1. A-V pattern Horizontal 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