Tomographic and multifocal electroretinographic features of idiopathic epimacular membranes

Objective: To determine the relationship between the tomographic and electrophysiologic characteristics of the retina with an idiopathic epimacular membrane. Methods: Sixty patients with unilateral idiopathic epimacular membranes underwent optical coherence tomography and multifocal electroretinography (mfERG). The mfERGs were elicited by a pseudorandom m-sequence stimulus with 37 hexagonal elements, and the mfERGs in area 1 (central 4.1°), area 2 (ring from 4.10°-7.15°), and area 3 (ring from 7.15°-13.75°) were compared with the tomographic features of the corresponding area. The data from the normal fellow eyes served as control. Main Outcome Measures: The retinal thickness, amplitudes, and implicit time of the mfERG. Results: On optical coherence tomographs, the retina was thickest in area 1, followed by area 2 with low tissue reflectivity of the outer retina, and area 3 was of normal thickness. Electroretinography showed the amplitude ratio (affected vs fellow eyes) of mfERGs from areas 1, 2, and 3 was significantly lower than that of the controls (P<.01), and the implicit times were significantly delayed (P<.01). The amplitude ratio was reduced the most in area 1, and the implicit time was delayed the most in area 3. The foveal thickness was negatively correlated with visual acuity (p = -0.46; P<.001). The mfERG amplitude in area 1 was not significantly correlated with the visual acuity. Conclusions: It is likely that retinal thickness is correlated with neural dysfunction, but mfERGs demonstrated various physiological changes in the retina.