Abstract
Abstract: :
Purpose: To evaluate macular function before and after successful surgical peeling of idiopathic epimacular membranes (EMM) by means of Focal Electroretinogram (ERG). Methods: Snellen visual acuity (VA) and Focal (9x 9 central degrees) ERGs in response to a 30 Hz sinusoidally flickering uniform field or in response to sinusoidal gratings (2 cycles/degree, contrast 80%, reversed at the rate of 8 Hz) have been assessed in 15 eyes of 15 patients (mean age 63.13±12.03 years) with EMM, before and after successful macular peeling. The amplitudes of the fundamental harmonics of Focal–ERG responses were measured (1F for sinusoidally flickering uniform field stimuli and 2P for grated stimuli). 1F is related to the function of the preganglionic macular elements, while 2P reflects the bioelectric activity of the innermost macular retinal layers (see Parisi and Falsini, Semin Ophthalmol. 1998; 13:178–88, 1998, for a review). Pre–operative VA, 1F and 2P amplitudes observed in EMM eyes were compared to those of 15 age–matched controls. The postoperative period was 6 months. Results: In the pre–operative evaluation, EMM eyes showed a significant (ANOVA, P<0.01) reduction in VA (0.29±0.15), 1F amplitude (0.47±0.12 microvolt) and 2P amplitude (0.46±0.14 microvolt) when compared to controls (VA: 1.0±0; 1F amplitude: 1.43±0.23 microvolt; 2P amplitude: 1.47±017 microvolt). In EMM eyes, the decrease in VA was significantly correlated (Pearson’s test, P<0.01) to the reduction in 1F and 2P amplitudes. During the post–operative evaluation, EMM eyes showed a significant (ANOVA, P<0.01) increase in VA (0.46±0.18), 1F amplitude (0.68±0.26 microvolt) and 2P amplitude (0.62±0.16 microvolt) with respect to the pre–operative values. The percentage increase in VA was significantly correlated (P<0.01) with the percentage increase in both 1F and 2P amplitudes. Conclusions: In EMM eyes, the decrease in visual acuity is related to a dysfunction of both the innermost and outer macular retinal layers. The successful surgical removal of the EMM could induce an improvement of the function of both the inner and outer macular retinal layers, leading to a related increase in visual acuity.
Keywords: macula/fovea • electroretinography: clinical • vitreoretinal surgery