Binocular vertical diplopia due to subretinal neovascular membrane.

Diplopia is an uncommon finding in patients with subretinal neovascular membranes. We present two patients with binocular diplopia secondary to subretinal neovascular membranes and the foveal displacement syndrome. Subjective diplopia was not improved by prism therapy in either case. In one patient, diplopia was transiently relieved by removal of the choroidal neovascular membrane, but a subsequent subretinal hemorrhage resulted in severe visual loss. In the second patient, diplopia developed following laser therapy for a subretinal neovascular membrane. It is presumed that misalignment of the foveomacular receptor elements between the two eyes produced a central-peripheral fusional mechanism rivalry resulting in binocular diplopia. Ophthalmologists should be aware that a subretinal neovascular membrane may cause binocular diplopia and may mimic neuromuscular strabismus.