In spite of the hope that a large volume of data accumulation would lead to clarification of the mechanism of VPL, which in turn would lead to the development of highly effective ways to greatly restore or improve damaged or deteriorated vision, the general tendency of the research field has been to oppose the establishment of such a mechanism. In reality, instead of different models converging on a unified view, several issues that highly relate to core mechanisms of VPL are becoming incrementally more controversial.