Association of electroretinogram and morphological findings in branch retinal vein occlusion with macular edema

The objective of this study is to evaluate the relations among electroretinogram parameters (cone a-wave, cone b-wave, and 30-Hz flicker), retinal thickness, and retinal volume in patients with branch retinal vein occlusion (BRVO) and macular edema. We prospectively examined 33 patients (33 eyes) with BRVO and macular edema. The amplitude and implicit time of the a-wave cone, b-wave cone, and 30-Hz flicker were calculated automatically from the ERG. Retinal thickness and volume were measured by optical coherence tomography (OCT) in nine macular subfields. Then, correlations between the ERG parameters and morphological parameters were analyzed. The 30-Hz flicker amplitude was significantly smaller in the eyes with BRVO and macular edema than in the unaffected contralateral eyes. Thirty-hertz flicker and cone b-wave implicit times were significantly longer in the eyes with macular edema than in the unaffected eyes. The implicit time of the cone b-wave was correlated with both retinal thickness and retinal volume in the temporal subfields. Thirty-hertz flicker amplitude was correlated with both retinal thickness and volume in the temporal and superior outer (site of occlusion) subfields, while 30-Hz flicker implicit time was correlated with retinal thickness and volume in the outer temporal subfield. Multiple regression analysis demonstrated that the retinal thickness and volume of the temporal subfields were significant “determinants” of the implicit time for the cone b-wave and 30-Hz flicker, as well as the 30-Hz flicker amplitude. These findings suggest that OCT parameters of the temporal region may reflect postreceptoral cone pathway function in BRVO patients with macular edema.