This document discusses different types of alphabet patterns in strabismus, including A and V patterns. An A pattern is defined as a horizontal deviation that is less divergent in upgaze than downgaze, usually caused by superior oblique overaction. A V pattern is more divergent in upgaze than downgaze, commonly due to inferior oblique overaction. Treatment of significant patterns may involve weakening overacting muscles and vertical translations of horizontal recti. Other patterns like Y, λ, and X patterns are also briefly described.

1. Alphabet Patterns
By
Dr Alshymaa Moustafa
Ophthalmology Specialist

2. Introduction

3. • Horizontal deviations may vary in size according to vertical
position.
• The deviation is measured at 30° upgaze, 1° position, and 30°
downgaze, while fixing on a distance target.
• The difference between upgaze and downgaze must be >10 pD in
"A" pattern and >15 pD in "V" pattern.

4. Causes

5. • Imbalance in tertiary abducting action of the obliques. greatest
effect in upgaze from IO overaction (IOOA) vs downgaze from SO
overaction.
• MR action causes greater adduction in depression, LR greater
abduction in elevation.
• The adducting force from the vertical recti causes greatest
adduction in their field of action.
• Anomalies of orbital structures, such as craniosynostosis (extorted
orbits and V pattern).

6. • Abnormalities/ heterotopy of eOM pulleys.
• Neural mechanisms such as abnormal supranuclear circuits.
• Loss of fusion predisposing the oculomotor system to
cyclodeviations of the eyes.
• Ocular torsion may predispose to alphabet strabismus.

7. Causes of alphabet patterns

8. V pattern

9. Definition
• this is defined as a horizontal deviation, which is more divergent
(or less convergent) in upgaze than in downgaze.

10. Clinical features
• V-pattern esotropia: usually arises from IOOA or SO palsy; it is
also associated with antimongoloid palpebral fissures (perhaps
altering the recti insertions). patients may adopt a chin down
posture.
• V-pattern exotropia: usually arises from IOOA. patients adopt a
chin up posture.

11. Downward slant of palpebral fissure seen
in V pattern horizontal deviation

12. V pattern ET
V pattern XT

13. V pattern ET overelevation , and limited depression in adduction

14. V pattern XT, with moderate overelevation in adduction
With no of SOUA

15. Treatment
• Surgical treatment for significant V patterns may require:
1. IO weakening (if overacting).
2. Vertical translations of the horizontal recti (when operating on
paired recti; upward for LR, downward for MR).
3. Correction of the horizontal component (e.g. MR recession for
esotropia; LR recession for exotropia).
• For both A and V patterns, the acronym MALE identifies the
direction of vertical translation: MR to Apex, LR to Ends. When
a horizontal muscle is transposed, its 1° action decreases, while it
gains a new action in the direction of transposition.

16. "MALE, or MALB"

17. A pattern

18. Definition
• This is defined as a horizontal deviation, which is less divergent
(or more convergent) in upgaze than in downgaze.

19. Clinical features
• A-pattern esotropia: usually arises from SO overaction; it may
also be associated with mongoloid palpebral fissures. patients may
adopt a chin up posture.
• A-pattern exotropia: usually arises from SO overaction. patients
adopt a chin down posture.

20. A pattern ET
A pattern XT

21. A pattern ET , underelevation and overdepression in adduction ,
more in LT eye.

22. A pattern XT , overdepression
and underelevation in adduction.

23. Treatment
• Surgical treatment for significant A patterns may require:
1. SO weakening (if overacting) with a posterior disinsertion
(division of posterior fibres, with preservation of the anterior
torsion fibres).
2. Vertical translations of the horizontal recti (when operating
on paired recti; upward for MR, downward for LR).
3. Correction of the horizontal component (e.g. MR recession for
esotropia; LR recession for exotropia).

24. Other Patterns

25. Y pattern
• Exotropia in upgaze only.
• It is usually due to bilateral IOOA (seen in congenital esotropia or
exotropia).
• It can be treated by IO weakening alone.

26. λ pattern
• Exotropia in downgaze only, seen with bilateral SO overaction or
IR under action.
• It may be treated by downward translation of both LR.

27. X pattern
• Exotropia in upgaze and downgaze, but straight in the 1°
position.
• It usually arises in long standing exotropia with overaction of
all four oblique muscles or is iatrogenic.

28. “
”
Thanks