Strabismus The art of harmony Extraocular muscles Remember

Strabismus The art of harmony

Extraocular muscles

Remember � All EOMs originate from orbital apex posteriorly except IO which originates anteriorly. � The shortest EOM belly is SO. � The EOM with the longest tendon is SO.

Axes � Visual axis. � Orbital axis. � Muscle axis.

Ocular positions � Primary position. � Position at rest. � 6 cardinal positions. � 9 diagnostic positions.

Field of action

SR

SO

Muscle action � Primary. � Secondary. � Tertiary. � Vertical. � Horizontal. � Torsional.

Ocular movements Monocular(Duction) Horizontal Adduction Abduction Vertical Supraduction Infraduction Torsional Supraduction Infraduction Binocular Vergences Convergence Divergence Version Dextrovrsion Levoversion Supraversion Infraversion

Actions of EOMs Muscle Primary action Secondary & tertiary actions Field of action (Test position) MR Adduction - In Abduction - Out SR Elevation Adduction Intorsion Up & Out IR Depression Adduction Extorsion Down & Out SO Intorsion Depression Abduction Down & In IO Extorsion Elevation Abduction Up & In LR

� Recti………………Adduction. � Obliques…………. Abduction. � Superiors…………. . Intorsion. � Inferiors……………. Extorsion.

� Muscle axis in line with visual axis…………. full action. � Muscle axis perpendicular to visual axis………. Nil action.

Ocular movements Smooth pusuit Saccadic

Physiology of ocular rotations � Listing’s Law. � Axes of Fick.

� Sherrington’s Law( Law of reciprocal innervation) � Agonist vs Antagonist: MR × LR SR × IR SO × IO

� Synergists:

� Hering’s law of yoke muscles.

Remember �Sherrington’s law and Synergists………. . Single eye movements. � Hering’s law of yoke muscles………………Binocular eye movements.

Normal ocular alignment

Orthotropia & Orthophoria

Strabismus