According to ZAM there is "an evil eye prisoner" but no "an Evil Eye". I've seen two Evil Eyes, one where the prisoner is supposed to spawn in the pool and a second one in a room with spikes right next to it.
I believe having regular evil eyes is a mistake and that the prisoner does not have a place holder.
I'm assuming that the prisoner does spawn because I've seen people selling the observer staff. So I'm guessing the evil eye in the pool is a place holder?
See ZAM mob listing to see no regular evil eyes:
http://eqbeastiary.allakhazam.com/search.shtml?zone=27