Macular dystrophy as a retinal model of fixation disparity

In patients with obligate fixation disparity central objects may be seen double when peripheral fusion manifests. The diplopia cannot be treated with prisms because fusional power of the peripheral retina breaks down central fusion. A different cortical integration of the peripheral and central retina is supposed to be the underlying cause. The authors report on the clinical findings of a 45-year-old man with macular dystrophy who complained about binocularly perceived vertical diplopia up to Id`. Investigation with Aulhorn's phase difference haploscope revealed an inhomogeneous retinal correspondence in the vertical plane with a displacement of the visual field center relative to the periphery by 0.6 degrees. Paracentral scarring was associated with a displacement of central retinal receptors. The center of the visual field and the peripheral field could not be fused simultaneously. The case reported may represent a model for a retinal origin of fixation disparity.