Forum:Voldemort and Occluimency

In the half-blood prince, voldemort practices occlumency against harry so he cant see into his mind, also stopping the pain in harrys scar. but in deathly hallows, harrys scar hurts and he sees into voldemorts mind. why does that happen? does this mean voldemort stopped using occlumency against harry in deathly hallows?