The same albino allele that produces coloured points means that Siamese cats' blue eyes lack a "tapetum lucidum", a structure which amplifies dim light in the eyes of other cats. The mutation in the tyrosinase also results in abnormal neurological connections between the eye and the brain. The optic chiasm has abnormal uncrossed wiring; many early Siamese were cross-eyed to compensate, but like the kinked tails, the crossed eyes have been seen as a fault, and due to selective breeding the trait is far less common today. Still, this lack of a "tapetum lucidum" even in uncross-eyed cats causes reduced vision for the cat at night. This trait has led to their dependence and interest in humans, as it affects their hunting ability, a desirable trait for many owners. However, it also makes them vulnerable to urban dangers such as night-time vehicular traffic. Unlike many other blue-eyed white cats, Siamese cats do not have reduced hearing ability.