Pyramid Head’s helmet is closely related to the triangular hood of an executioner, which ties into the concept that he is meant to be James’ punisher and bringer to justice. The helmet was purposefully designed to look very uncomfortable. It acts as a torture device as well as Pyramid Head’s symbol of authority. If you examine his helmet closely in game footage, you’ll notice the insides of the two halves are lined with thick spikes which are more then likely digging into his skull. So while acting as the punisher, Pyramid Head also represents the suffering of the victim.
It is unknown how Pyramid Head can see, because his helmet obviously obscures all vision. However, when James is hiding in the closet from him, there is a moment when Pyramid Head puts his fingers into the mesh holes of his helmet and moves his hand around in a strange fashion, possibly a way of “seeing”, or at least sensing for something since it allowed him to notice James hiding.
There are also moments in the game where one can see Pyramid Head shrugging his shoulders up against the helmet and on occasion trying to tug at it or pull it weakly off, showing that it is indeed uncomfortable for him to wear, but this would be in vain considering that it is attached to him at the neck. It is completely unknown what Pyramid Head looks like under his helmet, but the most common theory is that he resembles Valtiel from Silent Hill 3, with a leathery, featureless face.