Multifocal electroretinograms in patients with branch retinal artery occlusion

PURPOSE. To investigate the usefulness of second-order multifocal electrore tinograms (MERGs) for detecting inner retinal disorders. METHODS. The MERG from 5 patients with branch retinal artery occlusion (BRA O) was recorded. Twelve eyes of 12 normal subjects were also tested. MERGs were recorded using 61 hexagons. Bright flash ERGs were also recorded to me asure the oscillatory potentials (OP). Root mean square (RMS) measures of t he local first- and second-order MERGs (fMERG and sMERG) were compared in t he affected and unaffected areas. The first negative trough (N1) and first positive peal; (P1) were also used for measuring the amplitudes and latenci es of the fMERG. RESULTS. The fMERG RMS-amplitudes decreased significantly (r = 0.56, P < 0. 05) in the affected area compared with normal values. The fMERG latencies o f N1 and P1 increased significantly (P < 0.05) in the affected area. Furthe rmore, the sMERG RMS-amplitudes decreased almost to the noise level (r = 0. 28, p < 0.001) in the affected areas. The interocular ratio of the sMERG RM S-amplitudes (affected/normal) significantly correlated with that of the fM ERC (r = 0.69, P < 0.001). The fMERG latencies significantly correlated wit h the sMERG RMS-amplitude (r = 0.37 similar to 0.69, P < 0.05 <similar to> 0.001), but only began to increase after a 30% to 50% loss of the sMERG amp litude. The summed OP amplitude decreased to the same extent as the sMERG i n the affected eye (0.5 of the normal eye). CONCLUSIONS. Although the fMERG amplitude and latency were significantly ch anged, the sMERG was much more affected by BRAO. The marked reduction of th e sMERG in the affected area strongly suggested its main source was from th e more inner layers of the retina compared to the fMERG. The sMERG appeared to be a sensitive indicator of inner retinal dysfunction.