Danzo wasn't having sharingan at that time.
He got those on his hands after the Uchiha Massacre. And he got the right eye after Shisui joined the Anbu.
lol , shisui never joined the anbu.
Shisui was a part of anbu. He was in the same outfit that to of Itachi's when they were talking in that genjutsu flashback
yet , we never saw 100 % clarification of that :|
but don't you agree that danzo didn't have all those sharingans that time?
We can't be sure that shisui was in the anbu along side itachi,i think he was in the police force.