Board Thread:General Discussion/@comment-25614818-20150525120225/@comment-25614818-20150527074937

ChristopherRedfield246 wrote: I was gonna guess either reunite his daughter, but it seems irrelavent since they were there in Rise of the Turtles too. I think its either something to do with the Turtles. If not, I think that Splinter has had it before Shredder's attack on Splinter, Tang Shen and Miwa- So that maybe Splinter's wish was to make it up with Saki again (so that they're brothers again), but that obviously didn't happen, therefore the doll's been without an eye since then...

Those are my biggest theories...