sharp bend over the
superior border of the petrous
temporal bone and the downward
shift of the brainstem (towards the
foramen magnum) produced by
raised intracranial pressure.
LATERAL RECTUS

15. SUPERIOR OBLIQUE
ORIGIN
Body of sphenoid bone, Above and medial to optic
foramen
INSERTION
Superolateral aspect of eyeball ( deep to rectus
superior, via trochlea orbitae)
ACTION
Abducts, depresses (in adduction), internally rotates
eyeball (in abduction)
INNERVATION Trochlear nerve
BLOOD
SUPPLY
Ophthalmic artery

16. ▸Longest and thinnest extraocular muscle -
60 mm.
▸Trochlear nerve lies outside the muscle
cone , hence not paralysed in retrobulbar
block.
▸Runs parallel to medial wall of orbit and
changes direction from trochlea to run
posterolaterally , this angle being 54 degree.
▸Trochlea acts as a functional origin of the
superior oblique muscle.
SUPERIOR OBLIQUE

17. SUPERIOR OBLIQUE - TROCHLEA
▸Fibrocartilagenous pulley attached to spina
trochlearis on under aspect of frontal bone , at
superomedial angle b/w the anterior most parts
of superior and medial walls of orbit. (Medial -
bony-> lacrimal bone, Lateral- cartilagenous)
▸Becomes tendinous 10 mm before trochlea.
▸Brown’s syndrome- also called as superior
oblique tendon sheath syndrome is the
inflammation of the tendon in conditions such
as rheumatoid arthritis, scleritis, etc. , is
characterised by limitation of the active and
passive elevation in adduction .

18. ▸Runs underneath SR, inserted behind equator of the
globe. So, when it contracts , it lifts up the posterior
part of the globe thus acting as a depressor of the
globe.
▸Anterior end is 4 mm posterior to lateral part of SR
and 14 mm from limbus , responsible for intorsion .
▸Posterior part is 14 mm posterior to medial part of
SR and 20 mm from limbus responsible for
depression.
▸Posterior part lies in close association with the
superior vortex vein- act as an anatomical landmark
which signifies posterior end of the muscle i.e. if the
veins are visible while hooking the muscle, probably
whole of the muscle has been hooked .
SUPERIOR OBLIQUE

19. INFERIOR OBLIQUE
ORIGIN
Orbital surface of maxilla, lateral to lacrimal
groove
INSERTION
Inferolateral aspect of eyeball ( deep to
lateral rectus muscle )
ACTION
Abducts, elevates , externally rotates
eyeball
INNERVATION Oculomotor nerve
BLOOD SUPPLY Ophthalmic artery , infraorbital artery

20. ▸Shortest EOM:37 mm.
▸Only muscle originating from anterior orbit.
▸Courses in posterolateral direction, passes
superficial to inferior rectus , gets inserted behind
lateral rectus muscle.
▸Anterior end of insertion is 10 mm behind LR
insertion.
▸Anterior fibers : Extorsion
▸Posterior fibers: Elevation
▸Posterior end of insertion is very close (1 mm below
and 1 to 2 mm in front ) to a point on sclera which
corresponds to fovea .
INFERIOR OBLIQUE

21. CONTD.
▸As functional origin of the oblique muscles lie anteriorly in the orbit , they tend to
come anterior on disinsertion while operating.
▸Unlike the obliques, the recti have origin behind the globe, so they need to be
sutured first before disinserting as they can easily retract and slip posteriorly.

22. FASCIAL
EXTENSI
ONS
▸Each extraocular muscle has an extracapsular (outside Tenon’s capsule) and an intracapsular part. The extracapsular part of each
muscle is surrounded by a fascial sheath (muscle capsule or muscle sleeve).
▸The Tenon’s capsule and the muscle sleeves form the barriers between the orbital fat and globe and extraocular muscles. When
muscle sleeve is traumatically violated, fat adherence can occur. It can occur as a complication of almost any extraocular surgery,
e.g. strabismus surgery, buckling procedure.

23. ▸The sheaths of the four rectus muscles
are joined to each other by a fascial
membrane called the intermuscular
septum .
▸This membrane divides the orbital cavity
and orbital fat into a central and a
peripheral part.
▸The intermuscular septa fuse with the
conjunctiva 3 mm posterior to the limbus.
INTERMUSCULAR SEPTUM

24. ▸Suspensory ligament of Lockwood: It is a
thickened sling or hammock of fascial sheath
extending from the posterior lacrimal crest to the
lateral orbital tubercle, on which rests the eyeball.
It is formed by fusion of expansions from the
muscular sheaths of the medial rectus, inferior
oblique, inferior rectus and lateral rectus muscles
joined with the thickened inferior part of Tenon’s
capsule.
▸Superior transverse ligament of the Whitnall: It
is a thickened band of orbital fascia which extends
from the trochlear pulley to the lacrimal gland and
its fossa. It is formed by a condensation of the
superior sheaths of the levator muscle joined
medially by the sheath of the reflected tendon of
superior oblique muscle. It forms a true check
ligament of the levator muscle.
FASCIAL EXTENSIONS

25. CONTD.
▸While operating on vertical recti, their connections with the fascia of
corresponding lids should be removed properly. If not done so , it can change the
lid position.
▸Example- SR recession: lid retraction, SR resection: drooping

26. ▸Superior suspensory ligament of the
fornix is formed by the continuation
forward of the fibrous tissue between
the superior rectus and levator
muscles to the upper fornix. During
ptosis surgery, if this ligament is cut,
fornix conjunctiva can prolapse.
▸ Similarly, the inferior suspensory
ligament of the fornix is formed by
the continuation forward up to the
inferior fornix of the fibrous tissue of
lower lid retractors.
FASCIAL EXTENSIONS

27. NERVE SUPPLY
▸Superior division of
oculomotor nerve - LPS, SR
▸Inferior division of oculomotor
nerve- MR, IR.IO
▸Abducens : LR
▸Trochlear nerve: SO

28. BLOOD SUPPLY

29. BLOOD SUPPLY
▸Medial and lateral muscular arteries,
branches of ophthalmic artery
▸MMA (larger): MR , IR , IO
▸LMA: LR , SR , SO , LPS
▸Muscular arteries divide to form 7
anterior ciliary arteries, these are
additional arteries supplying the recti
: 2 for each except for the LR (only 1)
.

30. CONTD.
▸Anterior ciliary artery pierce sclera and combine with long posterior ciliary
artery to form MAJOR ARTERIAL CIRCLE present at the root of iris.
▸Also responsible to form episcleral plexus.
▸It is peferred not to operate >2 recti as it can lead to anterior segment
ischemia.

31. ACTIONS
▸The last 4 muscles are known as
cyclovertical muscles owing to their
actions.

32. ACTIONS RECTI
▸When the eye is abducted: visual axis and
orbital axis of vertical recti coincide , so they
become prime vertical movers i.e.
SR: prime elevator
IR: prime depressor
It is the best position to test the recti.
▸When the eye is adducted: visual axis and
orbital axis of vertical recti will come closer to
90 degree , so they become prime
cyclotorters i.e.
SR: prime intorter
IR: prime extorter

33. ACTIONS RECTI

34. ACTIONS OBLIQUES
▸When the eye is adducted 51 °, visual axis
and axis of pull of obliques coincide, so
they become prime vertical movers i.e.
SO: pure elevator
IO: pure depressor
It is the best position to test the OBLIQUES as
the movement is easier to note compared to
cyclotorsion.
▸When the eye is abducted 39°,visual axis
and oblique muscles become 90 degree ,
so they become prime cyclotorters
SO: prime intorter
IO: prime extorter

35. ACTIONS OBLIQUES

36. ACTIONS CONTD.

37. ACTIONS CONTD.
▸Primary position: E
▸Secondary positions:
B, D, F, H
▸Tertiary positions :
A, C, G, I

38. ACTIONS CONTD.

39. ARC OF CONTACT
▸The distal portion of each extraocular
muscle or muscle tendon lies flush
against the globe for a variable
distance before it blends into the
sclera (anatomic insertion).
▸ The point at which the centre of the
muscle or its tendon first touches the
globe is the tangential point. It is also
referred to as the physiologic or
effective insertion of the muscle,
▸The position of this point changes,
when the muscle contracts or relaxes
and the globe rotates.
▸The arc of contact is the distance on the
scleral circumference between the tangential
point (T) and the centre of anatomic insertion
of the muscle (A) on the sclera. The lengths of
the contact area for various extraocular
muscles in primary position of the gaze .

40. ARC OF CONTACT
▸Since the power of a muscle is
proportionate to its length and arc of
contact -
Retroplacement of the insertion of
muscle (recession) weakens the action
of the muscle by shortening its effective
length and by reducing its arc of contact
in the various positions of gaze.
Advancement of an extraocular muscle
has a strengthening effect because of
the increase in the effective length as
well as its arc of contact.

41. ▸Nerves to the rectus muscles and the superior oblique muscle enter the muscles
about one-third of the distance from the origin to the insertion (or trochlea, in the
case of the superior oblique muscle). It is possible to damage these nerves during
anterior surgery.If an instrument is thrust more than 26 mm posterior to the rectus
muscle’s insertion, injury to the nerve may occur.
▸The sclera is thinnest just posterior to the four rectus muscle insertions. This is
the site for most muscle surgery, especially for recession procedures. This risk
can be best minimized by using spatulated needles with swedged sutures;
working with a clean, dry, and blood-free surgical field.
APPLIED : MISCELLANEOUS

42. THANK
YOU.