Electronegative electroretinograms in two siblings with bradyopsia, an underdiagnosed pediatric inherited retinal disorder.

In the scotopic flash response of the full-field electroretinogram (ffERG), the downward a-wave reflects photoreceptor response and the upward b-wave is indicative of bipolar cell function. If the b-wave is equal to or smaller than the a-wave, the waveform (and the ffERG) is termed electronegative. For pediatric inherited retinal disorders this finding narrows the differential diagnosis to certain conditions, most commonly congenital stationary night blindness if multimodal imaging is grossly normal. We describe 2 siblings with reduced vision in the setting of normal multimodal imaging. Inherited retinal disorder was suspected, and ffERG was performed. Both had electronegative ffERGs, suggesting an incomplete form of congenital stationary night blindness (cone-rod synaptic disorder). However, genetic testing (biallelic RGS9 pathogenic variants) and phenotypic reassessment confirmed an actual diagnosis of bradyopsia. This report expands the differential diagnosis for an electronegative ffERG to include bradyopsia and highlights features of this underdiagnosed pediatric inherited retinal disorder.