1. FOURTH NERVE / SUPERIOR OBLIQUE PALSY FNP / SOP
LIONEL KOWAL
RVEEH / CERA
MELBOURNE

2. Types of apparent FNP / SOP All of these LOOK THE SAME
1. Definite SOP
Only true HALF the time that it is diagnosed!
2. Possible SOP or Resolved SOP
3. Idiopathic oblique dysfunction & other
synonyms for …“CycloVertical Dysfunction of uncertain cause” = CVD
Mostly due to minor anatomical ‘errors’
4. Pulley heterotopy radiological diagnosis
5. Something quite different Graves’, old fracture, other vertical rectus disease, post ret-det surgery, …

3. Definite SOP / Possible SOP / CVD / pulley heterotopy ….. can all 
Vertical misalignment
Disrupt horizontal fusion &  horizontal misalignment
Head tilts
Vertical greater to one side
Apparent IO OA, SO UA
CLINICAL PICTURE CAN BE THE SAME IN ALL THESE TYPES OF SOP & PSEUDO - SOP

4. Is it important to differentiate?
LUMPERS
Traditional UK approach
All SOPs get similar
treatment
Lumpers vs splitters
It’s a bit like the old wars between the americans and the British
SPLITTERS
Post 1950’s US approach
Individualise treatment
to specific subtype of
SOP

5. Lumpers
If it looks / smells / sounds … a bit like SOP, then call it SOP.
‘Congenital SOP’ label used with NO evidence of true palsy
Rx: inf obl weakening IO-
Some lumpers: one size fits all. Some : 2-3 different ops
Nucci: Milan, EJO sectional editor, trained Italy & Chicago, 62 articles in PubMed,…

6. Splitters Knapp: important to split some pts do well with IO-
7 different types based on detailed measurements and versions
Later subclassified further by others
some pts do well with IO-
others will do better with SO plication or SR weakening……
Selection bias: strabismus specialist tends to see pts with inadequate results after IO-
LK: a splitter

7. Lumpers vs Splitters & EBM
21st Century: issues resolved by randomised prospective trial - still waiting
Eminence based medicine
Loudest most forceful & charismatic medical conference personality defines clinical practice.
MOST strabismus specialists are splitters

8. Splitting…… 1. Careful measurements in cardinal positions
Allows classification into Knapp types [or more modern variants] and likely surgical solution

9. Splitting…… 2. Radiology: Is it a True SO atrophy:
More likely to have floppy SO
?less likely to respond to IO-
?more likely to need SO+

10. MRI X-sectional area of SO segregates SOP from normal SO
When strabismus specialists made clinical diagnosis of SOP, they were wrong 50% of the time!!
MRI X-sectional area of SO segregates SOP from normal SO

11. Splitting…… 3. Reserve final surgical plan until intra-operative FDT
If SR is tight, more likely to need SR-
If SO floppy,….
If IO is tight,…
If IR is tight,…
Need a MUCH larger surgical repertoire than Lumpers

12. R SOP
HEAD TILT
TO LEFT

13. ADAPTATION
TO WEAK SO
R IO OA
ADAPTATIONS
MAY DOMINATE
THE CLINICAL
PICTURE
CORE DEFECT
R SO UA
ADAPTATION
TO CHRONIC
HYPERTROPIA
TIGHT RSR RIR ‘UA’

14. SOP image
LSO OK RSO ?absent

15. Case #1 Atrophic SO SO UA IO OA SOUA > IO OA
IR UA [presumed tight SR from having had a ‘chronic hypertropia’]
LUMPERS : Inf obl weakening
SPLITTERS : Final decision after FDT

16. Splitters Atrophic SO and SO UA: More likely to find floppy SO
More likely to need SO plication
Apparent IR UA
Probably tight SR
Needs SR- or will have DG diplopia
If FDT on SO & SR are OK: IO-

17. Principles of treatment
Acquired SOP : 12 mo [can Rx earlier if getting worse]
Long standing: Acquired suppression makes it harder to characterise
SPLITTERS:
Usually have to treat the muscular consequences of the SOP rather than the SOP itself

18. Principles of treatment
Make it better - don’t over correct
Trauma: look for bilateral SOP
Accurate measurements
SPLITTERS
Tighten floppy muscles
Recess tight muscles

19. Principles of treatment : IO-
Parks’ IO Rc for ∆ height in PP
≈ 20 ∆ To lateral edge IR
≈ 25 ∆ 2mm ant to edge IR

20. Principles of treatment Tight SR
‘Chronic hypertropia’ may  tight SR, spread of comitance & [apparent] IR UA wch may come to dominate the clinical picture.
SR Rc required
Recessing SR will increase extorsion unless it is temporally transposed

21. TREATMENT EXPECTATIONS
LK audit early 90’s n=450
Unilateral SOP [all sorts]:
1.3 surgeries
90+% Very Good to excellent

22. SOP Difficult area of strabismus Lumpers vs Splitters : unresolved
Splitters more likely to see the more complex pts & believe that a more complicated approach is the correct one

23. The contralateral inferior rectus
Lumpers
1st op: inf obl
2nd op: c/l inf rectus
Splitters
Consider c/l inf rectus if tight or if SO UA without SO floppiness

24. The contralateral inferior rectus
MRI of the Functional Anatomy of the Inferior Rectus Muscle in Superior Oblique Muscle Palsy.Jiang L, Demer JL.UCLA Ophthalmology. November
PURPOSE: Biomechanical modeling consistently indicates that SO muscle weakness alone is insufficient to explain the large hypertropia often observed in SOP. MRI : to investigate if any size or contractility changes in IR may contribute.
17 pats with unilateral SOP and 18 orthotropic controls.
Diagnosis of SOP based on clinical presentations, subnormal contractility & small SO muscle size

25. The contralateral inferior rectus
OUTCOME MEASURES: X-sectional areas of IR & SO.
RESULTS: Patients had 16+/-7∆ of central gaze hypertropia and exhibited ipsilesional SO muscle atrophy and subnormal contractility.
CONCLUSIONS: ..the contralesional IR is larger and more contractile than the ipsilesional IR, reflecting likely neurally mediated changes that augment the relatively small hypertropia resulting from SOP.
Recession of the hyperfunctioning contralesional IR in SOP is a physiologic therapy.