The CSF shunt valve includes an elongate, hollow housing and a valve unit disposed within the housing. A hole-side convex portion 80 is formed in each opening 12 at one or more locations in a circumferential direction, and a door-side rib 70 is formed on each door body 30. Such optimization can be achieved using reliabilities, preferences and policies concerning handling the attempted contact based on a deterministic specification or through inferring reliability, context, content and task under uncertainty by employing decision-theoretic inferences. A non-reflective region generally in the plane of at least one of the first and second reflective elements is adjacent the first corner.