User blog comment:Godisme/Swords of Origin/@comment-2220308-20130117192809/@comment-5695542-20130117222718

Theres a saying i hear alot in tv/books/moives that the eyes are the doorway to the soul.

So it may mean that they don't have a soul or a full soul yet. Has they by what the guy said they are the base for imprinting the Shinigami soul into it forming a Zanpukto.