I'm a psyker and in pvp how am I supose to cast distort vision?

If you're asking how to adjudicate the effect, that's what the GM is for. Dark Heresy is not a tactical skirmish game. It's a roleplaying game that assumes the PCs are on the same side (most of the time) and requires a GM. Inquisitor, by GW's Specialist Games division, is a tactical skirmish game, set in the same universe as DH. It is also also available as a free pdf download from Specialists Games website. As a game, it is designed for this kind of play and therefore has rules to handle issues like this.

Zephyrus said:

You're not supposed to be doing PVP.