A hereditary night blindness that is characterized by hemeralopia with a moderate loss of visual acuity and caused by defective photoreceptor-to-bipolar cell signaling with common ERG findings of reduced or absent b-waves and generally normal a-waves. [ http://purl.obolibrary.org/obo/ECO_0007646 http://purl.obolibrary.org/obo/ECO_0007636 http://purl.obolibrary.org/obo/ECO_0007645 ]