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Strabismus > Alphabet patterns 2 > Flashcards

Alphabet patterns 2 Flashcards

1
Q

V pattern dioptres diff

A

15 dioptres difference b/w elevation and depression in horizontal deviation

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1
Q

A pattern dioptres diff

A

10 dioptres difference in horizontal deviation

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2
Q

V pattern elevators

A

o/a of IO and u/a of SR Greater relative divergence

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3
Q

V pattern depressors

A

u/a of SO and o/a of IR

Greater relative convergence

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4
Q

A pattern elevators

A

u/a of IO and o/a of SR Greater relative convergence

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5
Q

A pattern depressors

A

o/a of SO and u/a of IR Greater relative divergence

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6
Q

35BI, 25BI, 10BI

A

V EXO- more divergence looking up

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7
Q

35∆BO, 25∆BO, 10∆BO

A

A EXO- more divergence looking down

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8
Q

10∆BI, 25∆BI, 35∆BI

A

A ESO- more convergence looking up

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9
Q

10∆BO, 25∆BO,35∆BO

A

V EXO- more convergence looking down

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10
Q

tests to diagnose alphabet pattern

A
  • CT then OMs
  • Measurements in PP, direct elevation and depression
  • PCT
  • 6m to eliminate accommodation
  • May also want to measure at 1/3m if interested in what happens when accommodate
  • Synoptophore
  • Lees screen if there is a tilt it shows A/V pattern
  • Field of BSV
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11
Q

What are BSV tests a guide for

A

surgical management

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12
Q

Important investigation info

A
  • Symptomatic
  • Diplopia
  • Constant
  • Intermittent e.g. Decompensate on prolonged reading
  • Asthenopic e.g. frequent headaches
  • Ocular alignment
  • Objective assessment of torsion
  • Indirect ophthalmoscopy or fundus photography
  • Potential for BSV or retaining BSV
  • Assess risk of over-correcting a patient requiring strabismus surgery
  • Assess value of combining strabismus surgery & correcting alphabet pattern at the same time
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13
Q

Reasons for managing pattern

A
  • To create a larger and more useful field of BSV
  • To achieve a better ocular alignment
  • To reduce the risk of consecutive exotropia and give a more stable angle
  • Assess risk of overcorrection in PP or other postions
  • Obtain/retain BSV
  • Create a larger and more useful field of BSV
  • Achieve better ocular alignment if they are suppressing
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14
Q

Surgical management dependent on

A

aetiology or the presence of significant oblique over-action

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15
Q

Surgical principle

A

If associated vertical muscle over- & under-actions: operate on vertical muscles
If no/ mild vertical muscle over- & under-actions: operate on horizontal muscles

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16
Q

V pattern with IO over action aim

A

weakening of the IO muscle allows more convergence on elevation i.e. cause SR over-action and increased ad-duction

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17
Q

V pattern with IO over action surgical options

A

— IO recession -most common and less abduction and V pattern closes
— IO myectomy
— Anterior transposition of IO
— Horizontal surgery (recess/resect) performed at same time or subsequent sitting
Oblique muscle placed more anterior weakens its ab-ducting force
Gobin proposed the V pattern was caused by the IO insertion was too posterior

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18
Q

More surgical options

A

— Anterior transposition of IO as advocated by Gobin now mostly used in DVD
— In acquired bilateral SO palsy with V-Eso
— Harado-Ito or SO tuck will reduce V pattern

19
Q

A pattern with SO over action surgical options

A

— SO posterior tenectomy
— SO posterior tenotomy
— SO z-tenotomy
— SO split lengthening
— SO tendon spacer (silicon expander)
— Operate on both SO if moderate/marked o/a of SO
— Alternative
— Bilateral IR resection

20
Q

A pattern with SO over action aim

A

weakening the SO muscle allows more convergence on depression i.e. cause IR over-action increased ad-duction

21
Q

A pattern with SO over action further surgical options + success

A

Horizontal surgery (recess/resect) performed at same time or subsequent sitting
Combining SO Z-tenotomy, SO posterior tenectomy or tenotomy, and recess/resect of horizontal rectus muscles:
Success rate of 60-90% (Lee and Rosenbaum, 2003;Ron et al. 2009)

22
Q

A pattern with SR over-action aim

A

weakening of both SR muscles allows more divergence on elevation i.e. cause IO over-action, Increased ab-duction

23
Q

A pattern with SR over-action surgical options

A

bilateral SR recession

24
Q

A pattern with SR over-action further surgical options

A

Transposition of horizontal muscles

25
Q

A pattern with SR over-action H transposition surgical options

A

— Bilateral recession & transposition of muscles
— Move LR in Exo & MR in Eso
— Move in the direction of greatest deviation
— Insertion of MR moved towards apex
— Insertion of LR moved towards wide end
— MR always moved towards the apex!
— Theory is based on the hypothesis:
— Lateral recti work more for distance and on elevation
— Medial recti work more for near and on depression
— Eso deviation interested in action of MR
— Exo deviation interested in action of LR
— MR more slack going down and more abduction so more A pattern going down

26
Q

What happens when insertion is moved down

A

the action of that muscle to be more slack on depression

27
Q

V eso transposition

A

Transpose MR insertion downwards

28
Q

A eso transposition

A

Transpose MR insertion upwards

29
Q

Transposition

A

The main aim of transposition surgery is to realign the eyes in primary position. Although the results of a transposition procedure are usually good, patients must understand that the ductions in the direction of action of a paralyzed muscle might not improve much

30
Q

V exo transposition

A

Transpose LR insertion upwards

31
Q

A exo

A

Transpose LR insertion downwards

32
Q

Muscle transposition reasons

A

Advocated if no or minimal oblique muscle over- and under-actions
Also possible to combine recess/resect procedure, moving one up & one down
Complications: risk of inducing torsion if work on one eye

33
Q

Slanting muscle insertions principle

A
  • Horizontal muscle tension is stronger at upper margin than lower margin on elevation
34
Q

Boyd technique slanting muscle insertions can be combined with

A

horizontal surgery

35
Q

Bietti 1970 slanting muscle insertions

A

Introduced the surgical technique of slanting horizontal muscle insertions
Advocated in the absence of marked over-actions of the oblique muscles

36
Q

Correcting A exo complications

A

SO weakening
Vertical displacement of horizontal muscles may induce torsion

37
Q

Closing V

A

Upper margin of LR recessed > than lower margin to reduce V-exotropia
i.e. less ab-duction on elevation

38
Q

Closing A

what margin and muscle is recessed

A

Lower margin of LR recessed > than upper margin to reduce A-exotropia
i.e. less ab-duction on depression

39
Q

Opens A

A

Upper margin of MR recessed > than lower margin to reduce A-esotropia
i.e. less ad-duction on elevation

40
Q

Opens V

A

Lower margin of MR recessed > than upper margin to reduce V-esotropia
i.e. less ad-duction on depression

41
Q

In what circumstances may surgery be modified to prevent an A exo post-operatively?

A
  • When performing horizontal muscle surgery
    -Consecutive exotropia may be associated with A pattern due to SO over-action
    -Large recession of IR for Graves Orbitopathy move insertions nasally will prevent A-exo post-operatively
42
Q

Modifying horizontal muscle surgery

A

— Abnormally low insertion of MR is noted. This muscle may be transposed upwards.
— If the insertion of the LR muscle is found to be abnormally high this muscle may be transposed downwards.
— This will minimise the risk of an A-exo post-operatively

43
Q

Modifying consecutive XT surgery with A pattern association due to SO o/a

A

Combined horizontal muscle surgery with SO weakening procedure may reduce the risk of A exo post-operatively

44
Q

Modifying IR recessions for GO to prevent A pattern post op

A

move insertions nasally will prevent A-exo post-operatively
i.e. moving insertion nasally increases ad-duction, moving insertion temporally decreases ad-duction

45
Q

Aetiology and surgery

A

Pathology/Symptomatic influences surgical choice

46
Q

Tables and pp on slides

A

PP

Strabismus (46 decks)

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