Any ghost that has excessive power that rivals the Observants must have an eye removed. Or more accurately, it just sorta… Leaves. It’s weird. As such, Clockwork had their left eye removed (seeing into the future), as well as Nocturne (seeing into desires and fears to make dreams or nightmares, and Pariah Dark had his right eye removed (due to his allusions to Odin, it is possible it was for wisdom or power instead of removed normally, like the others did, which is why it was his right eye and not his left). It is possible it’s due to their differing personalities and motives. Pariah was definitely a villain, while both Clockwork and Nocturne are not quite villains and not quite heroes, as their motives can be interpreted as neutral (even though Clockwork is more aligned with good and Nocturne us more aligned with bad).
But of course, who knows? Maybe they’re actually mirror wounds of some kind, or maybe they connect the three… Received at the same time or something… But they can’t not be connected. They’re very powerful ghosts and they’re all missing an eye and the Observants only have one eye to start… Surely, there is a connection.