Not much has been shown about these ocular Jutsu in the anime, with Izanami being shown only once. But at least Izanangi has been shown twice, firstly used by Danzo and later on by Obito in his fight against Konan.
Here we will look at the jutsu origins, as much was explained by Itachi after he had defeated Kabuto, I guess he did it as another one of his parting gift to his brother as at that time Izanami had saved the day.
As for Izanangi, it was fully explored during Sasuke’s fight with Danzo, as he was driven with greed and managed to influence complete annihilation of the Uchiha clan, with only one surviving member left. It was during this time that he managed to collect so much sharingaans for his own plots and to make sure that he controls them he had been doing his schemes with Orochimaru and managed to get Senju cells implanted into him.