congenital stationary night blindness type 1B (CSNB1B)

Genetics

• autosomal recessive
• associated with defects defects in GRM6

Clinical manifestations

• patients are night blind from an early age
• when maximally dark-adapted, they can perceive lights only with an intensity equal to or slightly dimmer than that normally detected by the cone system.

Diagnostic procedures

• negative electroretinogram (ERG) waveform
• ERGs in response to single brief flashes of light have clearly detectable a-waves, which are derived from photoreceptors, & greatly reduced b-waves, which are derived from the second-order inner retinal neurons
• ERGs in response to sawtooth flickering light indicate a markedly reduced ON response & a nearly normal OFF response
• no subjective delay in the perception of suddenly appearing white vs black objects on a gray background

More general terms

• congenital stationary night blindness type 1 (CSNB1)

Database

• OMIM: https://mirror.omim.org/entry/257270