Prevalence and associations of central-peripheral rivalry-type diplopia in patients with epiretinal membrane

IMPORTANCE The prevalence and clinical associations of patients with epiretinal membrane (ERM) who develop central-peripheral rivalry (CPR)-type diplopia are unknown. OBJECTIVES To determine the prevalence of CPR-type diplopia in retinal disease clinic patients with ERM and to determine clinical findings associated with CPR-type diplopia. DESIGN, SETTING AND PARTICIPANTS A prospective cross-sectional study of 31 patients with ERM from retinal disease clinics to determine the prevalence of CPR-type diplopia. A retrospective case cohort of 25 additional patients with ERM, selected from adult strabismus clinics, was added (total = 56) to determine clinical associations with CPR-type diplopia. All data were collected between June 2014 and November 2016; prospective cohort data were collected from June 2016 to November 2016. MAIN OUTCOMES AND MEASURES The presence of diplopiawas determined by patient history and diplopia questionnaire responses. Visual acuity and ocular alignment were recorded. Metamorphopsia was documented qualitatively by evaluation of the door frame and Amsler grid and measured quantitatively using M-charts and D-charts. Aniseikonia was determined by subjective description and results of the Awaya new aniseikonia test. Retinal misregistration testing consisted of optotype-frame test and synoptophore; CPR-type diplopia was defined as diplopia associated with evidence of retinal misregistration when other causes did not fully explain diplopia. Outcomes were as follows: prevalence of CPR-type diplopia in patients with ERM seen in retinal disease clinics, and whether or not clinical findings differed between patients with ERM and CPR-type diplopia vs patients with ERM without CPR-type diplopia. RESULTS Of the 31 patients with ERM seen in retinal disease clinics, 16 were women and 15 were men; the mean (SD) age was 69 (10) years. The prevalence of any diplopia was 23%(7 of 31; 95%CI, 10% to 41%), with CPR-type diplopia present in 16%(5 of 31; 95%CI, 5%to 34%). For analysis of associations, 12 of 56 patients (21%) had CPR-type diplopia and 37 (66%) had no diplopia. Seven of the 56 patients were excluded for other types of diplopia. Patients with CPR-type diplopia had better worse-eye visual acuity (mean difference, -0.23; 95%CI, -0.37 to -0.09 logMAR, P = .003), and more severe quantitativemetamorphopsia (mean M-score difference 0.6; 95%CI, 0.05 to 1.1, P = .01) than patients without diplopia, but similar aniseikonia (Awaya new aniseikonia test; mean difference 0.6%; 95%CI, -2.9%to 4.0%, P = .33) and similar evidence of retinal misregistration (100% vs 73%; P = .09) by any test. CONCLUSIONS AND RELEVANCE Our findings suggest that CPR-type diplopia is not uncommon in patients with ERM. On average, patients with CPR-type diplopia have better visual acuity and more metamorphopsia than those without CPR-type diplopia, but there is considerable individual variability. Aniseikonia and retinal misregistration are similar between patients with ERM associated with CPR-type diplopia and those without CPR-type diplopia. Retinal misregistration with coexistent metamorphopsia appears necessary but is not sufficient for CPR-type diplopia.