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Ji Eun Lee, Hyun Woong Kim, Sung Il Kim, Jong Ho Park, Ik Soo Byon; Correlation of pattern electroretinogram and visual acuity in idiopathic epiretinal membrane. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2789.
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Idiopathic epiretinal membrane (ERM) is a disease having glial proliferation on the surface of the retina. Its mechanical traction is reported as a main mechanism to cause visual dysfunction. Recent studies using optical coherence tomography indicated that defects of the photoreceptor layer are correlated with postoperative visual acuity. However, the photoreceptor layer is the farthest portion of the retina from ERM, and damage to the inner retina would precede the outer retinal abnormality. Pattern electroretinogram (PERG) represents function of the macula and the ganglion cell layer, which is the closest cell layer to ERM. This study was conducted to investigate correlation of PERG and visual acuity in idiopathic ERM.
Eyes which underwent vitrectomy and membrane peeling for idiopathic ERM and followed up for 6 months or more were included. PERG was performed before operation. PERG and medical records were reviewed retrospectively. Implicit time and amplitude of P50 and N95 were assessed, and ratio of the values in the affected eye to the values in the normal eye was calculated. The parameters were analyzed to find correlation with pre-and postoperative visual acuity.
Total 21 eyes were included in the study. Visual acuity (logMAR) improved significantly from 0.61 to 0.38 and central subfield thickness decreased significantly from 488 to 369 at 6months. Implicit time was not delayed, but amplitude was reduced significantly in the affected eye. Ratio of P50 was 0.65±0.31, and ratio of N95 was 0.68±0.37. There was no correlation between visual acuity and amplitude of P50 or implicit time of P50 and N95. Amplitude of N95 had significant correlation with postoperative visual acuity at 6 months (P=0.036, r=0.460).
PERG provided useful information to assess postoperative outcomes. It was reported that N95 represents the ganglion cell layer, whereas P50 represents the outer retina of the macula. Correlation of postoperative visual acuity with N95 but not with P50 indicates that status of the ganglion cell layer would be a important factor for visual function in ERM.
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