SlideShare utilise les cookies pour améliorer les fonctionnalités et les performances, et également pour vous montrer des publicités pertinentes. Si vous continuez à naviguer sur ce site, vous acceptez l’utilisation de cookies. Consultez nos Conditions d’utilisation et notre Politique de confidentialité.
SlideShare utilise les cookies pour améliorer les fonctionnalités et les performances, et également pour vous montrer des publicités pertinentes. Si vous continuez à naviguer sur ce site, vous acceptez l’utilisation de cookies. Consultez notre Politique de confidentialité et nos Conditions d’utilisation pour en savoir plus.
SUP:Frontal nerve runs above the superior rectus & levator separating it from the orbit INF:The nasociliary nerve and ophthalmic artery run below.The tendon for insertion of the SO muscle runs below the anterior part of the SR LAT:Lacrimal A and Nerve run b/w Sup and Lat Recti MED:Ophthalmic A and Nasociliary N b/w SR above and MR and IO below
since the insertion on the globe is lateral as well ,contraction will produce rotation about the vertical axis toward midline Secondary action is adduction
Finally, because the insertion is oblique, contraction produces torsion nasally
SUP:Separated from eyeball by Optic N, Inf. Div of 3rd N INF:Floor of the orbit roofing the maxillary sinus Orbital Palatine process Infraorbital vessels and nerves IO crosses below IR , their sheaths being united here LAT:Nerve to IO runs b/w IR and LR
SUP: Lacrimal A and N Anteriorly , lacrimal gland INF: Floor of the orbit and IO Tendon MED: 6TH N,Ciliary Ganglion, Ophthalmic A Nerve to IO between LR and IO LAT: Posteriorly periorbita, Anteriorly perimuscular fat and most anteriorly Lacrimal gland
Here the two 'heads' of the lateral rectus and the rest of the annular tendon enclose part of the superior orbital fissure, often called the oculomotor foramen.
Structures passing through this opening, separated by a thin bar of bone from the optic foramen and nerve, are often said to pass between the two heads of the lateral rectus. They are the superior oculomotor division, nasociliary nerve, a branch from the internal carotid sympathetic plexus, inferior oculomotor division, ophthalmic veins, and also the abducent nerve
Above the upper head of LR (and hence above the annulus) are the trochlear, frontal and lacrimal nerves, recurrent meningeal br of lacrimal artery, and superior ophthalmic vein. these structures do not traverse the narrow superolateral part of the superior orbital fissure,which is closed by dense fibrous tissue, but pass just above the annulus. Below the annulus is the inferior ophthalmic vein only.
Sclera in front of the equator The line connecting the insertion of the recti in series is spiral & is known as spiral line of Tillaux
Medial rectus is susceptible to injury during anterior segment procedures
important anatomical landmark when performing surgery. The insertions are located progressively further away from the limbus in a spiral pattern. the medial rectus insertion is closest . Superior rectus is farthest.
5.5 mm long, 4 mm high and 4 mm deep with an AP long axis a loop of fibrocartilage closed above by fibrous tissue attached to the fovea or spina trochlearis on the inferior surface of the frontal bone a few mm behind the orbital margin. The trochlear tendon is 1.5 mm w1de, composed of 275 loosely interconnected fascicles/bundles. The trochlea is surrounded by a thick fibrous sheath 1 mm thick which attaches the trochlea to the trochlear fossa medially. A loose fibrovascular sheath, 0.5 mm thick invests the tendon and is separated from the saddle by a bursa lined by flattened non-endothelial cells and connective tissue. This highly vascular tissue is thought to permit repair of the working elements of the trochlea.
Movement of the tendon During relaxation the muscle is thought to insert into the tendinous cup; During contraction the situation is reversed, and the tendinous fibres are drawn into the muscle
Obliques are inserted behind equator & form an angle of 51° with visual axis. SO elevates the back and hence depresses the front of the eyeball
The oblique muscles always course below the corresponding vertical rectus muscle
The medial branch, the larger of the two Two arteries emerge from each tendon, except for the lateral rectus muscle, which has only one
However, the various extensions of the muscle sheaths to the sheaths of other muscles, the orbital wall, and Tenon’s capsule fulfill the task of checking the action of these muscles.
3 axes are perpendicular to each other 1. The transverse axis is mediolateral, and around it the centre of the cornea ascends (elevation) or descends (depression). 2.The vertical axis, around which the centre of the cornea and visual axis moves laterally (abduction) or medially (adduction). 3. The sagittal axis is, anteroposterior. Around it, so-called wheel rotation takes place, better defined as intorsion or extorsion as the 'twelve o'clock' on the cornea moves nasally or temporally.
These traditional concepts do not take into account the recently discovered muscle pulleys and their effect on the linearity of the muscle paths of the rectus muscles.
CSA of horizontal recti is maximum
10mm -25 % of normal resting length Thus muscle resection during surgery reduces amplitude of eye rotation.
Rotataions arnd Vertical axis –Adduction and abduction Hor axis- Sursumduction (elevation ) and Deorsumduction These 4 are cardinal movements of the eye Rotations arnd AP axis of globe , cycloductions rotate upper pole of cornea nasally (incycloduction) temporally (excycloduction )
When gazing right the right lateral rectus contracts along with the left medial rectus during convergence right and left medial rectus muscles the head is tilted to the left,the muscles group controlling excycloduction of the right eye and incycloduction of left eye
When patient fixates with squinting eye, excess innervation required to paralysed muscle to fixate And concomitant excess supply to yoke muscle from the normal eye causes excess contraction leading to more secondary deviation
in a patient with RSO paresis, fixating with Right eyeon an object located up and to the left Less innervation of its antagonist muscle – RIO is required to move the eye into this gaze position , as it doesn’t have to overcome the normal antagonistic effect of RSO This less innervation is received by RIO ‘s Yoke muscle – LSR This could lead to the impression that LSRis paretic
Inhibitional Palsy of the antagonist of the yoke muscle of paretic muscle
eg. The right eye’s right gaze would involve a contraction of the right lateral rectus and a relaxation of the right medial rectus
Torsion means rotation about line of sight,torsion is directly related to the rotation of image dat v perceive of the surounding level
Sliding of thin filaments over thick filaments Width of A band constant while Z lines move closer together.
Action potential transmiytted to fibrils release of Ca from the terminal cisterns, Ca binds to trop C TROP I bound to actin weakened and Tropomysosin coverin active site of myosin head moves laterally Uncovers binding site for myosin head
Atp split contraction
Anatomy and physiology of extraocular muscles and applied aspects
Presenter : Dr. Reshma Peter
Anatomy and Physiology
Extra Ocular Muscles
Its Applied Aspects
They are six in number
Two oblique muscles:
SUPERIOR RECTUS MUSCLE
Superior part of common annular tendon of Zinn
Passes anterolaterally beneath the levator
At 23 degrees with the globe ‘s AP axis
Pierces Tenon s capsule
into sclera by flat tendinous 10 mm broad insertion
7.7 mm behind sclero-corneal junction.
42 mm long
9 mm wide
Sup division of 3rd N
Lateral Muscular br. of Ophthalmic A
SR loosely bound to LPS muscle.
• During SR resection- eyelid may be pulled forward narr
owing palpebral fissure
• In hypotropia pseudoptosis may be present
Origin of SR and MR are closely attached to the dural sheat
h of the optic nerve
pain during upward & inward movements of the globe in
• SUP:Frontal nerve
• INF:Nasociliary nerve
tendon of SO muscle
• LAT:Lacrimal A and Nerve
• MED:Ophthalmic A
• In primary position ,SR muscle plane forms an angle of
23 degrees with the y-axis (the median plane of the eye)
and therefore does not coincide.
• Thus, in primary position,
SR not only elevates the globe but also adducts it and r
otates it around AP Y-axis, causing incycloduction
If the globe is abducted
its axis of rotation approaches the y-axis more and more
when it is abducted 23 degrees
Axis of rotation and Y axis coincide.
SR becomes a pure elevator ,no longer has a cycloducting component
The elevating action of SR maximal in abducted positions of the eye.
SR- Only elevator in full abduction becau
se IO is ineffective .Thus when SR is paral
ysed , abducted eye cant be elevated
The opposite effect applies to incycloduction
The more the globe is adducted
the greater the incycloduction effect.
If the globe could be adducted 67 degrees
SR would produce pure incycloduction.
Since the globe cannot adduct that far, there is some elevating
component to the action of the SR, even in adduction.
Inferior part of common tendon of Annulus of zinn below
the optic foramen
Passes anterolaterally along the floor of the orbit
At an angle of 23 degrees
obliquely in the sclera 6.5 mm behind sclero corneal junction
by a 5.5mm long tendon
40 mm long
9 mm wide
Attached to lower lid by fascial sheath
Inf. division 3rd N
Med. muscular br. of Ophthalmic A
APPLIED:In Thyroid orbitopathy, MR and IR thicken. especially
near the orbital apex - compression of the optic nerve as it
enters the optic canal adjacent to the body of the sphenoid b
Alteration of IR – ass with palpebral fissure changes
IR Recession –widens palpebral fissure
IR Resection –narrows palpebral fissure
• SUP:Optic N
Inf. Div of 3rd N
• INF: Floor of the orbit roofing the maxillary sinus
Orbital Palatine process
Infraorbital vessels and nerves
• LAT:Nerve to IO
• Fascial attachments below attached to inferior lid coordinate
depression and lid opening.
Subsidiary actions are adduction and extorsion.
Depression increases in abduction,becomes nil in full adduction.
Subsidiary actions increase with adduction
• Widely attached medial and inf to optic foramen by common
tendon of annulus of zinn
• from optic nerve sheath
Course :Passes along medial wall of the orbit
in sclera 5.5mm behind sclero-corneal junction by a tendon
3.7 mm in length
40 mm long
Largest ocular muscle
Thicker than the others
In Thyroid orbitopathy, MR and IR thicken;Visibility
of Muscle insertion through conjunctiva allows
swelling to be detected in Endocrine Exophthalmos
Pain in Retrobulbar neuritis- Origin close to dural
sheath of Optic Nerve
Medial rectus inserts closest to the limbus and is
therefore susceptible to injury during ant. segment
Inadvertent removal of the MR is a well known
complication of Pterygium removal
lower division of 3rd N
the specific branch runs along the inside of the muscle cone on
the lateral surface.
Medial muscular branch of Ophthalmic A
Primary adductor of the eye in Primary position
If axis elevated or depressed by other muscles , horizontal recti
no longer exert purely around vertical axis, also exerts
Slight elevator or depressor movements.
APPLIED :Such small movements
Significant when displacing insertions of
horizontal Recti for vertically incomitant
• SUP: Separated from SO by
• INF: Floor of the orbit
• MED: Peripheral fat
Orbital plate of ethmoid
• LAT: Central orbital fat
Annular Tendon of zinn where it crosses Sup Orbital Fissure,cont
inuous with spina recti lateralis on greater wing of sphenoid
At first adjoins lateral orbital wall separated by fat
More anteriorly , it passes medially and pierces tenon ‘s Capsule
on the sclera 6.9mm behind sclerocorneal junction by a tendon
abducent nerve which enters the muscle on the medial surface.
Lateral muscular branch of Ophthalmic A
48 mm long
2/3rd CSA of MR
Lacrimal A and N
Anteriorly , lacrimal gland
Floor of the orbit
Nerve to IO
INSERTION OF THE RECTI
Sclera is thinnest (0.3mm
) just posterior to 4 recti
Site for most procedures,
specially Recession Risk of Scleral perforation
Risk minimized by
• Spatulated needles
• Clean dry blood free field
• Loupe magnification
• Head mounted fibreoptic light
SPIRAL OF TILLAUX
Imaginary line joining the insertions of the 4 recti
• Longest and thinnest EOM
body of sphenoid above and medial to optic canal.
Attached superomedially to optic foramen by narrow te
ndon overlapping the levator
Passes forwards b/w roof and medial wall of the orbit to
its trochlea or pulley
Becomes a rounded tendon 1 cm posterior to trochlea ,
turns posterolaterally at 55 degrees(Trochlear angle )
Pierces tenon‘s capsule, descends inf to SR
This is the only extraocular muscle with a rich vascular tunic.
Posterosuperior quadrant of sclera behind equator of eyeball.
Line of insertion :10.7 mm long
Nerve supply- trochlear nerve
Sup. Muscular branch of Ophthalmic A
Subsidiary actions-abduction and depression.
It is the only Adductor in depression.
• When the globe is adducted to 51 ͦ, the visual axis
• coincides with the line of pull of the muscle, the SO acts as
• When the globe is abducted to 39 ͦ, the visual axis and the
SO make an angle of 90 ͦ, the SO causes only intorsion
Anteromedial part of orbital floor, from a small depression on
orbital plate of maxilla lateral to nasolacrimal groove.
Inclined posterolaterally at an angle of 45 degrees with AP plane ,
almost parallel with tendon of SO
posteroinferior surface of globe near the macula(2.2 mm from it)
oblique line of attachment 9.4mm long
• Primary action-extorsion
• Subsidiary actions-elevations and abduction.
• Only elevator in adducted position of eyeball
inferior division of 3RD N
Infraorbital and medial muscular br. of Ophthalmic A.
• Parasympathetic supply to Sphincter pupillae and ciliary
muscle accompanies N. to IO , pupillary abnormalities from
surgery in this area
• N. To IO enters lateral portion of muscle where the muscle
crosses IR- chance of damage in this area
Actions of EOM
ACTION PRIMARY SECONDARY TERTIARY
MR ADDUCTION ------ ---------
LR ABDUCTION ------ ---------
SR ELEVATION INTORSION ADDUCTION
IR DEPRESSION EXTORSION ADDUCTION
SO INTORSION DEPRESSION ABDUCTION
IO EXTORSION ELEVATION ABDUCTION
Gracilis orbitis or comes obliqui superioris
• originates from the proximal dorsal surface of the SO and
inserts on the trochlea or its surrounding connective tissue.
• It is supplied by the trochlear nerve
Accessory lateral rectus muscle
• is a single slip . sometimes found in the monkey
• homologous to the nictating membrane.
• It is supplied by the abducent nerve
Two anomalous muscles may occasionally be associated with the
LPS. Both muscles are supplied by the superior division of the ocul
• arises from the medial border of the levator muscle
• inserts into the trochlea or its environs.
attaches between the medial and lateral walls of the orbit, connec
ting with the levator muscle en route.
• The arteries to the four rectus muscles give rise to the
anterior ciliary arteries.
• IO and IR also receive a branch from the infraorbital artery,
and the medial rectus muscle receives a branch from the lacr
• The veins from the extraocular muscles correspond to the ar
teries and empty into the superior and inferior orbital veins,
• Accident risk of severing of Vortex veins during IR and SR Rece
ssion or Resection , IO muscle weakening and SO muscle tendo
• Blood supply to EOM supplies most of anterior segment ,Part
of nasal half supplied by Long Posterior ciliary artery…thus sim
ultaneous surgery on 3 recti induce Anterior
• The anterior ciliary arteries pass to the episclera, give branches
to the sclera, limbus, and conjunctiva, and pierce the sclera
not far from the corneoscleral limbus.
• These perforating branches cross the suprachoroidal space to
terminate in the anterior part of the ciliary body.
• Here they anastomose with the lateral and medial long ciliary
arteries to form the major arterial circle of the iris.
APPLIED :Variations in the number of anterior ciliary arteries
supplied by each muscle become clinically relevant with regar
d to the anterior segment blood supply when disinserting mo
re than two rectus muscle tendons during muscle surgery
Muscle Sheaths and Their Extensions
• EOM pierce Tenon’s capsule, enter the subcapsular space, and
insert into the sclera.
• In their extracapsular portions, muscles are enveloped by a
muscle sheath- reflection of Tenon’s capsule and runs
backward for 10 to 12 mm.
APPLIED :During Strabismus sx, Buckling for RD , Periocular t
rauma ,care must be taken to avoid penetration of Tenon ‘s
If integrity lost 10 mm posterior to limbus,
Fatty tissue prolapse forms restrictive adhesion
limit ocular motility
• The muscle sheaths of 4 recti are connected by intermuscu
lar membrane, which closely relates these muscles to each
• Numerous extensions from all the sheaths of EOM, form an
intricate system of fibrous attachments interconnecting the
muscles, attaching them to the orbit,supporting the globe,
and checking the ocular movements.
The fascial sheath of the SR muscle
closely adheres in its anterior external surface to the undersurface of
the sheath of LPS of upper lid
In front of the equator it also sends a separate extension obliquely for
ward that widens and ends on the lower surface of the levator muscle.
The fascial sheath of the IR muscle
divides anteriorly into two layers:
an upper one, which becomes part of Tenon’s capsule
a lower one, which is about 12 mm long and ends in the fibrous tissue
between the tarsus of the lower lid and the orbicularis muscle
This lower portion forms part of Lockwood’s ligament.
APPLIED :The fusion of SR and LPS accounts for the coop
eration of upper lid and globe in elevation of the eye, a
fact that must be kept in mind during surgical procedure
s on the superior rectus muscle
The fascial sheath of the reflected tendon of SO muscle
consists of two layers of strong connective tissue .
The two layers are 2 to 3 mm thick, so the tendon and its sheath ha
ve a diameter of about 5 to 6 mm.
Many attachments extend from the sheath of SO
to the sheath of the levator muscle
to the sheath of the SR muscle
to the conjoined sheath of these two muscles
to Tenon’s capsule, behind,above, and laterally.
Numerous fine fibrils that connect the inner surface of the sheath t
o the tendon
APPLIED :Potential space between the sheath and the te
ndon is continuous with the episcleral space.
Material injected into Tenon’s space therefore may pen
etrate into this space
The fascial sheath of the inferior oblique muscle
covers the entire muscle.
• It is rather thin at the origin but thickens as the muscle continues
laterally and develops into a rather dense membrane where it
passes under IR
• At this point, the sheath of the IO muscle fuses with the sheath of
IR muscle suspensory ligament of Lockwood .
• This fusion may be quite firm and complete or so loose that the tw
o muscles may be relatively independent of each other.
The extensions that go from there upward on each side to the sheaths
of the MR and LR muscles form a suspending hammock, which suppo
rts the eyeball
Includes extensions of fibrous bands to the tarsal plate of the lower lid
, the orbital septum, and the periosteum of the floor of the orbit.
Near the insertion of the muscle the sheath of the inferior oblique m
uscle also sends extensions to the sheath of LR muscle and to the shea
th of the optic nerve.
• well-developed fibrous membranes
• extend from the outer aspect of the muscles to the correspon
ding orbital wall
The check ligament of LR
appears in horizontal sections as a triangle
apex is at the point where muscle sheath pierces Tenon’s ca
goes forward and slightly laterally
fans out to attach to the zygomatic tubercle, the posterior as
pect of the lateral palpebral ligament, and the lateral conjunc
The check ligament of the MR
extends from the sheath of the muscle
attaches to the lacrimal bone behind the posterior la
crimal crest and to the orbital septum behind.
triangular and unites at its superior border with
a strong extension from the sheath of LPS
a weaker extension from the sheath of SR
Inf border is fused to extensions from the IO and IR
The other EOM do not have clearly distinct check ligam
Intracapsular Portion of the Muscle
• The muscles move freely through the openings in Tenon’s capsule
• In the intracapsular portion, they have no sheath but are covered
by episcleral tissue fused with the perimysium.
• This tissue expands laterally, going along the muscle on each side
, from the entry of the muscle into the subcapsular space to the
• Posteriorly,this tissue attaches to the capsule and laterally to the
• At the tendon this tissue becomes rather dense and appears to s
erve to fixate the tendon, forming the falciform folds of Gue´rin
or adminicula of Merkel.
• Merkel and Kallius remarked that these structures make it difficul
t to determine accurately the width of the insertions.
Thus, the position of the center of rotation of the eyeball remains f
airly constant in relation to the orbital pyramid
Due to the action of the check ligaments, the eye movements beco
me smooth and dampened.
As the muscles contract, their action is graduated by the elasticity
of their check systems, which limits the action of the contracting m
uscle and reduces the effect of relaxation of the opposing muscles
This ensures smooth rotations and lessens the shaking up of the co
ntents of the globe when the eyes suddenly stop or change the dire
ction of their movement.
Functional Role of the Fascial System
• Serve as a cavity within which the eyeball may move
• Connect the globe with the orbit
• Supporting and protecting the globe
• In the control of the eye movements.
• It prevents or reduces retractions of the globe, as well as movements in t
he direction of action of the muscle pull.
Developmental Anomalies of Extraocular Muscles and the Fascial
• Patients with congenital absence of a muscle present with th
e clinical picture of complete paralysis
There may be no preoperative clues to alert the surgeon that th
e apparently paralyzed muscle is absent. Consequently, the surg
eon must be prepared to use alternative surgical approaches if a
muscle cannot be located at the time of the operation.
Anomalies of the fascial system
• more common
• act as a check to active and passive movements of the globe i
n certain directions, although the muscles that should produc
e the active movement may be quite normal anatomically an
• various forms of strabismus fixus and the SO tendon sheath
Syndrome of Brown
• The primary position is assumed by the eye in binocular
when one is looking straight ahead
with body and head erect
object of regard is at infinity
lies at intersection of sagittal plane of head and horizontal
plane passing through centres of rotation of 2 eyeballs
• The adducted, abducted, elevated, or depressed position
s of the globe are designated as secondary positions.
• The oblique positions of the eye are termed tertiary posi
Diagnostic positions of gaze:-9
1 Primary position of gaze:-assumed by eyes when fixating
a distant object with head erect.
4 tertiary positions
6 cardinal positions :- to test 12 EOM in their main fiel
d of action
2. Laevo version
3. Dextro elevation
4. Leavo elevation
5. Dextro depression
6. Laevo depression
Centre of Rotation
• The eye performs rotary movements around a center of
rotation within the globe
• Centre of rotation moves in a semicircle in the plane of
rotation- Space centroid
• In primary position the center of rotation is located 13.5
mm behind the apex on the cornea on the line of sight
1.3 mm behind the equatorial plane
(in myopes--- posterior -14.5 mm
In hyperopes --anterior )
• For practical purposes, one may assume that a line
connecting the middle of the lateral orbital margins
goes through the center of rotation of the two eyes if
they are emmetropic
Action of an individual muscle is controlled by the dire
ction of its pull to 3 axes around which the globe rota
• Ocular movements take place round a centre correspondin
g approximately to that of the eye, which is therefore not s
• The movements defined relative to 3 primary axes which p
ass through the centre of movement at right-angles to eac
Elevation & Depression – Around the transverse axis (X)
nasal -> temporal
Adduction & Abduction – Around the vertical axis (Z)
superior -> inferior
Intortion & Extortion – Around the AP axis (Y)
anterior -> posterior
These axes intersect at the center of rotation - a fixed
point, defined as 13.5 mm behind cornea.
• The body can move sideways, up or down, and forward
• the center of the body moves with it
• it can rotate around a vertical, horizontal, or anteropost
• the center would not shift its position
• it would have zero velocity.
• The posterior pole of the eye moves in an opposite di
rection, except in torsional movements.
• Despite their formalized terms, all movements are rota
tions, and are not necessarily confined to the above ar
bitrary axes, the movements of which are sometimes c
• Because of the geometric relations between the orbita
l and global attachments of each muscle, each acts to g
reatest effect in one plane, and this is known as its pri
The point at which the center of the muscle or of its tendon first
touches the globe is the tangential point.
indicates the direction of pull of that muscle.
The position of this point changes when the muscle contracts or
relaxes and the globe rotates
• The arc of contact is the arc formed between the tangenti
al point and the center of the insertion of the muscle on t
• Since the position of the tangential point is variable, the a
rc of contact changes in length as the muscle contracts.
• It is longest when the muscle is relaxed and its antagonist
contracted and shortest when the muscle is contracted an
d its antagonist relaxed.
• The muscle plane is determined by the tangent to the globe at the
tangential point and the center of rotation.
• It is the plane determined by the centers of origin and insertion an
d the center of rotation
• The muscle plane describes the direction of pull of the muscle an
d determines the axis around which the eye would rotate if the pa
rticular individual muscle were to make an isolated contraction
• Axis of rotation, which is perpendicular to the muscle plane erect
ed in the center of rotation, corresponds to each muscle plane.
Factors involved in mechanics of EOM action
1.Cross sectional area of the muscle
Muscles exert force in proportion to their crosssectional a
2.Length of the muscle
For normal amplitude of rotation 45-50 degres 10mm ch
ange in muscle length is required in each direction
APPLIED :Antagonists such as medial and lateral recti are similar in siz
e –balancing opposing forces
APPLIED : Sacrifice of muscle length during resections reduces the am
plitude of eye rotations
3. The arc of contact
Distance between the anatomic and physiologic insertion
The power of the muscle is proportionate to its length and arc
APPLIED :Recession weakens muscle action by shortening its effective
length and its arc of contact in various positions of gaze
Advancement of EOM has strengthening effect because ef increase in
effective length as well as arc of contact
Ductions – only one eye is open, the other covered/closed te
sted by asking the patient to follow a target in each direction
Types of ductions:-
Binocular ,simultaneous, conjugate movements in same direct
both eyes open, attempting to fixate a target &moving in sam
Abduction of one eye accompanied by adduction of other eye
is called conjugate movements.
• binocular,simultaneous,disjugate/disjunctive movements (o
Convergence– simultaneous adduction
Divergence– outward movement from convergent position
Agonist,Antagonist,synergists and yoke mu
• Agonist :a muscle producing movement on contraction
• Antagonist muscles : A muscle producing a movement in the
direction opposite produced by agonist.
EG -sup.&inf. Recti ,sup.&inf.oblique
• Synergists muscles :Two muscles moving an eye in the same
direction are synergists.
Ex:-sup.rectus & inf.oblique----elevators
• Yoke muscles :Muscles that cause the two eyes move in sam
Ref. to muscles which are
primary muscles (one from
each eye) that accomplish
(contract) a given version.
Laws of ocular motility
1.Hering’s law of equal innervation
During any conjugate movement equal & simultaneous inner
vation flows to yoke muscles to contract or relax
• For movements of both eyes in the same direction, the cor
responding agonist muscles receive equal innervation
Isolated innervations to an extraocular muscle of the e
ye do not occur nor can the muscles from the one eye a
lone innervated ,
to perform an eye movement, impulses are always
• In patient with paralytic squint,
Secondary Deviation > primary deviation
Primary dev- deviation of squinting eye, when patient fixates
with normal eye
Sec dev- deviation of normal eye under cover, when patient fix
ates with squinting eye
Excess innervation is required to the paralysed muscle to fixat
e, when patient fixates with squinting eye
Concomitant excess supply to yoke muscle causes excess contr
action leads to more secondary deviation
Inhibitional palsy of contralateral antagonist muscle in pa
ralytic squint is also based on Hering’s law
Eg – In RSO paresis,
fixating with Right eye on an object located up and to the
Less innervation of its antagonist RIO is required less i
nnervation of LSR
Inhibitional Palsy of the
antagonist of the yoke muscle of paretic muscle
LSR LIR RSO
2. Sherrington law of reciprocal
Increased innervation to an EOM is accompanied by r
eciprocal decrease in innervation to its antagonist.
The antagonist relaxes as the agonist contracts
• Occurrence of strabismus following paralysis of EOM is e
xplained by the law
• Reciprocal innervation must be kept in mind while perfo
rming surgery of extraocular muscles
• Duane’s retraction syndrome co-contraction of
antagonistic muscles instead of relaxation antagonist
muscle occurs. In duane s , it limits the amount of movem
During fixation, saccades and smooth pursuit the eye rotates
freely in horizontal and vertical dimensions but torsion is cons
trained. This restriction on ocular torsion is described by dond
er’s law and listing’s law.
Donder stated that each position of line of sight belongs to t
he definite orientation of vertical and horizontal retinal meri
dian relative to the coordinate of the space.
Orientation of retinal meridian is always same irrespective ir
respective of the path the eye has taken to reach that positio
n and depends upon the amount of elevation or depression
and lateral rotation of the globe, after returning to the initial
position the retinal meridian is oriented exactly as it was bef
ore the movement was initiated
Listing ‘s law states that each movement of the eye fro
m the primary position to any other position involves a
rotation around a single axis lying in the equatorial plan
e ,also called as listing’s plane.
This plane was defined earlier as being fixed in the orb
it and passing center of rotation of the eye and its equa
tor, when the eye is primary position
Any position of the eye can described by specifying the
orientation of the axis of rotation in listing’s plane and
magnitude of rotation from primary position
• Listing’s law implies that all eye movements from prima
ry position are true to the meridians and occurs withou
t torsion with respect to the primary position.
• This law is obviously true for movements around horizo
ntal and vertical axes in the equatorial plane.
• Listing’s law holds during fixation, saccades, smooth pur
suit but not during sleep .
Extraocular muscles structure
• EOM consists of cross striated fibres.
• They show a high degree of differentiation
• Perform functions of both white and red muscles.
• The motor units are small, with only from 5 to 18
muscle fibers contact by each motor nerve
Differ from other skeletal muscles in terms of
Diameter of these fibres is small
Richly supplied by nerves and vessels
Contains enormous amount of fibroelastic tissue
Contain both slow and fast fibres
Require and receive more O2
Each muscle is made up of large no: of muscle fibres.
• Each muscle fibre is a long cylindrical multinucleated cell , s
urrounded by a cell membrane –Sarcolemma
Sarcotubular system –Sarcolemma+Sarcoplasm
Each fibre has a diameter of 5-40 um (c/f 10-100 um in sk
punctiform appearance in transverse section and a striate
d appearance in longitudinal section.
• Vessels and nerves enter each muscle belly at its hilum.
• The blood supply of the recti is greater than that of the
myocardium, primarily due to richness of the closed type
capillary network in the orbital layer.
• This blood supply is required by the larger numbers of fa
st twitch fibres in the orbital layer, which have a highly a
• Blood flow is thought to be highest in the MR, although
that in SR may be higher
Each myofibril consists of linearly arranged thick and thin myofil
aments, which form the chief element of fibre's repeating unit,
THIN- Actin. Tropomyosin, Troponin T, I , C
• Between myofibrils are two membranous systems involved i
n excitation and contraction :
the transverse tubular system and the sarcoplasmic reticulum
Rapid 'twitch' fibres
Fibres of larger diameter
With a 'fibrillenstruktur' having a regular distribution of myofi
brils and abundant sarcoplasm.
Innervation is by single, 'en plaque' endings (i.e.motor end pla
tes) These fibres resemble somatic striated fibres elsewhere
Two types of striated twitch fibres are described
Slow or 'tonic' fibres
so-called 'felderstruktur‘ ill-defined and myofibrillar arrangem
ents and little sarcoplasm.
Their respiratory metabolism is chiefly aerobic
innervated by diffuse ('en grappe') myoneural endings.
• Mitochondria are in general fewer in skeletal than in extraocu
lar muscle fibres .Although fibres are smaller in the orbital zo
nes than in global zones, both contain mixtures in size of fibre
Type I muscle fibres
'slow, oxidative and fatigue resistant'
stain weakly for myosin ATPase at pH 9.4 but strongly at acid pH
strongly for oxidative enzymes but weakly for glycolytic enzymes.
Type II muscle fibres
stain strongly for ATPasc at pH 9.4.
stain poorlv on preincubation at pH 4.6 and pH 4.3
oxidative and glycolytic features
resistant to fatigue on repeated stimulation
stain poorly at only pH 4.3.
found chiefly in infancy and differs from that shown in adult muscle.
The extraocular muscles possess a resident population of imm
unocompetent cells including numerous macrophages and a s
maller number of HLA-DR positive cells and T cells; B cells are a
The majority of the T cells are CD8 (suppressor/cytotoxic) p
ositive, whereas in skeletal muscle, CD4-positive (helper) ce
The medial and inferior recti contain about twice as many
macrophages as the lateral rectus and superior oblique mus
APPLIED :Of importance in certain orbital immune disorders such
as endocrine ophthalmopathy.
ORBITAL AND GLOBAL ZONES
• at birth fibre size -generally uniform
• later an outer shell of smaller-diameter fibres is distinguished from a
core of larger fibres
• this pattern is retained into adult life
• These zones are referred to as
orbital (outer; facing the orbit)
global (inner; facing the globe and contents of the muscle cone)
• Orbital fibre diameter - 5 and 15 IJ.m,
global fibres diameter - 10 and 40 IJ.m.
• The global layer of SO is totally enclosed by the orbital layer,
• In the recti orbital zones are deficient on their internal surfaces, so th
at the global layer is exposed to adjacent adipose tissue around the o
ptic nerve at a 'hilum'.
• The recti are strap-like, with maximum width at their global insertion
• the global fibres are longer than the orbital and only the global tonic
fibres appear to run the full length of the muscle belly which maximi
zes the possible change in length of the muscle in contraction, and co
Types of eom
Spencer and Porter nomenclature
• Type 1: Orbital singly innervated
• Type 1 fibres small and make up 80% of the orbital layer
• accounts for most of the sustained force generated by the mu
• Mitochondria occur in abundant clusters
• Individual fibres are ringed by capillaries and motor endplates
• Abundant and well-delineated SR and T-system and a regular
• They correspond to skeletal type II differs from skeletal IIA by i
ts high fatigue resistance and unique myosin profile.
• coarse, fast twitch fibres
• rich in oxidative enzymes (e.g. SOH) but also capable of anaer
• singly innervated
Type 2: Orbital multiply innervated fibres
a slow fibre comprising 20% of the orbital zone.
• It stains strongly for myosin ATPase after acid preincuba
tion, but variably with alkaline ATPase
• associated with a structural variation along their length
• The staining properties not uniform along the length of
the muscle fibre; thus acid-stable myosin ATPase is foun
d only in the proximal and distal thirds of the fibre.
• moderate oxidative activity.
• has sparse membranous systems and an irregular myofi
brillar arrangement by electron microscopy.
• Although they are multiply innervated, they show a twitch ca
pability near their centre and a slow contractility proximally a
• Centrally the fibres resemble skeletal fast twitch fibres (IIC) (
but with a lower oxidative capacity),
• At either end they show the ultrastructural features and slow
ATPase of slow contracting fibres and contain embryonidneo
Type 3: Global red singly innervated
• This makes up 30% of the global layer.
• It stains coarsely
• resembles the orbital singly innervated fibre.
• It is highly oxidative and glycolytic
• regarded as fast-twitch and fatigue-resistant fibre.
• does not show longitudinal structural variation
• Contains no coexpressed fast or embryonidneonatal
• fibre does express myosin IIA isoform along its length,
but differs from skeletal IIA by its high mitochondrial c
Type 4: Global intermediate singly innervated
• This fibre makes up 25% of the global layer.
• Ultrastructure and ATPase content suggest that it is a fa
st-twitch fibre and myosin reactivity suggests a resembl
ance to skeletal type IIB
• fibre is granular and there are moderate levels of oxidat
ive and aerobic enzymes.
• There are numerous small mitochondria, singly or in clu
• Myofibril size and sarcoplasmic reticulum content are in
termediate between that of the other 2 singly innervat
• Type 5: Global pale singly innervated
• This fibre comprises 30% of the global layer.
• a fast twitch fibre used infrequently because of low fatigu
• It resembles type lIB skeletal
• Mitochondria are small and few and arranged singly betw
• Fibre diameter increases from types 3 to 5.
• All show a regular myofibrillar arrangement on electron
microscopy with well-developed sarcoplasmic reticulum a
nd T systems in types 3 and 4 and slightly less so in type 5
• They are singly innervated.
Type 6: Global multiply innervated fibres
• makes up 10% of the global layer
• a slow fibre with strong acid-stable ATPase features
and weak oxidative properties.
• Ultrastructurally, it shows a felderstruktur with very
large myofibrils, sparse membranous systems and
occasional mitochondria in single file.
• multiply innervated, with numerous en-grappe endi
ngs along its length.
• All EOM develop from 3 distinct masses of Primordial c
• 3 masses correspond to Rhombomeres and 3 cranial ne
rves innervate them accordingly
• Premandibular condensation gives rise to eye musces
innervated by 3rd N ( SR, MR, IR, IO)
• LR and SO arises from its own adjacent tissue mass in
• LR and SO lie as B/l masses close to stalk at 13.5 mm s
tage(6 weeks )
• 4 Recti differentiate at 20 mm stage ( 7 weeks )
• LPS differentiates from SR in its medial part at 8 weeks
• Later it grows laterally on a higher plane than SR at 3
• Critical development occurs at 6-8 weeks ( maybe upt
o 12 weeks
APPLIED :Close proximity of analgens may facilitate development of ano
malous innervation of eye muscles
DUANES RETRACTION SYNDROME
Congenital absence of 6th N
Abnormal innervation of Lateral Rectus by 3rd N
• Eom develop in at least 2 waves of Myogenesis, formin
g primary and secondary generation fibres.
• Global multiply innervated fibres are phylogenetically ol
d and formed first while orbital layers mature last.
• EOM Pulleys –
sleeves of Collagen, elastin , smooth muscle
encircle EOM and are attached to orbital wall and adjacent c
Muscle with sheath passes through these pulleys
Located near the equator of globe
Seem to deflect anterior part of the muscle in gazes other th
an primary gaze
Act as functional origin
APPLIED :in abnormal situations, pulleys may be heterotropic , may cause
ocular motility problems
• Wolff’s anatomy of eye -8th e
• Clinical Anatomy of the eye –SNELL
• Von Noorden, A. Edward
• A.k.Khurana Anatomy and physiolog
y of the eye- 5th e
• Strabismus by Pradeep Sharma