The multifocal electroretinogram (MERG) can assess regional retinal responses using analysis which gives both first-order and second-order nonlinear responses from multiple retinal regions. The retinal responses from both types of analysis showed amplitude reduction in glaucoma, suggesting that the outer and inner retinal layers are affected. These findings are in accord with the damage which has been reported in advanced glaucoma. The macular response showed a larger amplitude reduction in b-waves (first-order response) and N2P (second-order response) than did peripheral retinal responses. This indicates that loss of macular response is an important sign in glaucoma.