Incomitant strabismus

1. Incomitant strabismus Nadia Northway

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

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

6. Systemic Diseases • Diabetes • Thyrotoxicosis • Hypertension • Aneurysm • Giant cell arteritis • Multiple Sclerosis • Myasthenia Gravis

7. Investigation • History and symptoms • External Examination • Cover test • Motility • Ophthalmoscopy • Fields

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

9. External Examination • Strabismus • Lid position • Injury- chemosis, oedema • Proptosis • Pupils • Asymmetry

10. Abnormal Head Postures • Always turn in direction of action of palsied muscle 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 • Always tilt to lower eye

11. Findings on Cover Test • 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

12. Ocular Motility • Know muscle actions • Take patients eyes into extremes of gaze • Use objective and subjective assessment- corneal reflexes and CT. Do not rely on pt reporting diplopia since suppression or poor VA may affect results. • Hess chart and diplopia chart.

13. Secondary actions • 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

14. Muscles Sequelae • Original palsy • Overaction of the contralateral synergist • Overaction of the ipsilateral antagonist • Inhibitional palsy • This applies to neurogenic palsy and after all stages of sequelae have occurred concomitancy is achieved

15. Muscle actions IO IO SR SR MR LR LR IR SO SO

16. Mechanical sequelae • Overaction of contralateral synergist only • Left Brown’s syndrome overaction of right superior rectus is seen

17. Interpretation of Hess Plot • Look for smallest field to identify affected eye • Look at center circle to determine deviation in primary position • Look for area with greatest deflection to identify affected muscles

18. Bielchowsky Head Tilt Test • Used to differentiate between SR and SO palsy • Muscle sequelae identical • In left SO palsy deviation will increase when head tilted to left due to unopposed action of the LIO

19. BHTT

20. Head tilting test

21. Third Nerve Palsy • Complete or partial • Rare to find individual muscles affected but Congenital SR palsy quite common • May also be multiple muscle involvement including pupil and ciliary body

22. Third Nerve Anatomy

23. Superior Rectus Palsy • Hypotropia of affected eye and may be slightly exo • Chin elevation • Can be longstanding -usually have enlarged fusion range and some suppression

24. Inferior Rectus Palsy • Hypertropia in primary position

25. Inferior Oblique Palsy • Hypotropia in primary position with possible slight eso.

26. Medial Rectus palsy • Exo deviation

27. Aneurysm site to cause IIIrd CN palsy

28. Complete Third Nerve Palsy • Exotropia with hypotropia, ptosis and possible dilation of pupil and accommodation palsy

29. Aberrant Regeneration

30. Sixth nerve anatomy

31. Sixth Nerve Palsy • Esotropia which is greater on distance fixation

32. Fourth Nerve Anatomy

33. Fourth Nerve palsy • Hypertropia with slight eso , eye also extorted, greater at near

34. Duane’s Retraction Syndrome

35. Left Duanes on Left gaze

36. Duanes syndrome

37. Duane’s

38. Duane’s

39. Browns Syndrome • Small devation in primary position but hypotropia of affected eye on elevation in adduction

40. Brown’s Syndrome

41. Blow Out Fracture • May be hypotrpia or hypertropia • Infraorbital anaesthesia • Chemosis • Vertical diplopia • Restricted eye movement in upgaze and downgaze

42. Blowout fracture

43. Blowout fracture

44. Dysthyroid eye disease • 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 retraction and lid lag

45. Thyroid eye disease

46. Differentiation of mechanical and neurogenic palsy • Neurogenic • Large deviation in pp • Ductions better than versions • Gradual failure of movement • No pain • No upshoots and downshoots • Mechanical • Small deviation in pp • Ductions and versions equal • Ceasing of movement abrupt • Pain • Reversal of diplopia • Upshoots and downshoots

47. Differentiation of mechanical and neurogenic palsy • Mechanical • Muscle sequelae- only overaction of contra syn • Hess chart -pointed field which look squashed • Neurogenic • Full muscle sequelae • Smoother filed on Hess

48. Differentiate Longstanding and Acquired Deviations • Newly acquired • Pt aware of AHP and uncomfortable • Diplopia • Sudden onset • No enlarged fusion range • Longstanding • AHP - fixed and pt usually unaware • No diplopia • Enlarged fusion ranges • Old photographs • Gradual onset of symptoms usually • Amblyopia • Suppression

49. Differentiate SR and SO palsy • SO • Eso deviation more typical • AHP - chin depression • V eso pattern • Greater vertical deviation at near • Bielchowsky +ve • Diplopia greatest on depression • SR • Exo deviation more typical • AHP- chin elevation • V exo pattern • Greater deviation in distance • Bielchowsky -ve • May have history of ptosis • Diplopia greatest on elevation

50. V exo pattern