What is the appropriate evaluation and management for a patient who develops diplopia after Mohs micrographic surgery?

Diplopia After MOHS Surgery: Evaluation and Management

Diplopia following MOHS surgery requires urgent ophthalmologic evaluation to determine whether the cause is muscle damage, nerve injury, or restrictive scarring, with management ranging from observation for transient cases to prism correction or surgical intervention for persistent diplopia beyond 6 months. 1

Initial Evaluation

Critical History Elements

• Timing of symptom onset relative to the MOHS procedure 1
• Type of anesthesia used (retrobulbar/peribulbar blocks increase risk of myotoxicity versus topical anesthesia) 1
• Location of MOHS excision (proximity to extraocular muscles, particularly medial rectus if periocular) 1
• Pattern of diplopia (constant vs intermittent, direction of gaze affected, presence of torsional component) 1

Essential Examination Components

• Detailed sensorimotor evaluation including cover testing in all positions of gaze 1
• Assessment of ocular motility to identify restriction versus paresis 1
• Forced duction testing (in-office if tolerated, or intraoperatively) to determine mechanical restriction 1
• Evaluation for ocular torsion using indirect ophthalmoscopy or sensory testing, as torsional diplopia occurs in approximately 50% of post-surgical restrictive strabismus cases 1
• Inspection for conjunctival scarring or visible muscle damage 1
• Dilated fundus examination to assess for any concurrent pathology 1

Mechanism of Injury

MOHS surgery can cause diplopia through three primary mechanisms: 1

• Direct muscle injury from surgical dissection near extraocular muscles (most commonly medial rectus if periocular) 1
• Florid scarring involving adjacent tissue, including plica, which can create restrictive strabismus 1
• Anesthetic myotoxicity if retrobulbar or peribulbar blocks were used (though less common with MOHS, which typically uses local infiltration) 1

Natural History and Prognosis

Diplopia persisting beyond 6 months is unlikely to resolve spontaneously and warrants definitive intervention. 1, 2 Many cases improve within 8-15 months if caused by local injury or hemorrhage without permanent muscle damage or significant scarring. 1

Management Algorithm

Acute Phase (0-6 Months)

Monitor/Observe if: 1

• Symptoms are mild, occasional, and well-tolerated
• Patient demonstrates progressive improvement
• Patient declines treatment

Nonsurgical Management: 1, 3

• Fresnel prisms for temporary correction while awaiting stabilization 1, 3
• Partial occlusion using Bangerter foils, Scotch Satin tape, or occlusive contact lenses if prisms inadequate 1, 3
• Complete occlusion with patch if diplopia is intractable 3

Chronic Phase (>6 Months)

Surgical Intervention Indicated When: 1

• Diplopia persists beyond 6 months without improvement
• Diplopia occurs in primary or reading position
• Compensatory head positioning develops
• Quality of life significantly impaired

Surgical Approach: 1

• Surgery on affected eye when limited ocular rotations present 1
• Contralateral eye surgery may be considered to match restrictions or when minimal mechanical involvement makes this preferable 1
• Multiple surgeries may be required due to incomitant nature of restrictive strabismus 1
• Adjustable sutures are often helpful given the complexity of these cases 1

Critical Pitfalls and Caveats

Complete elimination of diplopia is difficult, if not impossible, in most cases of post-surgical restrictive strabismus due to multifactorial etiology and incomitant misalignment. 1 The incomitance and potential torsional component make prism correction rarely satisfactory long-term. 1

Prisms are generally most useful as a temporizing measure during the observation period or for residual diplopia after surgical correction. 1, 3

The restrictive nature of post-surgical strabismus (from scarring and tissue adhesion) makes these cases more challenging than paretic strabismus, often requiring more aggressive surgical approaches. 1, 3

Referral and Multidisciplinary Care

Immediate referral to ophthalmology (preferably strabismus specialist, pediatric ophthalmologist, or neuro-ophthalmologist) is warranted for any persistent diplopia after MOHS surgery. 1, 2 Working with orthoptists under ophthalmologic supervision can assist in examination, diagnosis, and nonsurgical management. 1

Close communication with the dermatologic surgeon who performed the MOHS procedure helps clarify the extent of tissue manipulation and proximity to extraocular structures. 1