Will Sleeping With Too High Pillow Affect The Spine?

hi doctor , my father is suffering from slip disc and the spinal chord bone is pressing some vein and he is loosing his affects and control in his left leg, now he is having neck pain every now and then the doctors have askd to go for the operation but he is not ready . my query is that my father while sleeping takes two to three pillows i mean it creates a lot of height is this harming his spin please suggest ........ thanking you mirza