Week 2 - Overview Incomitant Strab

Question 1

What is the definition of incomitant strabismus?

Answer 1

• Deviation varies with size and or direction if gaze
• In truth nearly all forms of strabismus are incomitant to a degree but clinically there is usually more than 5° difference before incomitancy is noted

Question 2

What is the classification of congenital incom strabismus?

Answer 2

• Neurogenic
- Third nerve palsy
- Fourth nerve palsy
- Sixth nerve plasy

• Mechanical
- Brown’s Syndrome
- Duane’s Syndrome

Question 3

What is the classification of acquired incom strabismus? (adults and childhood)

Answer 3

• Neurogenic
- Third nerve palsy
- Fourth nerve palsy
- Sixth nerve plasy

• Mechanical
- Brown’s Syndrome
- Duane’s Syndrome (Rare)

• Myogenic
- Dysthyroid Eye disease
- Myasthenia Gravis

Question 4

What is the aetiology of incom strabismus?

Answer 4

• Vascular affects all nerves equally
• Head trauma more commonly affects IVth nerve but may affect all
• Aneurysm most commonly affects Illrd nerve
• Neoplasm
• Unknown
• Other

Question 5

What are systemic diseases that may be associated with incom strabismus?

Answer 5

• Diabetes
• Thyrotoxicosis
• Hypertension
• Aneurysm*
• Giant cell arteritis*
• Multiple Sclerosis
• Myasthenia Gravis

Question 6

What investigations can be done for incom strabismus?

Answer 6

• History and symptoms
• External Examination : Proptosis?
• Cover test
• Motility
• Ophthalmoscopy
• Fields
• Colour vision: d20

Question 7

What are the symptoms of incom strabismus?

Answer 7

• Diplopia
• Abnormal head posture-chin, turn and tilt
• Acuity
• Associated symptoms
• General health
• Injury

Question 8

What external examinations signs can be found?

Answer 8

• Strabismus
• Lid position
• Injury - chemosis, oedema
• Proptosis
• Pupils
• Asymmetry

Question 9

What are the 3 rules of abnormal head postures?

Answer 9

• Always turn in direction of action of palsies muscles E.G LMR palsy will turn to right
• Always move chin in direction of action of palsied muscle, e.g LSR palsy will elevate chin
• Aways tilt to lower eye

Question 10

What do findings on cover test show?

Answer 10

• Small deviation in primary position may indicate very recent onset, <36 hours or mechanical problem
• In Palsy - will be greater when fixing with the affected eye, and usually larger size of deviation

Question 11

What is important to remember when doing ocular motility?

Answer 11

• Know muscle actions
• Take patients eyes into extreme of gaze
• Use objective and subjective assessment - corneal reflexes and CT, do not rely on Px reporting diplopia since suppression or poor VA may affect results
• Use HESS chart and Diplopia Chart

Question 12

What is the definition of RADSIN?

Answer 12

• RAD SIN- Recti Adduct And Superiors Intort
- Recti muscles pull the eye in the direction of their name in the abducted position
- Obliques push the eye in the direction opposite to their name in the adducted position

Question 13

What are the steps in a muscle sequelae?

Answer 13

1. Original Palsy
2. Over action of the contralateral synergist
3. Over action if the ipsilateral antagonist
4. Inhibition palsy

This applies to neurogenic palsy and after all stages of sequelae have occurred concomitancy is achieved

Question 14

What is Mechanical Sequelae?

Answer 14

• Over-action of contralateral synergist only
• Left Brown’s syndrome over action of right superior rectus is seen

Question 15

How are HESS PLOTS interpreted?

Answer 15

• Look for smallest field to identify affected eye
• Look at centre circle to determine deviation in primary position
• Look for area with greatest deflection to identify affected muscles

Question 16

What is the BIRLCHOWSKY head tilt test?

Answer 16

• used to differentiate between SR and SO palsy
• Muscle sequelae idential
• In LEFT SO deviation will increase when head tilted to left, due to unopposed action if LIO

Question 17

Is a third nerve palsy complete or partial?

Answer 17

• Rare to find individual muscles affected but congenital SR Palsy quite common
• May also be multiple muscle involvement including pupil and ciliary body
• Complete or partial

Question 18

What symptoms show with superior rectus palsy?

Answer 18

• Hypotropia of affected eye, may be slightly exo
• Chin elevation
• Can he long lasting, usually have enlarged fusion range and some suppression

Question 19

What symptoms show with inferior oblique palsy?

Answer 19

• Hypotropia in primary position with possible slight eso

Question 20

What symptoms show with medial rectus palsy?

Answer 20

• Exo-deviation

Question 21

What symptoms show with a complete third nerve palsy?

Answer 21

• Exoteopia with hypotropia, ptosis and possible dilation of pupil and accommodation palsy

Question 22

What symptoms show with a sixth nerve palsy?

Answer 22

• Esotropia which is greater on distance fixation

Question 23

What symptoms show with a fourth nerve palsy?

Answer 23

• Hypotropia with slight Eso, eye extorted, greater at near

Question 24

What are the types of fourth nerve palsy?

Answer 24

• Type 1, Type 2 and Type 3
• Browns syndrome

Question 25

What symptoms show with Browns syndrome?

Answer 25

• Small deviation in primary position but hypotropia of affected eye on elevation in adduction

Question 26

What symptoms show with Blow out fracture?

Answer 26

• May be hypotropia or hypertropia
• Infraorbital anaesthesia
• Chemosis
• Vertical diplopia
• Restricted eye movement in upgaze and downgaze

Question 27

What symptoms show with Dysthyroid eye disease, and what are the phases?

Answer 27

• Wet phase when muscles swell - Myogenic
• Dry phase when eye movement restrictions become mechanical in characteristics
• Muscles affected - IR, MR, SR, Rarely LR
• Proptosis or exophthalmos
• Check fields
• Lid refraction and lid lag

Question 28

What are the differences between mechanical and neurogenic palsys regarding: Deviation, Ductions/Versions and movement of eye?

Answer 28

• Small deviation vs large deviation
• Ductions and versions equal vs ductions better than versions
• Ceasing of movement abrupt vs gradual failure in movement

Question 29

What are the differences between mechanical and neurogenic palsys regarding pain, reversal of diplopia and “shoots”?

Answer 29

• Pain vs no pain
• Reversal of dipliopia vs none
• Upshoots + downshoots vs no upshoots + downshoots

Question 30

What are the differences between mechanical and neurogenic palsys regarding: muscle sequelae and hess chart findings?

Answer 30

• Muscle sequelae - only over-action of contralateral synergist vs full muscle sequelae
• Pointed field which look squished vs smoother filled on hess

Question 31

What symptoms are specific for longstanding deviations?

Answer 31

• Abnormal head posture - Fixed and px unaware
- can see in old photographs
• No diplopia
• Enlarged fusion ranges
• Gradual onset of symptoms usually
• Amblyopia
• Suppression

Question 32

What symptoms are specific for acquired deviations?

Answer 32

• Px aware of abnormal head posture and uncomfortable
• Diplopia
• Sudden onset
• No enlarged fusion range

Question 33

Differentiation between SO and SR Palsy : Deviation, AHP and V pattern?

Answer 33

• Eso deviation vs exo deviation (more typical£
• AHP : Chin depression vs chin elevation
• V eso pattern vs V exo pattern

Question 34

Differentiation between SO and SR Palsy : Distance/near, Bielchowsky test and diplopia?

Answer 34

• Greater vertical near vs greater deviation distance
• Buelchowsky +ve vs -ve
• Diplopia greatest on depression vs elevation

Question 35

If a px has these four signs/symptoms when should the Px be referred?

Answer 35

• Sudden onset diplopia
• Imcomitant deviation previously unidentified
• uncomfortable head posture
• Px has localisation disturbance
• Px symptomatic