I personally have not had that kind of a sensation, but I have had several other kinds of sensations in the face. I think Maureen is onto something about the PWS being involved into the nerve itself. It would diffently explain a couple of my sensations. Maybe there is two or more nerves that are attached some how from the PWS or are rubbing just right. A nerve doctor would be able to give you a better theory then I would be able to why it is doing it.
I would strongly recommend getting an eye exam just to make sure that the sensation is not causing any damage to your eye. Plus, being that your PWS is that close to the eye also have them check for glaucoma since you do have the risk of it. Being that I have had vision loss because of my PWS because I have PWS in my eye but do not have glaucoma I have always said better to be safe then sorry if something is happening and you would not know until it is to late. Glaucmoa is that why.
One other thing after you get your insurance something you might want to consider is trying some laser treatment on your PWS that could possibably slow down the pulsing. I have that also. It happens to most people when they are active, angry, in the shower, or anything else that could get the heart pumping. Some PWS will even go to the extent of getting darker for a short period of time like mine does when I lift weights.
If you are interested in laser treatment you might be able to find a dermatologist in your area in the resource section that is at the top of this page. If you can not find one let use know and someone on this group might be able to recommend someone.
I hope this helps and if you have any other question please ask we are all here for you.