Human Phenotype Ontology identifier HP_0007984 (ERG: Reduced dark-adapted b-wave amplitude) is a dark-adapted bright flash electroretinogram in which the b-wave that is of markedly lower amplitude than the associated a-wave. Also known as: Electronegative ERG, Electroretinogram: reduced b-wave amplitude, Reduced ERG amplitude of b-wave, Reduced amplitude of dark-adapted bright flash electroretinogram b-wave, Reduced electroretinogram rod b-wave.