After losing his eye while battling Death Eaters (Pm), Alastor Moody received a magical replacement that could swivel around in all directions (GF14) and even see through Harry’s Invisibility Cloak (GF25).
- Round and "electric blue," Moody's eye could see through walls and doors, and even look behind him (OP3).
- While attending the trials of Igor Karkaroff, Bellatrix Lestrange and Barty Crouch Jr., which Harry saw in the Pensieve, Moody still had two good eyes (GF30). This means that Moody lost his eye while battling the Dark Arts after Voldemort was vanquished in 1981.
- While working in London to protect Harry for the Order of the Phoenix, Mad-Eye wore a bowler hat at an angle to hide his disturbing eyeball (OP22).
- Moody was killed during the Battle of the Seven Potters and his magical eye disappeared (DH5). Harry later found it on the door of Dolores Umbridge's office at the Ministry of Magic attached to a telescopic device through which she could spy on other workers (DH13). He removed the eye and later buried it in a forest under "the oldest, most gnarled, and resilient-looking tree" he could find (DH14).
Barty Crouch Jr. had an almost perfect disguise as Fake Moody because of the magical eyeball. Dumbledore could usually tell what was on someone's mind, but even he would have had a hard time doing a Legilimens spell on Fake Moody due to the lack of eye contact. And indeed their friendship might have kept Dumbledore from trying to search Fake Moody's mind anyway, since he knew the real Moody was already paranoid and suspicious. Snape did not trust Fake Moody and even tried to stare him down as if doing Legilimens in the corridor, but could not see through his disguise (GF25)