Diplopia secondary to aniseikonia associated with macular disease.

OBJECTIVE To provide an explanation for diplopia and the inability to fuse in some patients with macular disease. METHODS We identified 7 patients from our practices who had binocular diplopia concurrent with epiretinal membranes or vitreomacular traction. A review of the medical records of all patients was performed. In addition to complete ophthalmologic and orthoptic examinations, evaluation of aniseikonia using the Awaya New Aniseikonia Tests (Handaya Co Ltd, Tokyo, Japan) was performed on all patients. RESULTS All patients were referred for troublesome diplopia. Six of the patients had epiretinal membranes and 1 had vitreomacular traction. All 7 patients had aniseikonia, ranging from 5% to 18%. In 5 of the patients the image in the involved eye was larger, and in the other 2 patients it was smaller than in the fellow eye. All patients had concomitant small-angle strabismus and at least initially did not fuse when the deviation was offset with a prism. Response to optical management and retinal surgery was variable. CONCLUSIONS Aniseikonia caused by separation or compression of photoreceptors can be a contributing factor to the existence of diplopia and the inability to fuse in patients with macular disease. Concomitant small-angle strabismus and the inability to fuse with prisms may lead the clinician to the incorrect diagnosis of central disruption of fusion. Surgical intervention does not necessarily improve the aniseikonia.