EOMs and Ocular Motility

What are agonists?

the muscle that contracts to bring about a movement

What are antagonists?

the muscle that brings about a movement in the opposite to that of the agonist

What are synergists?

two synergistic muscles, one in each eye, that cause both eyes to move in the same direction

What does ipsilateral mean?

same eye

What does contralateral mean?

opposite eye

What does dextro mean?

right

What does laevo mean?

left

What does duction mean?

one eye

What does version mean?

two eyes

What are the actions of the medial rectus?

Adduction, depression

What are the actions of the lateral rectus?

Abduction, elevation

What are the actions of the superior rectus?

Elevation, Incyclorotation, Adduction

What are the actions of the inferior rectus?

Depression, excyclorotation, adduction

What are the actions of the superior oblique?

Incyclorotation, depression, abduction

What are the actions of the inferior oblique?

Excyclorotation, elevation, abduction

What are the agonists in dextro-elevation?

RSR, LIO

What are the agonists in dextro-version?

RLR, LMR

What are the agonists in dextro-depression?

RIR, LSO

What are the agonists in laevo-elevation?

RIO, LSR

What are the agonists in laevo-version?

RMR, LLR

What are the agonists in laevo-depression?

RSO, LIR

What is Herring’s Law called?

Hering’s Law of Equal Innervation

What is Hering’s Law of Equal Innervation?

When a nervous impulse is sent to a muscle causing it to contract, an equal impulse is sent to its contralateral synergist in order to maintain parallelism of the visual axes

What is Sherrington’s Law called?

Sherrington’s Law of Reciprocal Innervation

What is Sherrington’s Law of Reciprocal Innervation?

When a muscle contracts its direct antagonist relaxes to an equal extent, allowing smooth movement to take place 

What should you look for when testing smooth pursuit?

Underactions/overactions

Limitations/Restrictions

End-point or pathological nystagmus

Lid abnormalities

Presence of any cyclorotary movement

Sudden cessation of movement

Quality of movement

Range of movement

Ability to maintain position in extreme gazes

How should ocular movement abnormalities be recorded?

Describe the abnormality of the eye in the relevant position of gaze, not he muscle involved

Which muscle is weak/underacting in exotropia?

Medial rectus

Which muscle is weak/underacting in esotropia?

Lateral rectus

Which muscle is weak/underacting in hypertropia?

Inferior rectus

Which muscle is weak/underacting in Hypotropia?

Superior rectus

What does sequelae mean?

pathological effect resulting from disease, injury or trauma

What is a muscle sequelae?

the process of extra ocular muscle undevraction and overreaction as a result of primary muscle weakness/inability to move fully

What does the cover test do?

Reveal the deviation in the primary position

What must be done after the cover test?

Smooth pursuit

What does smooth pursuit reveal?

Which muscles are responsible for the deviation seen on cover test

What are the 4 stages of muscle sequelae?

1. Underaction of the affected muscle
2. Overreaction of the contralateral synergist (Herring’s Law of Equal Innervation)
3. Contracture (overaction) or the ipsilateral antagonist (Sherrington’s Law of Reciprocal Innervation)


1. Secondary inhibition (undevraction) of the contralateral antagonist (Herring’s Law of Equal Innervation) occurs due to the contracted antagonist in the affected eye requiring less innervation

What is the muscle sequelae for an affected LMR?

Overaction of RLR

Contracture of LLR

Underaction of RMR

What is the muscle sequelae for an affected LLR?

Overaction of RMR

Contracture of LMR

Underaction of RLR

What is the muscle sequelae for an affected LSR?

Overaction of RIO

Contracture of LIR

Underaction of RSO

What is the muscle sequelae for an affected LIR?

Overaction of RSO

Contracture of LSR

Underaction of RIO

What is the muscle sequelae for an affected LSO?

Overaction of RIR

Contracture of LIO

Underaction of RSR

What is the muscle sequelae for an affected LIO?

Overaction of RSR

Contracture of LSO

Underaction of RIR

What is the muscle sequelae for an affected RMR?

Overaction of LLR

Contracture of RLR

Underaction of LMR

What is the muscle sequelae for an affected RLR?

Overaction of LMR

Contracture of RMR

Underaction of LLR

What is the muscle sequelae for an affected RIO?

Overaction of LSR

Contracture of RSO

Underaction of LIR

What is the muscle sequelae for an affected RSO?

Overaction of LIR

Contracture of RIO

Underaction of LSR

What is the muscle sequelae for an affected RIR?

Overaction of LSO

Contracture of RSR

Underaction of LIO

What is the muscle sequelae for an affected RSR?

Overaction of LIO

Contracture of RIR

Underaction of LSO