Vertical diplopia onset with first-time bifocal

A 39-year-old white female presented with symptoms of constant diplopia onset with a first bifocal correction. The association of these conditions required a careful differential diagnosis and special management considerations. Testing indicated an esotropia with a longstanding nonconcomitant superior oblique paresis which became manifest when she began wearing bifocals. A regimen of horizontal vergence range training in combination with a relieving vertical prism in a near correction were prescribed. An amount of prism which allowed comfortable sensory-motor fusion through both the distance and near portion of a bifocal spectacle correction was eventually ascertained. Information regarding etiology, etiologic incidence, differential diagnosis, and management of superior oblique paresis is also presented.