Tobirama Killed a Blind Izuna

[Uchihabrat1560]

Dude, kishi trolled us... first he stated that Izuna gave his eyes to Madara and went blind and got killed in a battle..

and now he says that Izuna died cause of the would by Tobirama .. it's during his death that he donates the eye.. not sure which to follow..

 

[baka baka]

half blinded probably. like itachi.

 

[USSJ Future Trunks]

just more proof databook has been retconned out of canonicity

 

[Lost Woods Denizen]

I believe that the databooks are only supplementary for the chapters published at the time. I believe that the information in that databook covers information up until Sasuke and Tobi's alliance, and at that point in the manga it was fact for us that Tobi was Madara, in addition to his story on Izuna being fact.
The details that have since been revealed tell otherwise, and as such we have had to "update" our "facts." As revealed in Hashirama's flashback, Izuna did indeed have his own eyes, though the status on how well he was actually able to see through those eyes is arguable.
We are potentially due for four more data/fanbooks in the future (based on the naming system for them) so I assume things will be further cleared up then. However, until then I will assume that Hashirama's story is the actual history.