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Monocular Elevation Deficiency (Double Elevator Palsy)
Strabismus
Key Points
- •MED is a unilateral inability to elevate one eye in all horizontal gaze positions; the most common mechanism (~70%) is IR restriction (not true SR + IO paresis), making 'double elevator palsy' a misnomer
- •The forced duction test is the key investigation: negative FDT → supranuclear/paretic cause (Knapp procedure); positive FDT → IR restriction (IR recession first)
- •Bell's phenomenon is present (intact) in supranuclear MED (Type 3) but absent/poor in IR restriction (Type 1, ~70%) and paresis (Type 2) - a critical bedside test for determining the mechanism
- •The Knapp procedure (transposition of MR + LR to the SR insertion) is the definitive surgical treatment for supranuclear/paretic MED (FDT-negative types), correcting 20–30 PD of hypotropia
- •Pseudoptosis is common - resolves when hypotropia is corrected; always correct the strabismus FIRST before considering ptosis surgery
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17 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Risk factors and associations