Glaucoma is common cause of blindness in the world It results from imbalance between the IOP and the perfusion pressure and results into damage of the ganglion cell layer which cause damage of the RNFL and visual field defects. This damage are always asymptomatic at early stages and visual field defects don’t appear before 25-35% of the RNFL is damaged.So the object of interest has been shifted to many functional and structural tests that can help in early glaucoma detection and go beyond limitations of standard automated perimetry.This essay will discuss in details the multifocal ERG with its guidelines and its clinical applications in glaucoma and ocular hypertension.