A-V pattern Horizontal strabismus - PowerPoint PPT Presentation

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A-V pattern Horizontal strabismus

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A-V pattern Horizontal strabismus
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A-V pattern Horizontal strabismus

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  1. A-V patternHorizontal strabismus A R Zandi Feiz hospital

  2. Change in magnitude of deviation in upgaze and downgaze

  3. A-V pattern is a vertical incomittancy

  4. A pattern • More convergent in upgaze compared with downgaze

  5. V pattern • More convergent in downgaze compared with upgaze

  6. An A or V pattern is found in 15%-25% of horizontal strabismus

  7. Cause • Bilateral oblique muscle dysfunction

  8. IO overaction is associated with V pattern

  9. SO overaction is associated with A pattern

  10. These associations reflect the ancillary abducting action in upgaze and downgaze

  11. Cause…. • Horizontal rectus muscle dysfunction

  12. Cause…. • Vertical rectus muscle dysfunction

  13. Clinical features • Measurement of the alignment in downgaze and upgaze

  14. When in 25` from the primary position at least 10^ difference in deviation is detected, the clinically significant A pattern is present

  15. To be a clinically significant V pattern the difference must be at least 15^

  16. Management • Surgery for= Clinically significant pattern

  17. Surgery for pattern • Most often in combination with correction of the underlying horizontal deviation

  18. Patients with large A or V pattern usually also have significant corresponding oblique muscle dysfunction

  19. If the pattern is related to overaction of the oblique muscle,these are weakened as part of the surgical plan

  20. Weakening the IO muscles or tucking the SO tendons corrects up to 15-25^ of V pattern

  21. Bilateral SO tenotomy correct up to 35-45^ of A pattern(they produce 35-45^ esoshift in downgaze)

  22. Displacing the horizontal rectus muscle insertions is indicated when there is no oblique dysfunction

  23. The amount of displacement usually is ½ to a full tendon width

  24. MR are always moved toward the direction where convergence is greater or divergence is less(upward in A pattern and downward in V pattern)

  25. This displacement has no net horizontal,vertical or torsional effect in the primary position

  26. For example for V pattern when MR is displaced downward(and LR upward) in downgaze MR will be relaxed and the LR will be tightened( thereby decreasing the V pattern)

  27. MALE

  28. The muscle is moved in the direction in which the muscle`s horizontal effect is to be lessened