week 3 binocular vision

What is abduction? *

Eye moves out (temporal direction)

What is adduction?*

Eye moves in (nasal)

What is supraduction?

• vertical movement around x-axis

• Moves upwards from primary to secondary position

What is infraduction?

• vertical movement around x-axis

• Moves downwards from primary to secondary position

What is torsion?

Rotation around the y-axis

Involuntary control

Occour in response to vestibular and proprioceptive neck reflex

What is intortion?

Rotation around the y-axis

Upper pole of eye rotates towards the nose

Involuntary

What is extortion?

Rotation around the y-axis

Upper pole of eye rotates away from the nose

Involuntary

RADSIN

What is version movement?

Conjugate movement of two eyes in the same direction

From primary to secondary position

supraversion?

Both eyes turn up

• superior recti and inferior oblique

Infraversion?

Both eyes turn down

Inferior recti and superior oblique

Dextroversion?

Both eyes turn to the right

RLR

LMR

Levoversion?

Both eyes turn to left

RMR and LLR

Primary position?

Eye looking straight and head is erect

Median and face planes are vertical

Secondary position?

Eye makes a purely horizontal/vertical movement starting from primary position

Arrives at secondary

Tertiary position?

Oblique movement

Both horizontal and vertical

From primary to tertiary position

Complete this

What are the muscle actions of the superior rectus? *complete same for all

Primary - elevation

Secondary - intersion

Tertiary - adduction

What’s hering’s law of equal innervation?

• innervation to the EOM is equal in both eyes

• Afk movement of two eyes are equal and symmetrical

• Identify underactions or overactions of EOMs

What is Sherrington’s law of reciprocal innervation?

Contraction of a muscle is accompanied by the simultaneous and proportional relaxation of its antagonist

Eg RLR contracts then RMR will relax

What are synergists and give an example?

Muscles of the same eye that cause similar movement

Eg LSR and RIO

What are antagonists and give an example

Muscles that oppose the action of each other

Eg RMR and RLR

What Can you infer if a muscle is overacting or under-acting?

*

• incomitant deviations

• Strabismus - differs depending upon direction of gaze and associated with defective movement of the eye

• Congenital or acquired

• Neurogenic/myogenic/mechnical

What happens when a muscle underacts?

• overacting of the contralateral synergist

• Over action of the ipsilateral antagonist

  • Inhibition (under action of the contralateral agonist)

• LR palsy:

• Right lateral rectus under action

• Left medial rectus overaction

• Right medial rectus overaction

• Left lateral rectus underaction

What happens during lateral rectus palsy (underaction)*

• Left medial rectus overaction - herrings law

• Right medial rectus overaction - Sherrings law

• Left lateral rectus underaction- herrings law

Do you get primary overaction?

No. There is an underaction

If patient reports diplopia in up gaze, what do you ask?*

• which image is higher

• Indicates lower eye

If patient reports diplopia in the left gaze, what do you ask?

Which image is further to the left

If patient reports diplopia in right gaze, what do you ask?

Which image is further to the right?

If patient reports diplopia in down gaze, what do you ask?*

Which image is lower?

Indicates lower eye

incomitant deviations?

• Strabismus - differs depending upon direction of gaze and associated with defective movement of the eye

• Congenital or acquired

• Neurogenic/myogenic/mechnica

What are indications of incomitant deviations?

• head tilt

• Face turn

• Chin elevation or depression

What effects are caused by third nerve palsy cause and incomitant eye movements?*

• ptosis (lavatory palprebrae?)

• Abduction in primary position (intact LR)

• Normal abduction

• Limited adduction, elevation, depression

• Mydriasis, defective accommodation

What effects are caused by fourth nerve palsy cause and incomitant eye movements?*

• if LE affected

• L hypertropia in primary position

• Increase in L hyperT on right gaze due to LIO o/a

• Limitation of left depresssion on adduction

• Normal left abduction, elevation and depression

(Only affects superior oblique?)

What effects are caused by sixth nerve palsy cause and incomitant eye movements?*

• SOT (esotropia) in primary position

• Limited abduction

What is brown’s syndrome?

• mechanical restriction of the SO muscle tendon

• Congenital and idiopathic

• Caused by trauma/inflammation

• Treatment not required if BSV is ok

• Related to trochlear nerve

• Limited elevation of eye in adduction

• Normal e;elation in abduction

What is DUane’s retraction syndrome?

• lateral rectus failure to be powered by the 6th CN

• Born with it

• Anomalous innervation of the LR by CN 3

• Often bilateral but asymmetrical congenital

What are the 3 types of Duane retraction syndrome?

Type I - limited abduction

Type II - limited adduction Normal left

Type III - both abduction and adduction are restricted

• slide 58

Slide 59

Slide 60

Which patients do you refer?

• any patient with sudden onset binocular diplopia (horizontal, vertical or torsional)

• Any patient with acquired diplopia which is worse in different positions - incomitant

• Any patient who requires an increase in their prismatic correction to keep them asymptomatic