Alphabet patterns

Significant incomitance in horizontal deviation depending on vertical position

Aetiology/theories

• Imbalance in tertiary abducting action of the obliques
• Abnormalities in the EOM pulleys
• Abnormal supranuclear circuits
• Greater adducting force from vertical recti in their fields of action

V pattern

• More divergence in upgaze compared to downgaze

  • Considered present when the difference is**>15PD**

• V pattern esotropia

  • Inferior oblique overaction(most common) or superior oblique palsy
    • IV nerve palsy(including bilateral and traumatic cases)
    • Brown syndrome
    • Superior rectus underaction
    • Craniofacial anomalies
  • Chin down posture

• V pattern exotropia

  • Inferior oblique overaction
  • Chin up posture

• Surgery

  • Surgical weakening of the inferior oblique or vertical translation of the horizontal recti can be considered
  • Bilateral inferior oblique myectomies causes 15-20 PD of esodeviation in upgaze (to correct V patterns)

A pattern

• More convergent in upgaze than downgaze

  • Considered present when difference is**>10PD**

• A pattern esotropia

  • Superior oblique overaction
  • Chin up posture

• A pattern exotropia

  • Superior oblique overaction
  • Chin down posture

• Inferior oblique palsy: most commonly seen after trauma or with myasthenia

• Surgery:

  • Surgical weakening of the superior oblique or again vertical translation of the horizontal recti
  • Bilateral superior oblique tenotomies cause approximately 40 prism dioptres of esodeviation in downgaze (to correct A patterns)