Strabismus Surgery

Strabismus Surgery: Fundamentals - Eye See You Not!

• Strabismus: Ocular misalignment; eyes don't look at the same object simultaneously.
• Types:
  • Esotropia (inward), Exotropia (outward).
  • Hypertropia (upward), Hypotropia (downward).
  • Comitant (angle constant) vs. Incomitant (angle varies with gaze).
• Key Evaluation:
  • Visual acuity, Cycloplegic refraction.
  • Cover tests (Cover-Uncover, Alternate Cover Test).
  • Corneal reflex tests: Hirschberg, Krimsky.
  • Prism tests (e.g., Prism Bar Cover Test - PBCT) for measurement.
• Surgical Principles: Aim to realign eyes.
  • Recession: Muscle insertion moved posteriorly (weakens action).
  • Resection: Muscle shortened, reattached at original insertion (strengthens action).

⭐ Hirschberg test: Assesses corneal light reflex. Normally slightly nasal. 1 mm of decentration approximates 7° of ocular deviation or 15 prism diopters (PD).

Strabismus Surgery: Scalpel & Sutures - Straightening Acts

• Goal: Align eyes, restore binocular single vision (BSV), expand visual field, improve cosmesis.
• Types of Procedures:
  • Weakening Procedures (Recession):
    • Muscle detached, reattached further back on sclera.
    • ↓ Muscle's effective pulling power.
    • For overacting muscles.
  • Strengthening Procedures (Resection):
    • Portion of muscle tendon excised, muscle reattached at original insertion.
    • ↑ Muscle's effective pulling power.
    • For underacting muscles.
  • Transposition Procedures:
    • Muscle path altered to change vector of action (e.g., Jensen's, Hummelsheim's for abducens palsy).
• Adjustable Sutures: Allow post-op alignment refinement.
• Complications: Over/undercorrection, diplopia, slipped/lost muscle, scleral perforation.

⭐ Faden Procedure (Posterior Fixation Suture): Weakens muscle only in its primary field of action, without affecting primary position; useful for incomitant strabismus.

Strabismus Surgery: Tricky Twists - Special Cases & Fixes

• Adjustable Sutures:
  • Post-op refinement (first 24 hrs).
  • For adults, reoperations, unpredictable cases.
• Botulinum Toxin (Botox):
  • Temporary paralysis (2-4 months).
  • For small angles, diagnostics, post-op residuals.
• Challenging Conditions & Fixes:
  • Duane Syndrome: Type 1 (↓abduction): Medial Rectus (MR) recession for esotropia (ET); avoid Lateral Rectus (LR) resection. Consider Vertical Rectus Transposition (VRT).
  • Brown Syndrome (Superior Oblique restriction): SO tenotomy/tenectomy or spacer for severe cases.
  • Superior Oblique Palsy (SOP): Harada-Ito for excyclotorsion. Knapp procedure for large hypertropia.
  • Thyroid Eye Disease (TED): Recess fibrotic muscles (Inferior Rectus common). Stable ≥6 months pre-op.
• Complications:
  • Lost/Slipped Muscle: Surgical emergency. Explore carefully. Presents with diplopia, ↓motility.

⭐ In Duane Syndrome Type 1, avoid resecting the lateral rectus as it can worsen globe retraction and palpebral fissure narrowing. Medial rectus recession is preferred for esotropia.

Strabismus Surgery: Oops & Aftercare - Post‑Op Pitfalls & Polish

Post-Op Pitfalls:

• Under/Overcorrection: Commonest. May need prisms or re-surgery.
• Diplopia: Often transient. Persistent (>6-8 weeks) may need prisms/revision.
• Infection (Endophthalmitis): Rare, severe. Prophylactic antibiotics.
• Slipped/Lost Muscle: Rare. Large deviation. Urgent re-operation.
• Scleral Perforation: Accidental. Monitor for RD, endophthalmitis.
• Anterior Segment Ischemia (ASI): Risk with ≥3 recti surgery.
• Suture Granuloma/Allergy: Local inflammation. Steroids/excision.

Post-Op Polish (Aftercare):

• Medications: Topical antibiotic-steroid drops for 4-6 weeks.
• Pain Relief: Oral analgesics for discomfort.
• Patching: Often 24h post-op (kids) for comfort.
• Activity: Avoid strenuous activity, swimming, eye rubbing (2-4 weeks).
• Follow-up: Monitor alignment, motility, healing, vision.
• Refraction: Update glasses/prisms once stable (post 6-8 weeks).

⭐ Persistent diplopia post-strabismus surgery beyond 6-8 weeks is significant, often requiring prisms or re-operation.

High‑Yield Points - ⚡ Biggest Takeaways

• Recession weakens a muscle; resection strengthens it.
• Adjustable sutures allow postoperative refinement of alignment.
• Commonest complication: residual strabismus or overcorrection.
• Slipped muscle is a serious complication, requires re-operation.
• Botulinum toxin can be used for small angle or temporary deviations.
• Faden operation (posterior fixation) weakens muscle in its primary field of action.
• Forced duction test (FDT) differentiates restrictive vs paretic strabismus.