X-linked congenital stationary night blindness (CSNB) is a rare
X-linked non-progressive
retinal disorder. It has two forms, complete, also known as type-1 (CSNB1), and incomplete, also known as type-2 (CSNB2), depending on severity. In the complete form (CSNB1), there is no measurable
rod cell response to light, whereas this response is measurable in the incomplete form. Patients with this disorder have difficulty adapting to low light situations due to impaired
photoreceptor transmission. These patients also often have reduced visual acuity,
myopia,
nystagmus, and
strabismus. CSNB1 is caused by mutations in the gene
NYX, which encodes a protein involved in retinal
synapse formation or synaptic transmission. CSNB2 is caused by mutations in the gene
CACNA1F, which encodes a
voltage-gated calcium channel Ca
V1.4.