What are the considerations for bilateral vs unilateral strabismus surgery?

Bilateral vs Unilateral Strabismus Surgery: Key Considerations

Both bilateral and unilateral strabismus surgery are effective approaches for correcting strabismus in adults, with the choice depending on the specific type and magnitude of deviation, surgical goals, and patient factors—both approaches achieve satisfactory alignment in approximately 80% of cases with one procedure. 1, 2

Surgical Approach Selection

When Bilateral Surgery is Indicated

Bilateral surgery is the preferred approach for:

• Divergence insufficiency esotropia: Bilateral lateral rectus muscle resection or bilateral medial rectus muscle recessions are proven successful techniques for this condition 1
• Sagging eye syndrome: Surgical resolution typically requires bilateral intervention, often with marginal insertional tenotomies, recessions, or superior and lateral rectus muscle myopexy 1
• Large-angle deviations: Complex or bilateral procedures requiring more extensive correction 1
• Longer, more complex procedures: General anesthesia is preferable for bilateral operations 1

When Unilateral Surgery is Appropriate

Unilateral surgery is effective for:

• Esotropia of various origins: Unilateral combined surgery (medial rectus recession with lateral rectus resection or plication) produces comparable results to bilateral recession surgery 3
• Small deviations: Single rectus muscle recession or tenotomy procedures can successfully treat deviations ≤8 prism diopters horizontally and <3 prism diopters vertically 1
• Anesthesia considerations: Regional ophthalmic block or topical anesthesia are viable options for uncomplicated unilateral procedures in cooperative adults 1, 4

Critical Technical Considerations

Surgical Dosing Differences

• Higher surgical doses are typically required for adult strabismus compared to childhood comitant strabismus tables, particularly when recessing medial rectus muscles for divergence insufficiency or sagging eye syndrome 1
• Convergence amplitudes should be checked preoperatively: Robust near convergence generally protects against postoperative diplopia with convergence insufficiency 1

Adjustable Sutures

• Adjustable sutures offer advantages including a second chance at alignment and potential to minimize postoperative diplopia risk 1
• Most beneficial in: Reoperations, unpredictable cases, restrictive strabismus, and paralytic strabismus 1
• Not universally necessary: Many surgeons achieve excellent results with fixed sutures, which reduce cost and patient anxiety 1

Common Pitfalls and Complications

Adult-Specific Challenges

• Stretched scars from childhood surgery are common in adults, appearing as weak muscle-sclera attachments with increased deviation in the field of action of previously operated muscles 1
• Slipped or lost muscles occur more frequently in adults (1 in 1,500 and 1 in 4,500 respectively) and make outcomes less predictable 1
• Intractable diplopia is more likely in adults (0.8%) compared to children 1

Surgical Planning Essentials

• Meticulous technique is required to distinguish weak non-muscular attachments from robust muscle tissue during reoperation—sutures placed in non-muscular tissue lead to early recurrence 1
• An experienced assistant is very helpful for complex adult cases 1
• Anticoagulation management: Many surgeons do not routinely stop anticoagulants, though consultation with the prescribing physician is advised; surgery can be safely performed on anticoagulated patients 1

Outcomes and Success Rates

• Approximately 80% of adult patients achieve satisfactory alignment with one surgical procedure, regardless of bilateral or unilateral approach 2
• Binocular function improvement occurs in most adults even with longstanding strabismus, typically as expanded binocular visual fields, and some patients regain stereopsis 2
• Serious complications are rare: Endophthalmitis (1 in 30,000-185,000), anterior segment ischemia (1 in 6,000, higher with ≥3 muscles operated), retinal detachment (1 in 10,000-40,000) 1