Evolution of idiopathic epiretinal membrane studied by optical coherence tomography.

PURPOSE To study the evolution of idiopathic epiretinal membrane (IERM) as examined by optical coherence tomography (OCT) in the 1-mm-diameter circle centered on the fovea. METHODS In a case series study 71 subjects (71 eyes) with idiopathic epiretinal membrane and macular thickness greater than 220-/+10 micro m were evaluated by OCT. The fellow healthy eye of 52 patients was used as the control group. The mean follow-up was 36 months. Measurements of macular thickness at baseline and at the final examination were performed. Best-corrected visual acuity was expressed as the number of letters read on the Early Treatment Diabetic Retinopathy Study chart. RESULTS Within the inner macular central circle of 1 mm diameter the thickness of the fovea increased by an average of 12.29% (p<0.001) during follow-up in the study group while in the control group the foveal thickness decreased by -0.44% (p=0.43). The mean increase of the fovea thickness was accompanied by a modest decrease of best-corrected visual acuity from a mean 43.26 letters at baseline to a mean 39.20 letters at the last examination (p<0.001). CONCLUSIONS In the study group the macular thickness increased during a mean follow-up period of 36 months. The average increase between the baseline and the final examination at the inner central circle of 1 mm diameter was 12.29%. Decrease of the macular thickness was not observed in any of the studied cases. The mean decrease of visual acuity was 9.4%. OCT also depicted with accuracy the changing morphology of the affected macula during the study period.