2. STRABISMUS: IS IT ‘STRABISMIC’ ? …. NEUROLOGICAL? OR BOTH?
LIONEL KOWAL
DIRECTOR, OCULAR MOTILITY CLINIC, RVEEH
SENIOR CLINICAL FELLOW, DEPT OPHTHALMOLOGY, UNIVERSITY OF MELBOURNE
FIRST VICE PRESIDENT, INTERNATIONAL STRABISMOLOGICAL ASSOCIATION,

3. OVERVIEW…. OF THE CAUSES, ASSOCIATIONS AND TYPES OF STRABISMUS
IDENTIFYING SOME COMMON / UNDER- RECOGNISED ASSOCIATIONS

4. STRABISMUS Any ocular misalignment INCLUDES:
Abnormalities of development of acuity
Abnormalities of development of binocularity
The variants of congenital nystagmus

5. CHILDHOOD STRABISMUS 1. Derive largely from refractive disorders
2. Pure neurological
3. Derive largely from abnormal early visual devpt
4. Special types

6. STRABISMUS: END RESULT OF A COMPLEX JIGSAW PUZZLE
Abnormalities in one / more of…
Sensory development
Refraction
Orbital anatomy
EOM anatomy / physiology
Cortical / supranuclear
Accommodation / convergence
either cause or are caused by strabismus

7. COMPLEX JIGSAW PUZZLE Abnormal Sensory development
Amblyopia
Suppression
Abnormal retinal correspondence

8. COMPLEX JIGSAW PUZZLE Abnormal Refraction
Hyperopia or ‘plus’ error *
Causes esotropia
Any asymmetric refractive error
Causes amblyopia, esotropia if +
*so-called ‘long sighted’ - NOT the mirror image of short sighted. The patient can see clearly by generating focusing effort = accommodation

9. COMPLEX JIGSAW PUZZLE Abnormal orbital anatomy1
Orbital pulley heterotopy
Changes muscle actions
Globe size distorting muscle cone
Causes pseudo- 6th
Shallow / deep orbit
Shallow: more prone to exotropia

10. COMPLEX JIGSAW PUZZLE Abnormal orbital anatomy 2
Intorted / extorted orbit
More prone to alphabet patterns
Plagiocephaly
More prone to oblique dysfunction

11. COMPLEX JIGSAW PUZZLE Abnormal EOM anatomy / physiology
Oblique muscle dysfunction
Abnormal elevation / depression in AB- or AD- duction
Globe torsion
Abnormal innervation [Duane's, CFEOM]
Strange incomitant strabismus

12. COMPLEX JIGSAW PUZZLE Abnormal cortical / supranuclear substrate 1
 motor fusion
oculomotor ‘shock absorber’ / ‘glue’ that tries to keep eyes straight
 sensory fusion
stereopsis
Abnormal binocular columns

13. COMPLEX JIGSAW PUZZLE Abnormal cortical / supranuclear substrate 2
Abnormal interneurons
Latent Manifest Latent Nystagmus = LMLN = Fixation Maldevelopment N
Just about any cause / association of devptl delay
Chiari
PVL

14. COMPLEX JIGSAW PUZZLE Abnormal Accom - Conv relationship
Accom  too much convergence
Conv  too much accommodation
*too little is rarely a problem

15. 1. Derives from refractive disorders
TYPES OF STRABISMUS
1. Derives from refractive disorders
2. Pure neurological
3. Derives from abn early visual devpt
4. Special types

16. NORMAL ACCOMMODATION Accommodation and convergence = Focus and Aim
are very tightly linked

17. ACCOMMODATIVE / ‘OPTOMETRIC’ ESOTROPIA
+4 : Abn degree of accommodation required to see clearly
Abn amount of accomm convergence is generated
competes against motor fusion [oculomotor shock absorber]

18. WHAT DOES +4 MEAN?
For distance, generates same accommodation that ‘perfect’ person generates when looking 1/4 m away.
For distance fixation, eyes will tend to a point 25cm away
When an object 25cm away, eyes will a point 12 cm away

19. ACCOMMODATIVE / ‘OPTOMETRIC’ ESOTROPIA
Exactly the same can happen with low + and abnormal accomm - convergence relationship*
Many of these  bifocals
*many synonyms - convergence Xs, high AC/A ratio

20. Developing an esotropia…
Prolonged accommodation  tendency to inappropriate convergence and increased tone in medial recti
Increased tone will eventually exceed motor fusional reserve and  esotropia!
Initially reversible with glasses
Eventually the medial rectus shortens so much that only botox or surgery will work
Glasses still required to prevent recurrence [and, when older, for clear vision]

21. Accommodative esotropia
Usually 2-5 yrs old
Usually high + [thick magnifying lenses]
Sometimes low / normal + with abnormal relation b/w accomm and convergence
Background of normal visual devpt in first 6mo of life

22. Developing an esotropia…
Happens more readily * if motor fusion is impaired:
chromosomal defect / devptl delay
Amblyopia
Orbital anomaly
LMLN
* younger, lower +

23. ‘Breakdown of pre- existing phoria…’
Only acceptable as a presumptive label if:
Wears thick magnifying lenses
± amblyopia
Accomm disturbed e.g. Ditropan

24. 2. Pure neurological TYPES OF STRABISMUS
1. Derives from refractive disorders
2. Pure neurological
3. Derives from abn early visual devpt
4. Special types

25. ‘Pure’ neurological strabismus
True cong sup obl palsy
6th
CFEOM [hypoplasia sup div 3rd; KIF mutation]
..have 2ary effects that are dependent on age of onset and associated factors such as refraction

26. R SOP
HEAD TILT
TO LEFT

27. R IO OA
R SO UA
TIGHT RSR RIR ‘UA’

28. True sup obl palsy
LSO OK RSO ?absent

29. REAL CONG R SOP
& CONG ET FIXING
WITH PARETIC R EYE

30. R SO atrophic

31. Fake SOP Conditions that simulate SOP False +ve diagnostic rate ?50%
Abnormal cyclovertical anatomy
Craniofacial anomalies
Posteroplaced trochlea [Bagolini]
Fink : 20% of SO and IO have > 30 degrees asymmetry in course
Demer: orbital pulley displacements
Abnormal physiology
Brodsky’s wild pitch

32. 3. Derives from abnormal early visual development
TYPES OF STRABISMUS
1. Derives from refractive disorders
2. Pure neurological
3. Derives from abnormal early visual development
4. Special types

33. 1. Abnormal symmetric acuity devpt  ‘Congenital Nystagmus’ * = CN
Bilateral bad refractive error
Albinism : optic n dysplasia, foveal hypoplasia
Bil optic n hypoplasia
Bil cataracts
CN degrades vision further
* aka Idiopathic Infantile N, Cong motor N, Cong Sensory N,…

34. ‘Congenital Nystagmus’ = CN
Pendular / jerk
Greater on lateral gaze
UNIQUE : CONVERGENCE NULL
Face turns
Pathognomonic waveform

35. CN: face turn null & convergence null
Null zone on R gaze
drives face turn / tilt to L
N to L when L of null
N to R when R of null

36. Convergence null : unique to CN

37. Abnormal binocularity devpt  Latent Manifest Latent N *
Caused by…
Any strabismus
Asymmetric refraction
Monocular vision reducing pathology - cataract, optic n hypo,….
* aka Fixation Maldevelopment N

38. Abnormal binocularity devpt  Latent Manifest Latent N
Jerk
Greater on ABduction
UNIQUE : Fast phase to fixing eye
Face turns :
RF  R face turn, LF  L face turn
Head tilts : RF  R tilt, LF  L tilt

39. LMLN VIDEO OF POST OP LMLN; NOW ‘PURE’ LN
Esophoria after Exotropia surgery
N to fixing eye

40. LMLN : N  fixing eye
Fast phase to fixing eye

41. LMLN
COMMONLY  CONGENITAL ESOTROPIA but can cause / be associated with other strabismus
Also CAUSES DISSOCIATED H & V DEVIATIONS

42. CONGENITAL ESOTROPIA

43. ASSOCIATIONS OF LMLN & Congenital ET
Down’s 30%
Severe neonatal course IVH /HC
near 100%
PVL

44. VERTICALS IN CONG STRAB : DVD Dissociated Vertical Deviation
Common pattern:
Right fixation: L
L fixation: R 
Contralateral DVD is the end result of ‘braking’ the torsional component of LMLN in the fixing eye to try and improve acuity

45. VERTICALS IN CET : DVD
RE fixing LE 

47. CONGENITAL STRABISMUS
Head turns / face tilts are common
Caused by attempts to minimise blur effect of the LMLN

48. Alternating Face Turn L Fixation : L Face Turn
R Fixation : R Face Turn
Ciancia’s syndrome: preference for fixation in adduction because recruiting medial rectus ‘brakes’ horizontal component of LMLN  improved vision
Alternating face turn has 2 causes. One is the H version of ciancia’s syndrome -If the L wants to see more clearly, then the H component of LMLN has to be lessened and this is done by recruiting the LMR, and the best way to do this is to adopt a L face turn,

49. Special case: Head tilt to fixing eye
LF drives HT to L
RF : no HT
Caused by Torsional LMLN
Here we have L tilt driven by L fixation. With RE fixation, there is no tilt. The
Usual cause of this situation is a type of congenital nystagmus with the
awkward name of LMLN. This is usually H, but may have a T component as
well. This is described well in the ISA Vancouver meeting proceedings.

50. LF drives HT to L Torsional LMLN
LMLN is the cong nystag seen with disorders of binocular development
[?always] Seen in cong ET
= Fixation Maldevelopment N.
Usually has H component, sometimes T as well
Fine torsional N on slit lamp
N degrades vision - vision improves when N blocked
This type of N [like any type of N] degrades vision. Vision improves when the
N is blocked. You can often see this N on the slit lamp. LMLN is seen in all
cases of cong ET, tho’ not all cases of cong ET have the torsional type.

51. Special case: Alternating Head Tilt
LF drives L tilt
RF drives R tilt
= Ciancia’s syndrome
If LF drives head tilt to L and RF drives head tilt to the R, this is the same mechanism - a need to see more clearly generates a need to suppress the T component of the N. A head tilt recruits SO which acts as a brake on the N and allows clearer vision.

52. Recap…Abnormal binocularity devpt  Latent Manifest Latent N
Features of this type of strab recognised by the accompaniments.
LMLN, + one/ more of…
Head tilt / face turn to fixing eye
DVDs
Large angle esotropia

53. ‘Ophthalmic’ PVL Optic n hypoplasia uni-/bi-
Cognitive visual problems - normal acuity
Reduced acuity
LMLN CN

54. THINGS THAT LOOK LIKE ‘STRABISMIC’ STRABISMUS
CHIARI – later onset
‘deterioration of old latent strabismus ‘ – there always has to be a credible background / predisposition. And a reason for breakdown

55. THINGS THAT LOOK LIKE ‘STRABISMIC’ STRABISMUS
Autoimmune neuropathies
Myesthenia

56. Strabismus syndromes
Duane’s
Brown’s

57. Brown’s
Tight superior oblique tendon
Restricted elevation in aDuction

58. Duane’s Retraction on adduction
Retraction R on L gaze
Restricted aDduction R
Restricted aBduction L
Co-firing Lateral rectus on aDuction

59. Duane’s Retraction L on R gaze Restricted aDduction L
Co-firing lateral rectus on aDuction

60. THANK YOU