(CSNB) is a rare 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 response to light, whereas this response is measurable in the incomplete form.
The vision problems associated with this condition are congenital, which means they are present from birth. They tend to remain stable (stationary) over time.
The prevalence of this condition is unknown. It appears to be more common in people of Dutch-German Mennonite descent. However, this disorder has been reported in families with many different ethnic backgrounds. The incomplete form is more common than the complete form.