[Focal macular electroretinogram in high myopia]

To investigate early changes of the macula in eyes with myopia, we compared 66 eyes with high myopia with 76 normal eyes by recording focal macular electroretinogram (ERG). The eyes with high myopia were divided into two groups; eyes showing only tigroid fundus (group 1) and those associated with posterior staphyloma involving the macula (group 2). The visual acuity of groups 1 and 2 was 1, 0 or better and 0.8 or better, respectively. The amplitude of the a-wave, b-wave in group 1 was significantly smaller than that of normal eyes, however the peak latency was within the normal range. The amplitude of a-wave, b-wave and oscillatory potentials in group 2 was significantly smaller and the peak latency was significantly longer than those in group 1. The abnormal amplitude with normal peak latency in group 1 suggests some reduction of numbers of cones, which is considered to be an early pathologic change in the macula with high myopia. The more reduced amplitude with delayed peak latency in group 2 suggests that, in the advanced stage, the macular pathologic finding includes some quantitative damage as well as further reduction of macular cones.