Night blindness, congenital stationary, 1B
A non-progressive retinal disorder characterized by impaired night vision. Congenital stationary night blindness type 1B is an autosomal recessive form associated with a negative electroretinogram waveform. Patients are night blind from an early age, and when maximally dark-adapted, they could perceive lights only with an intensity equal to or slightly dimmer than that normally detected by the cone system. ERGs in response to single brief flashes of light have clearly detectable a-waves, which are derived from photoreceptors, and 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 and a nearly normal OFF response. There is no subjective delay in the perception of suddenly appearing white vs black objects on a gray background.
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