Purpose To describe the causes of diplopia in patients with an epiretinal membrane (ERM) and presenting diplopia. Design Retrospective observational case series. Methods We reviewed patients diagnosed with an ERM, who had been seen by both retinal and strabismus specialists in a tertiary medical center. Data recorded: orthoptic evaluation, retinal misregistration (optotype-frame test, and synoptophore central peripheral superimposition slides at 5 and 10 degrees), and cause of any diplopia (retinal misregistration vs strabismus vs optical/refractive error). We defined central-peripheral rivalry–type diplopia as presenting symptomatic diplopia with evidence of retinal misregistration, and where other causes did not fully explain diplopia. The frequency of each cause of diplopia in patients with ERM was determined. Results Of 50 patients with ERM, 25 had symptomatic diplopia and 25 had no diplopia. Eleven of 25 diplopic patients (44%) had retinal misregistration as the sole cause (central-peripheral rivalry–type diplopia), 7 (28%) strabismus (1 of 7 initally appeared to have central-peripheral rivalry–type diplopia), 1 (4%) optical/refractive error (monocular diplopia), 2 (8%) mixed retinal misregistration (central-peripheral rivalry–type diplopia) and strabismus, and for 4 (16%) diplopia cause was indeterminate. Unexpectedly, 15 of 25 patients without diplopia (60%) had evidence of retinal misregistration. Conclusions Patients with ERM and presenting diplopia may have 1 of several causes of diplopia, most commonly retinal misregistration (central-peripheral rivalry–type diplopia). Nevertheless, diplopic patients with retinal misregistration may also have treatable strabismus or optical/refractive error as the primary barrier to single vision and therefore many potential barriers to single vision should be considered.
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