Farhana AdninB.Optom,4th Batch

ICO,CU

Extra Ocular Muscles ORIGIN-INSERTION

ACTION,NERVE SUPPLY

What is EOM . . . ???

There are 2 types of muscles ~4 Recti muscles ~Superior rectus (SR) ~Inferior rectus (IR) ~Medial rectus (MR) ~Lateral rectus (LR)2 Oblique muscles ~Superior oblique (SO) ~Inferior oblique (IO)

6 muscles . . .

annulusofzinn

Schematic diagram . . .

Common tendinous ring of zinn

Recti muscles

Origin Insertion Nerve supply

SR Superior part of common tendinous ring of zinn

sclera through the tendon about 7.7mm posterior to limbus.

3rd nerve(oculomotor )

IR inferior part of common tendinous ring of zinn.

sclera through the tendon about 6.5mm posterior to limbus.

3rd nerve (oculomotor )

LR Lateral part of common tendinous ring of zinn.

sclera through the tendon about 6.9 mm posterior to limbus.

6th nerve (abducent)

MR Medial part of common tendinous ring of zinn.

sclera through the tendon about 5.5mm posterior to limbus.

3rd nerve (oculomotor )

Cont…

Oblique muscles

Origin Insertion Nerve supply

SO At the apex of the orbitFrom body of sphenoidAbove & medial to the optic foramenBy a narrow tendon.

Behind the equator in the sclera

4th nerve (trochlear nerve)

Oblique muscles

ORIGIN INSERTION

NERVE SUPPLY

IO Arises by a rounded tendonFrom a shallow depressionOn the orbital plate of maxillaJust lateral to the orifice of the naso lacrimal duct.

Behind the equator ,in the lower & outer part of sclera,in temporal side, by a short tendon.

3rd nerve(oculomotor nerve)

Nerve supply…(SO4LR6)~REST 3

MR:Medial muscular branch of ophthalmic artery+Lacrimal artery

IR & IO :Medial muscular branch of ophthalmic artery + Infra orbital artery

LR,SR,SO: Lateral muscular branch

BLOOD SUPPLY…

MUSCLES PRIMARY SECONDARY TERTIARY

SR Elevation Intorsion Adduction

IR Depression Extortion Adduction

LR Abduction

MR Adduction

SO Intorsion Depression Abduction

IO Extorsion Elevation Abduction

ACTIONS . . .

CONT…

Fick’s axis Z

Fick’s law : 3 axes are perpendicular to each other & intersect at the centre of rotation.

A hypothetical point around which the eyeball performs rotatory movements

centre of

rotation

Centre of rotation

Describes 3 axes- 1) X (horizontal) axis. 2)Y (antero-posterior)axis. 3)Z (vertical) axis.

Fick’s law

Ocular movements…Monocular movement:-Duction

Binocular movement:-Version -

Vergence

1)Duction: the movement of one eye

Abduction Adduction Supraduction or elevation Infraduction or depression Incycloduction or intorsion Excycloduction or extorsion

Ocular movements…

Duction…

2)Version: the movement of two eyes in the same direction

1)Dextroversion 2)Levoversion 3)Supraversion 4)Infraversion 5)Dextroelevation 6)Dextrodepression 7)Levoelevation 8)Levodepression 9)Dextrocycloversion 10)Levocycloversion

Cont…

Version…

Diagnostic positions of gaze…

2 1 2

2

2

3

3

3

3

3)Vergence: the movement of two eyes in opposite directions

Convergence Divergence

Cont…

Vergence….

Terminology of Ocular Motility

Agonist Any particular EOM producing a

specific ocular movement.e.g for abduction LR in right eye.

Synergist Two muscles moving an eye in the

same direction E.g– SR / IO - Synergist for

elevation movement

Antagonist The muscles having opposite

action in the same eye Example – medial and lateral

rectus

Cont…

•Yoke muscle (Contralateral synergists)a pair of muscle one in each eye which contract simultaneously during version movement

• Pairs for six cardinal positions of gaze • Dextroversion – RLR- LMR• Levoversion – LLR- RMR• Dextroelevation – RSR-LIO• Levoelevation – LSR- RIO• Dextrodepression – RIR-LSO• Levodepression –LIR-RSO

Cont…

• Contralateral Antagonista pair of muscles, one in each eye having opposite action eg. RLR & LLR.

Cont..

Hering’s Law An equal and simultaneous innervation flows

from brain to a pair of muscle of both eyes which contracts simultaneously in different binocular movements.

Laws of EOM Movements

Clinical Significance:1.Secondary deviation > > Primary deviation2.Inhibition palsy of the contralateral antagonist

Sherrington’s Law During eye movement an increased flow of

innervations to the contracting agonist muscle is accompanied by an equal and simultaneous decreased flow of innervations to the relaxing antagonist muscle

Cont…

1.During dextroversion, an increased flow to the right LR & left MR is accompanied by a decreased flow to the right MR & left LR muscles.

2.

Example:

Donder's Law For each tertiary position, there is one

and only one orientation of the vertical and horizontal meridians of retina.

There is no rotation around the antero-posterior (Y) axis. (no torsion or twist occur).

The eye reaches all tertiary position without movement around the Y axis.

The eye always returns to the same orientation from which it started.

Cont…

Anatomy & Physiology of Eye by A.K.Khurana

Binocular vision & Ocular motility by Gunter K.Von Noorden

Internet

References…

THANK YOU FOR YOUR ATTENTION

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