Strabismus surgery

Only performed after thorough assessment and treatment of causative factors eg refraction and consideration of non-surgical options: botox, orthoptic exercises, prisms etc.

The deviation should be considered stable

Aims

• Produce straight eyes in primary position and downgaze
• Maintain largest possible field of BSV
• Reduce abnormal head postures

General principles

• Identify the direction of overaction
• Identify any incomitance
• Identify any oblique muscle dysfunction
• Weaken overacting muscle and strengthen its antagonist
• Use an unbalanced procedure if there is pre-existing incomitance
• Reduce oblique overaction

Risks

• 1 in 400 risk of complication

• Suture granuloma

• Globe perforation: most common severe complication (1:1000)

• Slipped muscle: second most common severe complication

  • Defined as patient suffering overcorrection with 50% or more reduction in muscle action.
  • More common in children
  • Typically due to suture problem/failure
  • Requires exploration and re-attachment of muscle

• Orbital infection: from orbital cellulitis to muscle insertion abscess

• Surgically induced necrotizing scleritis (SINS): very rare especially in children

• Lost muscle (perioperatively)

  • Medial rectus most common to lose (perhaps due to being frequently operated on, but also lacks an attachment to an oblique)

• Consecutive strabismus

• Postoperative diplopia

• RD

• Endophthalmitis

Effects

• 1mm vertical recession produces 3PD of correction
• 1mm horizontal recession produces 2PD of correction
• 1mm horizontal resection produces 4PD of correction

Kestenbaum procedure

• Bilateral recess/resect which moves the eyes towards the direction of the head turn to dampen nystagmus

Harada-Ito

• Preferred procedure for bilateral fourth nerve palsies causing torsional diplopia
• Displaces the anterior fibres of superior oblique temporally