Evaluation of macular function using focal macular electroretinography in eyes with macular edema associated with branch retinal vein occlusion.

PURPOSE To study the usefulness of focal macular electroretinography (fmERG) for evaluation of macular function in eyes with macular edema (ME) associated with branch retinal vein occlusion (BRVO). METHODS The authors prospectively performed fmERG on 34 patients with untreated unilateral BRVO at the initial visit and 12 months later. Amplitudes and latencies of the a-wave, b-wave, and photopic negative response (PhNR) were compared with visual acuity, with retinal sensitivity measured by microperimetry, and with measurements obtained by optical coherence tomography. RESULTS In eyes with ME from BRVO, amplitudes of the a-wave, b-wave, and PhNR were reduced significantly and latencies were prolonged significantly compared with those of healthy fellow eyes (P < 0.05). Relative amplitudes and latencies were not correlated with visual acuity but, rather, tended to be correlated with retinal sensitivity within the macular area. Among all parameters studied by fmERG, relative amplitude of the PhNR was most strongly correlated with central foveal thickness (r = -0.465; P = 0.007). In addition, the height of the serous retinal detachment showed a correlation with the relative amplitude of the PhNR (r = -0.376; P = 0.034). At 12 months, the amplitude of the b-wave and the PhNR improved significantly, in parallel with resolution of the ME (P = 0.015; P = 0.033). CONCLUSIONS In eyes with ME from BRVO, amplitudes and latencies seen by fmERG were correlated with other biological parameters. Based on findings of the present study, fmERG appears to be useful as a functional examination within the macular area affected by BRVO.