what is horner's syndrome in humans
Photos.com/Photos.com/Getty Images. Hornerâs syndrome is a neurological condition affecting the eye and facial muscles due to a dysfunction in the sympathetic nervous system. It affects humans as well as dogs, cats, horses and other animal species. The condition is not painful and does not affect an animalâs vision. While some cases of Hornerâs syndrome are due to an underlying cause, this is not always the case.