Alphabet patterns 2 Flashcards
V pattern dioptres diff
15 dioptres difference b/w elevation and depression in horizontal deviation
A pattern dioptres diff
10 dioptres difference in horizontal deviation
V pattern elevators
o/a of IO and u/a of SR Greater relative divergence
V pattern depressors
u/a of SO and o/a of IR
Greater relative convergence
A pattern elevators
u/a of IO and o/a of SR Greater relative convergence
A pattern depressors
o/a of SO and u/a of IR Greater relative divergence
35BI, 25BI, 10BI
V EXO- more divergence looking up
35∆BO, 25∆BO, 10∆BO
A EXO- more divergence looking down
10∆BI, 25∆BI, 35∆BI
A ESO- more convergence looking up
10∆BO, 25∆BO,35∆BO
V EXO- more convergence looking down
tests to diagnose alphabet pattern
- 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
What are BSV tests a guide for
surgical management
Important investigation info
- 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
Reasons for managing pattern
- 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
Surgical management dependent on
aetiology or the presence of significant oblique over-action
Surgical principle
If associated vertical muscle over- & under-actions: operate on vertical muscles
If no/ mild vertical muscle over- & under-actions: operate on horizontal muscles
V pattern with IO over action aim
weakening of the IO muscle allows more convergence on elevation i.e. cause SR over-action and increased ad-duction
V pattern with IO over action surgical options
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
More surgical options
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
A pattern with SO over action surgical options
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
A pattern with SO over action aim
weakening the SO muscle allows more convergence on depression i.e. cause IR over-action increased ad-duction
A pattern with SO over action further surgical options + success
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)
A pattern with SR over-action aim
weakening of both SR muscles allows more divergence on elevation i.e. cause IO over-action, Increased ab-duction
A pattern with SR over-action surgical options
bilateral SR recession
A pattern with SR over-action further surgical options
Transposition of horizontal muscles
A pattern with SR over-action H transposition surgical options
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
What happens when insertion is moved down
the action of that muscle to be more slack on depression
V eso transposition
Transpose MR insertion downwards
A eso transposition
Transpose MR insertion upwards
Transposition
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
V exo transposition
Transpose LR insertion upwards
A exo
Transpose LR insertion downwards
Muscle transposition reasons
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
Slanting muscle insertions principle
- Horizontal muscle tension is stronger at upper margin than lower margin on elevation
Boyd technique slanting muscle insertions can be combined with
horizontal surgery
Bietti 1970 slanting muscle insertions
Introduced the surgical technique of slanting horizontal muscle insertions
Advocated in the absence of marked over-actions of the oblique muscles
Correcting A exo complications
SO weakening
Vertical displacement of horizontal muscles may induce torsion
Closing V
Upper margin of LR recessed > than lower margin to reduce V-exotropia
i.e. less ab-duction on elevation
Closing A
what margin and muscle is recessed
Lower margin of LR recessed > than upper margin to reduce A-exotropia
i.e. less ab-duction on depression
Opens A
Upper margin of MR recessed > than lower margin to reduce A-esotropia
i.e. less ad-duction on elevation
Opens V
Lower margin of MR recessed > than upper margin to reduce V-esotropia
i.e. less ad-duction on depression
In what circumstances may surgery be modified to prevent an A exo post-operatively?
- 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
Modifying horizontal muscle surgery
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
Modifying consecutive XT surgery with A pattern association due to SO o/a
Combined horizontal muscle surgery with SO weakening procedure may reduce the risk of A exo post-operatively
Modifying IR recessions for GO to prevent A pattern post op
move insertions nasally will prevent A-exo post-operatively
i.e. moving insertion nasally increases ad-duction, moving insertion temporally decreases ad-duction
Aetiology and surgery
Pathology/Symptomatic influences surgical choice
Tables and pp on slides
PP
