Why does the narrator called the old mans Eye a vultures eye?

The narrator refers to the old man's eye as a "vulture's eye" because it has a pale blue color with a film over it, evoking a sense of decay and death. This comparison reflects the narrator's intense aversion and obsession with the eye, which he perceives as a symbol of malevolence and foreboding. The vulture, often associated with scavenging and death, amplifies the narrator's paranoia and contributes to the overall theme of madness in Edgar Allan Poe's story.