Unilateral Vertical Diplopia: Evaluation and Management
Unilateral vertical diplopia is concerning and warrants prompt evaluation as it may indicate serious underlying neurological or orbital pathology that could affect morbidity and mortality.
Causes and Clinical Significance
Unilateral vertical diplopia typically results from misalignment of the eyes in the vertical plane and can be caused by:
- Superior oblique palsy (SOP) - most common cause
- Cranial nerve palsies (especially CN III and IV)
- Skew deviation (associated with brainstem/cerebellar pathology)
- Myasthenia gravis
- Orbital disease including thyroid eye disease
- Trochlear schwannoma
- Giant cell arteritis
Diagnostic Approach
Initial Assessment
- Parks-Bielschowsky three-step test to confirm diagnosis of SOP (hypertropia greatest in opposite lateral gaze and head tilt to same side) 1
- Measure torsion and determine position of gaze with greatest deviation
- Document excyclotorsion with Double Maddox Rod or Lancaster Red Green testing 1
- Assess for torsional diplopia which may be a barrier to fusion
Concerning Features Requiring Urgent Neuroimaging
- Acquired symptomatic diplopia with poor fusional amplitudes 1
- Additional central nervous system signs or symptoms
- Acute onset without history of trauma
- Associated headache or pupillary abnormalities 2
- Small vertical fusional amplitudes in isolated SOP without trauma history 1
Management Algorithm
1. Determine Need for Neuroimaging
- Neuroimaging (MRI brain/orbit with contrast) is indicated if:
- Additional neurological signs/symptoms present
- Acute onset without trauma history
- Poor fusional amplitudes
- Suspected trochlear schwannoma
- Suspected skew deviation (which may indicate brainstem pathology)
2. Rule Out Urgent Conditions
- Check for giant cell arteritis (ESR, CRP, temporal artery tenderness) in older patients 1
- Evaluate for occult thyroid eye disease (which can present with vertical diplopia) 1
- Consider myasthenia gravis (test for fatigability)
3. Treatment Options
A. Conservative Management
- Observation if symptoms are mild, occasional, and not bothersome to patient 1
- Prism glasses for small vertical deviations (though lateral incomitance may limit effectiveness) 1
B. Surgical Management
Indicated for:
- Larger and incomitant deviations
- Torsion that is a barrier to fusion
- Symptomatic diplopia affecting quality of life
- Significant compensatory head posture
Surgical options include:
- Inferior oblique weakening (ipsilateral)
- Inferior rectus weakening (contralateral)
- Superior oblique strengthening (ipsilateral)
- Superior rectus weakening (ipsilateral) 1
Important Clinical Pearls
- Distinguish between skew deviation and fourth nerve palsy, as skew deviation often indicates more serious brainstem pathology 1
- In skew deviation, the hypertropic eye shows incyclotorsion (versus excyclotorsion in fourth nerve palsy) 1
- Microvascular causes of diplopia often resolve spontaneously within six months 2
- Target a small undercorrection with surgical management, as overcorrection (especially in downgaze) is poorly tolerated 1
- Forced ductions during examination or surgery may reveal lax superior oblique tendon or restrictive elements 1
Referral Considerations
- Refer to neuro-ophthalmologist if:
- Skew deviation is suspected
- Additional neurological signs/symptoms are present
- Etiology remains unclear after initial evaluation
- Diplopia persists despite treatment attempts
Remember that while many cases of isolated unilateral vertical diplopia may have benign causes, prompt and thorough evaluation is essential to rule out potentially serious underlying conditions that could affect patient morbidity and mortality.