This document provides an overview of the anatomy of the extraocular muscles. It discusses the seven extraocular muscles, which can be divided into two groups: muscles responsible for eye movement (the four recti muscles and two oblique muscles) and the levator palpebrae superioris muscle responsible for eyelid elevation. For each muscle, the document outlines their origin, insertion point, blood supply, size, relationships to surrounding structures, and innervation. The recti muscles originate from the annulus of Zinn, while the oblique muscles take an angular path to the eyeball.

2. EXTRAOCULAR
MUSCLES
ANATOMY
PREPARED BY:
RABIA AMMER
BSC.(OPTOM), M.PHIL.(OPTOM)
GOLD MEDALIST

4. INTRODUCTION
• The extraocular muscles are located within the orbit,
but are extrinsic and separate from the eyeball
itself. They act to control the movements of
the eyeball and the superior eyelid.
• There are seven extraocular muscles –
1. Levator Palpebrae Superioris
2. Superior Rectus
3. Inferior Rectus
4. Medial Rectus
5. Lateral Rectus
6. Inferior Oblique
7. Superior Oblique.

6. TYPES
• Functionally, they can be divided into two
groups:
1. Responsible for eye movement:
 Recti Muscles
 Oblique Muscles.
2. Responsible for superior eyelid Elevation:
 Levator Palpebrae Superioris

7. MUSCLES OF EYE
MOVEMENT
• There are six muscles involved in the control of
the eyeball itself. They can be divided into two
groups:
• The Four Recti Muscles,
• The Two Oblique Muscles.

8. RECTI MUSCLES
• The name recti is derived from the latin for
‘straight’ – this represents the fact that the recti
muscles have direct path from origin to
attachment. This is in contrast with the oblique
eye muscles, which have an angular approach to
the eyeball.

9. RECTI MUSCLES
• There are four recti muscles;
1. Superior Rectus
2. Inferior Rectus
3. Medial Rectus
4. Lateral Rectus

10. ANNULUS OF ZINN
• The four recti muscles arise from a short funnel-shaped tendinous
ring called the annulus of Zinn. The annulus of Zinn encloses the
optic foramen and a part of the medial end of the superior orbital
fissure.
• There are 2 tendons.
• The Lower Tendon (of Zinn) is attached to the inferior root of
the lesser wing of the sphenoid between the optic foramen and the
superior orbital fissure. The lower tendon gives origin to part of the
medial and lateral recti and all of the inferior rectus.
• The Upper Tendon (of Lockwood) arises from the body of the
sphenoid, and gives origin to part of the medial and lateral recti and
all of the superior rectus muscle. The superior and medial recti
muscles are much more closely attached to the dural sheath of the
optic nerve. This fact may be responsible for the characteristic pain
which accompanies extreme eye movements in retro-bulbar
neuritis.

11. RECTUS MUSCLES : ORIGIN
• Arises from a common
tendinous ring knows as
ANNULUS OF ZINN
• Common ring of connective
tissue
• Anterior to optic foramen
• Forms a muscle cone

15. SPIRAL OF TILLAUX
• This is the “spiral” that describes the insertion of
the rectus muscles in relation to the limbus. The
average values are medial=5.5mm, inferior=6.5,
lateral=6.9mm, and superior=7.7mm. In the OR,
however, I just remember “5,6,7,8.

16. SPIRAL OF TILLAUX
5.5 mm
6.5 mm
6.9 mm
7.7 mm

17. RECTI MUSCLES THICKNESS

18. EXTRAOCULAR MUSCLES
MOTOR UNITS
• The motor units are small, with only from 5 to 18
muscle fibers contact by each motor nerve

19. SUPERIOR RECTUS
• Origin – The superior rectus arises from the upper
part of the annulus of Zinn above and to the lateral
side of the optic foramen and from the sheath of the
optic nerve. This origin lies below that of the levator,
and is continuous on the medial side with the medial
rectus and on the lateral with the lateral rectus.
• Insertion – inserted superiorly, in vertical
meridian 7.7 mm from limbus
• Blood supply – Superior muscular branch of
ophthalmic artery and 2 anterior ciliary a.
• Size – 41.8 mm long; tendon is 5.8 mm long and
10.6 mm wide

22. SUPERIOR RECTUS
• Relations– Above the superior rectus is the levator and
the frontal nerve, which separate it from the roof of the
orbit. Below is the optic nerve, but separated by orbital
fat, the ophthalmic artery, and the naso-ciliary nerve.
Farther forwards the reflected tendon of the superior
oblique passes beneath the superior rectus to reach its
insertion. Laterally, in the angle between superior and
lateral recti, are found the lacrimal artery and
nerve.Medially,the ophthalmic artery and naso-ciliary
nerve lie in the angle between the superior rectus and the
medial rectus and superior oblique muscles.
• Innervation – The superior rectus is supplied by the
superior division of the oculomotor (3rd cranial), which
enters the under-surface of the muscle at the junction of
the middle and posterior thirds.

24. INFERIOR RECTUS
• It is shortest of the recti muscles.
• Origin–It arises below the optic foramen, from the
middle slip of the lower common tendon of the annulus
of Zinn at the apex of the orbit.
• Insertion– inserted inferiorly, in vertical meridian
about 6.5 mm from the limbus. The inferior rectus is also
attached to the lower lid by means of the fascial
expansion of its sheath.
• Blood supply – the inferior muscular branch of
ophthalmic artery and infraorbital artery, 2 anterior
ciliary vessels
• Size – 40 mm long; tendon is 5.5 mm long and 9.8 mm
wide

26. INFERIOR RECTUS
• Relations– Inferior division of the 3rd nerve lies above
the muscle, and the optic nerve is separated by orbital
fat, and the globe of the eye. Lateral – The nerve to the
inferior oblique runs in front of the lateral border of the
inferior rectus between it and the lateral rectus. Below is
the floor of the orbit, roofing the maxillary sinus. The
muscle is in contact with the orbital process of the
palatine bone, but more anteriorly it is separated by
orbital fat from the orbital plate of the maxilla.
• Innervation– The inferior rectus is supplied by the
inferior division of the 3rd nerve, which enters it on its
upper aspect at about the junction of the middle and
posterior thirds.

28. MEDIAL RECTUS
• It is largest of the ocular muscles and stronger than the
lateral.
• Origin- The medial rectus muscle, (number 2 in the picture)
arises from the annulus of Zinn. It has a wide origin to the
medial side of and below the optic foramen from both parts of
the common tendon, and from the sheath of the optic nerve.
• Insertion – The medial rectus inserts medially, in the
horizontal meridian about 5.5 mm from the limbus.
• Blood supply – The medial rectus is supplied by the inferior
muscular branch of ophthalmic artery and 2 anterior ciliary
arteries.
Size – The medial rectus muscle is 40.8 mm long; tendon is
3.7 mm long and 10.3 mm wide.

29. MEDIAL RECTUS
• Relationships– Above the medial rectus lies the
superior oblique. The ophthalmic artery and its anterior
and posterior ethmoidal branches and the posterior
ethmoidal, anterior ethmoidal and infratrochlear nerves
run between the medial rectus and superior oblique
muscles. Below the medial rectus is the orbital floor.
Medial to the rectus is orbital fat, separating it from the
orbital plate of the ethmoid (ethmoid air cells). Laterally
is the central orbital fat.
• Innervation– The inferior division of the 3rd nerve
innervates the medial rectus on its lateral surface at
about the junction of its middle and posterior thirds.

31. LATERAL RECTUS
• Origin – arises from the annulus of Zinn and spans the
superior orbital.
• Insertion – inserted laterally, in horizontal meridian 6.9 mm
from the limbus
• Blood supply – the lacrimal artery (the only rectus muscle
with a single blood supply a common board question!)
• Size – 40.6 mm long; tendon is 8 mm long and 9.2 mm wide.
The lateral or external rectus arises from both the lower and
upper parts of the common tendon from those portions which
bridge the superior orbital (sphenoidal) fissure.The origin is
said to assume form of the letter U placed so that the opening
faces the optic foramen, the limbs of the U being referred to as
the upper and lower heads of the muscle.

32. LATERAL RECTUS
• Relations– The structures which go through the two
heads of the lateral rectus, within the cone of muscles or
within the annulus of Zinn, have been referred to as the
oculomotor foramen. These structures from above
downwards are the upper division of the 3rd nerve, the
naso-ciliary, and a branch from the sympathetic, then
the lower division of the 3rd, then the 6th, and then
sometimes the ophthalmic vein or veins. The 6th nerve is
actually passing from being below the lower division of
the 3rd to lie lateral and in between the two divisions.
• Innervation– The 6th nerve (abducens) enters it on its
medial aspect, just behind its middle.

34. OBLIQUE MUSCLES
• There are two oblique muscles:
1. Superior Oblique
2. Inferior Oblique
• Unlike the recti group of muscles, they do not
originate from the common tendinous ring.
• From their origin, the oblique muscles take
an angular approach to the eyeball (in contrast
to the straight approach of the recti muscles).
They attach to the posterior surface of the sclera.

37. SUPERIOR OBLIQUE
• It is longest and thinnest eye muscle.
• Origin – arises above and medial to the optic foramen by a
narrow tendon which partially overlaps the origin of the
levator.
• Insertion – inserted to trochlea at orbital rim, on the medial
wall of the antero-superior-medial orbit on the frontal bone.
The muscle stops just before the trochlea and then proceeds
as tendon under superior rectus posterior to insert on the
temporal aspect of the eye behind the equator.
• Blood supply – the superior muscular branch of ophthalmic
artery supply blood
• Size – 40 mm long; tendon is 20 mm long and 10.8 mm wide.

38. SUPERIOR OBLIQUE
• Trochlea- The trochlea consists of a U-shaped piece of fibro-
cartilage. The cartilage merges imperceptibly above with
fibrous tissue, and is attached to the fovea or spina trochlearis
on the frontal bone a few millimeters behind the orbital
margin on the medial wall of the orbit. Immediately before
entering the pulley striated muscle joins the tendon, which is
enclosed in a synovial sheath, beyond which a strong fibrous
sheath accompanies the tendon to the eye.
• Innervation – The superior oblique is supplied by the 4th or
trochlear nerve which, having divided into three or four
branches, enters the muscle on the upper-surface near its
lateral border; the most anterior branch at the junction of the
posterior and middle thirds, the most posterior about 8 mm.
from its origin.

40. INFERIOR OBLIQUE
• Origin – The inferior oblique is the only extrinsic muscle to
take origin from the front of the orbit; arises from a rounded
tendon in a depression on orbital floor near orbital rim
(maxilla), just behind the orbital margin and lateral to orifice
of the naso-lacrimal duct. Some of its fibres may arise from
the fascia covering the lacrimal sac.
• Insertion – inserted posterior inferior temporal quadrant at
level of macula
• Blood supply – the inferior branch of ophthalmic artery and
infraorbital artery
• Size – 37 mm long; the shortest tendon of insertion
(essentially no tendon) and it is 9.6 mm wide at insertion.

41. INFERIOR OBLIQUE
• Relations – Near its origin the lower surface of the muscle
contacts the periosteum of the orbital floor, laterally it is
separated from the floor by fat. Just before the insertion of the
muscle, this surface which now faces laterally is covered by
the lateral rectus and Tenon's capsule. The upper aspect
contacts fat, then the inferior rectus, then finally spreading
out and becoming concave it moulds itself on the eye.
• Innervation– the inferior division of the oculomotor nerve,
crosses above the posterior border to enter the muscle on its
upper-surface at about the middle of the muscle.
• Blood-supply -comes from the infraorbital artery and the
inferior muscular branch of the ophthalmic artery.
.

43. LEVATOR PALPEBRAE
SUPERIORIS
• The levator palpebrae superioris (LPS) is the
only muscle involved in raising the superior
eyelid. A small portion of this muscle contains a
collection of smooth muscle fibres – known as
the superior tarsal muscle. In contrast to the
LPS, the superior tarsal muscle is innervated by
the sympathetic nervous system.

45. • It is a striated muscle to elevate the eyelid. The levator palpebrae
superioris arises from the under-surface of the lesser wing of the
sphenoid above and in front of the optic foramen by a short
tendon which is blended with the underlying origin of the
superior rectus. The flat ribbon-like muscle belly 40 mm in
length passes forwards below the roof of the orbit and on the
superior rectus to about 1 cm. behind the orbital septum (at the
upper fornix or a few millimeters in front of the equator of the
eye), where it ends in a membranous expansion or aponeurosis.
The tendon is about 10-15 mm in length and extend from the
equator forward. This spreads out in a fan-shaped manner, so as
to occupy the whole breadth of the orbit and thus gives the whole
muscle tendon complex the approximate form of an isosceles
triangle.
LEVATOR PALPEBRAE
SUPERIORIS

46. Attachments:
• (a) The main insertion of the levator is to the skin of the
upper lid at and below the upper palpebral sulcus. It
reaches this by intercalating with the fibres of the
orbicularis.
• (b) To the Tarsal Plate. – Some of the fibres of the
aponeurosis are attached to the front and lower part of the
tarsal plate, but the main attachment of the levator here is
via the smooth superior palpebral muscle of Muller. This is
continuous with the fleshy part of the levator, and is
attached to the upper border of the tarsus.
LEVATOR PALPEBRAE
SUPERIORIS

48. LEVATOR PALPEBRAE
SUPERIORIS
• Relations– Above the levator and between it and the
roof of the orbit are the 4th and frontal nerves and the
supraorbital vessels. The 4th nerve crosses the muscle
close to its origin from lateral to medial to reach the
superior oblique. The supraorbital artery is above the
muscle in its anterior half only. The frontal nerve crosses
the muscle obliquely from the lateral to the medial side.
Below the levator is the medial part of the superior
rectus.
• Innervation– The superior division of the 3rd nerve
reaches the muscle either by piercing the medial edge of
the superior rectus or curving around its medial border.

49. NERVE SUPPLY OF EOM

51. OPHTHALMIC
ARTERY
Medial
Muscular
Artery
MR,IR,IO
Lateral
Muscular
Artery
LR,SR,SO,LPS
BLOOD SUPPLY
• Ophthalmic Artery
• Seven branches
• Two for each recti
expect lateral rectus
which recieves only
one branch

52. BLOOD SUPPLY
Ophthalmic Artery
Medial Muscular Branch:
• Inferior Rectus
• Inferior Oblique
• Medial Rectus
Lateral Muscular Branch:
• Superior Rectus
• Superior Oblique
• Lateral Rectus
• Levator Palpebrae
Superioris